THE GLOBAL ATMOSPHERE WATCH PROGRAMME 25 YEARS of GLOBAL COORDINATED ATMOSPHERIC COMPOSITION OBSERVATIONS and ANALYSES WMO-No

THE GLOBAL ATMOSPHERE WATCH PROGRAMME 25 YEARS OF GLOBAL COORDINATED ATMOSPHERIC COMPOSITION OBSERVATIONS AND ANALYSES WMO-No. 1143

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ISBN 978-92-63-11143-2

Cover illustrations: The two photos show the changes in ozone observations from 1957 (International Geophysical Year) until now. On the left, Dobson instruments are being calibrated at the Tateno station in Japan before they are deployed to their individual stations. On the right, Dobson instruments have been set up for a modern intercomparison study. The spectrophotometers are the same, but the measurement and calibration process are now monitored by computers.

NOTE

The designations employed in WMO publications and the presentation of material in this publication do not imply the expression of any opinion what- soever on the part of WMO concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitation of its frontiers or boundaries.

The mention of speciﬁc companies or products does not imply that they are endorsed or recommended by WMO in preference to others of a similar nature which are not mentioned or advertised.

The ﬁndings, interpretations and conclusions expressed in WMO publications with named authors are those of the authors alone and do not neces- sarily reﬂect those of WMO or its Members. CONTENTS

1. History and background 2

2. Long-term objectives and applications 3

3. Organizational structure 4

4. Observations 5

5. Quality assurance 6

6. Focal areas 8

6.1 Ozone 8

6.2 Greenhouse gases 10

6.3 Reactive gases 12

6.4 Atmospheric wet deposition 15

6.5 Ultraviolet radiation 18

6.6 Aerosols 19

6.7 The GAW Urban Research Meteorology and Environment project 23

7. Global Atmosphere Watch data management 27

8. Training 35

9. Global Atmosphere Watch publications 36

10. The future of the Global Atmosphere Watch 37

Acknowledgements 40

References 41

List of abbreviations 43 1. HISTORY AND BACKGROUND

Scientific curiosity drove the early observation of spectrophotometer network to measure total atmospheric constituents. But those observations atmospheric ozone. raised many questions: To what extent were the observed increases in certain trace chemicals In the late 1960s, the Background Air Pollution connected to human activities? What human Monitoring Network (BAPMoN) was established, consequences would there be if the increase focusing on precipitation chemistry, aerosol and continued unabated? carbon dioxide measurements. The Network included regional and background stations and In the 1950s, the World Meteorological a WMO World Data Centre in the United States Organization (WMO) launched a programme of America. on atmospheric chemistry and the meteorological aspects of air pollution that transformed During the 1970s, three important atmospheric those early sporadic measurements into regular issues were addressed: (i) the threat of chloro- observations. The new programme soon deter- fluorocarbons (CFCs) to the ozone layer, (ii) the mined that adequate gathering of such data – and acidification of lakes and forests in large parts analysis of its anthropogenic impact on a global of North America and Europe, caused princi- scale – would require that all measurements be pally by the conversion of sulphur dioxide into expressed in the same units and on the same sulphuric acid by precipitation processes in the scale, so that measurements performed by dif- atmosphere, and (iii) global warming caused by ferent countries could be comparable. the build-up of greenhouse gases in the atmosphere. Each of these issues is now the subject The first steps towards reaching this objec- of international treaties or conventions. The tive were made during the 1957 International initial development of these agreements and the Geophysical Year. The World Meteorological subsequent assessments of the mitigation mea- Organization began developing standard pro- sures they contain rely heavily on the information cedures for uniform ozone observations and derived from the WMO atmospheric composition established the Global Ozone Observing System observations and analysis programme. (GO3OS), which involved ozonesonde intercom- parisons, preparation of the ozone bulletins In 1989, the two observing networks, BAPMoN and ozone assessments, and support of the and GO3OS, were consolidated into the cur- Ozone Data Centre in Toronto, Canada (later rent WMO Global Atmosphere Watch (GAW) to become the World Ozone and Ultraviolet Programme. As the networks evolved and grew, Radiation Data Centre). The Organization also so did the community involved in atmospheric coordinated the Dobson, and later Brewer, composition observations and analysis.

Evolution of the GAW greenhouse gas community: group photos of the 1st meeting of greenhouse gas experts in the Scripps Institution of Oceanography, United States, in 1975 (this page) and the 17th meeting in Beijing, China, from 10–14 June 2013 (opposite page)

2 2. LONG-TERM OBJECTIVES AND APPLICATIONS

The GAW Programme is driven by the need data can provide important information. These to understand the variability and trends in the application areas include: composition of the global atmosphere and the related physical parameters, and to assess the • Assessment of the health impacts of air pol- consequences thereof. The foremost challenges lution through health indices it needs to address are: • Air quality forecasting • Emission verifications using inverse modelling • Stratospheric ozone depletion and the increase techniques of ultraviolet (UV) radiation • Assessment of atmospheric composition • Changes in the weather and climate related changes and impacts on climate to human influence on atmospheric composi- • Eutrophication tion, particularly greenhouse gases, ozone • Ecosystem services and aerosols • Attribution of the sources of atmospheric • Risk reduction of air pollution on human health species and issues related to atmospheric deposition and the long-range transport of air pollution The GAW Programme is implemented by WMO Members and supported by the international Many of these challenges have socio-economic scientific community. Together, WMO Members consequences affecting weather, climate, human and scientists around the world perform long- and ecosystem health, water supply and qual- term observations of the chemical composition ity, and agricultural production. Advancing and selected physical characteristics of the atmo- the scientific understanding to address these sphere on a global scale, paying special attention challenges remains critical. At the same time, to quality assurance and quality control of the GAW increasingly focuses on service delivery data and providing integrated products and in a number of application areas where GAW services of relevance to users.

3 3. ORGANIZATIONAL STRUCTURE

The GAW Programme addresses six classes 4) The Programme is administered and managed of variables: ozone, UV radiation, greenhouse by the WMO Secretariat with the support of gases, aerosols, selected reactive gases and the Integrated Global Atmospheric Chemistry precipitation chemistry. For these variables, Observations (IGACO) office (for ozone- and GAW acts as a “steward of global coordination”, UV-related issues). supporting all components needed for a rational observing system. 5) General guidance of the Programme, its structural review, the selection of priorities, The organizational structure of the GAW implementation and other leadership activities Programme is outlined in Figure 1, which shows are conducted by the Environmental Pollution the various building blocks of the Programme. and Atmospheric Chemistry Scientific Steering Committee (EPAC SSC) under the WMO Com- 1) The global observing networks that deliver mission for Atmospheric Sciences (CAS). Each high-quality measurements constitute the of the six GAW focus groups has a Scientific core of the Programme. Advisory Group (SAG). An additional SAG exists for the GAW Urban Research Meteorology and 2) Observational data and data products are Environment (GURME) project. Data exchange used in a number of applications, and support issues and near real-time chemical data delivery and contribute to other systems, programmes are coordinated by respective expert teams and research projects. Several data prod- (the Expert Team on World Data Centres (ET- ucts are used to underpin international WDC), and the Expert Team on Near Real-time conventions. Chemical Data Transfer (ET-NRT CDT)).

3) Support for ensuring and controlling the The GAW activities are undertaken by WMO quality of observations and for data and Members with a substantial contribution by metadata management is provided by National Meteorological and Hydrological Services the institutions that act as GAW central (NMHSs). Many research institutes and univer- facilities. They play different roles in the sities contribute to and support the Programme quality assurance system as described in with measurements and data analyses. The col- section 5 and include Central Calibration laboration between NMHSs and academia is Laboratories (CCLs), Quality Assurance/ fundamental to the Programme’s success. Science Activity Centres (QA/SACs), World Calibration Centres (WCCs), Regional Cali- Capacity development constitutes an important bration Centres (RCCs), World Data Centres part of all GAW activities. It is organized within (WDCs) and the GAW Station Information and across thematic groups and is coordinated System (GAWSIS). by the WMO Secretariat.

Figure 1. Structure of the WMO Global Atmosphere Scienﬁc Advisory Groups ET-NRT EPAC SSC ET-WDC Watch Programme Ozone, UV, GHG, RG, Aerosol, Expert group s CDT PC, GURME

IGACO oﬃce Administraon WMO/GAW Secretariat management Ozone/UV

WCCs/ NMHSs CCentral facilies QA/SACs CCLs WDCs GAWSIS RCCs

Aircra Observing Contribung GAW staons networkse systems Global and Regional Satellite

Users and Parties to the Systems Programmes Operational Research applicaons Conventions GCOS, GEO… IGAC, iLeaps.. centres projects UNFCCC, Vienna

4 4. OBSERVATIONS

(a) (b)

Alert Ny-Ålesund Pt. Barrow Pallas/Sodankylä

Mace Head Jungfraujoch Zugspitze/Hohenpeißenberg Monte Cimone Mt. Waliguan Trinidad Head Izaña Pyramid Minamitorishima Mauna Loa Assekrem / Cape Verde Tamanrasset (e) Danum Valley Mt. Kenya BukitKoto Tabang

Samoa Arembepe

Cape Point

Amsterdam Island Cape Grim Lauder Ushuaia Figure 2. Map of the (c) Neumayer (d) Halley GAW global stations South Pole (status June 2014). The individual pictures show (a) Barrow, Alaska, United States, (b) Minamitorishima, Japan, (c) Halley station,

The surface-based observational network com- and wide-ranging CO2 data have been obtained Antarctica, United prises global and regional stations operated by by continuous-measuring equipment as part of Kingdom of Great Britain WMO Members. These stations are comple- the Comprehensive Observation Network for and Northern Ireland mented by various contributing networks. In Trace gases by Airliner project (CONTRAIL, http:// (courtesy of Anthony 2014, GAW coordinated activities and data from www.cger.nies.go.jp/contrail/) using commercial Dubber), (d) Neumayer,

29 global stations (see Figure 2), more than 400 passenger aircraft. The CO2 data collected by Antarctica, Germany, and regional stations, and around 100 stations oper- air sampling equipment between Australia and (e) Cape Grim, Australia. ated by contributing networks. All observations Japan since 1993 are available at the World Data are linked to common reference standards and Centre for Greenhouse Gases, based in Tokyo. the observational data are made available in the The In-service Aircraft for a Global Observing designated World Data Centres. Observations System (IAGOS) project is another aircraft-based at the GAW stations are performed using in situ contribution to the global observation of atmo- methods and surface-based remote-sensing spheric composition. It is setting up a network techniques. Examples of the contributing net- of commercial aircraft using small instrumented works that use remote-sensing techniques are packages on board of civil aircraft. The project the Total Carbon Column Observing Network deploys newly developed high-tech instruments (TCCON, https://tccon-wiki.caltech.edu/), the for regular in situ measurements of atmospheric individual networks contributing to the GAW chemical species (ozone (O3), carbon monoxide

Aerosol Lidar Observation Network (GALION, (CO), carbon dioxide (CO2), reactive nitrogen see GAW Report No. 178) and the Network for (NOy), nitrogen oxides (NOx) and water vapour the Detection of Atmospheric Composition (H2O)), aerosols and cloud particles. The project, Change (NDACC, http://www.ndsc.ncep.noaa. recognized as a European Research Infrastructure, gov/). Information about GAW stations and builds on the scientiﬁc and technological experi- contributing networks is summarized in the ence gained within the Measurement of Ozone GAW Station Information System (http://gaw. and Water Vapour on Airbus In-service Aircraft empa.ch/gawsis/). (MOZAIC) project and the Civil Aircraft for the Regular Investigation of the Atmosphere Based Surface-based observations are increasingly on an Instrument Container (CARIBIC) project. complemented by airborne and space-based A number of national aircraft campaigns (oper- observations, which help to characterize the ated, for instance, by the US National Oceanic upper troposphere and lower stratosphere, in and Atmospheric Administration (NOAA), the particular with regards to ozone, solar radiation, Japan Meteorological Agency and by Brazil) also aerosols and certain trace gases. High-frequency contribute to the GAW observational network.

5 5. QUALITY ASSURANCE

The primary objectives of the GAW quality assur- of measurement variables. Central facilities ance system are to ensure that the data in the are organizations or laboratories that play a World Data Centres are consistent, of known particular role in the quality assurance of the and adequate quality, are supported by compre- network, although individual GAW stations and hensive metadata and are sufficiently complete laboratories implement local quality assurance to describe the global atmospheric state with systems as well. One of the requirements within respect to spatial and temporal distribution. GAW is the traceability of all stations and labs to High-quality observational data are required to one network standard. Hence, all contributors provide reliable information to policymakers and to GAW are required to have the same set of to ensure confidence in the broader data use in reference materials (such as reference gases). different applications. If such reference materials are not available, comparisons are conducted to compare artificially Implementation of the quality assurance system created samples prepared by dedicated labora- requires that all aspects of atmospheric chem- tories (such as for precipitation chemistry), or istry observations are addressed, including instrumental comparisons are performed using training of station personnel, assessment of reference observational methods. infrastructures, operations and the quality of observations at the sites, documentation of The concept of the GAW quality assurance data submitted to the World Data Centres as system is presented in Figure 3. The set of well as improved quality and documentation central facilities supporting this system includes of legacy data at the WDCs. Central Calibration Laboratories that host primary standards, Quality Assurance/Science Five types of central facilities are operated by Activity Centres that coordinate activities of WMO Members and form the basis of quality other central facilities in countries, regions or assurance and data archiving for the GAW global within the thematic group, World Calibration observational network. Each of the central facil- Centres and Regional Calibration Centres that ities is associated with one of the six groups assist GAW stations to ensure the traceability

Central Analytical Laboratory for precipitation chemistry, Illinois State Water Survey, University of Illinois at Urbana- Champaign, United States DAVID GAY

6 Figure 3. Conceptual GAW quality assurance Primary WMO/GAW BIPM/NMI system Standardstandard Bureau International des Poids Secretariat Maintenance et Mesures/ National Metrological Institutes of scale (PS)

Designation of PS

Central Calibration Scientific Advisory Laboratory (CCL) Group (SAG)

Data quality objectives Secondary Intercomparison Standardstandard SOP

World/Regional Quality Assurance/ World Data Calibration Centre Science Activity Centre Centre (WDC) (WCC/RCC) (QA/SAC)

System audit Capacity-building SOP Calibration Data flagging Intercomparison Data classification Performance audit Data integrity GAW Ststation Calibration

of their observations to primary standards, and • Accurate and detailed documentation of all World Data Centres which are responsible for measurements using station logbooks con- archiving and providing access to GAW data. The taining comprehensive metadata related to the World Meteorological Organization collaborates measurements, maintenance and “internal” with the International Bureau of Weights and calibrations Measures (BIPM) on the development of several • Regular independent assessments (system primary standards. The Scientific Advisory and performance audits) Groups coordinate the implementation of quality • Timely submission of data and associated assurance systems within thematic groups with metadata to the responsible World Data Cen- support from the WMO Secretariat Research tre as a means of permitting independent Department. review of data by a wider community

A comprehensive list of the GAW central facilities To ensure network compatibility, World is available at http://www.wmo.int/pages/prog/ Calibration Centres for different GAW variables arep/gaw/gaw_cent_facil.html. regularly perform site audits, global and regional round-robin comparisons and intercomparison The GAW quality assurance system operates campaigns. Some results of comparison cam- under the following principles: paigns are presented in this brochure.

• Network-wide use of only one reference Long-term education, training, workshops, standard or scale (primary standard) calibration station audits/visits and twinning • Full traceability to the primary standard of all between stations are also provided to build measurements made by global and regional capacities in atmospheric sciences within the stations and contributing networks GAW network. These capacity-building activities • Deﬁnition of data quality objectives are of increasing importance as many GAW • Establishment of guidelines on how to meet stations in developing countries have become these quality targets, that is, harmonized operational. The GAW Training and Education measurement techniques based on meas- Centre (GAWTEC) at the Schneefernerhaus in urement guidelines and standard operating Germany provides an important contribution in procedures (SOPs) the training of station personnel.

7 6. FOCAL AREAS

6.1 OZONE 6.1.2 Monitoring of ozone under the Global Atmosphere Watch Programme 6.1.1 The importance of ozone Measurements of total ozone are performed Stratospheric ozone depletion, which leads to within the GAW Programme by Dobson spec- increased intensity of harmful solar ultravio- trophotometers (designed for manual operation) let radiation at the Earth’s surface, stimulated and Brewer spectrophotometers (designed for important scientiﬁc activities in the 1980s and automatic operation), thus providing two inde- 1990s, leading to the Montreal Protocol on pendent networks. A separate contribution is Substances that Deplete the Ozone Layer and made by the Russian Federation and some other its subsequent amendments. Recently (in the late countries, which operate ﬁlter instruments. An 2000s) the measures taken in the frame of this important aspect of the GAW implementation international agreement proved to be successful strategy is to support capacity-building for ozone in reducing the production and consumption of monitoring and research in developing countries ozone-depleting substances. The abundances of and countries with economies in transition, these substances in the atmosphere have started following the general commitments anchored in to decline for most of the concerned compounds, the Vienna Convention for the Protection of the and this will ultimately lead to the recovery of Ozone Layer. In this context, GAW coordinates the ozone layer. Ozone is directly linked with the relocation and refurbishing of instruments climate because it absorbs solar radiation and to these countries from stations that ceased is a greenhouse gas, but also indirectly because operation, and training of local personnel in ozone-depleting substances and their substitutes operational and calibration procedures. are greenhouse gases. The depletion of ozone in the stratosphere and the global increase in The vertical distribution of ozone is measured tropospheric ozone have opposing contributions either in situ with ozonesondes carried by small to climate change. An example of the total ozone balloons, or remotely from the ground by lidars, evolution during the ozone depletion season is microwave radiometers and Umkehr inversions shown in Figure 4. of data measured by ozone spectrophotometers

Figure 4. Total ozone maps for 6 October 2006 to 2013 based on 6 October 2006 6 October 2007 6 October 2008 6 October 2009 data from the Ozone Monitoring Instrument on board the Aura satellite. The data are processed and mapped at the Royal Netherlands Meteorological Institute (KNMI).

6 October 2010 6 October 2011 6 October 2012 6 October 2013

8 Figure 5. Antarctic ozone observations used in the preparation of the ozone Scale 1:68,000,000 S o u t h A t l a n t i c Azimuthal Equal-Area Projection bulletins 0 500 1000 Kilometers O c e a n 40 Anta 0 500 1000 Miles rctic Con ver gen ce

60 Neumayer 60 Scotia Sea Novolazarevskaya

Marambio 70 Syowa AR NA Ushuaia Queen Maud Land Río Gallegos Enderby Kerguelen Drake Halley Land Passag e Vernadsky Weddell Sea CHILE Belgrano Mac.R obertson 80 Land Punta Arenas Palmer Land Ro nne Ice Sh elf Amery Ice Sh elf Rothera and San Martin Davis and Zhong Shan Bellingshausen South Pole Sea Ellsworth I n d i a n Vinson Massif 90 W 90 E (highest point in Antarctica, 4897 m) Pe ter I Island Land Mirny O c e a n Bentley Subglacial Trench Vostokd (lowest point in Antarctica, -2540 m) n Shackleton a Ice Shelf Marie Byrd L S o u t h Land Ross s P a c i f i c Amundsen Ice Sh elf Dômee C k Sea 80 l O c e a n i McMurdo andW Arrival Heights Ross Sea average minimum extent of sea ice Victoria Land Dumont d’Urville 64 70 Scott Anta rctic Island Esperanza Circle BA LLENY 0 (ARG ENTINA) ISLANDS e 12 c n e 60 g Marambio 66 r (ARG ENTINA) ve Arturo Prat on (CHILE) Bernardo C 55 ic O'Higgins ct ar (CHILE) 60 nt e A ircl C S o u t h 62 tic rc Macquarie Island P a c i f i c Graham Anta O c e a n Ld

(Dobsons and Brewers). Ozonesonde stations addition, ground-based ozone observations operate worldwide, thus providing a sufficient are important for the validation of satellite-de- coverage particularly in areas of scientific interest rived ozone data and for ensuring the continuity like Antarctica and the tropics. among different satellite missions. Finally, an important exploitation of the network data is Quality assurance is maintained through inter- the dissemination of near real-time ozone maps, comparisons and laboratory experiments. a service which is provided by several institu- Recently, about 30 stations with records of more tions, such as the National Aeronautics and than 25 years have been reassessed and homog- Space Administration (United States), the Royal enized. Lidars provide the ozone profiles in the Netherlands Meteorological Institute, the German upper atmospheric layers, typically in the altitude Aerospace Centre and the European Organization range of 10–50 km, while microwave radiometers for the Exploitation of Meteorological Satellites. measure in the range of 20–70 km. The Umkehr Near real-time observations from Antarctic sta- provides estimates of the mean concentration tions, shown in Figure 5, are used to prepare the of ozone at a few layers. Antarctic ozone bulletins.

Data from ground-based networks are used to 6.1.3 Quality assurance of measurements support the Scientific Assessment of Ozone Depletion reports, prepared jointly by WMO and The quality of network ozone data is ensured the United Nations Environment Programme. through the GAW World Calibration Centres and These reports, published every four years, assess Regional Calibration Centres. The main tasks of the science and status of the ozone layer. In the calibration centres are to link observations

9 Photo taken the morning An important aspect of the GAW framework is of 30 March 2006 that all GAW participants focusing on greenhouse during the Sodankylä gases are asked to use standards to calibrate Total Column Ozone their analytical instruments derived from Central Intercomparison I Calibration Laboratories that maintain common campaign in Sodankylä, standard scales. Other central facilities help ensure Finland. Temperature the quality of measurements through standard was around –26 °C. and measurement comparisons and site audits.

GAW networks for measurements of three essen-

tial climate variables – carbon dioxide (CO2),

methane (CH4) and nitrous oxide (N2O) – are recognized as the Global Climate Observing System (GCOS) Global Baseline Observing Network and the Global Comprehensive Observing Network. While these GCOS networks normally fall within to world reference standards and to ensure operational regimes of the agencies involved, network comparability and compatibility through GAW greenhouse gas observations are driven intercomparison campaigns and regular audits. almost entirely by research needs. Long-lived For the network of Dobson spectrophotome- greenhouse gases are the main drivers of climate ters, the primary standard instrument (Dobson change, and long-term GAW observations, shown #83) is maintained by the National Oceanic and in Figure 6, are used to calculate radiative forcing

Atmospheric Administration at the Mauna Loa as shown in Figure 7. Since 1990, CO2 has been Observatory in Hawaii, United States, while for the largest contributor to the increase in radia- the network of Brewer spectrophotometers, the tive forcing, contributing 80%. It is followed by

primary standard is the Brewer triad maintained N2O at 7.5%, replacements of ozone-depleting

by Environment Canada in Toronto, Canada. substances at 6.5% and CH4 at 5%. Despite their Regional Calibration Centres support the inter- declining atmospheric abundances in recent comparison campaigns and the regular transfer years, the sum of the radiative forcing from of calibration to network instruments. trichloroﬂuoromethane (CFC-11) and dichloro- diﬂuoromethane (CFC-12) has increased by 1% 6.2 GREENHOUSE GASES since 1990.

The WMO GAW long-lived greenhouse gas (LLGHG) measurement community is largely a research community. High-quality measurements of LLGHGs and related tracers can be used to:

• Estimate the trends of these substances and the relation between such trends and the changes in radiative forcing • Constrain global and large-scale budgets • Estimate or verify regional and continental scale emissions based on spatial gradients

The Global Atmosphere Watch Programme provides a framework to ensure the quality of these Figure 6. Time series of measurements through: the ﬁve LLGHGs (monthly mean global averaged) • Meetings of measurement experts every two that have contributed years >95% of radiative forcing • Detailed recommendations on measurement since 1750. In panel (d), compatibility selected to meet scientific CFC-11 is in blue and requirements CFC-12 is in red. • Publication of measurement guidelines

10 lifetimes can be used to estimate emissions. A Figure 7. Increase in simple example is sulphur hexaﬂuoride (SF ), radiative forcing by 3 Total 6 C0 2 which is destroyed predominantly by photolysis LLGHGs since 1750, CH4 N O plotted for 1979 to 2013. ) 2 and reactions with electrons in the mesosphere

–2 CFC – 12

m CFC – 11 and has an estimated atmospheric lifetime of Carbon dioxide is the 15 Minor 2 3 200 years. With the long lifetime, the atmo- largest contributor to spheric rate of increase is directly related to total radiative forcing emissions and can be used to verify emission by LLGHGs, and it is the dominant contributor 1 inventories. Using atmospheric measurements, Levin et al. (2010) showed that emissions reported to the trend in radiative Radiative forcing (W forcing since 1990. to the United Nations Framework Convention on (Source: NOAA Annual Climate Change (UNFCCC) were underestimated 0 Greenhouse Gas Index; 1980 1985 1990 1995 2000 2005 2010 by 70% to 80% (Figure 8). Developed nations http://www.esrl.noaa. Year (which make up Annex I of the Framework, in gov/gmd/aggi/) essence) are significantly underestimating their emissions. This emphasizes the need for estimates Measurements of greenhouse gases by GAW of emissions to be verified by direct atmospheric members can be used in a mass-balance analysis measurements (Nisbet and Weiss, 2010). to provide an important constraint on global emissions when a lifetime can be defined. This Since atmospheric mixing is not instantaneous, approach is not as effective for atmospheric the observed spatial patterns in LLGHGs can be

CO2, which rapidly exchanges with the terrestrial combined with a chemical transport model to esti- biosphere and surface ocean. However, for gases mate emissions at continental to country scales. that are predominantly removed by atmospheric The quality of the emission estimates depends chemistry (for instance, reaction with hydroxyl on the compatibility (internal consistency) of radical (OH) and photolysis), knowledge of their the measurements used. Artificial gradients

(a) 7.5 Figure 8. (a) Globally averaged SF mole fractions 6.5 6 determined from GAW (ppt)

6 measurements; 5.5

SF (b) Comparison of the annual observation- 4.5 inferred global SF6 emissions (blue circles), the global emissions Data (b) estimated by the UNFCCC Annex I Emissions Database 8.0 EDGAR EDGAR Annex I for Global Atmospheric 6.0 Research (EDGAR) (cyan triangles), the emissions reported by the nations 4.0 listed in Annex I to the

Emissions (Gg) UNFCCC (red triangles) 6 2.0 and the emissions SF reported by the nations listed in UNFCCC 2000 2005 2010 2015 Annex I as estimated Year in EDGAR (purple diamonds) (Source: Levin et al., 2010)

11 11 6.3 REACTIVE GASES

From the viewpoint of an atmospheric chem- ist, the atmosphere is a huge reactor where many different molecules that are present in tiny amounts undergo a multitude of chemical reactions. A remarkable feature of the atmosphere is its ability to cleanse itself of air pollutants often via oxidation reactions which transform harmful air pollutants into other, more soluble substances that can then be removed from the atmosphere through rainfall or deposition. Some atmospheric reactions, however, lead to the formation of secondary air pollutants such as ozone, peroxyacetyl nitrate (PAN) or aerosols. Reactive gases and aerosols can have adverse effects on human health, the environment and 0.00.2 0.4 0.60.8 materials. Atmospheric chemical reactions have a direct impact on the climate system, for example by controlling the chemical lifetime of greenhouse gases such as methane or nitrous oxide or the abundance of tropospheric ozone, itself Figure 9. Annual mean resulting from some laboratories using different a greenhouse gas. Through their interaction –2 –1

N2O ﬂux (g m yr N) standards than others will result in errors in with plants and their involvement in aerosol averaged over 1999–2012 emissions. This is especially true for N2O, which and cloud formation, reactive gases also exert determined from GAW has relatively small, very diffuse emissions and indirect effects on the climate system. In contrast

N2O observations and a a 130-year lifetime. The pole-to-pole gradient to long-living greenhouse gases (for example chemical transport model at background sites for N2O is approximately CO2), the effects of reactive gases show strong (Source: Thompson et 1.4 parts per billion. With traditional analytical regional variations, and regional measures to al., 2014) methods, it is extremely difficult to reach the curb air pollution offer a means to potentially required compatibility of the network to detect slow the rate of climate warming. Some of these this small spatial gradient. In a model study by complex chemical interactions are shown in Thompson et al. (2014), data were used from Figure 10. Thus, reactive gases are an essential GAW partners and contributors to estimate global component of the understanding of both air fluxes. These estimates are shown in Figure 9 in quality and climate change. grams per metre squared per year of nitrogen –2 –1 (g m yr N). The largest source of N2O is from Within the GAW Programme, a substantial natural and fertilized soils, which is reflected in number of reactive gas compounds are being the flux map. Similar studies have estimated measured at a diverse range of locations

emissions of CH4 and other LLGHGs. around the world. The focus of the activities

Further importance of GAW’s long-term high-quality LLGHG measurements is seen in

the time series for CH4 in Figure 6, panel (b).

The stabilization of the global atmospheric CH4 burden from 1999 to 2006 was unexpected. It contradicted the estimates derived from trends in bottom-up emission inventories, which indicated GAW global station that emissions were increasing. While the speciﬁc Hohenpeissenberg, changes to methane’s global budget of emissions Germany, providing and sinks responsible for this stabilization are ozone time series since still under discussion, without high-quality GAW 1971 and continuous measurements from a globally distributed net- meteorological work of air sampling sites, we may have missed observations since 1781 this surprising development. STEFAN GILGE

12 12 Figure 10. Atmospheric

Short-lived greenhouse gases/Particles chemistry processes (OЈ, CHЉ͕...) and their relation to air quality and climate change (Courtesy of UV light Oxidation M. Schultz) Cloud chemistry/ Chemistry Washout

1 O3 O( D) O3 OH NO2 PAN HNO HO2 NO 3 Transport (Advection, Convection, Secondary air pollution Turbulence) (OЈ, PAN, particles͕...)

Emissions/Primary air pollution Deposition/Acidification/Eutrophication (NOx, CHЉ͕CO, VOC, SOЇ, NHЈ͕...) (HNOЈ, SOЇ, NHЈ͕...)

Nitrogen cycle/Carbon cycle

is on tropospheric ozone and its precursor network is the primary source of information on substances. Ozone was ﬁrst observed in the changes of atmospheric composition on a global nineteenth century. Current ongoing observa- scale, with a long-term vision and a globally tions started at a very small number of sites in uniform quality control. Monitoring the back- the early 1970s, for example at the GAW global ground levels of reactive gases is essential for station Hohenpeissenberg, Germany, at Barrow, understanding long-range transport processes, Alaska, United States, and at Mauna Loa, Hawaii, which in turn is crucial for assessing the success United States. After GAW was initiated in 1989, of regional to local emission reduction activities. the number of stations in the global network of Data from GAW are supplemented by a number surface ozone measurements grew rapidly, and of regional air pollution networks and national surface ozone is now measured and reported air pollution monitoring activities. Figure 11 from some 100 stations worldwide. The GAW presents a snapshot of monthly mean surface

Figure 11. Map of monthly mean surface mole fractions of ozone for July 2008 as measured by the stations in the GAW network and archived at the World Data Centre for Greenhouse Gases (WDCGG).

13 Figure 12. Monthly mean latitudinal variation of ethane from the ppt global reactive gases measurements in the 2600 GAW network (Source: 2200 World Data Centre for 1800 Greenhouse Gases) 1400 1000 600 200 80N 60N 40N 20N Latitude EQ 20S 40S 2011/01 60S 2010/01 2009/01 80S 2008/01 2007/01 2006/01 Year 0 1000 2000 3000 ppt

ozone concentrations from the GAW network in and Schultz (2013) (GAW Report No. 209). An July 2008. This clearly demonstrates the capa- overview of the quality assurance system is bilities of GAW to provide a global perspective shown in Figure 3. For reactive gases, Central on surface ozone, even though large areas of Calibration Laboratories were established for the map remain uncovered. ozone (at the National Institute of Standards and Technology, United States), carbon mon- Carbon monoxide has been a key measurement oxide (at the National Oceanic and Atmospheric within the GAW reactive gases programme, since Administration, United States) and GAW target it is both a contributor to, and a by-product of, non-methane hydrocarbons (at the National many atmospheric reactions. It is also an excellent Physical Laboratory, United Kingdom). World tracer of atmospheric emissions and transport. Calibration Centres exist for ozone and car- A reasonably good coverage of continuous CO bon monoxide (Swiss Federal Laboratories observations has been available since the mid- for Materials Testing and Research (Empa), 1990s. Over the last 20 years, a slight negative Switzerland), volatile organic compounds includ- global CO trend can be observed as a result ing non-methane hydrocarbons (Institute of of the reduction of anthropogenic emissions; Meteorology and Climate Research, Atmospheric however, CO concentrations feature a strong Environmental Research, Karlsruhe Institute of year-to-year variability driven by the extent of Technology, Germany), and nitrogen oxides biomass burning. More recent additions to the (Jülich Research Centre, Germany). For most of GAW Programme are nitrogen oxides (NO and the audited laboratories, the reported amount

NO2), sulphur dioxide (SO2) and a number of key fractions of tested GAW VOC targets are within volatile organic compounds (VOC) (see Figure the speciﬁed data quality objectives. The central 12), enabled by developments in measurement data archive for reactive gases is the World Data technology that now allow for reliable detection Centre for Greenhouse Gases, in Tokyo. of these gases at trace levels. All reactive gases activities are monitored by One of the central elements in GAW is the quality the Scientific Advisory Group for Reactive management framework including central facil- Gases, whose members are responsible for ities for calibration, guidelines for conducting establishing standard operating procedures in measurements and data archiving and distri- order to ensure globally consistent measure- bution. This system is regularly updated. For ments. Furthermore, they establish links between example, the new measurement guidelines for GAW and other regional and global monitoring tropospheric ozone are described by Galbally and research networks such as the Network

14 in Figure 13 for a three-month validation with Figure 13. Example of carbon monoxide1. the use of rapid-delivery data from GAW for 6.4 ATMOSPHERIC WET DEPOSITION evaluation of the MACC forecast system. Blue Wet deposition is an important process by which symbols show the GAW precipitation removes anthropogenic and nat- measurements of CO urally occurring gases and particles from the and black lines denote atmosphere. Quantifying the composition of the model results at wet and total deposition regionally and globally Cape Point, South Africa (bottom) and is important to understanding the cause and Minamitorishima, Japan effect of contemporary environmental issues (top), sampled at an such as acidification, eutrophication, smog and appropriate pressure climate change. To better understand these level. (Courtesy of issues, GAW’s Scientific Advisory Group for S. Gilge) Precipitation Chemistry (SAG-PC) was formed to ensure the harmonization of precipitation chemistry measurements conducted by regional and national programmes, to enable the quantifi- cation of patterns and trends of the composition of precipitation on global and regional scales, to improve understanding of biogeochemical for the Detection of Atmospheric Composition cycles of major chemical species, and to provide Change (NDACC), the European Monitoring and the data for evaluating ecosystem effects of Evaluation Programme (EMEP) network, the atmospheric deposition. Acid Deposition Monitoring Network in East Asia (EANET), the Clean Air Status and Trends Prior to the formation of the SAG-PC, deposition Network (CASTNET), the In-service Aircraft for monitoring programmes worldwide had varying a Global Observing System (IAGOS) programme degrees of success in addressing important issues on aircraft observations, or the Aerosols, Clouds, related to the causes and effects of atmospheric and Trace gases Research Infrastructure Network deposition. Station siting, sample collection (ACTRIS). They also promote the use of GAW methods, laboratory analytical procedures and data and seek communication with data users. quality assurance methodologies had not been standardized, resulting in data and information of Reactive gases data from the Global Atmosphere questionable quality and usefulness. To ensure Watch Programme have been used in a large the harmonization of measurements by national number of scientific studies, including review articles (Cooper et al., 2014), trend analyses Typical collector used for (Gilge et al., 2010; Parrish et al., 2012; Logan et precipitation chemistry al., 2012), process studies (Mannschreck et al., sampling 2004) and the evaluation of chemistry climate models (Parrish et al., 2014). GAW stations are often used as a location for short-term intensive measurement campaigns; the continuous and operational reactive gas programme allows such experiments to be placed in an appropriate long-term chemical context. Recently, there has been increasing demand for reactive gases data delivered with fast turnaround times to be used for the validation of global atmospheric composition forecasting systems. The European Monitoring Atmospheric Composition and Climate (MACC) project is such a system, 1 Regular updates of MACC validation plots can and GAW regularly contributes important data be found at http://www.gmes-atmosphere.eu/d/ to MACC. Examples of this data use are shown services/gac/verif/grg/gaw/gaw_station_ts/.

15 and regional programmes and improve the quality summary of the laboratories’ performance called of global data, the SAG-PC developed a Manual a ring diagram (Figure 14), based on a statistical for the GAW Precipitation Chemistry Programme analysis of the results of each chemical measure- (GAW Report No. 160). This manual established ment reported by all of the study participants. A data quality objectives and set standard oper- ring diagram is produced for each test sample ational procedures for sample collection and for each participating laboratory, indicating the handling, laboratory chemical analyses, quality quality of each analysis as acceptable, marginal assurance/quality control and data management or unacceptable. The diagrams serve to alert and analysis. The SAG-PC is working to update laboratory managers and data users of potential and produce an online version of this manual, problems and offer data users a tool for deciding originally published in 2004. whether the level of performance is appropriate for their needs. Results of the Laboratory Recognizing that one important key to the success Intercomparison Study are posted on the website of any precipitation chemistry measurement of the Quality Assurance/Science Activity Centre programme is the accuracy of sample chem- for the Americas (http://qasac-americas.org). ical analyses, the SAG-PC looked to the GAW Laboratory Intercomparison Study, presently Efforts to improve and document data quality conducted by the Quality Assurance/Science from the world’s major precipitation chemistry Activity Centre for the Americas. Initiated in 1978, measurement networks made it possible to this study was designed to track the performance address data appropriateness in state-of-the- of laboratories using simulated rain samples of science assessments at a level not previously known ion concentrations. The SAG-PC doubled possible. This was one of several scientiﬁc drivers the frequency of these laboratory intercompari- behind the production of “A global assessment son studies from one to two per year. Now, more of precipitation chemistry and deposition of than 80 independent laboratories around the sulfur, nitrogen, sea salt, base cations, organic world participate in these studies. Laboratory acids, acidity and pH, and phosphorus” (Vet et performance is assessed vis-à-vis accepted data al., 2014). The SAG-PC and other scientists with quality objectives for the major ions typically expertise in atmospheric deposition recognized found in precipitation. The Quality Assurance/ a need to update the global trends in precipita- Science Activity Centre develops a simple visual tion chemistry and deposition and improve the

Figure 14. Ring diagrams used to summarize the level of conﬁdence in precipitation chemistry samples from laboratories participating in the GAW Laboratory Intercomparison Study

16 Figure 15. Measurement- model wet deposition of non-sea-salt sulphur in kilogram per hectare per year (nssS in kg S ha–1 a–1). Measurement values represent three-year averages for 2000–2002; model results represent the 2001 model year. (Source: Vet et al., 2014)

availability of information, especially in areas Vet et al. (2014) offer a number of recommenda- poorly served by national and regional monitoring tions to address knowledge gaps and provide programmes. Nearly two decades had passed information that meets the needs of other scientific since the data supporting the first comprehen- communities. These recommendations, some sive Global Acid Deposition Assessment (GAW of which are summarized below, will shape the Report No. 106) had been collected, and much direction taken by the SAG-PC in the coming years. had changed concerning global emissions and deposition. Over that period, improvements in A strategic approach to monitoring is required global chemistry models had made it possible to for future improvements to estimating global complement precipitation chemistry measure- deposition. This will require increased spatial ments with chemical transport and deposition coverage of long-term and regionally represen- model estimates for poorly sampled regions. tative precipitation chemistry measurements in The response of the SAG-PC was to embark on locations where data are sparse or affected by an examination of precipitation chemistry and changing regional emissions and where ecosys- deposition data for sulphur, nitrogen, sea salt, tems are most vulnerable. A closer connection base cations, organic acids, acidity and pH, and to global and regional science programmes such phosphorus from almost every region of the as the Deposition of Biogeochemically Important world, including the oceans. Measurement data Trace Species (DEBITS), which is part of the and model results were used to generate global International Global Atmospheric Chemistry and regional maps of concentrations in precip- (IGAC) project, will be very important in the itation and deposition (see example in Figure establishment of new sites. 15). A major product of the assessment was a database of quality-assured ion concentration Monitoring site in and wet deposition data gathered from regional Bondville, Illinois, United and national monitoring networks. The database States, operated by the is available for download from the World Data US National Atmospheric Centre for Precipitation Chemistry (http://wdcpc. Deposition Program org/). The full assessment by Vet et al. (2014) is since 1979. Bondville is available online at http://dx.doi.org/10.1016/j. the flagship station of the atmosenv.2013.10.060 and in hard-copy form monitoring effort in the from the WMO. ROBERT LARSON United States.

17 In the future, we expect a greater demand for Sub-group associated with the SAG-UV, GAW total deposition estimates, defined as the sum has developed several documents (GAW Reports of wet (precipitation) and dry (particle and gas) No. 125, 164, 190 and 191) in order to define deposition. These estimates are needed in order instrument specifications and guidelines for to adequately characterize the contribution of characterization, which are necessary for reliable atmospheric pollutants to various environmental UV measurements. In addition, GAW Reports effects and problems. Accurate estimates of total No. 126, 146 and 198 were produced in order deposition will require a much greater empha- to promote the implementation of data quality sis on the development of a robust method to control and quality assurance at the stations. routinely estimate dry deposition. Collaboration A number of regional and global calibration among the SAG for Precipitation Chemistry, SAG facilities support quality assurance of the global for Aerosols and SAG for Reactive Gases can UV radiation observations. facilitate this effort. Given that it is not financially or logistically feasible to measure all compounds In the last three decades, the accuracy of UV of interest everywhere, information gaps will best measurements has substantially improved. An be addressed by combining long-term measure- important contribution of GAW in this sense has ments, including satellite and remote-sensing been the establishment of World Calibration observations, with chemical transport model Centres and Regional Calibration Centres for UV. information. Ongoing programmes designed to In addition, GAW has encouraged intercompar- establish and improve data quality, train new field isons and many of them have been carried out operators and adopt emerging field monitoring under the auspices of WMO. and laboratory efforts will continue as a basic role of the SAG-PC. The UV data requirements, archiving and distribution have been mainly centralized in the World 6.5 ULTRAVIOLET RADIATION Ozone and Ultraviolet Radiation Data Centre (WOUDC). At present, data are also submitted to The radiation component of GAW has concen- other data centres (such as to the European UV trated its efforts on UV radiation, while specialized Database and the NDACC database), with WOUDC WMO programmes have dealt with other aspects having a project underway to automate the of solar radiation (for example, radiation mea- mirroring of the data from NDACC into WOUDC. surements are part of the WMO Commission for Instruments and Methods of Observation). In Encouraging efforts to improve modelling of this frame, WMO established in 1994 the WMO the radiative transfer of UV has been an import- Scientific Steering Committee on UV Monitoring, ant part of GAW activities. This enhancement which, after March 1999, became the Scientific has made it possible to apply radiative transfer Advisory Group for UV Radiation (SAG-UV). models in the development of satellite-based methodologies to estimate UV irradiance at the During the last decades, the impact of total Earth’s surface. ozone on UV irradiance has been studied quite extensively. Since UV radiation is linked to health Ultraviolet monitoring from space is a power- issues, ecosystem effects and material damage, ful instrument, since it offers the opportunity the need to monitor surface UV radiation, estab- to achieve a global daily coverage of the UV lish a UV climatology and quantify future changes has been, and still is, of great interest. In this regard, GAW and associated stations have been successful in providing data for environmental studies covering different fields. The Physikalisch- Meteorologisches As a consequence of this interest in UV measure- Observatorium, World ments, many instruments have been developed Calibration Centre throughout the years. A wide range is available (PMOD/WRC) in Davos, at present, which includes spectroradiometers, Switzerland (http:// array spectroradiometers, broadband UV and www.pmodwrc.ch/ multichannel narrowband instruments and wcc_uv/wcc_uv.html) dosimeters. Through the UV Instrumentation PMOD/WRC

18 radiation ﬁeld. It is a useful tool in supporting environmental assessments and information for the public, for example in the form of a UV index. A comparison of ground and space measurements shows that satellite observations have an advantage of daily worldwide coverage, including oceans, while ground-based measurements can provide better space and time resolution, though the stations are scarce in some areas and are not available over the oceans. In addition, some discrepancies were noted between two sets of data showing that, while satellites are good for climatologies and seasonal data, local values derived from space measurements remain an issue, mainly due to aerosols, and also clouds and snow. Hence, harmonization of satellite and ground-based data remains a critical issue.

The Global Atmosphere Watch Programme collaborates with other programmes and agencies to produce documents related to public health and awareness. An important achievement for public information has been the UV Index (UVI), developed jointly with the World Health Organization, United Nations Environment Programme (UNEP) and the International Commission on The above-mentioned variations could lead to The UV Index for Non-Ionizing Radiation Protection (ICNIRP). In spectral, geographical and seasonal changes anywhere, anytime. addition, the GAW SAG-UV has established a in solar radiation reaching the Earth’s surface, Adjustments for altitude, public site where the UV index of anywhere in which would result in beneficial and detrimental ozone and variation the world can be checked. Another example changes in the effects of UV on living organ- due to parameters such of collaboration is the GAW Report No. 211, isms (erythema, vitamin D production, DNA as snow are available which was produced jointly with the International damage, etc.). This would have subsequent (http://exp-studies. Commission on Illumination (CIE). This report effects on humans and ecosystems, leading tor.ec.gc.ca/cgi-bin/ aims at rationalizing nomenclatures for differ- to socio-economic consequences. Long-term clf2/uv_index_calcula- tor?lang=e&printerver- ent UV doses. Members of the SAG-UV also UV measurements as well as measurements of sion=false&printfull- contribute as authors and/or reviewers to the all the parameters involved in this change will page=false&accessi- UNEP/WMO Scientific Assessment on Ozone be encouraged, with the aim of following the ble=off) Depletion reports and to the reports of UNEP evolution of UV radiation under global change. on the environmental effects of ozone depletion. 6.6 AEROSOLS In the last years, the focus of UV effects has been moving towards the positive effects of Comprehensive observational networks are UV radiation (from skin cancer and cataracts to foundational to all aspects of our understanding vitamin D and immune system benefits), and is of the environmental system and the interac- expected to continue in this direction. tions of society therewith. Without long-term observations, we would have little chance of In the past, UV objectives were mainly focused fully understanding the system, recognizing on climatologies and the increase of surface UV important processes and signals as they emerge radiation as a consequence of ozone depletion. and planning accordingly. All the assessments of Despite the fact that ozone recovery may lead climate change by the Intergovernmental Panel on to decreased UV irradiance, new UV objectives Climate Change (IPCC), beginning with the first appear triggered by climatological variations in in 1990, have strongly emphasized the analyses other parameters affecting UV, such as cloud cover of evidence of climate change from atmospheric and types, earth reflectivity (albedo), aerosols observations, highlighting the challenges for and other parameters related to global change. developing long-term, high-quality observation

19 records that can be used to constrain models few nanometers in diameter to mineral dust and at global and regional scales. While improved sea-salt particles, which can be as large as tens of monitoring capabilities developed in the last micrometres. The dynamics of aerosol particle pro- decades, both from satellites and ground-based duction, transformation and removal that govern stations, have clearly yielded more reliable data size distribution and composition are affected not records, the latest IPCC assessment report (IPCC, only by clear-air processes, but also by interaction 2013) still highlights the need for maintaining and with cloud processes and precipitation. The com- enhancing the capacity of observing atmospheric plexity of aerosol processes in our environment is composition to provide additional constraints, so great that it leads to large uncertainties in our in particular for the derivation of trends. quantitative understanding of their role in many One of the most recently of the major environmental issues listed above. established and the This is particularly true for aerosols, which con- For the Earth’s climate, the magnitude of aerosol highest GAW site in tinue to contribute the largest uncertainty in direct forcing is assessed to be –0.45 (–0.95 to the network of global estimates and interpretations of climate change. +0.05) Watts (W) m–2 if we consider the impact of stations, the Nepal Moreover, aerosol particles play a key role in air aerosol alone. When aerosol/cloud feedbacks are Climate Observatory – quality, human health, ozone depletion and the taken into account, this effect reaches –0.9 (–1.9 Pyramid has offered a –2 very comprehensive set long-range transport and deposition of toxics to –0.1) W m , though both effects have only a of aerosol (and trace and nutrients. Aerosols have many sources rang- medium level of conﬁdence. The uncertainty in gases) measurements ing from sea spray and mineral dust particles, the estimates of aerosol radiative forcing is still since 2006. In particular, which are mechanically generated by wind at the very high, despite the substantial progress made the record of equivalent Earth’s surface, to sulphate, nitrates and organics to understand climate-relevant aerosol processes. black carbon shows very produced by chemical reactions of gases in the These average estimates mask a very strong elevated values during atmosphere and which yield non-volatile prod- spatial and temporal heterogeneity resulting from the pre-monsoon season ucts that condense to form particles. Aerosols the relatively short lifetime of aerosol particles as shown in the insert. range in size from stable molecular clusters of a and the complexity of emission sources. P. BONASONIP.

20 The availability of long-term records of aerosol Several precision ﬁlter properties is the key to reducing this uncertainty, radiometers being but the required observations are complex, as calibrated against a large number of variables are needed for a the WORCC triad of comprehensive description of aerosol particle reference PFRs at Davos, properties. Aerosol particles cannot be charac- Switzerland terized solely in terms of mass concentration but also require measurements of their optical, chemical and physical properties and their spatio- temporal evolution as part of a 4D observing system. This explains why, while atmospheric records of 50 years or more exist for CO2 or O3, only a few time series spanning more than two decades are available for aerosol properties.

The GAW Programme played a key role in the initiation, 25 years ago, of the ﬁrst global network

for measuring aerosol properties and, since the C. WEHRLI very early stage, in recognizing the need for standardized techniques, harmonized measurement protocols, quality assurance, calibration and in climate models and in aerosol retrievals validation procedures across the network (GAW with satellite data. Report No. 153; Petzold et al., 2013). Despite the intrinsic complexity of aerosol observations, • The GAW Precision Filter Radiometer (GAW- GAW, through its network of 109 GAW and con- PFR) sun-photometer network for aerosol tributing stations, provides exceptional records optical depth is coordinated by the World to determine the spatio-temporal distribution Optical Depth Research and Calibration Centre of aerosol particle properties related to climate (WORCC). A total of 21 stations are currently forcing and air quality on multidecadal time- providing daily data to the WORCC. These data scales and on regional, hemispheric and global complement other ground-based network spatial scales. Through scientiﬁc and techno- data (such as the Aerosol Robotic Network logical recommendations to station operators, (AERONET) or SKYNET). Sun-photometer GAW managed to address changes in observing data provide highly accurate estimates for practices, the evolution of technologies and aerosol optical properties and even allow the evolving demand for additional monitored for estimates of microphysical properties in variables from the scientiﬁc community (Laj et terms of averages for the entire atmospheric al., 2009). column. They are thus complementary to ground in situ data. These data are essential The GAW network consists of three different for the calibration of satellite retrievals and components: are widely used to evaluate aerosol modules in climate models. • The GAW in situ aerosol network contains (as of July 2014) more than 34 regional stations • The GAW Aerosol Lidar Observation Network and 54 contributing stations, in addition to (GALION) provides the vertical component 21 global stations reporting data – some of of aerosol distributions through advanced them in near real-time – to the World Data laser remote-sensing in a network of globally Centre for Aerosols (WDCA) hosted by the distributed ground-based stations. Several Norwegian Institute for Air Research (NILU). regional lidar networks, such as the Asian These data are then made freely available to Dust and Aerosol Lidar Observation Network all. The GAW in situ network also receives (AD-Net); the Latin America Lidar Network contributions from regional networks such as (ALINE); the Commonwealth of Independ- EMEP in Europe or the Interagency Monitoring ent States (Belarus, Russian Federation and of Protected Visual Environments (IMPROVE) Kyrgyzstan) Lidar Network (CIS-LINET); the network in the United States. These data Canadian Operational Research Aerosol help calibrate aerosol-type representations Lidar Network (CORALNet); the CREST Lidar

21 Figure 16. Lidar proﬁle measured above Munich, Germany, during the 2010 Eyjafjallajökull eruption in Iceland. The plume was detected by the EARLINET component of GALION in Europe. (Source: Pappalardo et al., 2013)

Network for eastern North America; the Micro- and developing the proper level of scientific and Pulse Lidar Network (MPLNET); the European technical expertise, in particular linked to aerosol Aerosol Research Lidar Network (EARLINET); data collection, storage and distribution. The and the NDACC for the global stratosphere, GAW Training and Education Centre as well as are all participants in GALION. An example data management training within the World Data of the data from a lidar station is presented Centre for Aerosols have contributed to building in Figure 16, in which lidar observations of expertise all around the world. the vertical profiles of aerosol properties are used to detect volcanic ash layers. A direct result of the efforts initiated more than 20 years ago to better coordinate the observa- Overall, the GAW integrated network covers tion system and data distribution to the entire different types of aerosols including clean and scientific community is the capability to derive

polluted continental, marine, Arctic, dust, bio- long-term trends for non-CO2 climate forcers on mass burning, and free tropospheric aerosols. the global scale. The current picture shows the Quality assurance across the GAW network is consistent observation of important regional critical and addressed through World Calibration variability for the aerosol burden, with an appar- Centres, which include the World Calibration ent decline over Europe and the eastern United Centre for Aerosol Physics (WCCAP) hosted by States since the mid-1990s and, in contrast, an the Leibniz Institute for Tropospheric Research apparent increase over eastern and southern (TROPOS) in Leipzig, Germany, and the World Asia in the last decade (Asmi et al., 2013; Collaud Optical Depth Research and Calibration Centre Coen et al., 2013). However, despite large efforts hosted by the Physikalisch-Meteorologisches from GAW, the amount of data elsewhere in the Observatorium World Radiation Centre in Davos, world is insufficient to derive any long-term Switzerland. Education and training are essential trends with statistical significance. In fact, the for the success of the network and for maintaining lack of information along with the strong inter- annual variability, the regional heterogeneity of particle loads and the limited timespan of the Scientists involved in available records still limits the identification of calibration exercises at long-term trends. the World Calibration Centre for Aerosol Maintaining the capacity to monitor changes Physics at TROPOS in atmospheric composition will be essential in the next decades. Perturbations of the Earth’s biogeochemistry and climate caused by man are unlikely to stop anytime soon. Since natural cycles are highly variable and strongly influence aerosol composition and concentrations, estab- A. WIEDENSHOLER lishing a baseline in an ever-changing system is

22 extremely complex. Climate-induced feedbacks was convened in Geneva in October 1996 to may lead to the amplification or dampening of define issues and needs and to plan future WMO the aerosol/cloud climate forcing, leading to activities related to urban environments. This an even more complex picture (Carslaw et al., meeting led to the establishment of GURME in 2010). For example, some studies show that such the same year. feedback from natural processes only may lead to positive forcing on climate as high as 1 W m–2 Cities affect the atmosphere in many ways globally by the end of the century. In parallel, (Figure 17): by causing alterations in weather stronger regulations on anthropogenic emissions and climate due to changes in land use and for improving air quality will affect particle bur- surface properties and large increases in heat, dens, changing the climate forcing at least at the and through significant emission of pollutants regional scale. Climate change, together with air associated with transport, residential heating/ quality regulations, will therefore increase the cooling and other activities needed to support number of drivers of change in a very complex urban living. Because of the important roles – coupled system. economic, political and cultural – that cities play and the adverse effects on society of poor air One great challenge for the future will there- quality and high-impact weather events such as fore be to maintain and optimize the current heatwaves and floods, there is a growing need observing system at its nominal performance for more comprehensive weather, climate and over a sufficiently long time period to be able to environmental services to support urban areas. detect response from the system early enough to take action. It is equally important to develop The GAW Urban Research Meteorology and new observing capabilities where long-term Environment project was established to address measurements are critical for understanding these needs, with the following goals: Figure 17. GURME the rapidly changing environment. In this con- focuses on better text, it is obvious that the actions of GAW for • To enhance the capability of NMHSs to provide understanding the monitoring aerosol properties worldwide will, urban environmental forecasting and effective impacts of urban areas even more than before, be an essential pillar of air quality services, thus illustrating the link on the atmospheric this endeavour. between meteorology and air quality. environment.

6.7 THE GAW URBAN RESEARCH METEOROLOGY AND ENVIRONMENT PROJECT

The GAW Urban Research Meteorology and Environment (GURME) project is a component of GAW. It focuses on improving urban meteorological and environmental services through research applied to operations. The GURME project was set up in response to the requests for assistance from many NMHSs dealing with urban issues, recognizing that the management of urban environments requires special attention. The project originated in the Twelfth World Meteorological Congress (1995) where it was determined that meteorological and climatological aspects of urban environments should receive increasing attention within WMO programmes. In response, the WMO Executive Council added the ﬁeld of urban atmospheric environment to the terms of reference of the Executive Council Panel of Experts/CAS Working Group on Environmental Pollution and Atmospheric Chemistry. A Meeting of Experts on Atmospheric Urban Pollution and the Role of National Meteorological Services

23 • In collaboration with other WMO pro- outcome of this activity was the development of grammes, the World Health Organization a new air quality system for Santiago to forecast and environmental agencies, to better define urban PM2.5 pollution in winter. This system is meteorological and air quality measurements now run by the Chilean Meteorological Service, focusing specifically on those that support in collaboration with local universities. urban forecasting. • To provide NMHSs with easy access to More recently, a new initiative, Pollution and information on measurement and modelling its Impact on the South American Cryosphere techniques. (PISAC) was launched to deal with emission • To promote a series of pilot projects to dem- sources, measurement and transport of pol- onstrate how NMHSs can successfully expand lutants, monitoring stations and modelling of their activities to include urban environment the potential impacts of black carbon and co- issues, showcase new technologies at appro- pollutants on the Andean cryosphere, and policy priate conferences and provide examples. measures dealing with the impacts of pollution. This activity will involve the GAW stations in Pilot projects the region and promote the establishment of new stations. Pilot projects are an important mechanism for promoting air quality and related services. To System of Air Quality Forecasting and Research demonstrate how meteorological and other – The Indian Institute of Tropical Meteorology organizations can successfully expand their (IITM), in Pune, is spearheading the country’s first urban-focused services, GURME has promoted major air quality forecasting initiative known as a number of pilot projects, some of which are System of Air Quality Forecasting and Research described below. (SAFAR). This system was successfully tested during the 2010 Commonwealth Games for Latin American Cities – This project grew Delhi National Capital Region. It includes new out of the GURME meeting of experts held in comprehensive air quality monitoring networks Cuernavaca, Mexico, in October 2002, which was reporting data in near real-time, a citywide mete- attended by 25 participants from 11 countries. The orological and air quality forecast system at purpose of this activity is to build capacity and kilometre scale, and a multimedia forecast dis- share experiences in areas related to air quality semination system (Figure 18). The System of throughout Latin America. The first Workshop on Air Quality Forecasting and Research provides Air Quality Forecasting in Latin American Cities location-specific information on air quality in was held in Santiago, Chile, in October 2003. near real-time and forecasts 1–2 days in advance. It is complemented by the weather forecasting Since then, a number of workshops and training system designed by the India Meteorological events on air quality forecasting and modelling Department, in New Delhi. The ultimate objective have taken place in several Latin American cities. is to raise awareness among the general public of the air quality in their city, in a timely manner, In 2013, GURME hosted the Fifth International so that appropriate mitigation measures can be Workshop on Air Quality Forecasting Research taken to improve air quality and tackle related (IWAQFR) in Santiago, Chile. One notable health issues. The plan is to replicate SAFAR in other major cities in India, placing the country at the forefront of air quality forecasting research. Santiago (Chile) is often To date, SAFAR is operational in Delhi, Pune and, affected by air pollution as of August 2014, in Mumbai. in winter.

Air quality component of the Multi-hazard Early Warning System, Shanghai Expo 2010 – A new air quality component of the Multi- hazard Early Warning System (Figure 19) was presented at the Shanghai Expo in 2010. The project, under the leadership of the Shanghai Regional Meteorological Centre of the China PETE SAMWAYS Meteorological Administration, was designed to

24 explore the full potential of an air quality system protocols for conventional weather data; (b) to Figure 18. Components for urban life in the twenty-ﬁrst century. The illustrate the capacity of near real-time data to of the System of Air key objectives of the project were to disclose enhance the accuracy of air quality forecasts in Quality Forecasting and the physical and chemical mechanisms during China; (c) to develop a system for estimating Research (SAFAR) the formation, transport and transformation of emissions using near real-time data and inverse the main air pollutants in the Shanghai area; to modelling methodology; and (d) to exchange establish the air pollution prediction system for research results with other national and inter- the same area; and to improve the techniques national agencies. Figure 19. The public for assessing environmental quality. New and health component of comprehensive forecast products based on These projects illustrate some of the ways in the comprehensive various measurements (meteorological mea- which research is being applied to enhance service designed for the surements, environmental observations and weather and air quality services, particularly Shanghai metropolitan disease diagnostics) had been developed to through addressing the complex interaction area support public health services and were presented during the Expo. Through public health services such as those dealing with air quality, pollen-related allergies, food poisoning and heatstroke, effective measures to protect the health of individuals, especially those in sensitive groups, will be designed. This project is part of a comprehensive service designed for the Shanghai metropolitan area.

Near Real-time Data Application to Air Quality Forecasts – This is the newest pilot project under the leadership of the Chinese Academy of Meteorological Services. The project objectives are: (a) to develop and establish a near real-time chemical data transfer system to collect and process both ground-based and satellite observations, following the WMO data transfer

25 Collaboration

Collaboration is necessary to address the pressing problems facing urban environments. The GAW Urban Research Meteorology and Environment project actively collaborates with various partners on capacity-building, research and joint studies. Examples include the report on megacities developed jointly with the International Global Atmospheric Chemistry (IGAC) project, studies on short-lived climate pollutants done with UNEP, activities carried out with the World Health Organization, such as the publication of the Atlas of Health and Climate, and participation in a variety of research projects supported by the European Union and the European Cooperation in Science and Technology (COST).

Greater collaboration will be essential to tackle urban air quality issues. A large fraction of the Figure 20. Illustration of aerosols with the weather and climate sys- world’s population lives in large cities, and many of aerosol interactions tem (Figure 20). To support those services, of these are at risk from natural hazards besides with weather and modelling capabilities are being improved and air pollution (Figure 21). Within WMO there is an climate. The possibility meteorological and chemical observations in increasing focus on megacities and large urban of improving predictions, and around urban areas are being expanded. As complexes and GURME is expected to play a by assimilating near a result, the requirements for the near real-time major role in this area. real-time aerosols delivery of air chemistry observations for use observations, is in weather and environmental forecasting are Further details about GURME can be found at under study at the also increasing. http://mce2.org/wmogurme/. Chinese Academy of Meteorological Services.

Figure 21. Between half and two thirds of the cities with 1 million or more inhabitants are located in regions at high risk of exposure to natural disasters. (Source: United Nations, Multi-hazards exposed to City population No hazard 750 000–1 million Department of Economic Hazards not in top 3 deciles 1–5 million and Social Affairs, 1 hazard in top 3 deciles 5–10 million Population Division: 10 million or more 2 hazards in top 3 deciles World Urbanization 3+ hazards in top 3 deciles Prospects: The 2011 Revision. New York)

26 7. GLOBAL ATMOSPHERE WATCH DATA MANAGEMENT

The Global Atmosphere Watch subscribes to the rational evolution of the global observing a “fair use” data policy systems. The WMO Integrated Global Observing System (WIGOS) emphasizes the importance of “For scientific purposes, access to these [GAW] metadata for the efficient exchange of information data is unlimited and provided without charge. and adequate use of observations. By their use, you accept that an offer of co- authorship will be made through personal In 2006, the Expert Team on World Data Centres contact with the data providers or owners (ET-WDC) was established, formalizing a whenever substantial use is made of their long-standing tradition of cooperation among data. In all cases, an acknowledgment must data centres involved in GAW. The ET-WDC takes be made of the data providers or owners and on a leading role in improving interoperability of of the data centre when these data are used the existing WDCs and engaging with experts in within a publication.” Earth science data management worldwide. A crucially important aspect in this regard is the Statement endorsed by the WMO Executive standardization of metadata, both for metadata Council Panel of Experts/CAS Working Group representation and for terminology. Much of this on Environmental Pollution and Atmospheric effort goes unnoticed, but it is the prerequisite Chemistry for the efficient exchange of available data and for enabling users to make adequate use of the When the GAW Programme came into existence in information they obtain. Thus, the role of ET-WDC 1989, programme-wide data management became is that of a facilitator, building and maintaining possible through the establishment of GAW World bridges between data providers and data users. Data Centres. Two of these centres had been in exis- Specifically, ET-WDC works with other WMO tence for decades: the World Radiation Data Centre bodies to formulate GAW requirements relating (WRDC) which opened in 1964, while the World to data management and contributes to the devel- Ozone Data Centre had already begun fonctioning in opment of the WMO Information System (WIS). 1962. With the designation of the World Ultraviolet Radiation Data Centre, this became the World Ozone The future of GAW data management is all about and Ultraviolet Radiation Data Centre (WOUDC) further integration, improved interoperability in 1992. The World Data Centre for Greenhouse and better services for data users within the Gases (WDCGG) began operations in 1990. The overarching framework of WIGOS. The WMO World Data Centre for Aerosols (WDCA) was set up Information System is the Organization’s infor- in Ispra, Italy, and was integrated in 2007 with the mation highway for the twenty-first century. EMEP data centre. Given the importance of regional Most GAW WDCs already contribute directly to networks, the World Data Centre for Precipitation WIS, and GAWSIS provides machine-readable Chemistry (WDCPC) was established under the metadata for all GAW observations. The Expert auspices of NOAA as a portal providing links to Team on World Data Centres supports WIGOS existing data archives. The purpose of the GAW by defining and coordinating services for oper- World Data Centres, each focusing on a specific ational, time-critical applications so that GAW range of observations, is long-term management and other environmental observational data are of quality-assured GAW data and user-friendly available to users online and, when possible, in access to these data. near real time. The GAW World Data Centres are embracing the use of web services and other In 2001, the GAW Station Information System machine-to-machine interfaces to facilitate the (GAWSIS) was established as the official catalogue automatic exchange of information, while at the of stations and platforms contributing to the GAW same time paying attention to the legitimate network. The purpose of GAWSIS is to collect property rights of the data providers. The vision station metadata, including photos, information is one of seamless data flows from instruments to on all GAW-related observations and contact data users, whereby all significant interventions information, as well as to provide access to bib- between the acquisition of a raw signal and the liographic references, from both the GAW WDCs archiving of fully quality-assured datasets are and other long-term archives storing GAW data. properly documented with standardized meta- The GAW Station Information System is also linked data. Access to the (meta)data will be facilitated to the Observing Systems Capabilities Analysis through WIS, and adequate use of data will be and Review (OSCAR) tool, a central element for supported with WIGOS metadata.

27 Box 1. World Ozone and Ultraviolet Radiation Data Centre

(http://www.woudc.org)

A scientific archive and database for ozone and ultraviolet radiation data is maintained at the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) which is hosted and operated by Environment Canada. The Centre provides a variety of ozone datasets to the international scientific community, including total column ozone from ground-based ozonometers, as well as vertical profile data from ozonesonde flights and lidar measurements. Value added data products include total ozone time series graphs and near real-time ozone maps. The solar ultraviolet radiation dataset includes spectral, multiband and broadband ultraviolet measurements. After more than 50 years of service, WOUDC, under the supervision of the WMO Scientific Advisory Group for Ozone (SAG-Ozone) is currently under renovation with the inclusion of data centre metrics, restructured data products, calibration metadata, quality assurance summaries, automated quality control, linkages with related data centres and near real-time data submission. There are over 500 registered stations in the archive from more than 150 agencies (see figure below).

Maps of the stations that provide data to WOUDC

28 Box 2. World Data Centre for Greenhouse Gases

(http://ds.data.jma.go.jp/gmd/wdcgg/)

Operated by the Japan Meteorological Agency, the World Data Centre for Greenhouse

Gases (WDCGG) gathers greenhouse gas (CO2, CH4, N2O, SF6, CFCs, etc.) and reactive gas

(tropospheric ozone, CO, NOx, SO2, VOC, etc.) observations. Thanks to close cooperation with the relevant scientiﬁc communities, the archive has been growing steadily over the last 25 years and today comprises some 230 1°x1° grid cells with data (see ﬁgure below). The World Data Centre for Greenhouse Gases is one of the Data Collection or Production Centres (DCPCs) of the WMO Information System.

Observational locations submitting data to WDCGG

29 Box 3. World Data Centre for Aerosols

(www.gaw-wdca.org)

Operated by the Norwegian Institute for Air Research (Norsk institutt for luftforskning, NILU), the World Data Centre for Aerosols (WDCA) gathers observational data on chemical, optical and microphysical properties of aerosols in the atmosphere, from around 120 stations (see ﬁgure below). About 45 stations also submit data in near real time. The World Data Centre for Aerosols is co-hosted on the EBAS database, which contains data from a large number of research projects, and by the European Monitoring and Evaluation Programme (EMEP).

Observational stations with data records in WDCA

30 Box 4. World Radiation Data Centre

(http://wrdc.mgo.rssi.ru/)

Operated by the Main Geophysical Observatory of the Russian Meteorological Service (Roshydromet), the World Radiation Data Centre (WRDC) stores mostly daily totals of various radiation balance components from some 1 500 stations. The majority of datasets (ca 1 250 stations) consist of global radiation observations and sunshine duration (ca 1 350 stations). A subset of ca 250 stations is labelled as GAW stations that provide hourly data on global, direct, diffuse, and/or spectral radiation (see ﬁgure below).

GAW stations listed in WRDC

31 Box 5. World Data Centre for Precipitation Chemistry

(http://wdcpc.org/)

Operated on behalf of the Air Resources Laboratory of the National Oceanic and Atmospheric Administration (United States), the World Data Centre for Precipitation Chemistry (WDCPC) receives and archives precipitation chemistry data and complementary information from stations around the world (see ﬁgure below). Precipitation chemistry data from regional and national programmes that maintain their own websites are accessible via links between WDCPC and those sites. Researchers and other users can readily assess the quality of data for their applications through links between WDCPC and the Quality Assurance/Science Activity Centre for the Americas.

Precipitation chemistry monitoring stations, 2000–2007. Sites shown include stations archived and those linked to collaborating networks via WDCPC. (Source: Vet et al., 2014)

32 Box 6. World Data Centre for Remote Sensing of the Atmosphere

(https://wdc.dlr.de)

Operated by the German Aerospace Centre (Deutsche Luft- und Raumfahrt, DLR), the World Data Centre for Remote Sensing of the Atmosphere (WDC-RSAT) is both a data archive and a portal providing information on space-based observations of atmospheric composition. Satellite retrievals of aerosols can complement ground-based measurements, while the latter are needed for a thorough validation of all underlying assumptions in the retrievals. To facilitate access to satellite data, a one-stop shop (http://wdc.dlr.de/data_products/ AEROSOLS/) was set up at WDC-RSAT. It provides a list of satellite-based aerosol products (see example below) with a standardized description of each product, including algorithm characteristics, and direct links to other products and relevant documentation.

An example of a data product available at WDC-RSAT

33 Box 7. GAW Station Information System

(www.meteoswiss.ch/gawsis)

Operated by the Federal Office of Meteorology and Climatology MeteoSwiss, the GAW Station Information System (GAWSIS) is the official catalogue of surface-based GAW stations/platforms, both fixed and mobile. It hosts metadata provided by individual station operators and GAW World Data Centres, as well as a number of other data archives.

Statistics of the datasets available from GAW, 19−Jun−2014 contributing networks and predecessor programmes in WDCs 60oN s

30oN

30oS

60oS

GAW global station GAW regional station Contributing station Open symbols denote closed or inactive stations.

Datasets available from GAW Source: GAWSIS (June 2014) les

Other gas iab 20000 r POPs Archived sample va Radio nuclide Reactive gas

Greenhouse gas 15000 Ozone Aerosol Precipitation chem Radiation Meteo 10000

Total ozone from Arosa since 1928 5000

CO2 from Mauna Loa since 1969 0 # of annual datasets individual 1924 1936 1948 1960 1972 1984 1996 2008

34 8. TRAINING

Education and training are critical to the long-term success of the GAW Programme, particularly in those developing countries that have committed themselves to maintaining and operating global or regional stations. In addition to training in the operational aspects of the GAW Programme, there is a need to enhance the overall scientific capacity and further expand the scientific infrastructure in the host developing countries. The development of scientific capacity requires a commitment by the host country to providing university trained scientists who will remain in the GAW Programme for many years, to put into practice the GAW specific training they have received.

As part of the WMO capacity development strategy, the German Quality Assurance/Science Activity Centre, funded by the German Federal • Aerosol optical depth The GAW Training Environment Agency (Umweltbundesamt) and • Precipitation chemistry and Education Centre the Bavarian State Ministry of the Environment • Ultraviolet radiation at the Environmental and Public Health, established the GAW Training • Carbon monoxide Research Station and Education Centre (GAWTEC) in 2001. • Volatile organic compounds Schneefernerhaus, • Nitrogen oxides Germany The GAW Training and Education Centre (http:// • Greenhouse gases www.gawtec.de) is located at the Environmental • Data evaluation and quality control Research Station Schneefernerhaus, just below the summit of the Zugspitze (2962 m above In addition to GAWTEC activities, GAW pro- sea level), the highest mountain in Germany. vides support for young scientists who wish to The Centre provides scientific guidance and participate in other training events, such as the instructions to personnel from GAW global and GURME training courses, the MACC workshops, regional stations. These courses are organized at the educational activities of the Atmospheric GAWTEC twice a year and cover measurement Composition Change – The European Network and laboratory techniques, the theoretical back- (ACCENT), the summer schools organized by ground of atmospheric physics and chemistry, the Siberian Center for Environmental Research and data handling and interpretation. These and Training, and the European Research Course courses are intended mainly for station operators on Atmospheres, run by the National Centre for and junior scientists from GAW stations located Atmospheric Science, in Leeds (United Kingdom). in developing countries and from those stations Furthermore, GAW facilitates the participation that still do not meet the required high-quality of early career scientists in the Programme, by measurement criteria. supporting their attendance at large international conferences and symposia. Between its establishment (in 2001) and 2014, more than 280 persons from 58 countries were Group photo of GAWTEC trained at GAWTEC. The Centre not only helps trainees, in May 2014, at with knowledge transfer but also facilitates inter- GAWTEC 26 national networking between the operators of GAW stations.

Each course deals with two or three major topics, covering all relevant parameters in the GAW measurement programme:

• Surface ozone • Physical properties of aerosols

35 9. GLOBAL ATMOSPHERE WATCH PUBLICATIONS

The GAW WDCs provide convenient access to the Data from GAW feed several bulletins, including: observational data required to generate products and international environmental assessments. As • WMO Antarctic ozone bulletins (http://www. highlighted in the chapters related to GAW foci, wmo.int/pages/prog/arep/gaw/ozone/index. there are several application areas that utilize or html) can potentially utilize GAW data, including chemical data assimilation in numerical weather prediction • Greenhouse gas bulletins (http://www.wmo. systems and air quality models, chemical reanalysis, int/pages/prog/arep/gaw/ghg/GHGbulletin. inverse modelling, validation of chemical climate/ html) weather modelling systems and trend analysis. • Aerosol bulletins (http://www.wmo.int/pages/ One major aspect of the GAW mission is to orga- prog/arep/gaw/aerosol.html) nize, participate in and coordinate assessments of the chemical composition of the atmosphere on The Global Atmosphere Watch community a global scale. In this way, GAW provides reliable contributes to the preparation and publication Cover page of the scientific information for national and interna- of GAW reports which include measurement WMO/UNEP Scientific tional policymakers, supporting international guidelines, standard operating procedures, rec- Assessment of Ozone conventions on stratospheric ozone depletions, ommendations, and reports of workshops and Depletion climate change and long-range transboundary expert meetings (http://www.wmo.int/pages/ air pollution. The Global Atmosphere Watch data prog/arep/gaw/gaw-reports.html). are used in the following assessments: A number of scientific papers have been pub- • WMO/UNEP Scientific Assessment of Ozone lished, based on the individual station data Depletion (http://www.esrl.noaa.gov/csd/ and as overview papers (see Collaud Coen et assessments/ozone/) al., 2013; Asmi et al., 2013; Cooper et al., 2014; Petzold et al., 2013). The GAW community is • Global Precipitation Chemistry Assessment encouraged to mention the Programme in its (http://www.sciencedirect.com/science/ publications to ensure even better visibility journal/13522310/93/supp/C) of GAW.

36 10. THE FUTURE OF THE GLOBAL ATMOSPHERE WATCH

episodic events such as volcanic eruptions, sand/ Dobson Langley Absolute dust storms, wildﬁres and nuclear accidents. Calibration Campaign Surface-based observations will continue to be at Izana Observatory, useful in the validation of retrievals of atmospheric Tenerife, in September– chemical constituents from satellite radiance October 2012 measurements. This use will become ever more important as the space-based observing system evolves and the assimilation of satellite retrievals of aerosols and trace gases in weather forecast systems and climate models grows.

The GAW products and services will further expand to meet the needs of megacities and large urban complexes. These will require enhanced efforts to downscale GAW networks and to extend collaborations across a wide spectrum of organizations and authorities such as local governments, public health services, city planning and environmental agencies.

The Global Atmosphere Watch will have to direct efforts at: While much has been accomplished over the past 25 years, GAW will continue to evolve in • Encouraging and supporting the use of GAW response to societal needs for meteorological data for global and regional scale model and environmental services to reduce risks from evaluation. high-impact weather and air pollution, and to • Improving observational systems and data mitigate the impacts of, and adapt to, changing processing to allow near real-time provision climate. These services will move towards user- of GAW data for data assimilation. driven products that require integrated observing • Supporting scientific and technical integra- and prediction systems. tion of surface, vertical profile and column datasets from different platforms to provide The future will rely on the GAW measurement a unified understanding of aerosol and gas networks, which remain the backbone of the distributions. Programme by providing long-term “climate quality” data on trends and the spatial dis- Further efforts will be made to minimize gaps in tributions of important chemical and climate the in situ measurement networks at the Earth’s parameters. In order to ensure the availability surface and in vertical profiles, particularly in of reliable information when needed, it will be data-poor regions like the tropics, climate- of paramount importance to maintain a healthy sensitive regions like the Arctic and other regions and robust global measurement network and where observations are used to verify compliance to further expand the network in areas that are with emission-reduction treaties. still under-sampled. The comprehensive information on atmospheric chemicals provided by These activities will need to be accompanied by GAW will continue to be used in a wide range enhanced database architectures, allowing for of applications: to estimate changes in radiative improved metadata exchange and interoperabil- forcing, to constrain budgets of emissions and ity to promote and facilitate the near real-time losses at global and regional spatial scales, and delivery of data, fully integrated with WIGOS to verify bottom-up emission inventories and and WIS. process models. The GAW Programme is at the dawn of a new The GAW data will be used increasingly to sup- and exciting phase of its evolution. There is port advanced numerical weather prediction and much to look forward to, building on the signif- climate models, and to further develop warning icant achievement over the 25 years since its networks for long-range tracking of intense, establishment.

37 38 WE LOOK FORWARD TO CONTINUED AND EXPANDED COLLABORATIONS AROUND THE GLOBE TO CARRY OUT THE OBSERVATIONS AND RESEARCH NEEDED TO ENABLE SERVICES!

39 ACKNOWLEDGEMENTS

This brochure is the result of a joint effort of The current composition of the GAW scientific the Environmental Pollution and Atmospheric advisory groups, expert teams and Scientific Chemistry Scientific Steering Committee, GAW Steering Committee is available at: scientific advisory groups and expert teams, who contributed the text and plots and reviewed http://www.wmo.int/pages/prog/arep/gaw/ the brochure. The GAW community at large is ScientificAdvisoryGroups.html acknowledged for contributing photos and for its loyalty and commitment to the Programme http://www.wmo.int/pages/prog/arep/gaw/ over many years. ExpertTeams.html

http://www.wmo.int/pages/prog/arep/gaw/ JSC_OPAG_EPAC.html

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42 LIST OF ABBREVIATIONS

ACCENT Atmospheric Composition Change – DEBITS Deposition of Biogeochemically The European Network Important Trace Species

ACTRIS Aerosols, Clouds, and Trace gases DLR German Aerospace Centre Research Infrastructure Network EANET Acid Deposition Monitoring AD-Net Asian Dust and Aerosol Lidar Network in East Asia Observation Network EARLINET European Aerosol Research Lidar AERONET Aerosol Robotic Network Network

AGGI Annual Greenhouse Gas Index EDGAR Emissions Database for Global Atmospheric Research ALINE Latin America Lidar Network EMEP European Monitoring and Evaluation BAPMoN Background Air Pollution Monitoring Programme Network EPAC SSC Environmental Pollution and BIPM International Bureau of Weights and Atmospheric Chemistry Scientiﬁc Measures Steering Committee

CARIBIC Civil Aircraft for the Regular ET-NRT CDT Expert Team on Near Real-time Investigation of the Atmosphere Chemical Data Transfer Based on an Instrument Container ET-WDC Expert Team on World Data Centres CAS Commission for Atmospheric Sciences GALION GAW Aerosol Lidar Observation Network CASTNET Clean Air Status and Trends Network GAW Global Atmosphere Watch Programme CCL Central Calibration Laboratory GAWSIS GAW Station Information System CFC chloroﬂuorocarbon GAWTEC GAW Training and Education Centre CIE International Commission on Illumination GCOS Global Climate Observing System

CIS-LINET Commonwealth of Independent GHG greenhouse gases States (Belarus, Russian Federation and Kyrgyzstan) Lidar Network GO3OS Global Ozone Observing System

CONTRAIL Comprehensive Observation GURME GAW Urban Research Meteorology Network for Trace gases by Airliner and Environment

CORALNet Canadian Operational Research IAGOS In-service Aircraft for a Global Aerosol Lidar Network Observing System

COST European Cooperation in Science ICNIRP International Commission on Non- and Technology Ionizing Radiation Protection

DCPC Data Collection or Production IGAC International Global Atmospheric Centre Chemistry

43 IGACO Integrated Global Atmospheric ppb parts per billion Chemistry Observations ppm parts per million IITM Indian Institute of Tropical Meteorology ppt parts per trillion

IMPROVE Interagency Monitoring of Protected PS primary standard Visual Environments QA/SAC Quality Assurance/Science Activity IPCC Intergovernmental Panel on Climate Centre Change RCC Regional Calibration Centre IWAQFR International Workshop on Air Quality Forecasting Research SAFAR System of Air Quality Forecasting and Research KNMI Royal Netherlands Meteorological Institute SAG Scientiﬁc Advisory Group

LLGHG long-lived greenhouse gas SAG-PC Scientiﬁc Advisory Group for Precipitation Chemistry MACC Monitoring Atmospheric Composition and Climate SAG-UV Scientiﬁc Advisory Group for Ultraviolet Radiation MOZAIC Measurement of Ozone and Water Vapour on Airbus In-service Aircraft SOP standard operating procedure

MPLNET Micro-Pulse Lidar Network SSC Scientiﬁc Steering Committee

NDACC Network for the Detection of TCCON Total Carbon Column Observing Atmospheric Composition Change Network

NILU Norwegian Institute for Air Research TROPOS Leibniz Institute for Tropospheric Research, Germany NMHSs National Meteorological and Hydrological Services UNEP United Nations Environment Programme NOAA National Oceanic and Atmospheric Administration, United States UNFCCC United Nations Framework Convention on Climate Change OSCAR Observing Systems Capabilities Analysis and Review UV ultraviolet

PAN peroxyacetyl nitrate UVI UV Index

PFR Precision Filter Radiometer VOC volatile organic compound

PISAC Pollution and its Impact on the WCC World Calibration Centre South American Cryosphere WCCAP World Calibration Centre for Aerosol PMOD/WRC Physikalisch-Meteorologisches Physics Observatorium World Radiation Centre, Switzerland WDC World Data Centre

POP persistent organic pollutant WDCA World Data Centre for Aerosols

44 WDCGG World Data Centre for Greenhouse WIS WMO Information System Gases WMO World Meteorological Organization WDCPC World Data Centre for Precipitation Chemistry WORCC World Optical Depth Research and Calibration Centre WDC-RSAT World Data Centre for Remote Sensing of the Atmosphere WOUDC World Ozone and Ultraviolet Radiation Data Centre WIGOS WMO Integrated Global Observing System WRDC World Radiation Data Centre

45 For more information, please contact: World Meteorological Organization 7 bis, avenue de la Paix – P.O. Box 2300 – CH 1211 Geneva 2 – Switzerland

Communications and Public Affairs Ofﬁce Tel.: +41 (0) 22 730 83 14/15 – Fax: +41 (0) 22 730 80 27 E-mail: [email protected]