SC0UT-03/ACTIVE High-Altitude Aircraft Measurements Around Deep Tropical Convection

SC0UT-03/ACTIVE High-altitude Aircraft Measurements around Deep Tropical Convection

BY G. VAUGHAN, C. SCHILLER, A. R. MACKENZIE, K. BOWER, T. PETER, H. SCHLAGER, N. R. P. HARRIS, AND P. T. MAY

A multinational field campaign in Australia studied the effect of deep convection on the composition of the tropical tropopause layer.

FIG. I. Montage showing the aircraft used in the campaign, with a brief description of their function and altitudes of operation.

his article describes the Stratospheric-Climate (UTLS). The campaign involved four aircraft (Fig. 1) Links with Emphasis on the Upper Troposphere equipped with a variety of in situ and remote sensing Tand Lower Stratosphere (SC0UT-03) and instruments, with ancillary measurements from Aerosol and Chemical Transport in Deep Convection ozonesondes. These observations were supported by (ACTIVE) field campaign conducted in Darwin, an extensive network of ground stations, including a Australia (12.47°S, 130.85°E), from 10 November polarimetric weather radar (Keenan et al. 1998) and to 10 December 2005, to investigate the transport a lightning interferometer network (Betz et al. 2004). of water vapor, aerosols, and chemicals into the Measurements were made in the vicinity of deep con- tropical upper troposphere and lower stratosphere vection (the so-called Hector storms, which appear

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC most days over the Tiwi Islands, north of Darwin), There has been considerable discussion over the and also in clear air well away from convection. years as to whether a globally significant amount Aircraft flight patterns ranged from direct penetra- of air is transported into the stratosphere through tions of convective turrets and anvils to long survey deep convection (e.g., Newell and Gould-Stewart flights in air well away from convection. The ground- 1981; Danielsen 1993; Sherwood and Dessler 2001; based support data provided information on the Holton and Gettelman 2001). Some studies show that intensity and microphysical structure of the parent a subset of the most intense cells reaches the height convection. of the surrounding cold point and frequently appears The thermal structure of the tropical troposphere to have significant overshoot (e.g., Liu and Zipser is determined by radiative-convective equilibrium up 2005; May and Ballinger 2006). One of the aims of to 12-14 km, which is the level of maximum outflow the SCOUT-03/ACTIVE campaign was to identify from convective storms (Folkins 2002). Above this air that remained in the stratosphere following such level, convective outflow drops off with altitude, and deep overshooting convection. Quantifying the con- at the cold point tropopause, the outflow is very much tribution of air lofted in convection compared to that reduced (Highwood and Hoskins 1998; Thuburn and transported over much longer distances in the TTL Craig 2002). The layer of the tropical atmosphere is important for understanding the water vapor and between the main convective outflow and the cold trace gas budgets in the stratosphere. point tropopause is known as the tropical tropopause Below the level of zero net radiative heating, layer (TTL). At some altitude within it, the net radia- convective transport becomes increasingly domi- tive heating changes from cooling to warming. This nant. Convection is fast and chemical reactions take is around 15 km in clear air, though it depends quite place in cloud droplets or on ice crystals; thus, air sensitively on the cloud cover in and below the TTL. transported by deep convection to the TTL has dis- Above this altitude, large-scale dynamics dominate tinctive chemical properties. Measurements of trace and the corresponding vertical diabatic transport is a gases with a wide range of lifetimes (from hours to slow background on top of which rapid adiabatic os- decades) can be used to understand the dynamical cillations occur. Air will tend to ascend slowly into the and chemical processes that govern their distribution tropical middle stratosphere, although there is some and input into the stratosphere. Short-lived chemicals isentropic exchange with the extratropical lowermost originating near the surface can be deposited virtually stratosphere (Chen 1995; Levine et al. 2006). This unchanged at high altitudes, for example, the source part of the TTL forms the base of the Brewer-Dobson gases for halogen radicals (particularly bromine and circulation, determining the eventual composition of iodine), which may destroy ozone in the TTL and the global stratosphere. the lower stratosphere (see chapter 2 of WMO 2002). Lightning in deep convection generates copious amounts of NOx (Huntrieser et al. 2002), which, AFFILIATIONS: VAUGHAN AND BOWER—School of Earth, with hydrocarbons and CO lifted from a polluted Atmospheric and Environmental Sciences, University of boundary layer, can generate ozone in the TTL. The Manchester, Manchester, United Kingdom; SCHILLER— ACTIVE and SCOUT-03 missions were designed to Forschungszentrum Julich, Institut fiir Chemie und Dynamik der investigate both convective and large-scale transport Geosphare, Jiilich, Germany; MACKENZIE—Environmental Science and to distinguish their relative contribution to TTL Department, Lancaster University, Lancaster, United Kingdom; PETER—ETH, Zurich, Switzerland; SCHLAGER—Deutsches Zentrum composition. The missions were complementary, but fiir Luft- und Raumfahrt, Oberpfaffenhofen, Germany; HARRIS— had somewhat different foci as follows: Centre for Atmospheric Sciences, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom; MAY— i) The transport of water (as vapor and ice) into the Bureau of Meteorology Research Centre, Melbourne, Australia stratosphere was a key focus of the SCOUT-03 CORRESPONDING AUTHOR: G. Vaughan, School of Earth, Darwin campaign. One minor, but indispensable, Atmospheric and Environmental Sciences, University of channel of the global hydrological cycle occurs Manchester, Oxford Road, Manchester MI3 9PL, United Kingdom E-mail: [email protected] in the TTL, where cirrus clouds form and water is transported across the tropopause. Tropical The abstract for this article can be found in this issue, following the thunderstorms inject relatively moist air into table of contents. the TTL. This moist air moves away from storm DOI: 10.1175/BAMS-89-5-647 centers in the readily recognizable anvils of the In final form 27 June 2007 ©2008 American Meteorological Society storms, which can exist for hours after the initiat- ing storm has dissipated. Most, but by no means

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC all, of this moist air injection occurs at the base clouds observed in the TTL. ACTIVE s focus was of the TTL, as we have just discussed. Studies on the main convective outflow and the nature of using global reanalysis datasets suggest that the particles observed therein as a function of convec- tropical west Pacific-Maritime Continent region tion type (whether isolated deep thunderstorms in Northern Hemisphere winter is a "hot spot" for or more extensive maritime convection). SCOUT- air entering the TTL, for air crossing the tropical 03's focus was on how cirrus clouds (injected by tropopause, and for air encountering the coldest convection or formed in situ) change the trans- temperatures (Fueglistaler et al. 2004, 2005). port of tracers through the TTL (e.g., by changing Generally the lower the temperature experienced the height where the net radiative heating changes by an air parcel the lower its water content will from cooling to warming). be. ii) The transport and transformation of aerosol by These investigations were complemented by the cam- deep convection was a major focus of the ACTIVE paign conducted by ACTIVE and the Tropical Warm component of the campaign. Soluble aerosol is re- Pool International Cloud Experiment (TWP-ICE) moved by precipitation during convective uplift, in the monsoon period after Christmas (May et al. but not all aerosol is soluble. Trace gases trans- 2008). ported into the anvil may be oxidized to nucleate new ultrafine particles (Raes et al. 2000); indeed, THE EXPERIMENT. The rationales of both Twohy et al. (2002) found condensation nuclei ACTIVE and the SC0UT-03 campaign spoke concentrations more than an order of magnitude strongly in favor of the investigation of tropical greater within a thunderstorm anvil than outside convection in a region where i) the convection is it. Cirrus clouds in the TTL region have a substan- regular, ii) the convection is isolated, iii) aspects tial impact on the Earths radiation budget, and of the convection have already been documented, their properties depend on the nucleating aerosol and iv) a good infrastructure exists to support the population. ACTIVE/SCOUT-03 addresses the measurements. In the premonsoon period (mid- scarcity of systematic measurements of aerosols November-mid-December), convection in the in and around tropical convective outflow. Darwin area is dominated by single isolated storms. iii) Of importance to both ACTIVE and the Spectacular examples occur over the Tiwi Islands SCOUT-03 Darwin experiment was the nature of north of Darwin (Fig. 2), due to convergence of sea

FIG. 2. Map of Darwin area, superimposed on the track taken by the Geophysica and Falcon on the transit flight from Germany and local flights from Darwin. Color shows the potential temperature of the Geophysica during flight.

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC breezes over the islands (Carbone et al. 2000). These These experiments established the conditions that are the Hector storms, which occur regularly over the cause deep convection and showed that a multiair- islands in the afternoon or early evening. These giant craft experiment of the type described here was both thunderstorms reach (and sometimes penetrate) the feasible and likely to be scientifically fruitful when synoptic tropopause at 17 km, thus directly injecting conducted from Darwin. air into the TTL and tropical lower stratosphere (TLS). Their predictability and isolation also make The ACTIVE component ACTIVE is a consortium of them excellent natural laboratories for comparing eight institutions led by the University of Manchester the aerosol-chemical input to, and output from, the and funded by the U.K. Natural Environment TTL, and for studying the transport of water near Research Council (NERC). Its main focus is on the tropopause. Aircraft can easily cross or circum- measurements of aerosol and chemical species in navigate the storms; coordinated flying is easier the inflow and outflow of deep tropical convection, because pilots can often see the storm center and and its secondary aim is to map out the overall dis- edges, and modeling the storms on the mesoscale is tribution of these constituents in the Darwin region. not such a formidable task as for more extensive, or To this end the following two aircraft were used: less topographically locked, convection. Darwin also the NERC Airborne Research Facility Dornier-228 has excellent facilities to support a campaign of this for low-level measurements (up to 4 km) in clear type, including advanced radar systems operated by air around the storm base, and Airborne Research the Australian Bureau of Meteorology. This infra- Australia's Grob G520T Egrett aircraft for measure- structure is described more fully in the companion ments in the anvil outflow at 12-14 km. Details of the article (May et al. 2008). payloads of these two aircraft are given in Tables 1 The SCOUT-03/ACTIVE campaign was first to and 2. The Dorniers instrument package made com- study Hector storms in the premonsoon period with prehensive measurements of aerosol size spectra and aircraft that observed the full altitude range from composition, meteorological variables, and chemical the bottom of the convective inflow to the top of the species, while the Egrett carried cloud physics probes outflow. However, a number of previous campaigns in addition to determine the nature of ice particles in in the Darwin area have investigated the nature of the anvil. Supporting measurements were made by 23 the convective storms and their impact on the TTL ozonesondes launched from the Darwin meteorologi- and TLS. In January-February 1987 (during the cal station during the campaign, giving ozone profiles monsoon period), the National Aeronautics and Space into the stratosphere. Administration (NASA) ER-2 aircraft was deployed in The specific scientific objectives of ACTIVE are Darwin for the Stratosphere-Troposphere Exchange as follows: Project (STEP) tropical experiment (Russell et al. 1993). This campaign found that air of recent tropospheric i) To relate measurements of aerosol and chemical origin was transported into the stratosphere and species in the outflow of deep convection, and in dehydrated to water vapor concentrations consistent the surrounding TTL, to low-level sources; with local cold point tropopause temperatures (Russell ii) to determine how deep convection modifies the et al. 1993; Danielsen 1993 and accompanying papers). aerosol population reaching the outflow, and thus More meteorological in focus was the Australian evaluate its impact on cirrus nucleation in the Monsoon Experiment (AMEX) (Holland et al. 1986), TTL; which coincided with STEP, the Island Thunderstorm iii) to compare the concentration of aerosol and Experiment (ITEX) in 1988 (Keenan et al. 1989), and chemical tracers (with a range of lifetimes and the Maritime Continent Thunderstorm Experiment origins) in the outflow with that in the back- (MCTEX) in 1995 (Keenan et al. 2000). Measurements ground TTL, and therefore determine the con- of the aerosol and chemical background in the Darwin tribution of convection to the composition of the area during the dry season were made during the TTL over Darwin; Biomass Burning and Lightning Experiment (BIBLE) iv) to use latitudinal surveys of tracers, together with in 1998 and 1999 (Kondo et al. 2003). Of direct im- high-resolution global models, to determine the portance to the present campaigns was the Egrett contribution of large-scale transport to the com- Microphysics Experiment with Radiation, Lidar, and position of the TTL; Dynamics in the Tropics (EMERALD-2) experiment v) to compare the effects of isolated very deep con- conducted in Darwin in November 2002 to study vection with that of widespread but less penetra- the nature of cirrus clouds in the outflow of Hector. tive convection on the composition of the TTL;

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC TABLE 1. Egrett payload.

Instrument Measurement Principal investigator

Basic meteorology and position Pressure, temperature, wind, GPS (1 Hz) Jorg Hacker, Airborne Research Australia Aerosol particle size distribution Droplet measurement technology (DMT) (0.2-1.0 fjm), light absorbing fraction and Hugh Coe, University of Manchester single-particle soot photometer (SP-2)* composition 2 x TSI-3010 condensation particle counter (CPC) Total condensation particles > 10 and > 100 nm Martin Gallagher, University of Manchester Cloud-droplet spectrum, aerosol/small DMT cloud, aerosol and precipitation particle asymmetry, aerosol refractive index Andy Heymsfield, NCAR spectrometer (CAPS) (diameter 0.3-2000 jtvm) Cloud particle size distribution (diameter DMT cloud-droplet probe (CDP) Martin Gallagher, University of Manchester 2-62 pm) Cloud particle/ice CCD images, (diameter SPEC cloud particle imager CPI-230 Martin Gallagher, University of Manchester 10-2,300 pm) Buck Research CR-2 frost-point hygrometer Ice-point temperature (0.05 Hz, ± 0.1 °C) Reinhold Busen, DLR Open-path tuneable diode laser hygrometer Water vapor concentration (1 Hz, ±1 ppmv) Jim Whiteway, York University, Canada Closed-path tuneable diode laser hygrometer Water vapor concentration (1 Hz, ± 1 ppmv) Geraint Vaughan, University of Manchester Andreas Volz-Thomas, Forschungszentrum Vacuum UV fluorescence CO analyzer Carbon monoxide (1 Hz, ± 2 ppbv) (FZ)Julich Miniature gas chromatograph Halocarbons (CI, Br, 1; 3-6 min, ±5%) Neil Harris, University of Cambridge TE-49C UV ozone sensor Ozone concentration (± 2 ppbv, 10 s) Reinhold Busen, DLR Automatic tube sampler (ATS); 15 samples per C4-C9 nonmethane hydrocarbons, Alastair Lewis, University of York, United flight monoterpenes, OVOCs Kingdom ±200 ppt at 10 Hz; ± 30 pptv with 4-s NO and N02 chemiluminescent detector* Andreas Volz-Thomas, FZJiilich integration *Alternates (only one flown at any time).

TABLE 2. Dornier payload

Instrument Measurement Principal investigator

GPS position, pressure, temperature, relative Aventech AIMMS-20 probe David Davies, ARSF humidity, winds, 1 Hz Aerodyne aerosol mass spectrometer Aerosol size and composition (30-2000* nm) Hugh Coe, University of Manchester TSI30I0 condensation particle counter Aerosol concentration > 10 nm, 1 Hz Martin Gallagher, University of Manchester Aerosol size distribution (0.3-2* jum, bins Grimm optical particle counter model 1.108 Martin Gallagher, University of Manchester 0.1-0.2 pm, 0.16 Hz) Aerosol size distribution (0.1-0.8 pm, 7.5-nm Ultra-high-sensitivity aerosol spectrometer Martin Gallagher, University of Manchester bins, 1 Hz) Aerosol size distribution (0.2-2* pm, bins DMT aerosol spectrometer probe ASP-100 Martin Gallagher, University of Manchester 0.03-0.5 pm, 0.1 Hz) Forward scattering spectrometer probe Aerosol and cloud-droplet size distribution Martin Gallagher, University of Manchester (FSSP) (0.5-32 pm, bin 0.8 pm, 0.1 Hz) Black carbon concentration (aerosol) Particle soot absorption spectrometer (PSAP) Andreas Minikin, DLR (± 1 pg nr3, 0.2 Hz) Coarse aerosol composition, whole flight Filters Keith Bower, University of Manchester accumulation Alastair Lewis, University of York, United 2B technologies model 202 ozone monitor Ozone concentration (±2 ppbv, 0.1 Hz) Kingdom Alastair Lewis, University of York, United Aerolaser AL5003 Carbon monoxide concentration (± 1 ppbv, 1 Hz) Kingdom C4-C9 nonmethane hydrocarbons, Automatic tube sampler (ATS), 15 samples Alastair Lewis, University of York, United monoterpenes, oxygenated volatile organic per flight Kingdom compounds (OVOCs) James Lee, University of York, United Chemiluminescence/catalysis NO/NO /NO x y Kingdom Miniature gas chromatograph Halocarbons (CI, Br, 1; 3-6 min, ±5%) Neil Harris, University of Cambridge *Upper bound limited by inlet efficiency.

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC vi) to determine the contribution of deep convection TTL and where air is just entering the TLS. As already to the NOx and 03 budget in the TTL; and mentioned, large-scale modeling studies suggest that vii) to measure how much black carbon reaches the the tropical west Pacific/Maritime Continent is an outflow regions of the storms. important region for such transport into, and out of, the TTL; it is the region of coldest temperatures ACTIVE participated in both Darwin field globally at these altitudes. During the campaign the campaigns, with SC0UT-03 before Christmas lower-stratospheric winds were basically from the east and TWP-ICE afterward in January and February. so that air passing over Darwin area at tropopause Details of the latter are given by May et al. (2008), level was from this region of coldest temperatures, but the aim was to study isolated island convection giving the SCOUT-03 aircraft the chance to sample in the first campaign and more widespread monsoon air that recently entered the stratosphere. In addition, convection in the second. In fact, both monsoon and the vigorous island convection near Darwin provides a isolated convection were experienced in the second direct route for rapid injection of boundary layer air to campaign and ACTIVE will be able to compare the the TLS (Danielsen 1993). Contrasting measurements Hector storms from the premonsoon and monsoon made close to convection with those from farther away break periods. will allow the relative importance of convective and large-scale transport into the TLS to be assessed. The SC0UT-03 component. The SC0UT-03 The SCOUT-03 Darwin deployment consisted of Tropical Aircraft Experiment Darwin 2005 (here- the M-55 Geophysica aircraft and the DLR Falcon, after SC0UT-03 Darwin) is part of the SC0UT-03 flying out from central Europe to meet a small support Integrated Project of the European Commission team for logistics, weather prediction, and more general (online at www.ozone-sec.ch.cam.ac.uk/scout_o3/). modeling. The transfer flights from Europe to Darwin The overarching aim of SC0UT-03 as a whole is represent an integral part of the campaign, extending to predict the evolution of the coupled chemistry- the measurement coverage and permitting extra sci- climate system, with emphasis on ozone change in the ence missions. The aircraft payloads were somewhat lower stratosphere and the associated UV and climate different on transfer flights and local sorties; these are impact. SCOUT-03 Darwin feeds into the following detailed in Tables 3 and 4, for the Geophysica and the three aspects of this overarching aim: Falcon, respectively. During the transfer flights, priority was given to remote sensing measurements of the TTL: • to understand the tropical mechanisms of tropo- water vapor measurements by upward-looking differ- sphere-to-stratosphere transport (TST), ential absorption lidar (DIAL) from the DLR Falcon, • to understand past changes in stratospheric trace lidar aerosol measurements from the Falcon (zenith) gas concentrations and humidity, and and the Geophysica (nadir), and limb-scanning chemi- • to enable a prediction of future stratospheric trace cal measurements from the Geophysica. On the out- gas concentrations and humidity. ward transfer flight, the Geophysica and Falcon were accompanied by a Swiss Lear jet, carrying a microwave This, in turn, led to the following objectives for spectrometer for the retrieval of stratospheric profiles the SCOUT-03 Darwin experiment: of water vapor and ozone. Coverage of the tropical UTLS by the SC0UT-03 Darwin transfer flights is i) How does air undergo TST? summarized in Fig. 3, and discussed briefly at the end ii) Where is air transported from the troposphere to of "First results from two selected missions." During the stratosphere? the local flights, priority was usually given to in situ iii) How is air processed during its passage through measurements of water vapor, particles, reactive chemi- the TTL and what is its composition? cal species and tracers, at or just below the main anvil iv) How is air dehydrated during TST? outflow altitude (Falcon), and from anvil top through v) How well do numerical weather prediction the TTL to the lower stratosphere (Geophysica). models represent mesoscale and large-scale trans- Satellite data were used to place the localized air- port processes in the tropical Pacific/Maritime craft measurements in a larger-scale context. Most Continent region? notably, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) experiment onboard Meeting these objectives requires measurements the European research satellite ENVISAT was oper- of the chemical composition of air in the TTL and ated in a special mode for the period and location in the TLS, particularly where air is just entering the of the SCOUT-03 flights from Darwin and during

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC TABLE 3. Geophysica payload.

Instrument Measurement Principal investigator

Myasishchev Design Bureau, Zhukovsky, Basic meteorology (UCSE) Pressure, temperature, wind, position Moscow, Russia

Genrikh Shur, Central Aerological Meteorology probe (TDC) Temperature, wind (10 Hz, 0.5 K, 1 m s_l) Observatory (CAO), Dolgoprudny, Moscow, Russia

Vertical profile of temperature and potential Mike Mahoney, Jet Propulsion Laboratory, Microwave temperature profiler (MTP) temperature California

F. Ravegnani, Consiglio Nazionale delle FOZAN chemiluminescence ozonometer Concentration of ozone (1 Hz, 0.01 ppmv) Richerche (CNR), Bologna; A. Ulanovski, CAO

FISH fluorescence hygrometer Concentration of total water (1 Hz, 0.2 ppmv) Cornelius Schiller, FZJuelich

FLASH fluorescence hygrometer Concentration of water vapor (8 s, 0.2 ppmv) Vladimir Yushkov, CAO

ACH frost-point hygrometer Concentration of water vapor (60 s) Vladimir Yushkov, CAO

Concentration of NO, NO , particle NO SIOUX chemiluminescence detector Hans Schlager, DLR (1 Hz, 10%)

HALOX chemical conversion fluorescence Concentration of CIO and BrO (20/100 s, Fred Stroh, FZJuelich detector 20%/35%)

HAGAR gas chromatograph and IR Concentration of N20, F11, F12, halon 1211, Michael Volk, University of Frankfurt absorption SF6 (90 s, 2%/4%); C02 (5 s, 0.5%)

ALTO tunable diode laser spectrometer Concentration of CH4 (3 s, 10%) Francesco DAmato, CNR

COLD tunable diode laser spectrometer Concentration of CO (4 s, 9%) Silvia Viciani, INOA

Long- and short-lived source gases, trace gas Whole-air sampler Thomas Rdckmann, University of Utrecht isotopes

CN concentrations in three size bins, COPAS condensation nuclei counter Stephan Borrmann, University of Mainz nonvolatile CN

Forward scattering spectrometer probe Size-speciated particles 0.4-40 jL/m Stephan Borrmann, University of Mainz (FSSP300 and FSSPI00)

Cloud particle imager Particles > 100 /jm Stephan Borrmann, University of Mainz

Multiwavelength aerosol scatterometer Aerosol optical properties and concentration Francesco Cairo, CNR (MAS)

Aerosol and cloud profile below aircraft Microjoule lidar (MAL) Valentin Mitev, Obs. Neuchatel altitude

Vertical profile of H20, CH4, N20, 03, Fl 1, MIPAS infrared limb sounder Cornelis Blom, FZ Karlsruhe HN03, and others, clouds

Vertical profile of H20, 03, Fl 1, HNOB, and CRISTA-NF infrared limb sounder Martin Riese, FZJuelich others, clouds

Brian Kerridge, Rutherford Appleton Labo- MARSCHALS microwave limb sounder Vertical profile of H20, CO, and 03 ratory, United Kingdom

the transfers from and to Europe, with enhanced were conducted around the Tiwi Islands. Typically, coverage in the North Australian/Indonesian region. the Dornier took off around midday, before the deep ENVISAT measures a large number of atmospheric convection started, and measured profiles of com- trace gases and cloud parameters in the upper position and meteorological variables from 100 to troposphere, stratosphere, and mesosphere with 3200 m upwind, downwind, and north and south of quasi-global coverage (Nett et al. 2001). the islands (consistent with the Seabreeze circulation, temperature profiles north and south of the islands Flight patterns. The aim of the Dornier flight program were consistently warmer than off the east and west was to characterize the aerosol and chemical input coasts). This took about 2 h, after which time the into deep convection. Because the focus of the field remaining 2 h of the flight were used to fly around campaign was on Hector, most of the Dornier flights and across the island at constant altitudes chosen by

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC TABLE 4. Falcon payload.

Instrument Measurement Principal investigator

Basic meteorology [inertial navigation system (INS), Position, wind (1 m s~' horizontal, 0.3 m s~' Andreas Giez, DLR GPS, five-hole probe, Rosemount] vertical), temperature (0.5 K) Aerosol and cloud (backscatter and polarization) Lidar Andreas Fix, DLR profile above aircraft (1 s, 10%)

Differential absorption lidar (DIAL) H20 profile above aircraft (60 s, 10%) Andreas Fix, DLR Absorption hygrometer Concentration of total water (1 Hz, 0.3 g m~3) Andreas Giez, DLR FISH fluorescence hygrometer Concentration of total water (1 Hz, 6%) Cornelius Schiller, FZJuelich OJSTER tunable diode laser spectrometer Concentration of water vapor (10 Hz, 10%) Cornelius Schiller, FZJuelich

Chemiluminescence detector (with converter for NOy) Concentration of NO and NOy (1 Hz, 2 and 5 pptv) Hans Schlager, DLR Vacuum ultraviolet (VUV) fluorescence detector Concentration of CO (5 s, 3 ppbv) Hans Schlager, DLR Hans Schlager, DLR and F. Ar- Chemical ionization mass spectroscopy Concentration of S02 nold, University of Heildelberg CN counter Condensation nuclei (1 Hz, 10%) Andreas Minikin, DLR Filter sampler Aerosol composition and size distribution Martina Kramer, FZJuelich

the on-board mission scientist to probe any distinc- tive layers (constant-altitude flight legs were the optimum choice for the aerosol mass spectrometer). Three survey missions were also conducted—two over Arnhem Land and a third around the Cobourg Peninsula, at the end of which an intercomparison leg was conducted at 3200 m flying in close formation with the Egrett. Most of the Egrett flights concentrated on the outflow from Hector, typically flying reciprocal legs across the anvil outflow at three to four altitudes between 12,800 and 14,300 m, with a final along- anvil leg. Flights were designed to measure in clear air as well as in-cirrus cloud, to sample the transition between recently uplifted and background air. At the end of the campaign two survey flights were conducted—one to measure the NO left behind after X the passage of a huge MCS, and one to measure the properties of aged, thin cirrus remaining in the TTL well away from convection. The aim of the Falcon flight program was to characterize the TTL upwind of cirrus outflow, the TTL cirrus itself, and the aerosol and chemical output from deep convection. The first two of these targets were addressed remotely using the aerosol and water DIAL system; the output from deep convection was

FIG. 3. Lat-potential temperature coverage of the SC0UT-03 flights, with a schematic of atmospheric compartments overlaid, (top) Data points colored by wind speed. The Geophysica was in the region of the westerly subtropical jet between Lanarca (35°N) and Dubai (25°N; circle-dot symbol), and in the region of an equatorial easterly jet (circle-cross symbol) at Brunei (5°N). (middle) Data points colored by ozone mixing ratio (ppbv), and (bottom) data points colored by total water mixing ratio (ppmv).

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC investigated using in situ measurements complemen- Queensland coast (Fig. 4a). This easterly flow reached tary to those on the Dornier. Falcon flight patterns up to around 300 hPa. Near the surface, strong sea typically consisted of ascent to a holding pattern breezes developed during the morning, serving to upwind of the Tiwi Islands at 11,600-m altitude, held initiate convection along lines parallel to the coast. until convection was well established, and then tran- The strong steering level flow advected these storms sects below the developing anvil followed by entry to the west, so that the Darwin area generally experi- into the anvil itself. enced thunderstorms in the evening. In addition, sea The aim of the Geophysica flight program was breezes from the Gulf of Carpentaria to the east of to characterize the TTL under quiescent conditions Darwin often developed into squall lines (extensive and above convection. To characterize quiescent organized regions of convection, or mesoscale con- conditions, flights consisted of long cross-wind (i.e., vective systems). Westward passage of these systems north-south) flight segments between 14,600 and over Darwin, usually during the night, left behind 18,400 m, often with final ascents to the operational a cooled and stabilized boundary layer, delaying ceiling of the aircraft of 20,000 m. For characteriza- the onset of convection the following day. Typical tion of convection, sorties generally began with ascent convective available potential energy (CAPE) values to a holding pattern upwind of the Tiwi Islands, held of 2000-4000 J kg-1 indicate a convectively unstable until the convection was reaching its most intense troposphere, while convective inhibition (CIN) of phase, and then ascent to an altitude above the highest -100-300 J kg-1 allows energy to build up in the convective tower followed by slow descent toward, and boundary layer to be released in deep convection. penetration of, a tower. Sorties of this kind generally As previously mentioned, the Hector storms on the involved two or three of these tower interceptions; see Tiwi Islands were a particular focus of the campaign. Fig. 10 for an example of a Geophysica flight to char- These deep storms develop through the interaction acterize the TTL above convection. For all Geophysica between sea breezes advancing from north and flights, ascent and descent rates were made at 7.5 m s-1, south of the islands with cold pools set up by earlier or less, giving time for accurate vertical profiles to be convection (Carbone et al. 2000). Visible satellite measured. imagery depicts the development of these storms: early in the day (around 0900 LT) isolated boundary METEOROLOGICAL CONDITIONS. For layer convection occurs all over the islands. As the most of the field campaign, the low-level flow sea breezes advance, the convection is swept into around Darwin was dominated by strong easterly bands oriented east-west, and deepens. From mid- winds at 700 hPa originating in confluence along the day onward, usually around 1400 LT, the interacting

FIG. 4. Flow over Northern Australia (a) 700 hPa (the steering level) and (b) 200 hPa (the main convective outflow level) at 0000 UTC 16 Nov 2005. Colors denote wind speed (kt). Analyzed fields are from the Bureau of Meteorology's Extended Limited Area Prediction System (TXLAPS) model.

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC cold pools provide enough impetus to overcome the cal jet stream, pushing filaments of midlatitude air convective inhibition and initiate Hector. deep into the tropics over Darwin. At the same time In early November the very strong easterly winds the Queensland ridge retreated eastward, bringing at the steering level meant that the deepest convec- westerly winds at middle levels over Darwin and tion was found over Bathurst Island, with isolated monsoonal conditions at the surface with oceanic single-cell Hectors blown rapidly out to sea, where convection. Ozonesonde ascents during this period they decayed. The detached anvil resulting from such revealed ozone-rich layers of stratospheric origin a case was intensively studied by the four aircraft around 7 km, contrasting markedly with the very uni- on 16 November. Later in the season deep convec- form profiles measured the following week (Fig. 6). tion occurred all over the islands and multicellular An important feature of the premonsoon period storms were the norm, organizing into squall lines was revealed by the Dornier aerosol and chemistry that propagated across the islands. The intensive measurements. During the dry season, and extending case study of 30 November was of this type, when into November, widespread biomass burning char- the Geophysica penetrated the tops of the convective acterizes the top-end region (Russell-Smith et al. turrets (at 18 km) and the Egrett probed the anvil 2000); it is a custom of the native people to burn outflow. Both of these days are further described off surplus vegetation during this season, and other below. A summary of the meteorological conditions fires are started by lightning. As the season pro- during each day of the campaign, together with the flights of each aircraft, is given in Fig. 5. For most of the field campaign the subtropical jet stream was well south of Darwin (Fig. 4b), and easterly winds increased in strength with altitude above 100 hPa. At the altitude of the main convective outflow (150-200 hPa) conditions were more complex. For the first half of November northerly winds prevailed (Fig. 4b), blowing the Hector anvils south toward the Darwin area. In December conditions were more variable, with some days having almost no background wind at these levels; the anvils on such days spread in all directions like mushrooms. An exception to these conditions was experienced during the period of 18-24 November, when pronounced Rossby wave activity occurred along the subtropi-

FIG. 6. Ozonesonde profiles measured from Darwin between 22 Nov (marked 221105) and 6 Dec. The FIG. 5. Table showing the type of convection occurring nine profiles measured between 30 Nov and 6 Dec are on the Tiwi Islands each day of the campaign, with the shown in black; they show a remarkably consistent days that each aircraft flew. Joint missions of all four profile below 14 km with some variation in the TTL. were performed on 16 and 30 Nov; D = Dornier 228, The four colored profiles show the influence of Rossby E = Egrett, F = DLR Falcon, and G = Geophysica. The wave breaking to the south of Darwin, with elevated Falcon and Geophysica made two flights on 30 Nov. ozone around 7 km and (on 22 Nov) in the TTL also. Letters are colored according to the kind of flight A profile measured on 13 Nov was consistent with the undertaken on that day. black profiles.

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC gressed, biomass burning abated, and by the second days present a contrast between two extreme cases campaign, during the TWP-ICE experiment, very of Hector—a single cell producing a rapidly detached low aerosol concentrations were observed (less than 1 anvil in the TTL, and an extensive convective com- particle per cubic centimeter, for sizes > 300 nm). This plex producing a much longer-lived storm and an change from polluted conditions at the beginning of anvil covering the whole island. Here we present a November to very clean conditions in February (when short overview of these two days with a flavor of some meteorological conditions were similar to those of the of the results obtained. premonsoon) offers us an unprecedented opportunity On 16 November, strong easterly steering- to study the impact of aerosols on deep convection level winds (Fig. 4) pushed the deep convection to and is one of the main avenues of research being Bathurst Island, where a single-cell Hector blew up pursued within ACTIVE. around 1510 LT (Fig. 7). Its anvil soon detached and Another remarkable feature of the meteorol- was advected southward over the Timor Sea by the ogy was the large variation in tropopause tempera- prevailing northerly winds at 150-200 hPa (Fig. 8). tures over Darwin. A warm phase between 9 and Transects of this anvil were made by the Egrett at 15 November was followed by a cold phase lasting 13,100 and 13,700 m and by the Falcon at 12,600 m, up to 21 November with tropopause temperatures as shown in Fig. 8. The Geophysica concentrated on about 4°-6°C colder than before and with absolute the top of the storm, descending from above. Dornier values near -87°C. A preliminary analysis shows measurements on this day, flying around the Tiwi the presence of a large-amplitude Kelvin wave over Islands, revealed extensive biomass-burning residue the equatorial region with possibly important effects above 550 m. This burning probably contributed, on cirrus formation and on the dehydration of air along with lightning, to the elevated NO (in excess entering the stratosphere (Fujiwara et al. 2001). The of 220 pptv) measured by the Falcon while flying at effects of the wave were likely seen on the flights on the height of the main Hector anvil, and measured 19 and 23 November, which showed particularly low by the Geophysica at 15,500-16,400-m altitude (or H20 mixing ratios at the hygropause of well below 360-370-K potential temperature). 2 ppmv. Further analysis of these observations, com- On 30 November Hector was much larger, begin- bined with the detailed measurements of aerosol and ning over east Melville Island at around 1330 LT. cirrus particles, should lead to new insights into the Deep convection developed all over Melville Island, processes affecting dehydration in the TTL and the arranging itself into a squall line propagating south- role of Kelvin and other waves causing temperature ward (Fig. 7). Light upper-level winds meant the fluctuations on various scales. anvil flowed radially out from the storm complex, with a slight northeastward drift. The Dornier again FIRST RESULTS FROM TWO SELECTED flew around the Tiwi Islands, measuring profiles MISSIONS. Of the 14 Egrett and 12 Dornier between 550 and 3200 m. Biomass burning was still missions, 7 were joint Hector experiments, with the influencing the lower atmosphere on this day, but the Dornier flying around the storms at low level while pollution was waning. With such an extensive anvil, the Egrett flew in and around the anvils. A further the Egrett and Falcon could only sample one part of four Hector missions were flown with the Egrett it in detail, and the Egrett concentrated on the radial alone. In addition to three survey missions with the flow over northeast Melville Island. It flew seven legs Dornier and one with the Egrett, two test flights of across the outflow between 11,600 and 14,000 m, both aircraft were conducted at the beginning of the remaining in cloud throughout, with a final radial campaign. There were eight sorties of the Geophysica, run toward the convective core at 13,000 m (Fig. 9). of which five were directed at Hector, and nine sorties The Falcon surveyed three sides (north, south, west) of the Falcon, of which again five were directed at of the Tiwi Islands and flew a triangular pattern Hector, but usually contained a substantial element with an east-west leg about 150 km north of the of larger-scale survey. The objectives of the other islands. Cirrus was observed throughout the flight, SCOUT-03 flights were larger-scale surveys (making at altitudes between about 14 and 17 km; close to use of the longer range of these aircraft), synoptic- the convection this cloud deck expanded to cover scale cirrus investigations, and study of a mesoscale altitudes between 9 and 18 km (although the deck convective system, which had developed over the was usually too thick for the lidar to penetrate so the Northern Territory. morphology of the cloud top is difficult to determine). On two days—16 and 30 November—joint flights The Geophysica probed the tops of collapsing con- were conducted with all four aircraft. These two vective turrets over south Melville Island (Fig. 10).

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC FIG. 7. Reflectivity measured by the c-band dual-polarization Doppler radar (C-Pol) at Gunn Point, just north of Darwin (left) at 0630 UTC (1600 LT) 16 Nov 2005, and (right) at 0540 UTC (1510 LT) 30 Nov 2005. (top) The results of azimuthal scans, and (bottom) elevation scans along the lines shown in the corresponding volume scan are shown. Convection on 16 Nov was limited due to short-lived intense towers reaching ~I6 km; that on 30 Nov was more extensive, more organized, and longer-lived, and reached up to 18 km. Colors in each image denote radar echo intensity (dBZ), with bright red around 60 dBZ.

Nadir-pointing lidar data corroborate the 18-km lofted by Hector. Because tropopause-level winds cloud-top near the storm center, surrounded by anvil were light, the aircraft were able to perform zigzag with cloud top 1 km lower. survey maneuvers close to the Tiwi Islands; however, Later on the evening of 30 November, less than the light winds also made the position of the out- 4 h after landing, the Falcon and Geophysica took flow from Hector uncertain. Both aircraft observed off again in an attempt to resample the air masses extensive cirrus decks covering an area of approxi- mately 60,000 km2 just north of Darwin. Evidently, cirrus clouds remnants of Hector, and the other sea-breeze-initiated convection of the afternoon (see Fig. 9), had coalesced to form a nearly uniform deck between 12- and 16-km altitude, with much thinner ribbons of cloud, disconnected from the main deck, at altitudes up to 18 km. The trace gas mixing ratios

FIG. 8. Images of aircraft flight tracks on the MTSAT image, 16 Nov. This image is at 1723 LT: Geophysica (green; probing the convective cores), Egrett (red, probing outflow), Falcon (blue), and Dornier (magenta). Solid circle denotes exact position of plane at the time of the image; Geophysica and Falcon tracks are shown at 20 min on either side of this time and Egrett and Dornier at ±40 min. Note the storm is blown off the island to the west while the anvil has gone south, allowing a clear separation of the Hector anvil from the massive system over the Top-End mainland (I3°S).

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC FIG. 9. Images of aircraft flight tracks on MT-SAT IR FIG. 10. Aircraft flight tracks superimposed on radar image, 30 Nov. This image is at 1623 LT. Geophysica reflectivity (dBZ) at 10 km, for 0530 UTC (1500 LT) (green; probing the convective cores), Egrett (red; 30 Nov. Geophysica (green; probing the convective probing outflow), and Falcon (blue; probing upwind cores), Egrett (red; probing outflow), Falcon (blue), region). Solid circle denotes exact position of plane at and Dornier (magenta). Solid circle denotes exact the time of the image; Geophysica and Falcon tracks position of plane at the time of the image; Geophysica are shown at 20 min either side of this time and Egrett and Falcon tracks are shown at 20 min on either side at ±40 min. Very thin cloud at the edge of the anvil does of this time and Egrett and Dornier at ±40 min. not show up in this image, hence the Egrett and Falcon appear to be sampling out of cloud. ratios throughout the troposphere above Brunei. An at tropopause level showed high degrees of variability; increase in ozone with altitude through the TTL (i.e., for example, CO mixing ratios showed 15%-20% 340-380 K), as described previously by Folkins et al. variability around the mean, which is about twice (1999), is present in the profiles above Hyderabad, as large as the variability observed at these altitudes Bangkok, and Brunei, but is not shown clearly above on the survey flight of 23 November (Fig. 11). This Darwin, probably as a result of the targeted flight larger variability at tropopause levels on 30 November around Hector. Above Dubai the profile becomes is indicative of pools of air recently lofted by convec- more typical of the extratropics, with evidence of a tion to the TTL. midtropospheric intrusion of stratospheric air, and a chemically defined tropopause ("chemopause") at SC0UT-03 TRANSFER FLIGHTS. As well as about 360 K. Water mixing ratios were low throughout the local flights from Darwin, the transfer flights of the stratosphere, but somewhat higher in the most the SCOUT-03 aircraft from and to Europe were con- poleward measurements. This poleward increase in ducted as fully instrumented measurement flights. The water mixing ratios along an isentrope is consistent aircraft required five intermediate stops for refuelling with the Brewer-Dobson circulation bringing down and/or instrument maintenance, in Larnaca (Cyprus), air in which methane has been oxidized to water. At Dubai (United Arabian Emirates), Hyderabad (India), the base of the TTL (340 K), the air is much moister U-Tapao (Thailand), and Brunei on Borneo Island. than at the same potential temperature in the sub- Coverage of the tropical and subtropical UTLS by tropics; convection, that is, the upward branch of the all the SC0UT-03 flights is summarized in Fig. 3; Hadley circulation, is an efficient source of moisture the transfer flights sampled across 62° latitude and to the bottom of the TTL. Moving upward through 120° longitude. The Geophysica was in the region the TTL, the water mixing ratios decrease by about of the subtropical jet between Larnaca (35°N) and two orders of magnitude although, again, because Dubai (25°N; circle-dot symbol), and in the region of the focus on flying around Hector, this decrease of an equatorial easterly jet (circle-cross symbol) at is not so evident in the Darwin profiles as presented Brunei (5°N). Strong westerly winds extended into in this figure. the wintertime (northern) extratropical stratosphere. The influence of midlatitude Rossby wave breaking Above 400 K, ozone mixing ratios were highly corre- on the ozone profiles around Darwin during the lated with potential temperature; below 400 K, the deep period of 22-27 November has already been noted tropical ozone profiles (south of Dubai) show a high (Fig. 6). Away from this period the ozone profiles degree of variability, with markedly low ozone mixing show values of around 20 ppbv at the surface, rising to

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC wealth of in situ data on the background atmosphere and in the vicinity of deep convection. Final datasets from all the instruments are still being prepared, but it is already clear that the missions were very successful and will allow us to address the project objectives effectively. Highlights identified so far are as follows:

a) Clear midlatitude stratospheric layers were measured in the midtroposphere by the ozonesondes due to Rossby wave influences. b) The transition from polluted to clean conditions at low levels was observed as the biomass burning abated. c) The TTL above Darwin and in the inflow region over Indonesia during November and December 2005 were characterized by very low temperatures down to -87°C, with modulations by Kelvin waves. A persistent layer of cirrus was observed between about 14 and 16 km. In addition, a layer of very thin cirrus was present just below the cold point tropopause for much of the time. Accordingly, low water vapor mixing ratios below 2 ppmv were observed close to the cold point. d) Perturbations in the concentrations of a number of trace gases were observed in the anvil outflow; for example, increased NOx produced by lightning and enhanced NOx, H20, and CO from uplift.

These results are currently being prepared for FIG. II. Box-and-whisker plots for 5-K potential publication, and considerable progress is also being temperature bins of CO data on the survey flight of made on the impact of aerosol on deep convection; 23 November 2005 (top panel) and the second sortie the overshooting of convective turrets into the of 30 November 2005 (bottom panel). The average stratosphere, and the consequent transport of water position of the tropopause on these sorties is also vapor and short-lived halogen compounds across the shown. The boxes and whiskers show median (asterisk), tropopause; and the impact of deep convection on the 25th- and 75th-percentiles (box edges) and the adjacent aerosol population of the TTL. values (whiskers). Adjacent values are the highest (lowest) values inside the fences defined by the quartile plus (minus) 1.5 times the interquartile range. ACKNOWLEDGMENTS. Without the cooperation of a large team of specialists this experiment would not 55 ppbv between 6 and 10 km before falling to around have been possible. We thank in particular the pilots, 40 ppbv at 14 km, with considerable variability up aircraft scientists, and ground crew of the four aircraft to the tropopause at -17 km. This is consistent with for ensuring that the missions were so successful, and the TTL climatology presented by Gettelman and the staff of the Bureau of Meteorology (BoM) Regional Forster (2002). Centre in Darwin for their invaluable support both for forecasting and logistics. We thank also the SC0UT-03 CONCLUSIONS. The ACTIVE/SCOUT-03 forecasting team, the SC0UT-03 and ACTIVE science campaign in Darwin was a resounding success, with teams, and the BoM radiosonde station, Darwin, for their excellent data being measured by aircraft, sondes, and vital role in the experiment, and the Royal Australian Air ground-based systems. Twelve science missions by the Force for allowing us to use the airfield in Darwin and Egrett and Dornier, and nine by the Geophysica and for supporting us on the ground and in the air. We thank Falcon in addition to the transit flights, collected a Piero Mazzinghi, Francesco D'Amato, and Silvia Viciani,

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC of Istituto Nazionale di Ottica Applicata, for permis- Holland, G. J., J. L. McBride, R. K. Smith, D. Jasper, and sion to show CO data. Finally, we thank the U.S. Natural T. D. Keenan, 1986: The BMRC Australian Monsoon Environment Research Council (Grant NE/C512688/1) and Experiment: AMEX. Bull. Amer. Meteor. Soc., 67, NERC Airborne Remote Sensing Facility for supporting 1466-1472. ACTIVE, and the European Commission (Contract Holton, J. R., and A. Gettelman, 2001: Horizontal COCE-CT-2004-505390) for supporting SC0UT-03. transport and the dehydration of the stratosphere. Geophys. Res. Lett., 28, 2799-2802. Huntrieser, and Coauthors, 2002: Airborne measure- REFERENCES ments of NOx, tracer species, and small particles Betz, H. -D., K. Schmidt, W. P. Oettinger, and M. Wirz, during the European lightning nitrogen oxides 2004: Lightning detection with 3-D discrimination of experiment.}. Geophys. Res., 107, 4113, doi:10.1029/ intracloud and cloud-to-ground discharges. Geophys. 2000JD000209. Res. Lett., 31, L11108, doi:10.1029/2004GL019821. Keenan, T. D., M. J. Manton, G. J. Holland, and B. R. Carbone, R. E., J. W. Wilson, T. D. Keenan, and J. M. Morton, 1989: The Island Thunderstorm Experiment Hacker, 2000: Tropical Island convection in the (ITEX)—A study of tropical thunderstorms in the absence of significant topography. Part I: Life cycle Maritime Continent. Bull. Amer. Meteor. Soc., 70, of diurnally forced convection. Mon. Wea. Rev., 128, 152-159. 3459-3480. , K. Glasson, F. Cummings, T. S. Bird, J. Keeler, and Chen, P., 1995: Isentropic cross-tropopause mass J. Lutz, 1998: The BMRC/NCAR C-Band polarimetric exchange in the extratropics. /. Geophys. Res., 100, (C-POL) radar system. /. Atmos. Oceanic Technol, 15, 16 661-16 674. 871-886. Danielsen, E. F., 1993: In situ evidence of rapid, vertical, , and Coauthors, 2000: The Maritime Continent irreversible transport of lower tropospheric air into Thunderstorm Experiment (MCTEX): Overview the lower tropical stratosphere by convective cloud and some results. Bull. Amer. Meteor. Soc., 81, turrets and by larger-scale upwelling in tropical 2433-2455. cyclones. /. Geophys. Res., 98, 8665-8681. Kondo, Y., M. Ko, M. Koike, S. Kawakami, and T. Ogawa, Folkins, I., 2002: Origin of lapse rate changes in the 2003: Preface to special section on Biomass Burning upper tropical troposphere. /. Atmos. Sci., 59, and Lightning Experiment (BIBLE). /. Geophys. Res., 992-1005. 108, D08397, doi:10.1029/2002JD002401. , M. Loewenstein, J. Podolske, S. J. Oltmans, and Levine, J. G., P. Braesicke, N. R. P. Harris, N. H. Savage, M. Proffitt, 1999: A barrier to vertical mixing at and J. A. Pyle, 2006: Pathways and timescales for tro- 14 km in the tropics: Evidence from ozonesondes posphere-to-stratosphere transport via the tropical and aicraft measurements. /. Geophys. Res., 104, tropopause layer and their relevance for very short 22 095-22 102. lived substances. /. Geophys. Res., 112, D04308, Fueglistaler, S., H. Wernli, and T. Peter, 2004: Tropical doi:10.1029/2005JD006940. troposphere-to-stratosphere transport inferred from Liu, C., and E. J. Zipser, 2005: Global distribution trajectory calculations./. Geophys. Res., 109, D03108, of convection penetrating the tropical tropo- doi:10.1029/2003JD004069. pause. J. Geophys. Res., 110, D23104, doi:10.1029/ , M. Bonazolla, P. H. Haynes, and T. Peter, 2005: 2005JD006063. Stratospheric water vapor predicted from the May, P. T., and A. Ballinger, 2006: The statistical char- Lagrangian temperature history of air entering the acteristics of convective cells in a monsoon regime stratosphere in the tropics. /. Geophys. Res., 110, (Darwin, Northern Australia). Mon. Wea. Rev., 35, D08107, doi:10.1029/2004JD005516. 82-92. Fujiwara, M., F. Hasebe, M. Shiotani, N. Nishi, H. Vomel, , J. H. Mather, G. Vaughan, C. Jakob, G. M. Mc- and S. J. Oltmans, 2001: Water vapor control at the Farquhar, K. N. Bower, and G. G. Mace, 2008: The tropopause by equatorial Kelvin waves observed over Tropical Warm Pool International Cloud Experi- the Galapagos. Geophys. Res. Lett., 28, 3143-3146. ment. Bull Amer. Meteor. Soc., 89, 629-645. Gettelman, A., and P. M. de F. Forster, 2002: A climatol- Nett, H., J. Frerick, T. Paulsen, and G. Levrini, 2001: ogy of the tropical tropopause layer. J. Meteor. Soc. The atmospheric instruments and their applica- Japan, 80,911-924. tions: GOMOS, MIPAS and SCIAMACHY. ESA Highwood, E. J., and B. J. Hoskins, 1998: The tropi- Bull, 106, 77-87. cal tropopause. Quart. J. Roy. Meteor. Soc., 124, Newell, R. E., and S. Gould-Stewart, 1981: A strato- 1579-1604. spheric fountain? /. Atmos. Sci., 38, 2789-2796.

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Unauthenticated | Downloaded 10/04/21 04:23 AM UTC Raes, F., R. van Dingenen, E. Vignati, J. Wilson, J. Sherwood, S. C., and A. E. Dessler, 2001: A model for P. Putaud, J. H. Seinfeld, and P. Adams, 2000: transport across the tropical tropopause. /. Atmos. Formation and cycling of aerosols in the global Sci., 58, 765-779. troposphere. Atmos. Environ., 34, 4214-4240. Thuburn, J., and G. C. Craig, 2002: On the temperature Russell, P. B., L. Pfister, and H. B. Selkirk, 1993: The structure of the tropical substratosphere. /. Geophys. tropical experiment of the Stratosphere-Troposphere Res., 107, 4017, doi:10.1029/2001JD000448. Exchange Project (STEP): Science objectives, opera- Twohy, C. H., and Coauthors, 2002: Deep convection tions, and summary findings. /. Geophys. Res., 98, as a source of new particles in the midlatitude upper 8563-8589. troposphere. /. Geophys. Res., 107,4560, doi:10.1029/ Russell-Smith, J., G. Allan, R. Thackway, T. Rosling, and 2001JD000323. R. Smith, 2000: Fire management and savanna land- Whiteway, J. A., and Coauthors, 2004: Anatomy scapes in northern Australia. Fire and Sustainable of cirrus clouds: Results from the Emerald air- Agricultural and Forestry Development in Eastern borne campaigns. Geophys. Res. Lett., 31, L24102, Indonesia and Northern Australia, J. Russell-Smith doi:10.1029/2004GL021201. et al., Eds., Australian Centre for International WMO, 2002: Scientific assessment of ozone depletion: Agricultural Research, 95-101. 2002. Global Ozone Research and Monitoring Project Rep. 47, 498 pp.

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