Guide to Instruments and Methods of Observation Volume II – Measurement of Cryospheric Variables 2018 edition WEATHER CLIMATE WATER CLIMATE WEATHER WMO-No. 8 Guide to Instruments and Methods of Observation Volume II – Measurement of Cryospheric Variables 2018 edition WMO-No. 8 EDITORIAL NOTE METEOTERM, the WMO terminology database, may be consulted at http://public.wmo.int/en/ resources/meteoterm. Readers who copy hyperlinks by selecting them in the text should be aware that additional spaces may appear immediately following http://, https://, ftp://, mailto:, and after slashes (/), dashes (-), periods (.) and unbroken sequences of characters (letters and numbers). These spaces should be removed from the pasted URL. The correct URL is displayed when hovering over the link or when clicking on the link and then copying it from the browser. WMO-No. 8 © World Meteorological Organization, 2018 The right of publication in print, electronic and any other form and in any language is reserved by WMO. Short extracts from WMO publications may be reproduced without authorization, provided that the complete source is clearly indicated. Editorial correspondence and requests to publish, reproduce or translate this publication in part or in whole should be addressed to: Chair, Publications Board World Meteorological Organization (WMO) 7 bis, avenue de la Paix Tel.: +41 (0) 22 730 84 03 P.O. Box 2300 Fax: +41 (0) 22 730 81 17 CH-1211 Geneva 2, Switzerland Email: [email protected] ISBN 978-92-63-10008-5 NOTE The designations employed in WMO publications and the presentation of material in this publication do not imply the expression of any opinion whatsoever 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. PUBLICATION REVISION TRACK RECORD Part/ Date chapter/ Purpose of amendment Proposed by Approved by section CONTENTS Page CHAPTER 1. GENERAL. 1 1.1 Observation of the cryosphere ................................................ 1 1.2 Observing systems of the cryosphere .......................................... 1 1.3 General siting and exposure requirements for a station measuring cryospheric variables 1 1.4 Measurement standards and best practices ..................................... 1 1.4.1 Snow .............................................................. 2 1.4.2 Glaciers and ice caps ................................................. 4 1.4.3 Ice sheets ........................................................... 5 1.4.4 Ice shelves .......................................................... 5 1.4.5 Icebergs ............................................................ 5 1.4.6 Sea ice ............................................................. 6 1.4.7 Lake ice ............................................................ 8 1.4.8 River ice ............................................................ 9 1.4.9 Permafrost .......................................................... 9 1.4.10 Seasonally frozen ground ............................................. 10 1.4.11 Surface meteorology (at CryoNet stations). 11 1.5 Uncertainty of measurements ................................................. 11 References and further reading ..................................................... 12 CHAPTER 2. MEASUREMENT OF SNOW ........................................... 13 2.1 General .................................................................... 13 2.1.1 Definitions, units and scales ........................................... 13 2.2 Siting and exposure ......................................................... 15 2.3 Snow depth ................................................................ 16 2.3.1 Manual measurements of snow depth .................................. 16 2.3.1.1 Measurement techniques ................................... 16 2.3.1.2 Measurement procedures and best practices .................... 18 2.3.1.3 Sources of error ............................................. 20 2.3.2 Automated measurements of snow depth ............................... 21 2.3.2.1 Measurement techniques ................................... 21 2.3.2.2 Measurement procedures and best practices ................... 21 2.3.2.3 Sources of error ............................................. 25 2.4 Water equivalent of snow cover ............................................... 27 2.4.1 Manual measurements of water equivalent of snow cover .................. 27 2.4.1.1 Measurement techniques. 27 2.4.1.2 Measurement procedures and best practices .................... 30 2.4.1.3 Sources of error ............................................. 34 2.4.2 Automated measurements of water equivalent of snow cove ............... 35 2.4.2.1 Measurement techniques. 35 2.4.2.2 Measurement procedures and best practices .................... 37 2.4.2.3 Sources of error ............................................. 38 2.5 Snow properties ............................................................ 39 2.6 Depth of snowfall ........................................................... 39 2.6.1 Manual measurements of depth of snowfall .............................. 39 2.6.1.1 Measurement techniques ................................... 39 2.6.1.2 Measurement procedures and best practices .................... 40 2.6.1.3 Sources of error ............................................. 41 2.7 Presence of snow on the ground .............................................. 41 2.7.1 Manual measurements of presence of snow on the ground ................. 41 2.7.1.1 Measurement techniques. 41 2.7.1.2 Measurement procedures and best practices .................... 41 2.7.1.3 Sources of error ............................................. 42 References and further reading ..................................................... 43 CHAPTER 1. GENERAL 1.1 OBSERVATION OF THE CRYOSPHERE The cryosphere collectively describes components of the Earth system that may very often contain water in its frozen form; it includes solid precipitation, snow, glaciers and ice caps, ice sheets, ice shelves, icebergs, sea ice, lake ice, river ice, permafrost and seasonally frozen ground. Permafrost, however, can be “dry” and therefore the cryosphere also includes any natural material in frozen form. The cryosphere comprises elements that occur on or beneath the Earth’s surface or that are measured at the surface, as in the case of solid precipitation, excluding ice clouds. The cryosphere is global, existing not just in the Arctic, Antarctic and mountain regions, but at various latitudes in approximately one hundred countries. It provides some of the most useful indicators of climate change, yet is one the most under-sampled parts of the Earth system. Improved cryospheric monitoring and integration of such monitoring is essential to fully assess, predict and adapt to climate variability and change. 1.2 OBSERVING SYSTEMS OF THE CRYOSPHERE WMO, in cooperation with other national and international bodies and organizations, and using its global observing and telecommunication capability, is in a position to provide an integrated, authoritative, continuing assessment of the cryosphere – the Global Cryosphere Watch (GCW). The GCW surface observation network is considered as the cryospheric component of the WMO Integrated Global Observing System (WIGOS), contributing to the Global Climate Observing System (GCOS) and the Global Earth Observation System of Systems (GEOSS). The Global Cryosphere Watch facilitates the establishment of high-latitude and alpine stations with co-located measurements of key variables, especially permafrost and snow cover, thus enhancing GCOS and Global Terrestrial Observing System (GTOS) networks for permafrost, glaciers and hydrology. 1.3 GENERAL SITING AND EXPOSURE REQUIREMENTS FOR A STATION MEASURING CRYOSPHERIC VARIABLES The characteristics of the measurement site should be captured in the station metadata. Important siting details include, but may not be limited to, surface type (mineral soil or organic layers, vegetation type, ice, etc.), prevailing wind direction, site layout and exposure to both wind and solar radiation. The measurement area should be representative of the surrounding landscape. At alpine stations, measurements on areas with higher exposure than the surrounding landscape should be avoided to guard against unrepresentative measurements. Finally, siting should take into consideration accessibility and permanence, which will ultimately impact the continuity of the record. For automated measurements, the source of available power and communications may also be a consideration for siting. 1.4 MEASUREMENT STANDARDS AND BEST PRACTICES To ensure high quality and consistent observations, measurements of cryospheric variables at GCW stations will be made in accordance with accepted standards. Many measurement standards have been compiled by GCW and other networks, though the compilation is not exhaustive for several cryospheric measurements. An initial inventory of existing documents describing measurement practices, or in some cases best practices for processing the observations, can be found on the GCW website. 2 GUIDE TO INSTRUMENTS AND METHODS OF OBSERVATION - VOLUME II Some cryosphere networks have their own standards. It will be a major effort for GCW to establish standards in agreement