World Meteorological Organization Working together in weather, climate and water Snowfall Measurement Challenges WMO SPICE Solid Precipitation Intercomparison Experiment WMO; Commission for Instruments and Methods of Observationwww.wmo.int WMO

Snow vs. rain measurement 2 Jan 28-29, 2009: snow event T max = deg C Weighing Gauges Heated Tipping Buckets Optical System Feb 11-12, 2009: rain event T min = 6.8 deg C Results: CARE (Canada) Snowfall measurements are confounded by many factors (shield, gauge, heating, wind, microphysics, etc.): measuring rainfall is not similar to measuring snowfall;  SPICE focus!

What is SPICE? SPICE, a WMO/CIMO project led by Environment Canada, will contribute to improve automatic in-situ measurements of : Precipitation amount over various time periods (minutes, hours, days, seasons), as a function of precipitation phase (liquid, solid, mixed) Snow on the ground (snow depth) including linkages with snowfall The project will also foster linkages with radar and satellite communities, to enable areal and global estimates. 3

SPICE Objectives Define field references using automatic instruments Characterize currently operational and emerging automatic instruments measuring snow : gauge/shield combination for different collection conditions/climates Derive adjustments to be applied to measurements, as a function of wind, temperature, precipitation type Assess the minimum practicable temporal resolution for reporting a valid snow measurement Configure a comprehensive intercomparison dataset for further data mining (e.g. radar- and/or satellite-based snowfall estimation) 4

SPICE deliverables Recommendations of automatic field reference systems Performance characterization of existing and emerging technologies measuring solid precipitation A comprehensive data set for legacy use Update of relevant chapters of the CIMO Guide (WMO No 8) Guidance to Members on transition to automation Recommendations made to manufacturers on instrument requirements and improvements 5

SPICE key data Official start: October 1 st 2013 Duration : Two winter seasons (Report on the Field Reference System in 2014, Final Report in 2016) Number of participating sites : 20, ranging from 100 to 5’000 m asl over 15 countries Number of participating instrument providers : > 20 Total number of instruments : approx. 400 instruments from 30 different models 6

Need for references 7

Participating instruments Catchment type: Weighing gauges, tipping buckets Instrument type : Optical sensors, particle disdrometers, hot plates, snow depth sensors (GPS, acoustic, laser), snow water equivalent sensors Wind shield type: Alter, Tretyakov, Belfort, wood Shield configuration type : single, double, small wooden 8

Jan 28, 20139

10 Centre for Atmospheric Research and Experiments (CARE) Environment Canada, 251 m asl

11 Weissfluhjoch (Davos), MeteoSwiss and Swiss Institute for Snow and Avalanche Research (SLF), 2500 m asl

Opportunities for Collaboration WMO Working Group for Forecast Verification: engaged in the analysis and interpretation of the results WMO Commission for Climatology NASA Global Precipitation Mission (GPM) – Ground Validation: – Canadian SPICE sites – Sodankyla (Finland) Global Cryosphere Watch (GCW) Demonstration Project: impact of automation on the measurement of solid precipitation 12

Jan 28, Project leader: Rodica Nitu, Environment Canada,