The migration from human to automatic observations has introduced new challenges with respect to the quality, consistency, compatibility, and representativeness of hydro-meteorological measurements. The measurement of precipitation (rain, mixed, freezing rain, snow grains, snow, ice crystals, ice pallets, hail, etc) at auto stations has unique challenges that significantly affect the ability to acquire accurate measurements over the expected range of conditions and timescales.

Although precipitation measurement, in general, has been the subject of a multitude of studies, there has been limited coordinated assessment of the ability and reliability of automatic sensors to accurately measure solid precipitation.

With the objective of determining the nature and extent of automation of solid precipitation measurements, the 14th session of the WMO Commission for Instruments and Methods of Observation (CIMO), has tasked the Expert Team on Surface-Based Instrument Intercomparisons and Calibration Methods (ET-SBII&CM), to assess the needs and methods of measurement and observation of solid precipitation at automatic stations.

The presentation will include the preliminary results on the national summaries of methods, instruments and associated metadata for the automatic measurement of precipitation, solid precipitation in particular. The compilation of these results will facilitate a better understanding of the global configuration of precipitation measurement and lead to concrete steps to identifying and addressing gaps.

The goal of the CIMO initiative is to assess the need for an intercomparison of methods and equipment for automatic snowfall/snow depth/precipitation measurements, and develop the intercomparison plan.