Solid precipitation is one of the more complex atmospheric variables to be observed and measured by automatic sensors and systems. Since the WMO Solid Precipitation Measurement Inter-comparison of 1989-1993 (WMO CIMO IOM Report No. 67, WMO/TD-No. 872, 1998), significant advancements have been made in developing automatic instruments for measuring solid precipitation and snow on the ground. New non-catchment type techniques are increasingly used operationally for measuring solid precipitation, e.g. light scattering, microwave backscatter, mass and heat transfer. In parallel, the traditional techniques, tipping bucket and weighing type gauges, have new features (heating, temperature compensation, software corrections), which further diversify the range of data obtain with such instruments. New and emerging applications (e.g., climate change, nowcasting, water supply budgets, avalanche forecast and warnings, satellite ground validation, etc.) require precipitation data of increased accuracy and increased temporal and spatial resolution. A large variety of automatic instruments are being used for measuring solid precipitation, worldwide, including within the same country. This variety exceeds by far the existing range of manual standard precipitation gauges (Goodison et al., 1998).

The Solid Precipitation Intercomparison Experiment (WMO SPICE) commenced in 2011, being endorsed at the Sixteenth Congress of the World Meteorological Organization (WMO). SPICE is organized by the Commission for Instruments and Methods of Observation (CIMO) of WMO. Building on the results and recommendations of previous studies and intercomparisons, the mission of SPICE is to investigate and report the measurement and reporting of:

a) Precipitation amount, over various time periods (minutes, hours, days, season), as a function of the precipitation phase, with a focus on solid precipitation;

b) Snow on the ground (snow depth); as snow depth measurements are closely tied to snowfall measurements, the intercomparison will investigate the linkages between them.

The SPICE experiments are organized as simultaneous field tests in a range of climate conditions, over several winter seasons, in the Northern and Southern hemispheres, which have started in December 2012, and continuing until the end of the winter season 2015.

The Inter-Journal WMO SPICE Special Issue invites submissions directly reporting on results obtained within the WMO SPICE project and beyond, including studies relevant to WMO SPICE objectives but carried out independently, and studies focusing on application of WMO SPICE outcomes, such as cold region climate change, snow hydrology, remote sensing of snow cover and snowfall, and land surface modeling over the cold/high latitude regions.