NASA Logo, National Aeronautics and Space Administration
LPVS website  banner


small LPV logo

Focus Area on Snow Product Validation

Carrie Vuyovich, NASA Goddard Space Flight Center, USA
Juha Lemmetyinen, Finnish Meteorological Institute, Finland


Snow Product Definitions

WMO definitions of snow cover

NSIDC In general, the accumulation of snow on the ground surface
UNESCO In general, the accumulation of snow on the ground surface, and in particular, the areal extent of snow-covered ground (NSIDC, 2008); term to be preferably used in conjunction with the climatologic relevance of snow on the ground. See also snowpack.
METEOTERM Covering of the ground, either completely or partially, by snow.

These definitions are relevant to a specific user community but are ambiguous for the purpose of validation exercises. In this respect we refine these definitions of snow extent as:

Snow extent (SE) is defined as the unique area of snow covered surfaces projected on the local horizontal datum within a spatial mapping unit at a specified time. Here unique implies that the projected area from two vertically superimposed snow covered surfaces is only counted once. Also expressed as snow cover area or snow cover fraction (fractional snow cover).

Binary snow cover: snow/non-snow.
Snow cover fraction: expressed as a percentage or m2.

WMO definitions of Snow Water Equivalent

UNESCO The depth of water that would result if the mass of snow melted completely.
NOAA Hydrologic Terms The water content obtained from melting accumulated snow.
NSIDC The water content obtained from melting.
NOAA Snow/Ice The water content obtained from melting accumulated snow.

Snow Water Equivalent (SWE) : mm w.e. or kg m-2

Highest Validation Stage Currently Reached for Satellite-Derived Snow Cover Products

Validation stage 1-2 (LPV validation stage hierarchy) - The highest LPV validation stage reached for satellite-derived snow cover products. Limitations to reaching a higher validation stage include a limited number of validation sites, spatial and temporal gaps of in situ reference data coverage.

  • Binary snow cover: LPV Stage 2
  • Fractional snow cover: LPV stage 2
  • Snow water equivalent: LPV stage 1

Validation Good Practices

Snow extent and SWE validation good practices will be compiled on the ESA Satellite Snow product Intercomparison and Evaluation Experiment (SnowPEx). See the SnowPEx documents page.

Snow Cover Validation Reference Data Sets

Open reference data sets are planned to be compiled by SNOWPEX. See the in situ data availability page.

USA: SnowEx, SNOTEL, Airborne snow observatory data hosted at NSIDC 

European Alps: Observed snow depth trends in the European Alps: 1971 to 2019

Global: International Network for Alpine Research Catchment Hydrology (INARCH), Research Basins


NASA Logo -