Hemispheric Snow Cover and Surface Albedo for Model Validation

Abstract

Accurate information concerning snow cover, and associated impacts of snow on regional surface albedo, needs to be available for empirical studies and for the validation of climate models. Here, a new integrated dataset for Northern Hemisphere lands is discussed, including files of visible and microwave satellite-derived snow estimates and in situ station data. These files will be used to examine snow extent, snow depth and surface albedo over five-day intervals, and have been generated using geographic-information system techniques. Visible and station observations extend from 1972 to present, and microwave estimates from 1979 to present, The 1×1° gridded files permit the strengths and weaknesses of the individual data sources to be identified and quantified. Also included is a hemispheric time series of snow extern derived from the visible satellite file. Of note are the two pronounced regimes of Northern Hemisphere extent during the past several decades. Between 1972 and 1985, 12 month running means of snow extent fluctuated around a mean of 25.9 × 10 km2. An abrupt transition occurred in 1986 and 1987, and since then mean annual extern has been 24.2 × 106km2. Recent decreases are found from late winter to early summer.