How is the Earth's Snow Cover Responding to a Warming Climate?

The extent and variability of seasonal snow cover are important parameters in climate and hydrologic systems due to effects on energy and moisture budgets. Northern Hemisphere snow cover extent, comprising about 98 percent of global seasonal snow cover, is the largest single spatial component of the cryosphere, with a mean maximum extent of 47 millions square kilometers (nearly 50 percent of the land surface area). During the past four decades much important information on Northern Hemisphere snow extent has been provided by the NOAS weekly snow extent charts derived from visible-bank polar orbiting and geo-stationary satellite imagery. This product is available from NSIDC as the Northern Hemisphere EASE=Grid Weekly Snow Cover and Sea Ice Extent Version 2. Because of the ability to penetrate clouds, provide data during darkness and the potential to provide an index of snow depth or water equivalent, passive microwave satellite remote sensing offers an additional source for hemispheric scale snow monitoring with the availability of a twenty-three year data record (Scanning Multichannel Microwave Radiometer (SMMR) 1978-1987 and Special Sensor Microwave/Imager (SSM/I) 1987-present). However, trend analysis on the passive microwave record is complicated by the change in sensors from the SMMR to SSM/I and by the short overlap period. We present analysis of land surface stable targets as detected by SMMR and SSM/I brightness temperatures during the overlap period to quantify possible discontinuities in sensor observations and derived snow extent and SWE. (Abstract only)