87th AMS Annual Meeting

Tuesday, 16 January 2007
Snow cover assessment and updating for denied areas using AVHRR and SSM/I
Exhibit Hall C (Henry B. Gonzalez Convention Center)
Steven F. Daly, U.S. Army Corps of Engineers, Hanover, NH; and E. Ochs, S. Newman, J. Hardy, C. Vuyovich, J. Gagnon, and B. Tracy
We prepared regular assessments on the snow conditions in Eastern Turkey and Afghanistan using AVHRR and SSM/I satellite imagery. The AVHRR imagery was analyzed to produce snow covered area (SCA) maps with pixel sizes of 1.0 km. Our processing and algorithms resulted in maps of the observed SCA. The image processing involved a number of steps including geo-registration; spectral un-mixing, cloud masking, snow detection, and final pixel-by-pixel determination of SCA. We analyzed the maps to provide information on the elevation distribution of SCA throughout selected watersheds. The SSM/I imagery was analyzed to produce estimates of the total snow water equivalent (SWE) of selected watersheds. Each SSM/I sample measures passive microwave radiation for an areal pixel size of about 25 km2. The SSM/I data extends from the winter of 1987-88 through the present. The historical SWE information was processed for each watershed to develop charts of the average SWE and extremes throughout the winter season. Each assessment of SWE was placed into this historical context, allowing users to quickly make an “above average” or “below average” determination and compare the current SWE to the previous year.

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