Associations between spatially autocorrelated patterns of SSM/I-derived prairie snow cover and atmospheric circulation

Passive-microwave derived observations of snow cover show potential to prov ide synoptically sensitive, and hydrologically and climatologically signifi cant, information because of all-weather imaging capabilities, rapid scene revisit time and the ability to derive quantitative estimates of snow water equivalent (SWE). In this study, we seek to identify the dominant patterns of clustering in SWE imagery using the Getis statistic, a local indicator of spatial association, The SWE data were derived from five day-averaged Sp ecial Sensor Microwave/Imager (SSM/I) brightness temperatures using the Can adian Atmospheric Environment Service dual channel algorithm. The analysed data span one winter season (December-February 1988-1989) and are limited t o a ground-validated prairie scene. National Center for Environmental Predi ction (NCEP) gridded atmospheric data (500 mb geopotential height; 700 mb t emperature) were incorporated into the study to investigate whether the spa tial orientation of the Getis statistic clusters provides information on in teraction between snow cover and the atmosphere. Results show that the dire ction of atmospheric airflow as expressed by the 500 mb geopotential height field corresponds strongly to the orientation of surface snow cover cluste rs with no time lag, The 700 mb temperature field is also a controlling inf luence on the snow cover clusters both through modifying cluster orientatio n and reinforcing cluster magnitude, (C) 1998 John Wiley & Sons, Ltd.