Winter season variability in North American Prairie SWE distribution and atmospheric circulation

Passive-microwave derived observations of snow cover show potential to prov ide synoptically sensitive hydrologically and climatologically significant information because of all-weather imaging capabilities, rapid scene revisi t time, and the ability to derive quantitative estimates of snow water equi valent (SWE). In this study, 10 winter seasons (December, January, February 1988/89 to 1997/98) of five day averaged (pentad) passive-microwave derive d SWE imagery are utilized to examine the seasonal snow cover characteristi cs of a ground-validated North American Prairie study area. Principal compo nents analysis (PCA) is used to identify the dominant spatial patterns thro ugh time for three passive-microwave derived datasets: (1) pentad SWE, (2) pentad SWE anomalies based on the 10 season mean and standard deviation, an d (3) change-in-pentad SWE (Delta SWE) calculated by subtracting each SWE p attern from the previous. Interpretation of the component loading patterns indicates that the Delta SWE time series is best suited for the climatologi cal application of identifying associations between snow cover and atmosphe ric circulation. Two dominant patterns are identified within the Delta SWE time series: the positive (negative) phase of principal component 1 capture s a pattern of widespread SWE ablation (accumulation) in the south with acc umulation (ablation) to the north. The positive (negative) phase of princip al component two characterizes a meridional accumulation (ablation) zone or iented from the northwest to southeast of the study area. The National Cent er for Environmental Prediction (NCEP) gridded atmospheric data (500 mb geo potential height; 700 mb temperature) are investigated in conjunction with the first two Delta SWE principal components to identify whether consistenc y exists in the atmospheric patterns associated, at no time lag, with these dominant Delta SWE modes. An investigation of composite and anomaly atmosp heric fields illustrates that unique and consistent atmospheric circulation patterns are linked to the SWE components. Copyright (C) 2000 John Wiley & Sons, Ltd.