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

Abstract

Passive-microwave derived observations of snow cover show potential to provide synoptically sensitive hydrologically and climatologically significant 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, 10 winter seasons (December, January, February 1988/89 to 1997/98) of five day averaged (pentad) passive-microwave derived SWE imagery are utilized to examine the seasonal snow cover characteristics of a ground-validated North American Prairie study area. Principal components analysis (PCA) is used to identify the dominant spatial patterns through time for three passive-microwave derived datasets: (1) pentad SWE, (2) pentad SWE anomalies based on the 10 season mean and standard deviation, and (3) change-in-pentad SWE (ΔSWE) calculated by subtracting each SWE pattern from the previous Interpretation of the component loading patterns indicates that the ΔSWE time series is best suited for the climatological application of identifying associations between snow cover and atmospheric circulation. Two dominant patterns are identified within the ASWE time series: the positive (negative) phase of principal component 1 captures a pattern of widespread SWE ablation (accumulation) in the south with accumulation (ablation) to the north. The positive (negative) phase of principal component two characterizes a meridional accumulation (ablation) zone oriented from the northwest to southeast of the study area. The National Center for Environmental Prediction (NCEP) gridded atmospheric data (500 mb geopotential height; 700 mb temperature) are investigated in conjunction with the first two ASWE principal components to identify whether consistency exists in the atmospheric patterns associated, at no time lag, with these dominant ASWE modes. An investigation of composite and anomaly atmospheric fields illustrates that unique and consistent atmospheric circulation patterns are linked to the SWE components.