Contemporary Variability, Future Changes and Human Dimensions of Snowpack Water Resources Over the Western United States

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9634329 Serreze A research team combining skills in data analysis, remote sensing, modeling and the human dimensions of global change will conduct an integrated assessment of the variability and sustainability of snowpack water resources over the western United States under contemporary and possible future climate states. Emphasis will be placed on the Colorado and Columbia basins and sub-basins. Contemporary variability will be assessed using blended data sets incorporating daily snow water equivalent (SWE), temperature and precipitation records from SNOTEL (SNOwTELemetry) sites and synoptic reporting stations as well as SWE derived from passive microwave brightness temperatures. In conjunction with National Meteorological Center (NMC) 'reanalysis' atmospheric fields, we will first focus on establishing large-scale and regional relationships between circulation and the seasonal accumulation/melt of the snowpack. This will be followed by analyses of extremes in the observed record and linkages between SWE variability and teleconnection patterns, emphasizing regional responses to El-Nino Southern Oscillation (ENSO) forcings. These investigations will also utilize ensemble forecasts from a version of NMC's Medium Range Forecast (MRF) model, forced by observed and idealized evolutions of sea surface temperature. Our empirical and modeling studies make use of circulation 'downscaling', whereby point or regional variables (e.g., SWE from SNOTEL sites average for sub-basins) are related to circulation through empirical relationships with the frequency/persistence of atmospheric circulation patterns based on principal component analyses. Following studies of contemporary variability, the circulation downscaling transfer functions will be applied to 2xCO2 output from at least two different general circulation models (GCMs). This technique makes the best use of today's GCMs to provide climate change scenarios through use of the large-scale circulation, which the models reproduce fairly well, while avoiding the uncertainties modeled point surface variables. Following diagnostic studies similar to those outlined above, reconstructed daily temperature, SWE and precipitation from the 2xCO2 scenarios will be coupled with a snowmelt runoff model, providing assessment of potential future changes in snowmelt runoff in a series of regional studies. Using information from the above investigations along with other existing data, different systems of water administration in the Colorado and Columbia basins will be examined as they relate to seasonal to international variations in SWE and conditions of global change. The objective is to improve predictions on the time and space scales most relevant to the management of waters resources at urban-rural interfaces and those appropriate to understanding hydrologic variability. These studies will focus on: 1) flexibility of water allocation among users in response to interannual variability and potential changes in water availability and 2) vulnerability of system outputs (agriculture, recreation, power, water quality) to possible extremes of climate variations, sequences of climate events and climate change.