ESRL/PSD Seminar Series

High Resolution Simulation of Seasonal Snowfall over Colorado and some Impacts of Climate Change

Roy Rasmussen


Snowpack is the most important water source in the western U.S., and thus it is critical that water managers be provided with as accurate as possible estimate of the likely changes expected of this resource in the future. Previous climate studies have shown that the head waters region of the Colorado river seems to be a particularly difficult area for climate model to handle, with inconsistent snowpack trends in this region from both the 3rd and 4th IPCC reports (2001, 2007), despite consistent prediction of temperature increases in this region from all climate models. In this study WRF simulations of snowfall between 1 November and 1 May were performed over the Colorado Headwaters region for: (1) retrospective years (2001-02, 2003-04, 2005-06, and 2007-8) at a horizontal grid resolution of 2 km, (2) 2007-08 season at coarser resolution of 6, 18, and 36 km using North American Regional Reanalysis data, and (3) future climate scenario at 2 km grid resolution using NARR data for the retrospective years perturbed with the CCSM3 model output for an A1B simulation conducted for the IPPC report to initialize the simulation. Key questions explored in this study are, (1) will the predicted increase in snowfall due to a warmer, moister climate be enough to offset the enhanced melting and sublimation due to the warmer temperatures, (2) will this be sufficient to maintain river flow at current levels, or is it expected to decrease, and (3) how high resolution of the regional climate model do we need to answer these questions. Results from on-going analysis will be presented.

Tuesday, January 11, 2011

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