Regional hydroclimate has major impacts on the available water resources, frequency of natural disasters such as flood, and the health of local ecosystems. Increasing populations and industrial activities in the region expands urban areas into steep hillsides and flood planes which, in turn, expose more populations and properties to natural hazards. Climate of the western U.S. is characterized by extreme contrasts in seasonal precipitation and strong orographic effects on precipitation and snow budget. Extreme seasonal bias in precipitation makes it important to efficiently maintain and operate water storage facilities. Complex terrain causes local heavy precipitation and rapid streamflow response that can cause severe flood damage. Long-term climate change may affect the timing of snow melt which directly affects summertime water supply and snowmelt-driven spring floods in mountainous areas. Therefore, accurate assessments and predictions of hydroclimate are crucial for improving water resources management, reduction of flood damages, and planning for sustainable developments.
We will investigate a fine-scale climate change scenario using a nested modeling method in which MAS-SPS model downscales a global scenario for todays climate and 2xCO2 climate projected from HadCM2. We will compare the downscaled HadCM2 results with an existing multi-year regional hindcast and climate change scenario based on the NCEP Reanalysis and SIM method, respectively. This investigation is focused on the shifts in precipitation amounts, rainfall-snowfall partitioning, snowmelt timing. Implications of the projected climate change on stream flow, flood frequency, and water resources in the western U.S. will be presented in a companion paper.
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