397767 - Evaluation of dynamically downscaled historical precipitation in Western Oregon based on three reanalysis datasets
Tuesday, June 5
10:30 AM - 12:00 PM
Location: Lake Superior B
Yoshihiko Iseri, 1 Shields Ave, Davis, CA – University of California Davis; Levent Kavvas, 1 Shield Ave, Davis, CA – University of California, Davis; Angela Duren, 333 SW 1st Ave Portland, OR 97204 – US Army Corps Of Engineers; John England, 12596 West Bayaud Ave, Suite 400 Lakewood, CO 80228 – U.S. Army Corps of Engineers
Dynamically downscaled precipitation is often used for evaluating sub-daily precipitation behavior on a watershed-scale and for the input to hydrological modeling because of its increasing accuracy and spatiotemporal resolution. Despite these advantages, systematic biases due to the dataset used for boundary conditions and physical parameterizations in regional models greatly influence the quality of downscaled precipitation dataset. In this study, the Weather Research and Forecasting (WRF) model is employed to obtain dynamically downscaled precipitation data over the Willamette watershed in Oregon. The goal of this study is to evaluate systematic biases and behaviors of dynamically downscaled precipitation using different boundary condition datasets and physics parameterizations. Three reanalysis datasets (20th Century Reanalysis V2c (20CRV2c), ECMWF twentieth century reanalysis (ERA-20C), and Climate Forecast System Reanalysis (CFSR)) which have different spatial and temporal resolutions are used to reconstruct historical precipitation at 4 km resolution. The physics options in the WRF model are optimized based on the Parameter-elevation Regressions on Independent Slopes Model (PRISM) dataset for each reanalysis dataset. The time series of basin-average precipitation over the target watershed (~7,000 sq mi) as well as the spatial distributions of precipitation during major winter storm events (7 to 60 day duration) are analyzed and compared between the three reanalysis datasets. Since the 20CRV2c dataset allows to reconstruct historical precipitation from 1851, trends of precipitation over the Willamette watershed for 165 years are also investigated.