A11F-0107
Evaluation of Northeast United States Winter Storm Impacts in a Suite of High Resolution Downscaled Climate Model Hindcasts
Monday, 14 December 2015
Poster Hall (Moscone South)
Paul C Loikith, Portland State University, Portland, OR, United States, Duane E Waliser, NASA Jet Propulsion Laboratory, Pasadena, CA, United States, Jinwon Kim, University of California Los Angeles, Los Angeles, CA, United States and Robert Ferraro, Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
The ability of a suite of NASA produced high-resolution downscaled climate model simulations to reproduce observed impact characteristics of winter storms over the Northeastern United States is evaluated. Simulations are produced using the NASA-Unified Weather Forecasting and Research (NU-WRF) regional climate model (RCM) and a downscaled version of the GEOS5 global climate model with boundary conditions provided by the second version of NASA’s Modern Era Retrospective-Analysis for Research and Applications (MERRA) reanalysis. The RCM is run at 24, 12, and 4 km horizontal grid resolutions over North America with and without spectral nudging and the GEOS5 run is produced at 12.5 km and nudged to MERRA. Storm impact metrics for model evaluation are based on individual events defined at each grid cell as one or more consecutive days with measureable precipitation. Impact metrics include storm frequency, intensity, duration, and total storm accumulated precipitation. Impact metrics are computed for all storms and separately for storms occurring when the concurrent temperature is below freezing, to gauge the ability of the models to simulate realistic partitioning of frozen and liquid precipitation in the storm climatology. Preliminary results suggest that all simulations capture the key geospatial features of the storm impact metrics at all grid resolutions and for both nudged and non-nudged runs. However, the RCMs have an overall systematic high bias in storm frequency, intensity, duration, and total precipitation. Some improvement in model skill is apparent in the nudged simulations over the non-nudged simulations, however such improvements are small. While higher resolution is able to capture more detail, including orographic effects on precipitation type and intensity, it is not clear whether higher resolution necessarily leads to improved simulation of Northeastern US winter storm impacts.
