21st Conference on Climate Variability and Change


Dynamical Downscaling of Short-Term Climate Fluctuations

Ana M. B. Nunes, SIO/Univ. of California, La Jolla, CA

Downscaling climate simulations is a challenging problem due to the broad range of the temporal and spatial scales involved. This diversity of scales, from regional and local forcings (e.g., complex topography and land-use characteristics) to larger scales anomalies such as the El Niņo-Southern Oscillation (ENSO), can synergistically interact to produce regional responses. The coarser-resolution Atmosphere-Ocean Global Circulation Models (AOGCMs) are characterized by high variability in their results for different regions of the world. By contrast, Regional Climate Models (RCMs) have demonstrated consistent improvement in spatial detail in their climate simulations. For instance, RCMs driven by observed boundary conditions (reanalysis) comparatively to free running AOGCMs have demonstrated lower biases. The North American Regional Climate Change Assessment Program (NARCCAP) was established to evaluate several RCM responses to the driven observational forcing and the global projections in order to regionally assess model uncertainties, current and future climate. The Experimental Climate Prediction Center (ECPC)-Regional Spectral Model (RSM) is among the NARCCAP RCMs. The ECPC-RSM climate, together with the analysis of the 1988 drought and 1993 floods will be addressed. The regional solution of these modeled events will then be compared to the regional and global reanalyses in order to evaluate the dynamical downscaling over the central United States, where the large-scale circulations affect the precipitation variability. This study focuses on the subtropical westerly jet positioning and its associated ageostrophic circulations to explain their contributions to these short-term climate fluctuations.

Session 16, Regional modeling - NARCCAP Part II
Thursday, 15 January 2009, 3:30 PM-5:00 PM, Room 129A

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