A variable‐resolution stretched‐grid general circulation model and data assimilation system with multiple areas of interest: Studying the anomalous regional climate events of 1998

[1] The new stretched-grid (SG) design with multiple (four) areas of interest, one at each global quadrant, is implemented into both a SG general circulation model (GCM) and a SG data assimilation system (DAS). The four areas of interest include the United States/northern Mexico, the El Nino area/central South America, India/China, and the eastern Indian Ocean/Australia. Both SG-GCM and SG-DAS annual (November 1997 to December 1998) integrations are performed with 50-km regional resolution. The efficient regional downscaling to mesoscales is obtained for each of the four areas of interest, while the consistent interactions between regional and global scales and the high quality of global circulation are preserved. This is the advantage of the SG approach. The global variable-resolution DAS incorporating the SG-GCM has been developed and tested as an efficient tool for producing regional analyses and diagnostics with enhanced mesoscale resolution. The anomalous regional climate events of 1998 that occurred over the United States, Mexico, South America, China, India, African Sahel, and Australia are investigated in both simulation and data assimilation modes. The assimilated products are also used, along with gauge precipitation data, for validating the simulation results. The obtained results show that the SG-GCM and SG-DAS are capable of producing realistic high-quality simulated and assimilated products at mesoscale resolution for regional climate studies and applications.

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