Extended Abstract (1.1M)P3.22
Development of a regional climate model (BCC_RegCM) and its simulation and hindcast over different regions
Yiming Liu, Beijing Climate Center, China Meteorological Administration, Beijing, China; and Y. Ding, J. C. L. Chan, and S. Saeed
The regional climate model of Beijing Climate Center (hereafter the BCC_RegCM) has been developed to study the Asian summer monsoon. This study presents the development of the BCC_RegCM and the analyses of a 10-year simulations and hindcasts (1991-2000) over different regions, such as South China (SC) and Pakistan.
Over South China, the model was initialized at April 1 and integrated up to the end of June for the ten years. The horizontal resolution is 60km. For the 10-year simulation experiments the initial atmospheric conditions and lateral boundary data used are from the European Centre for Medium-range Weather Forecasts “40-year” reanalyses. The BCC_RegCM can reproduce well the main features of the monsoon circulation and vertical structure of the atmosphere. The BCC_RegCM can simulate the intensification and northwestward displacement of the South Asian upper anticyclone from May to June, as well as the low-level moisture transport from the Bay of Bengal to the SC. In the simulation, the average South China Sea (SCS) summer monsoon onset occurs in the fourth pentad of May, which is consistent with the results from previous observational research. In addition, the BCC_RegCM can reproduce the main characteristics of the onset such as the change of the low-level zonal flow from easterly to westerly as well as the rapid increase in daily precipitation. The SC and SCS precipitation anomalies have the correct sign in almost all the years. The shortcomings of the model simulation include an under-prediction of the strength of the subtropical high over the northwest Pacific and the moisture transport from the Bay of Bengal to the Indochina Peninsula (IC) and SCS.
10-year hindcast experiments of the summer monsoon over Pakistan have been done by using the BCC_CGCM1.0 nested BCC_RegCM. The BCC_CGCM1.0 is established in open oceanic surface based on global atmospheric circulation model T63L30 AGCM_1.0 and global ocean circulation model T63L30 OGCM_1.0 through Daily Flux Anomaly coupling scheme exchange. The BCC_RegCM was initialized at May 1 and integrated up to the end of September for the ten years. The horizontal resolution is 50km. Three kinds of convective parameterization schemes (Kuo, Grell and Mass Flux Scheme) have been compared in this hindcast experiments. The regional climate model realistically hindcasts the interannual variability of the precipitation over Pakistan. Kuo overestimated the precipitation in almost all cases. BIAS in the Kuo hindcast of precipitation was found much higher than the other two schemes over Pakistan. The upper air patterns such as geopotential heights at 850hPa, 500hPa and 250hPa are well hindcasted by the Kuo scheme. The Mass flux and Grell Scheme reproduced very low heights compared to observed heights. Grell Scheme hindcasted very poorly the precipitation and underestimated the precipitation over Pakistan in all cases. The Mass Flux Scheme reasonably hindcasted the seasonal precipitation over Pakistan and the BIAS in the simulations is minimum compared to all other schemes. The minimum precipitation BIAS in the Mass Flux Scheme was found in the month of July and August. The ensemble results of precipitation and minimum temperature are found better over the South Pakistan. The over all performance of the model simulations with Mass Flux Scheme was found very encouraging over Pakistan.
Poster Session 3, Climate Model and Prediction Poster Session
Wednesday, 23 January 2008, 2:30 PM-4:00 PM, Exhibit Hall B
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