Multi-year simulations of the East Asian monsoon by using the regional climate model(RegCM NCC)
Yihui Ding (1), Qiaoping Li (1), Jin Zhang (1)
(1) National Climate Center, CMA
By using the regional climate model(RegCM-NCC), the East Asian mean circulations during 1998 to 2002 are simulated, and results show that the model can well reproduce the patterns and the intensity as well as seasonal march of the East Asian monsoon. Onset time and intensity of the summer monsoon are well identified, with the simulated onset or retreat time of West Pacific subtropical high, and the intensity and location of South Asia high being consistent with the fact. The spatial distribution and transport of moisture in lower layer are also well simulated. The seasonal variation of regional rainfall and temperature are reproduced in the model, with three northward shift time and intensity of the rain belts over the sub-regions(such as mid-lower Yangtze basins and South China) well corresponding to the observation, but rainfall in North China overestimated.
The simulated seasonal transition and intensity of winter monsoon is closer to the observation. The characters of Siberia cold high and outbreak frequency and main regions of ˇ°cold surgeˇ± over East Asia are also simulated with realistic manner.
However, the simulated summer monsoon is stronger compared with NCEP reanalysis field, with the location of subtropical high being farther to north by 2-3 degrees than normal. Error evaluation shows that there is a discernible systematic bias in the simulated mean circulation pattern, with air temperature bias being positive over the land and negative over the ocean in the lower troposphere in summer. The systematic bias exaggerates the summer temperature difference between the land and ocean, which may be a main responsible factor for the stronger simulated summer monsoon, thus resulting in the overestimated rainfall in North China.