Evaluation of Extreme Heavy Precipitation in Coupled Ocean-atmosphere General Circulation Models

Based on the surface observation of daily precipitation from 1961 to 1999 in China, the simulation capabilities of 18 coupled ocean-atmosphere general circulation models for extreme heavy precipitation in China are evaluated.The analysis of annual rainy days with different categories precipitation in models shows that the annual rainy days with 1—10 mm daily precipitation in China are overestimated in all of the 18 models.The annual rainy days with 10—25 mm daily precipitation are also overestimated in most areas of China in most of the models and the high value center locates in South China in observation northward to the mid-low reaches of Yangtze River Basin in some models although those models are able to capture the high value centers to some extent.The annual rainy days with 25—50 mm daily precipitation are obviously underestimated especially in the southern China in the models and the locations of high value centers are missed in most of the models.The annual rainy days with daily precipitation greater than 50 mm are also obviously underestimated in all of the models, the days in the models except MIROC3.2(hires) are less than 2 days in south of the Yangtze River.And most models are not able to simulate the right spatial distribution of heavy rain trend in eastern China.The analysis of extreme heavy precipitation in models shows that the thresholds of extreme heavy precipitation are generally underestimated in all of the models; similar increase trend in west part of Northwest China to observation are obtained in about half of the models, and the trend coefficients in some individual model are close to the observation.While opposite linear trend in northeast area and mid-low reaches of the Yangtze River is produced by most of the models, and the " +-+-" spatial mode in Eastern China for the extreme heavy precipitation can not be caught hold by any model; close standard deviations of annual rainy days with extreme heavy precipitation with observation are obtained by most models, which is maybe mainly due to the same analysis method among the observation and the models.In conclusion, it is very necessary to further improve the simulating capabilities of the coupled ocean-atmosphere general circulation models for extreme heavy precipitation.