Regional climate simulation over eastern China in spring by a variable resolution AGCM

A variable resolution global Atmospheric General Circulation Model LMDZ4 developed at Laboratoire de Météorologie Dynamique is used to simulate the spring climate in eastern Asia during 1958-2000. The model is forced by the ERA40 reanalysis data. The mean climate, interannual variability and interdecadal variability in AprilMay over eastern China simulated by the model are compared with the observation. The model can realistically simulate the climate distribution of the atmospheric circulation, precipitation and surface air temperature. The model has a better capability in reproducing the atmospheric circulation in the middle and upper troposphere than that in the lower troposphere. The model systematically overestimates the rainfall in the central part of eastern China and North China. The simulated biases of surface climate over eastern China show that it is in the warmer and wetter sides in the central and eastern parts of China and South China, whereas in the colder and wetter sides in North China. The simulated rainfall in central and eastern China is larger than the observation by about 1.6 mm/d. The simulated surface air temperature is lower than the observation by about 1.4℃ in North China, and higher than the observation by over 0.5℃ in central and eastern China and South China. Such biases are related to the stronger lowlevel southwest flow in South China and stronger northwest flow in North China. The model well simulated the interannual variability of the atmospheric circulation in the troposphere, especially in the middle and upper troposphere. The correlation coefficients of the variables are all above 0.6. The model well reproduced the interannual variability of the precipitation and surface air temperature in East China. The correlations between the simulation and the observation are all larger than 0.7 in North China, central and eastern China and South China. The analysis about the decadal change of the late spring climate shows that the model reproduced the interdecadal drought in central and eastern China and the interdecadal increase of the precipitation in northeastern China occurred in the late 1970s. The model also reproduced the interdecadal warming in the Huanghuai Basin. So the regional climate simulation over East Asia by this model is not only able to reproduce the mean climate status in spring, but also has a good capability in simulating the interannual and interdecadal variability of the spring climate in eastern China.