MRI GCM-IIによるアジアの夏季モンスーンのシミュレーションに対する水平解像度の効果

The MRI atmospheric general circulation model has been used to study the effect of horizontal resolution on the simulation of Asian summer monsoon. The model has been integrated for an eight year period with three different horizontal resolutions designated as Low (4°lat X 5°long), Medium (3°lat X 3.3°long) and High (2°lat X 2.5°long), respectively. The results indicate that the increase of horizontal resolution improved the simulation of mean sea level pressure and precipitation patterns. The high resolution model simulates a heat low and monsoon trough in agreement with the observations, while the low resolution model simulates an abnormal heat low over north India. The high resolution model simulates the precipitation maxima over the Bay of Bengal and the south Indian ocean, and a dry region over the Tarim basin better, while the low resolution model better simulates the precipitation maximum over the Arabian sea. All the models simulate weaker monsoon circulation while the increase of horizontal resolution leads to further weakening of low level monsoon westerlies. The results of this study conclude that the increase of horizontal resolution improved the simulation of many observed features of the Asian summer monsoon circulation, but certain features deteriorated indicating that the model parameterizations may need to be suitably modified.