Analysis of the Baiu Precipitation and Associated Circulations Simulated by the MIROC Coupled Climate System Model
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The major features of Baiu simulated by the climate model (MIROC_Hires) are examined by analyzing the differences between simulations and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data during 1981–2000, focusing on the evaluation of the model performances in reproducing the Baiu precipitation climatology as well as the associated 3-dimensional circulation systems, the relationship with Indian Summer Monsoon (ISM) and the configuration of upper and lower level jets. The results show that the model can reproduce heavy precipitation centers over the Yangtze-Huai River Basin during the Baiu period. The horizontal and vertical structures of the circulation systems during the Baiu period are also well simulated, such as an intensive meridional gradient of moisture and it’s equivalent potential temperature, the strong low-level southwesterly flow in the lower troposphere over East China, the location of the westerly jet in the upper troposphere, the strong ascending motion over heavy rainfall area (HRA) and compensatory descending motion over the northern and southern sides of HRA. However, obvious discrepancies occur in the overestimated precipitation over southeastern China during the Baiu period. In addition, our study suggests that the biases of the ISM and the configuration of upper and lower level jet results in deficiencies in the evolution of Baiu. The simulated onset of ISM is one pentad later than the reanalysis data, while the onset day of simulated Baiu is one pentad later than the reanalysis data, as well. The simulation showed southward shifting of the upper level jet and the stronger, lower level jet. These location and intensity biases essentially favor excess precipitation in southeastern China. Therefore, it is necessary for the coupled model to improve the configuration of upper and lower level jets in simulating the Baiu.
- Journal of the Meteorological Society of Japan. Ser. II
Journal of the Meteorological Society of Japan. Ser. II 89(6), 625-636, 2011
Meteorological Society of Japan