积云对流参数化方案对东亚夏季环流和降水模拟的影响

利用WRF（Weather Research and Forecasting）模式对东亚夏季区域气候模拟中最常选用的两种积云对流参数化方案进行对比分析，研究积云对流参数化方案选用对大尺度环流模拟的影响。结果表明:Kain-Fritsch（KF）方案对西太平洋副热带高压（简称副高）及环流的模拟效果较好，虽然KF方案模拟降水偏多，但是时空分布与TRMM降水分布接近；Grell-Freitas（GF）方案对流加热率过大，从而模拟的南海—菲律宾区域对流异常增强，在南海—菲律宾洋面上的垂直输送异常增大，非绝热加热的范围偏大，导致副高南侧下沉区辐散减弱，抑制了副高北抬西伸，进而影响到水汽输送和季风环流，最终对东亚夏季降水的模拟产生不利影响。修改GF方案对流加热率和干燥率的敏感性试验表明，减小对流加热率和干燥率参数能有效抑制南海—菲律宾区域过强的对流，东亚大尺度环流的模拟得到明显改进。

Impacts of Cumulus Convective Parameterization Schemes on Simulation of East Asian Summer Circulation and Rainfall

Two experiments have been conducted using WRF (Weather Research and Forecasting) model with different cumulus convective parameterization schemes in this paper. It is found that the model with the Kain-Fritsch (KF) scheme performs well for the simulation of summertime large scale circulation over East Asia, and the evolution/withdrawal of the rain belt and the spatial pattern are close to that retrieved from TRMM, although precipitation is overestimated in the simulation. With the Grell-Freitas (GF) scheme, however, there exist obvious biases in the simulation of precipitation and circulation. The possible reason for these biases is that the convective heating rate is overestimated with the GF scheme,which results in abnormally strong convection in the South China Sea-Philippine area and the diabatic heating is overestimated. As a result, the divergence on the southern side of the western Pacific subtropical high is weakened, which may inhibit the northward and westward extension of the subtropical high and influence water vapor transport and monsoon circulation as well as the summer climate in East Asia. It is also found that the simulation of large scale circulation can be improved in the sensitivity experiment by decreasing the convective heating rate and drying rate in the GF scheme.