华南大范围暴雨副热带高压的演变特征及可能机制

Evolution Characteristics and Probability Mechanisms of Sub-Tropical High Pressure during the Wide-Range Rainstorm in South China

利用多时间尺度ＮＣＥＰ／ＮＣＡＲ再分析资料、ＴＢＢ资料，通过合成分析、动力诊断、理论探讨和数值模拟等方法，对华南暴雨发生时副热带高压的短期变异进行了探讨。结果表明，华南暴雨发生前副热带高压有一西伸一东撤的过程，而华南暴雨发生在副高东撤到接近最东时。利用Ｌ９Ｒ１５谱模式模拟了孟加拉湾异常热源对副热带高压西仲的影响，数值模拟结果表明孟加拉湾异常热源可能是副热带高压西伸的可能机制。而正的涡度的局地变化可能是副高东撤的因素。

A probe into the short-term variation of sub-tropical high pressure during the rain- storm happened in South China is made by way of synthetic analysis, dynamic diagnosis, theoreti- cal studying and numerical model, etc., using multi-time scale NCEP/NCAR re-analysis informa- tion and TBB information. The results show that before the rainstorm in South China, the sub- tropical high pressure develops towards west while withdrawing towards the east, and rainstorm happens in South China when the sub-tropical high pressure withdraws to the most east. L9R15 spectrum model is adopted to simulate the effect of Bangladesh Bay abnormal heat sources on the westwards extending of sub-tropical high pressure. The result of numerical simulation shows that the Bangladesh Bay abnormal heat sources may be the probability mechanisms of the westwards extending of sub-tropical high pressure, while the local change of forward vorticity may be the rea- son for the eastwards withdrawal of sub-tropical high pressure.