汛期我国主要雨季进程成因及预测应用进展

汛期内我国中东部地区的雨季是东亚夏季风推进过程中的重要产物，主要包括华南前汛期、梅雨、华北雨季和华西秋雨等，各地雨季决定了我国中东部地区汛期的旱涝布局和旱涝演变，是我国汛期预测和服务的重点。该文回顾了4个雨季特征及影响因子方面的研究进展，在此基础上梳理物理概念预测模型。研究显示:海温异常是影响各区域雨季的重要先兆信号，但不同雨季的年际和年代际变化特征不同，海温作为外强迫信号的影响程度和时空形式也有差异。利用热带太平洋东西海温差指标能更好地解释华南前汛期降水的年际变化。而与梅雨的年际变化分量相关联的海温关键区主要分布于热带，与年代际或多年代际变化分量相联系的海温关键区则来自中高纬度。华北雨季降水的强弱不仅与ENSO循环的位相有关，更多受到ENSO演变速率的影响。而影响华西秋雨的海温关键区随着年代际背景的变化发生了改变，需要重新诊断和建模。

Advances of Research and Application on Major Rainy Seasons in China

The pre-rainy season in South China, Meiyu, rainy season in North China and autumn rainfall in West China are important phenomena influenced by the process of the East Asian summer monsoon (EASM). These regional rainy seasons determine the distribution and evolution of drought and flood during the flood season over mid-eastern China. Therefore, the prediction of regional rainy seasons plays an important role in the meteorological service of flood season.
The research progress on characteristics and influencing factors of major rainy seasons during flood season in China are reviewed. In order to meet the demand of prediction operation, the influence and mechanism of the previous sea surface temperature (SST) and related atmosphere circulation systems on climatic events are analyzed firstly, and the statistical prediction models can be established based on that.
Recent studies show that SST anomalies (SSTAs) are important forecast signals of rainy seasons. However, the influence and spatial-temporal pattern of SST vary with the interannual and interdecadal variation characteristics of different events. For instance, the interannual variation of precipitation in the pre-rainy season in South China can be better explained using the east-west SST contrast index in the tropical Pacific. Multiple timescale variation characteristics of Meiyu over the Yangtze River correspond to different SST forcing. Key regions of SST associated with interannual variation of Meiyu over the Yangtze River are in tropics. For the interdecadal or mutli-decadal time scale of Meiyu variations, the SST in middle and high latitudes may play an important role. The intensity of rainy-season precipitation in North China is not only coincident with the ENSO phase-switching, but also influenced by the developing speed of ENSO event. The key SST region that influences autumn rain in West China has changed with the inter-decadal changing background, which requires updating impact factors and models.
These results provide strong support for the real-time prediction of climate events in recent years. During 2015-2018, the prediction accuracy of the onset date and intensity (rainfall) of Meiyu and rainy season in North China is 75% and 81%, respectively.