中国冬季降水主导模态的时空特征及其与Enso的关系

The Temporal and Spatial Characteristics of the Leading Mode of Winter Precipitation in China and Its Relationship with ENSO

摘要: 文章利用NCEP逐月资料、ERSST海温资料和中国160站逐月降水资料，分析了中国冬季降水主模态的时空特征、环流背景及其与ENSO的关系。结论如下：中国冬季降水的主要模态为全国一致的正异常，大值区集中在珠三角地区，对应的时间序列显示冬季降水的振幅在20世纪70年代中期以后变大。与中国冬季降水PC1相关的海温显示，赤道太平洋东岸海温呈现出与ENSO成熟期异常相似的分布。厄尔尼诺事件发生时，海平面气压场表现为欧亚大陆高压强度偏弱，西伯利亚高压强度偏弱，东亚冬季风偏弱。850 hPa风场表现为热带西北太平洋低层出现异常反气旋，西侧的西南风气流源源不断地将来自热带海域的暖湿气流输送到我国，有利于我国冬季降水主模态的正位相，即南方地区降水偏多，拉尼娜事件背景下则相反。ENSO对中国冬季降水主模态的影响存在明显的年代际变化，在20世纪60年代末之前和90年代中期之后，ENSO对中国冬季降水有显著影响，但在中期影响并不显著。合成分析发现，ENSO对中国冬季降水影响的年代际不稳定性可能与热带北印度洋、西北太平洋的调制有关，当这些海区SST偏暖(冷)时，ENSO的影响更为显著(不显著)。

Abstract: Based on the monthly data of NCEP, the data of ERSST sea temperature and the monthly precipitation data of 160 stations in China, this paper analyzes the temporal and spatial characteristics of the main mode of winter precipitation in China, the circulation background and its relationship with ENSO. The conclusions are as follows: The main mode of winter precipitation in China is a consistent positive anomaly in the country, and the large-value area is concentrated in the Pearl River Delta region, and the corresponding time series showed the amplitude of precipitation in winter became larger after the mid-1970s. The SST associated with winter precipitation PC1 in China shows that the SST on the eastern coast of the equatorial Pacific presents a similar distribution to the abnormality of the ENSO mature period. When the El Niño event occurred, the sea level pressure field showed that the Eurasia high-pressure intensity was weak, the Siberian high-pressure intensity was weak, and the East Asian winter wind was weak. The 850 hPa wind field showed an abnormal anticyclone in the lower part of the tropical northwestern Pacific, and the southwesterly flow on the west side was continuous. The warm and humid air from the tropical sea is transported to China, which is beneficial to the positive phase of the main mode of winter precipitation in China. That is, the precipitation in the southern region is more than that in the southern region, and the opposite is true in the background of the La Niña event. Further research shows that the influence of ENSO on the main mode of winter precipitation in China has obvious interdecadal variations. Before the end of the 1960s and after the mid-1990s, ENSO had a significant impact on winter precipitation in China, but in the middle period, the impact was not significant. The synthetic analysis found that the interdecadal instability of ENSO’s influence on winter precipitation in China may be related to the modulation of the Tropical North Indian Ocean, Pacific Northwest. When the SST of these sea areas is warmer (cold), the impact of ENSO is more significant (not significant).