Impacts of Winter and Spring Snow Anomalies over the Tibetan Plateau on Summer Precipitation Frequency and Intensity in Eastern China

Based on various atmospheric reanalyses and precipitations, as well as the winter and spring snow data over the Tibetan Plateau obtained using gauged stations and satellites, this study first compares and validates the consistency of changes in different snow data sets on the interannual scale. Then, the impact of winter and spring snow anomalies on the frequency and intensity of summer precipitation over eastern China are further explored. Moreover, combined with the atmospheric physical diagnosis and numerical simulation, the possible causes of spatial differences in the impact of snow anomalies on summer precipitation in China are investigated.

The results of this study show the following: (1) The variation in the snow depth observed by gauged stations is consistent with that derived from the satellite data on the interannual variation scale. (2) The impact of Plateau snow anomalies on the frequency and intensity of summer precipitation in China exhibit significant spatial differences. During heavier snow during winter and spring in the Tibetan Plateau, the frequency of summer precipitation increases significantly in North China, the middle and lower reaches of the Yangtze River, and Northeast China. In contrast, the increase in the rainfall frequency in North China is mainly dominated by moderate and light rain in contrast with the increase in the heavy rain frequency in the middle and lower reaches of the Yangtze River. (3) In the years with heavier snow cover, the heat source over the Tibetan Plateau is weakened, resulting in the “negative–positive–negative” abnormal wave train structure on the 500 hPa potential height, the strengthened and southward westerly jet, and the southward subtropical high ridge. Under the influence of the above circulation background, the anomalous cyclonic circulation in the north of the anomalous anticyclone in the northwestern Pacific enhances the water vapor transport in the middle and lower reaches of the Yangtze River basin. With the strengthened atmospheric vertical movement, the intensity and frequency of heavy precipitation are increased in this region. However, North China is controlled by the circulation structure of the “saddle” field; the occurrence frequency of small precipitation increases significantly, whereas the water vapor transport is weak, and changes in the precipitation intensity are not significant.