Shanghai experienced the longest rainy days in 2018/2019 winter since 1988. The physical cause of such an unusual climate condition was investigated through the diagnosis of observational data. From a seasonal perspec...Shanghai experienced the longest rainy days in 2018/2019 winter since 1988. The physical cause of such an unusual climate condition was investigated through the diagnosis of observational data. From a seasonal perspective, a long persistent rainy winter was often associated with an El Ni?o condition in the equatorial Pacific. This abnormal oceanic condition induces a remote teleconnection pattern with pronounced low-level southerly anomalies over East China.The wind anomalies transported moisture from tropical oceans and caused persistent rainfall in East Asia. Meanwhile, the local rainfall time series exhibited a strong quasi-biweekly oscillation (QBWO). Three persistent rainy events were identified in the 2018/2019 winter and they all occurred during the active phase of the QBWO. The first two events were associated with a low pressure anomaly west of Shanghai. Southerly anomalies associated with the low pressure system advected high mean moisture into central eastern China, leading to the persistent rainfall there.The third event was associated with a high pressure anomaly in lower troposphere to the east of Shanghai, which induced anomalous southerlies to its west, favoring the occurrence of rainfall in Shanghai. The result suggests the importance of high-frequency variability in affecting seasonal rainfall anomalies.展开更多
基金Supported by the National Key Research and Development Program of China(2018YFC1505806)US NOAA(NA18OAR4310298)+4 种基金US NSF(AGS-1643297)National Natural Science Foundation of China(41875069,41575052,and 41575043)University of Hawaii SOEST(10867)IPRC(1418)National Key Research and Development Program of China Health Risk Assessment Program(2018YFA0606203)。
文摘Shanghai experienced the longest rainy days in 2018/2019 winter since 1988. The physical cause of such an unusual climate condition was investigated through the diagnosis of observational data. From a seasonal perspective, a long persistent rainy winter was often associated with an El Ni?o condition in the equatorial Pacific. This abnormal oceanic condition induces a remote teleconnection pattern with pronounced low-level southerly anomalies over East China.The wind anomalies transported moisture from tropical oceans and caused persistent rainfall in East Asia. Meanwhile, the local rainfall time series exhibited a strong quasi-biweekly oscillation (QBWO). Three persistent rainy events were identified in the 2018/2019 winter and they all occurred during the active phase of the QBWO. The first two events were associated with a low pressure anomaly west of Shanghai. Southerly anomalies associated with the low pressure system advected high mean moisture into central eastern China, leading to the persistent rainfall there.The third event was associated with a high pressure anomaly in lower troposphere to the east of Shanghai, which induced anomalous southerlies to its west, favoring the occurrence of rainfall in Shanghai. The result suggests the importance of high-frequency variability in affecting seasonal rainfall anomalies.
