Analysis of two extreme precipitation events and circulation anomalies in Yunnan province in winter of 2015

Abstract

Based on the daily precipitation data from 2 474 stations in China and the National Centers for Environmental Prediction-Department of Energy (NCEP-DOE) daily reanalysis data, the extreme characteristics of two heavy precipitation events in Yunnan in winter of 2015 and the evolution characteristics of circulation anomalies are analyzed, and the relationship between precipitation anomalies and atmospheric low-frequency oscillations is discussed. The results suggest that the South Branch trough, water vapor and the South jet have anomalous characteristics during the two heavy rainfall events. The abnormal intensity of the first event is obviously stronger than that of the second event. The energy dispersion of Rossby waves originating from the North Atlantic in the middle and high latitudes plays an important role in the extreme precipitation in Yunnan province. In addition, the southwest jet in front of the South Branch Trough and the northwest propagation of the Philippine subtropical system are closely related to the extreme precipitation in Yunnan province. The wave action energy propagation direction, the convergence degree and the significant vertical circulation circle of Philippines-south China sea-Indochina peninsula-Yunnan in the first event are more conducive to the enhancement of low-frequency precipitation in Yunnan than those in the second event, which leads to the fact that the range and intensity of the first precipitation event are stronger than that of the second precipitation event.

Keywords

• yunnan
• extreme precipitation
• circulation
• low frequency
• teleconnection wave train