Circulation characteristics of EP and CP ENSO and their impacts on precipitation in South China

Abstract EP and CP events have different effects on precipitation in South China (SC). In EP El Nino years, the winter precipitation increases and the summer precipitation is distributed in the form of a tri-pole; specifically, it increases in the northeastern and southwestern parts of SC and decreases in the central and northwestern parts. In EP La Nina years, the winter precipitation decreases in the most part of SC and the summer precipitation increases in the central part of SC and decreases in the eastern and southwestern parts. In CP El Nino years, the summer precipitation increases and the winter precipitation increases in the northeastern part of SC and decreases in the southwestern part. In CP La Nina years, the winter precipitation generally decreases and the summer precipitation decreases in the western and southeastern parts of SC but increases in the central and northeastern parts. The results of both numerical simulations and diagnostic analyses show that in EP El Nino winters, there is a northerly wind on the lower troposphere of SC conducive to the southward movement of cold air to SC, converging in the south and diverging in the north, in agreement with the distribution of the precipitation anomalies. In the lower troposphere of SC in summer, an abnormal southwester is dominant, facilitating the movement of warm and moist air in the southwest toward SC, which is conducive to an increase in precipitation there. In EP La Nina winter, there is a southwester anomaly in the lower troposphere of SC, which is adverse to the southward movement of cold air from the north to SC, with the divergence field diverging in the south and converging in the north, in agreement with the distribution of precipitation anomalies in this region. In EP La Nina summer, there is a northeaster anomaly in SC that is in the water vapor convergence area, which is conducive to precipitation in SC. In CP El Nino summer. There are northerly winds over SC and an anomalous cyclone over the western Pacific and South China Sea, which was beneficial to precipitation.