The Quasi-Biweekly Oscillation of Summer Rainfall in Southern China and Its Relationship With the Geopotential Height Anomaly Over the North Atlantic Ocean

Suxiang Yao,Qian Huang,Xinyu Yin

doi:10.3389/feart.2021.770253

Abstract

Summer precipitation in East Asia has significant quasi-biweekly (10–30-day) oscillation characteristics. By using gauge-based precipitation and ERA-Interim reanalysis data, the basic mode of the quasi-biweekly oscillation of summer precipitation in East Asia and the related circulation from 1979 to 2012 were analyzed. It was found that the middle and lower reaches of the Yangtze River and its south in China were among the key areas for the 10- to 30-day oscillation of summer precipitation. After selecting typical summer precipitation events with 10- to 30-day oscillation characteristics in key areas and conducting composite analysis, it is found that in the dry (wet) phase of quasi-biweekly precipitation in southern China, it is controlled by quasi-biweekly anticyclone (cyclone) at 500 hPa above the key area. During the evolution of quasi-biweekly precipitation, the ridge of the Northwest Pacific Subtropical High is located between 20 and 22°N latitude, and there is no significant variability in the large-scale background circulation. Furthermore, composite analysis of the precursory signal at 500 hPa during quasi-biweekly precipitation in southern China found that there was an obvious quasi-biweekly geopotential height anomaly over the North Atlantic Ocean almost 30 days before the peak day of quasi-biweekly precipitation. While the quasi-biweekly geopotential height anomaly at 500 hPa in the North Atlantic propagates eastward, it also leads the cold air to transport southward. Cold air from high latitudes and warm air from low latitudes converge in southern China, which affects the quasi-biweekly oscillation of precipitation. Hysteresis synthesis of precipitation based on 500 hPa geopotential height’s quasi-biweekly oscillation events over the North Atlantic Ocean comes to almost the same conclusion. Therefore, the 500 hPa geopotential height quasi-biweekly anomaly in the North Atlantic may have important prediction significance for an extended-range forecast of summer rainfall in China.

Highlights

Located in the East Asian monsoon region, China has complicated weather and climatic characteristics and frequent meteorological disasters
In the 10- to 30-day scale, the results show that during the dry phase of quasibiweekly precipitation in southern China, 500 hPa over the key area is controlled by abnormal quasi-biweekly anticyclone, and 850 hPa wind field shows obvious anticyclonic circulation (Figures 5A,B,G,H)
The north of Lake Baikal is controlled by an abnormal low pressure system, indicating that the polar vortex is moving southward, FIGURE 8 | First mode [EOF1, (A)] of the EOF analysis of 10–30-day filtered geopotential height at 500hPa over the North Atlantic Ocean and the composition of quasi-biweekly precipitation based on the geopotential height quasibiweekly oscillation (QBWO) events with 20-day lag (B) and 30-day lag (C)

Summary

Introduction

Located in the East Asian monsoon region, China has complicated weather and climatic characteristics and frequent meteorological disasters. In the 10- to 30-day scale, the results show that during the dry phase of quasibiweekly precipitation in southern China, 500 hPa over the key area is controlled by abnormal quasi-biweekly anticyclone, and 850 hPa wind field shows obvious anticyclonic circulation (Figures 5A,B,G,H).

Results

Conclusion