Spatiotemporal Variability of the Southern Second Mode and Its Influence on June Precipitation in Southern China

Abstract

AbstractBased on the Empirical Orthogonal Functions decomposition of the Sea level pressure (SLP) anomalies over the southern extratropic, the second pattern is defined as a southern second mode (SMD2), and its corresponding principal component is named the southern second mode index. The most significant feature of SMD2 is the seesaw pattern of SLP, which indicates the opposite phase of the Amundsen Low and surroundings. The spatial mode of EOF2 varies in different months but EOF2 in March is most similar to SMD2. This study shows that the March SMD2 is negatively associated with the June precipitation in southern China. The mechanisms can be briefly summarized as follows: The March SMD2 is negatively correlated with sea surface temperature (SST) in the midlatitude. Surface wind changes can affect surface heat flux and heat transport, leading to the SST changes. The SST anomaly acts as the “oceanic bridge” to preserve the March SMD2 signal and persists into late summer. The key area of SST is associated with Maritime Continent convective activity anomalies, which can excite and maintain the Pacific‐Japan pattern resulting in precipitation anomalies in south China. Through sea‐air interactions, the SMD2 can affect the precipitation in southern China across seasons. This work is expected to provide a new perspective for forecasting summer precipitation in southern China.