Strengthening Influence of El Nino on the Following Spring Precipitation over the Indochina Peninsula

Significance Statement Spring precipitation variation has profound economic and societal influences for the Indochina Peninsula (ICP) that consists of several agriculture-based countries. Moreover, the local soil moisture anomaly induced by the ICP spring precipitation is an important seasonal predictor for the East Asian summer monsoon and extreme climate. Here this study identifies a strengthening influence of El Nino on the following spring precipitation over the ICP, due to a relatively stronger intensity and longer duration of the El Nino-related warm SST anomalies over the tropical central Pacific since the early 1990s. This may provide an important implication for the seasonal predictions of summer monsoon and extreme climate over East Asia and thus potentially enhance the predictability of regional climate. El Nino is a dominant source of interannual climate variability around the world. Based on the observed and reanalyzed datasets for the period of 1958-2019, this study explores the influence of El Nino on the spring precipitation over the Indochina Peninsula (ICP). The results show that El Nino has a significant negative correlation with the following spring precipitation over the ICP. However, this climatic teleconnection of El Nino was unstable, with an obvious interdecadal strengthening since the early 1990s. During the decaying spring, the El Nino-related sea surface temperature (SST) anomalies would induce an abnormal downward motion along with an anomalous low-level anticyclone over the western North Pacific. Before the early 1990s, such El Nino-induced atmospheric circulation anomalies were located to the east of the ICP, exerting little influence on the spring ICP precipitation. In contrast, since the early 1990s, the abnormal downward motion and anomalous low-level anticyclone extended westward covering the whole ICP, hampering local spring precipitation. This interdecadal change is owing to a relatively stronger intensity and longer duration of the El Nino-related warm SST anomalies over the tropical central Pacific in the epoch after the early 1990s (1992-2019) than in the previous decades (1958-91). Our findings highlight a strengthening effect of El Nino on the following spring climate over the ICP since the early 1990s, which has great implications for the regional climate prediction.