Weakened Impacts of the East Asia-Pacific Teleconnection on the Interannual Variability of Summertime Precipitation over South China since the Mid-2000s

Abstract

The current study concentrates on the interdecadal shift in the interannual variability of summertime precipitation (IVSP) over South China (SC). Possible causes for the interdecadal shift are explored. The IVSP on a decadal time scale presents a significant weakening after the mid-2000s. The results show that the variances of the interannual precipitation variability over the SC region between 1993 and 2004 (hereafter S1) and 2005 and 2020 (hereafter S2) are 1.40 mm d−1 and 0.58 mm d−1, respectively. The variance of the IVSP has decreased by 58.6% since the mid-2000s. The current study reveals that the reduction in the IVSP over SC after the mid-2000s is prominently attributed to the weakened impact of the East Asia-Pacific (EAP) teleconnection. Before the mid-2000s, the interannual variation of the east-west movement of the western Pacific subtropical high was more significant. The warming over the tropical central-eastern Pacific (CEP) and cooling over the western Pacific (WP) suppress the Walker cell in the tropical Pacific and induce anomalous Hadley cell with its descending branch over the WP in the wet years. The anomalies of SST and atmospheric circulation show opposite phases in the dry years. This SSTA pattern enhances the northward propagation of the EAP teleconnection through a Rossby-wave-type response, which triggers an ascending/descending branch with active/suppressed convection over the northwestern Pacific in the wet/dry years. Therefore, the cooling WP and El Niño in its developing phase provide an ideal condition for more precipitation over SC. However, the above ocean–atmosphere interactions changed after the mid-2000s. The significant SST changes in the tropical CEP and the WP weaken the EAP teleconnection and atmospheric circulation anomalies over SC, leading to a significant interdecadal reduction in the IVSP over SC after the mid-2000s.