Connection between Two Leading Modes of Autumn Rainfall Interannual Variability in Southeast China and Two Types of ENSO-Like SSTA

Abstract

The interannual variability of autumn rainfall in Southeast China (SEC) is significant, with two major modes, namely, monopole and dipole modes. It is found that the monopole mode is closely related to EP ENSO-like sea surface temperature anomaly (SSTA), and the dipole mode is related to CP ENSO-like SSTA. During the warm phase of EP ENSO-like SSTA, an anomalous anti-Walker circulation emerges in the tropical Pacific, with an anomalous subsiding during 110°E–120°E and an anomalous ascending branch in SEC. These two branches of anomalous current are in the same longitude and form a closed meridional circulation. Besides, there also exists an anticyclone anomaly in the Northwest Pacific (NWP), transporting water vapor into SEC. These circulation configurations induced by the warm phase of EP ENSO-like SSTA are consistent with those of monopole mode positive anomaly year. The good correspondence between EP ENSO warm event and the positive monopole mode also helps to support the corresponding relationship between the EP ENSO-like SSTA and monopole mode of SEC autumn rainfall. After the diagnosis of the perturbation omega equation, the anomalous subsiding branch over SEC, as the key link of EP ENSO-like warm phase SSTA exerting impact on the monopole mode during positive anomaly year, is mainly related with the anomalous relative vorticity advection transported by basic zonal wind and temperature advection transported by meridional wind anomaly. As for the dipole mode, it is related to the CP ENSO-like SSTA, but the corresponding relationship is weaker than that of the monopole mode and EP ENSO-like SSTA. In special, during the warm phase of CP ENSO-like SSTA, an anomalous cyclone appears in the NWP and prevailing sinking motion over SEC, both of which favors the appearance of positive anomaly of the dipole mode. Specially, the local anomalous vertical motion mainly depends on anomalous relative vorticity transported by basic meridional wind. Generally speaking, the monopole (dipole) mode is closely associated with the EP (CP) ENSO-like SSTA, demonstrating some correspondence.

Interdecadal change in autumn rainfall over Southeast China and its association with tropical Pacific SST

“…The SST anomaly in the tropical Paci c is closely related to autumn rainfall in SEC (Liu et al, 2019;Jia et al, 2015;Gu et al, 2012); therefore, we also calculate the difference in SST and mixed layer sea temperature between 1991-2009 and 1971-1990 (Fig. 4).…”

“…Southeast China (SEC) includes Fujian, Guangdong, East Guangxi, Jiangxi, Hunan, South Hubei, and South Zhejiang, which is economically booming and a crucial tropical and subtropical agricultural production base in China (Liu et al, 2019). Therefore, the climatology and variation features of rainfall in SEC, as well as associated droughts and oods, have received much attention (Xin et al, 2006;Qiu et al, 2009;Wan et al, 2009;Jin et al, 2017;Liu et al, 2019).…”

Decadal Shift in West China Autumn Precipitation and its Association With Sea Surface Temperature

“…The interaction between northerly and water vapor from southerly is responsible for the precipitation events over West China. In addition, the surface thermal regime and snow cover on the Tibetan Plateau (Chen et al, 2001;Huo et al, 2014), sea surface temperature (SST) in the tropical Pacific (Gu et al, 2014;Wang et al, 2015;Zhang et al, 2014), and the Indian Ocean Dipole Mode (Liu & Yuan, 2006) also significantly affect the variability of WCAP.…”