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Ocean-atmosphere interactions and multi-scale climate variability in a changing climate
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Roles of tropical SST patterns during two types of ENSO in modulating wintertime rainfall over southern China
P-P2-11
Kang Xu* , State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
Qing-Lan Huang, Jiangmen Meteorological Service, Jiangmen, China
Chi-Yung Tam, Earth System Science Programme, The Chinese University of Hong Kong, Hong Kong, China
Weiqiang Wang, State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
Sheng Chen, State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
Congwen Zhu, State Key Laboratory of Severe Weather (LASW) and Institute of Climate System, Chinese Academy of Meteorological Sciences, Beijing, China
Presenter Email: xukang@scsio.ac.cn |
| The impacts of the eastern-Pacific (EP) and central-Pacific (CP) El Nino-Southern Oscillation (ENSO) on the southern China wintertime rainfall (SCWR) have been investigated. Results show that wintertime rainfall over most stations in southern China is enhanced (suppressed) during the EP (CP) El Nino, which are attributed to different atmospheric responses in the western North Pacific (WNP) and South China Sea (SCS) during two types of ENSO. When EP El Nino occurs, an anomalous low-level anticyclone is present over WNP/the Philippines region, resulting in stronger-than-normal southwesterlies over SCS. Such a wind branch acts to suppress East Asian winter monsoon (EAWM) and enhance moisture supply, implying surplus SCWR. During CP El Nino, however, anomalous sinking and low-level anticyclonic flow are found to cover a broad region in SCS. These circulation features are associated with moisture divergence over the northern part of SCS and suppressed SCWR. General circulation model experiments have also been conducted to study influence of various tropical sea surface temperature (SST) patterns on the EAWM atmospheric circulation. For EP El Nino, formation of anomalous low-level WNP anticyclone is jointly attributed to positive/negative SST anomalies (SSTA) over the central-to-eastern/ western equatorial Pacific. However, both positive and negative CP Nino-related-SSTA, located respectively over the central Pacific and WNP/SCS, offset each other and contribute a weak but broad-scale anticyclone centered at SCS. These results suggest that, besides the vital role of SST warming, SST cooling over SCS/WNP during two types of El Nino should be considered carefully for understanding the El Nino-EAWM relationship.
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