Abstract
Previous studies reported that boreal winter precipitation in southeastern China (SEC) tends to increase during El Niño. In this study, however, we find that most weak El Niño events are accompanied by below-normal precipitation in SEC, although strong El Niño events are accompanied by above-normal precipitation in SEC for both eastern Pacific El Niño and central Pacific El Niño. Both the cold SST anomalies in the western North Pacific (WNP) and the warm SST anomalies in the central tropical Pacific are important for the formation of anomalous anticyclone over the WNP, which favors above-normal precipitation over SEC by transporting more water vapor to SEC. The cold SST anomalies in the WNP only excite a weak anomalous anticyclone locally when the weak warm SST anomalies in the central tropical Pacific are accompanied by weak enhanced convection anomalies. In such condition, El Niño does not affect precipitation in SEC apparently.
Highlights
El Niño and Southern Oscillation (ENSO), the strongest interannual variability source, exerts significant impacts on global climate[1,2,3,4]
To quantify the precipitation in southeastern China (SEC), the SEC boreal winter precipitation index (SECPI) is derived by area-averaging the boreal winter precipitation amount over SEC, which is indicated by the box (110°E-122°E, 21°N-30°N) in Fig. 1a with 93 gauge stations being included
Previous studies reported that boreal winter precipitation in SEC is linked to ENSO, with asymmetric impacts of El Niño and La Niña on SEC precipitation
Summary
El Niño and Southern Oscillation (ENSO), the strongest interannual variability source, exerts significant impacts on global climate[1,2,3,4]. The impacts of El Niño and La Niña on precipitation are asymmetric[11]; only El Niño favors above-normal precipitation over southeastern China (SEC) by exciting the western North Pacific anomalous anticyclone (WNPAC) in the lower troposphere, which transports more water vapor to SEC by the southwesterlies[6,7,12,13,14]. Some studies indicated that the climate impact of El Niño is sensitive to its magnitude[22,23,24]. We investigate the relationship between boreal winter precipitation over the SEC and El Niño, with a focus on the impacts of different types of El Niño with different intensity on precipitation anomalies
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