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覃皓, 伍丽泉, 何慧. 2023. 夏季热带大西洋海温变化对华南前汛期降水的影响[J]. 大气科学, 47(5): 1309−1324. doi: 10.3878/j.issn.1006-9895.2108.21108
引用本文: 覃皓, 伍丽泉, 何慧. 2023. 夏季热带大西洋海温变化对华南前汛期降水的影响[J]. 大气科学, 47(5): 1309−1324. doi: 10.3878/j.issn.1006-9895.2108.21108
QIN Hao, WU Liquan, HE Hui. 2023. Impact of the Summer Tropical Atlantic Sea Temperature on the First Rainy Season Precipitation in South China [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 47(5): 1309−1324. doi: 10.3878/j.issn.1006-9895.2108.21108
Citation: QIN Hao, WU Liquan, HE Hui. 2023. Impact of the Summer Tropical Atlantic Sea Temperature on the First Rainy Season Precipitation in South China [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 47(5): 1309−1324. doi: 10.3878/j.issn.1006-9895.2108.21108

夏季热带大西洋海温变化对华南前汛期降水的影响

Impact of the Summer Tropical Atlantic Sea Temperature on the First Rainy Season Precipitation in South China

  • 摘要: 利用1979~2019年全国160站逐月降水资料、Hadley中心海表面温度资料、NOAA的向外长波辐射资料以及NCEP/NCAR再分析资料,结合相关分析、信息流以及合成分析方法,分析了夏季热带大西洋海温变化对华南前汛期降水的影响。结果表明:前一年夏季热带大西洋海温升高(降低)在一定程度上导致了华南前汛期降水的减少(增多)。关键区(10°S~5°N,35°W~10°E)海温偏暖增强了Walker环流导致赤道太平洋下沉辐散增强,造成赤道中西部太平洋上空的东风异常,在海气相互作用下促进了随后秋冬季La Niña的发展。海温负异常时形势则大致相反,促进了El Niño的发展。冬季太平洋La Niña(El Niño)发展到最盛期,西太平洋的对流增强(减弱)在其北侧低对流层激发出异常气旋(反气旋)。直到第二年的前汛期,仍存在残余的海温异常形势,这一方面使得西北太平洋异常气旋(反气旋)依然维持,有利于西太平洋副热带高压减弱东退(加强西伸),减少(增多)了南海水汽向华南的输送;另一方面有利于热带地区对流活跃(抑制)从而增强(减弱)了局地Hadley环流,造成华南地区为下沉(上升)运动异常,抑制(增强)了对流。除此之外,赤道东太平洋的海温负(正)异常激发了指向北美洲的类太平洋—北美波列,北大西洋的海温异常在其基础上进一步激发了向下游传播的欧亚波列,使得欧亚中高纬呈现负(正)—正(负)—负(正)的位势高度异常特征,不利于(有利于)冷空气南下影响华南,最终造成前汛期降水负(正)异常。

     

    Abstract: The impact of summer tropical Atlantic sea temperature (TAST) on the first rainy season precipitation in South China (FRSP) is investigated using monthly precipitation data from 160 stations in China, Hadley Center sea surface temperature (SST) data, National Oceanic and Atmospheric Administration (NOAA) outgoing longwave radiation (OLR) data, and NCEP/NCAR reanalysis data from 1979 to 2019. Correlation analysis and information flow theory indicate that a rise (reduction) in the previous summer TAST partially accounts for an increase (decrease) in FRSP. The SST increases in the critical zone (10°S–5°N, 35°W–10°E) may amplify the Walker circulation and produce abnormal subsidence across the Pacific, resulting in an easterly wind anomaly throughout the central and western equatorial Pacific during the summer. The ocean–atmosphere interactions aided in the formation of La Niña in the fall and winter that followed. The same forces govern the negative SST anomaly but in the opposite direction, which is favorable for the growth of El Niño. When the La Niña (El Niño) reaches its height in the Northern Hemisphere, convection heating intensifies (or is inhibited) in the western Pacific, triggering atypical cyclones (anticyclones) in the lower troposphere to its north. The anomalies persist until the first rainy season of the second year, resulting in the persistence of abnormal cyclones (anticyclones), which, on the one hand, contribute to the Western Pacific Subtropical High (WPSH) weakening and eastward retreating (strengthening its westward extension), thereby reducing (increasing) the transport of water vapor from the South. Thus, the WPSH reduces (increases) water vapor movement from the South China Sea to South China. On the other hand, in tropical regions, convective activity (suppression) is favorable to strengthening (weakening) the local Hadley circulation, resulting in the subsidence (ascent) anomaly in South China and suppressing (intensifying) convection. Additionally, the negative (positive) SST anomaly in the eastern Pacific energized a Pacific–North American-like wave train, and the SST anomalies in the North Atlantic energized the Eurasian (EU) wave train, resulting in negative (positive)– positive (negative) – negative (positive) geopotential height anomalies in the Eurasian mid-high latitudes region, which is unfavorable (favorable) for the cold air affecting South China.

     

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