双月刊

ISSN 1006-9895

CN 11-1768/O4

夏季热带大西洋海温变化对华南前汛期降水的影响
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1.广西壮族自治区气象台;2.广西气候中心

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国家自然科学基金项目(42065004)


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

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    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(35°W-10°E,10°S-5°N)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 Ni?a的发展。海温负异常时形势则大致相反,促进了El Ni?o的发展。冬季太平洋La Ni?a(El Ni?o)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:

    Using the monthly precipitation data of 160 stations in China, Hadley Center sea surface temperature (SST) data, NOAA outgoing longwave radiation (OLR) data and NCEP/NCAR reanalysis data from 1979-2019, the impact of the summer tropical Atlantic sea temperature (TAST) on the first rainy season precipitation in South China (FRSP) is investigated. Base on the correlation analysis and information flow theory, the results show that the increase (decrease) of previous summer TAST partly leads to the decrease (increase) of FRSP. The SST rising in the key region (35°W-10°E, 10°S-5°N) can enhance the Walker circulation and induces an anomalous subsidence over the Pacific, which lead to an easterly wind anomaly over the central and western equatorial Pacific in summer. The ocean-atmosphere interactions promoted the development of La Ni?a in the following autumn and winter. The same mechanisms act for the negative SST anomaly but with opposite sign, and conducive to the development of El Ni?o. When the La Ni?a(El Ni?o)reach its peak in winner, the convection heating intensify (suppressed) in the western Pacific which triggered abnormal cyclones (anticyclones) response in the lower troposphere to its north. The anomalies persist until the first rainy season in second year, causing the abnormal cyclones (anticyclones) maintained which, on the one hand, is conducive to the weakening and eastward retreat (strengthening its westward extension) of the Western Pacific Subtropical High (WPSH), thus reducing (increasing) the transport of water vapor from the South China Sea to South China. On the other hand, the convective activity (suppression) in tropical areas is conducive to strengthening (weakening) the local Hadley circulation, resulting in the subsidence (ascent) anomaly in South China, and suppressing (intensifying) the convection. In addition, the negative (positive) SST anomaly in the eastern Pacific excited a Pacific-North American (PNA) like wave train, and the SST anomalies in the North Atlantic further activates the Eurasian (EU) wave train that making the Eurasian mid-high latitudes region shows negative (positive)-positive (negative)-negative (positive) geopotential height anomalies, which is unfavorable (favorable) for the cold air affecting South China, and eventually cause FRSP negative (positive) anomalies.

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历史
  • 收稿日期:2021-06-26
  • 最后修改日期:2021-08-10
  • 录用日期:2021-10-22
  • 在线发布日期: 2021-11-17
  • 出版日期: