doi:  10.3878/j.issn.1006-9895.1609.16125
季节内振荡影响西太平洋副热带高压两次北跳的机制

A Mechanism Study for the Intraseasonal Oscillation Impact on the Two Northward Jumps of the Western Pacific Subtropical High
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基金:  国家自然科学基金项目41405056、41475052,福建省自然科学基金青年创新项目2015J05078,华东区域气象科技协同创新基金合作项目QYHZ201405
中文关键词:  季节内振荡  西太平洋副热带高压  北跳  江淮梅雨  ENSO
英文关键词:  Intraseasonal oscillation  Western Pacific subtropical high  Northward jump  Meiyu over the Yangtze- Huaihe River valley  ENSO
           
作者中文名作者英文名单位
苏同华SU Tonghua福建省气象台, 福州 350001;中国科学院大气物理研究所国际气候与环境科学中心, 北京 100029
薛峰XUE Feng中国科学院大气物理研究所国际气候与环境科学中心, 北京 100029
陈敏艳CHEN Minyan福建省气象台, 福州 350001
董啸DONG Xiao中国科学院大气物理研究所国际气候与环境科学中心, 北京 100029
引用:苏同华,薛峰,陈敏艳,董啸.2017.季节内振荡影响西太平洋副热带高压两次北跳的机制[J].大气科学,41(3):437-460,doi:10.3878/j.issn.1006-9895.1609.16125.
Citation:SU Tonghua,XUE Feng,CHEN Minyan,DONG Xiao.2017.A Mechanism Study for the Intraseasonal Oscillation Impact on the Two Northward Jumps of the Western Pacific Subtropical High[J].Chinese Journal of Atmospheric Sciences (in Chinese),41(3):437-460,doi:10.3878/j.issn.1006-9895.1609.16125.
中文摘要:
      夏季期间,西太平洋副热带高压(简称副高)存在两次明显的北跳,其中第一次北跳导致华南前汛期结束、江淮梅雨建立,而第二次北跳则意味着江淮梅雨结束、华北雨季开始。本文基于观测资料和再分析数据,利用快速傅里叶变换和合成分析方法,深入探讨不同时间尺度季节内振荡对气候态和异常年副高两次北跳的影响机制。结果表明:在季节内尺度上,平常年和异常年影响副高两次北跳的季节内振荡的主导周期不同。气候态上,以10~20天和准60天为主;第一次北跳异常年和第二次北跳偏早年,以30~60天为主;第二次北跳偏晚年,则呈现出10~20天和30~60天两个主导周期。不论气候态还是异常年,东亚—热带西北太平洋地区低频振荡在年循环背景下均呈现出明显的北传特征,这是导致副高发生两次北跳的重要原因之一。而印度季风区低频振荡在东北向传播过程中所引起的西风东伸是造成副高第一次北跳更为明显的原因。源自澳大利亚高压的冷空气入侵所激发的暖池对流的准双周振荡则是造成气候态和偏晚年副高第二次北跳更为显著的原因。由于前期春季西北印度洋海温出现异常,造成局地低频振荡发生位相迁移,进而导致副高第一次北跳发生异常。而副高第二次北跳异常则是因为ENSO改变了暖池地区季节内振荡的尺度和振幅所造成的。
Abstract:
      During summertime, the WPSH (western Pacific subtropical high) exhibits two northward jumps. The first jump signals the termination of pre-flood period in southern China and the start of the Meiyu over the Yangtze-Huaihe River valley; the second jump indicates the termination of the Meiyu and the start of rainy season in northern China. Based on the fast Fourier transformation and composite analysis of observational and reanalysis data, the authors investigated the impact of the intraseasonal oscillations (ISOs) on various time-scales on the northward jumps in the normal and abnormal years. The dominant periods of the ISOs are different in normal and abnormal years, i.e. 10-20 days and quasi-60 days in normal years, 30-60 days in abnormal years of the first jump and earlier years of the second jump, 10-20 days and 30-60 days in later years of the second jump. During the annual cycle, the ISOs tend to propagate northward in the East Asian-tropical northwestern Pacific region, leading to the northward jump of the WPSH. With the northeastward propagation of the ISOs over the Indian monsoon region, a more remarkable first jump is observed due to the eastward extension of the westerly. By contrast, the biweekly oscillation of the warm pool convection triggered by the cold air invasion from the Australian high plays an important role in a more evident second jump during the normal and later years. The sea surface temperature anomaly over the northwestern Indian Ocean in the preceding spring leads to the phase migration of local ISOs and associated abnormal first jump. Besides, the time-scale and amplitude of the ISOs in the warm pool can be regulated by ENSO, resulting in the abnormal second jump.
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