西太平洋热通量变化及其与中国夏季降水量异常的联系

Variation in heat flux in the Western Pacific and its relation to the summer rainfall anomaly in China

利用EOF方法分析了1951～2008年间西太平洋湍动热通量的时空特征,并探讨了中国夏季降水异常与同期西太平洋潜热通量时空格局的联系.结果显示,西太平洋潜热和感热通量距平场具有较相似的空间分布以及显著的年际变化,但潜热通量的变化幅度较感热通量大;潜热通量距平场的空间变化存在明显季节差异.冬季潜热通量变化的显著区域位于黑潮流域,而夏季则见于西太平洋暖池区.冬、夏季潜热通量除了具有准4a振荡周期外,还存在着明显的线性增强的长期变化趋势.进一步分析表明,夏季西太平洋潜热通量变异主要存在着偶极型、同一型和三极子型模态,其时间系数分别具有显著的准4a、准2a和29a的周期变化,它们分别对应着不同的中国夏季降水量异常的分布,而大范围的潜热通量负异常则与中国江淮流域大部和华北北部地区的降水偏多相对应.这为中国降水量的异常及机理研究提供了必要基础.

Spatio-temporal variations in the turbulent heat fluxes over the Western Pacific were analyzed using the EOF method and the possible connection between simultaneous latent heat flux and summer rainfall in China was examined.The latent heat flux anomaly and the sensible heat flux anomaly over the Western Pacific were found to have similar spatial pattern of dominance and significant annual variation.However,the changing amplitude of the latent heat flux was larger than that of the sensible heat flux and an obvious seasonal difference existed in the spatial variation of the latent heat flux anomaly field.The dominant region of the anomalous variation of latent heat flux over the Western Pacific was around the Kuroshio Area in winter and in the Western Pacific warm pool region in summer.The latent heat flux over the Western Pacific in summer and winter was subject a marked quasi-4a oscillation and had a significant long-term increasing linear trend.The latent heat flux over the Western Pacific exhibited three anomalous spatial modes in summer including dipole-type,the homo-type and the tripole-type,with significant periods as quasi-4a,quasi-2a and 29a,respectively.The composite analysis indicated that the excessive summer rainfall over most of the Yangtze and Huaihe Basins and the northern area of North China could result from the wide negative anomaly of latent heat flux in the Western Pacific.