前期春季西北太平洋潜热通量与中国南方秋季降水的联系及其可能的物理机制

利用中国科学院海洋研究所提供的印度洋—太平洋海洋热通量资料,研究了1989—2010年中国南方地区秋季降水与前期春季西北太平洋潜热通量年际变化的联系,并讨论了其可能的物理机制。结果表明,前期春季4月西北太平洋(15°—30°N,150°—170°E)潜热通量与中国南方秋季降水有显著的正相关,当前期关键区潜热通量偏高(低)时,则中国南方秋季降水偏多(少)。分析发现前期关键区潜热通量强弱主要由西北太平洋上空气旋性风切变造成,当前期4月关键区潜热通量偏大时,该关键区正处于西北太平洋上空气旋性风切变北侧大风区中,而在其南侧的赤道强西风使得日界线附近出现海温偏高。随后,次表层高海温伴随开尔文波东传,相应地其北侧的低海温伴随罗斯贝波西传,于秋季西传至热带西太平洋地区,并激发出菲律宾反气旋,从而有利于热带洋面暖湿水汽向中国南方输送,使得南方地区降水偏多,反之亦然。

Relationships between the prophase spring latent heat flux anomalies in the western North Pacific and autumn rainfalls over South China and its possible physical mechanism

Based on the Indian-Pacific Ocean heat flux data provided by the Institute of Oceanology in Chinese Academy of Sciences,a study is conducted with focus on the relationship between spring latent heat flux anomalies in the western North Pacific and autumn rainfalls over South China. Accordingly, the possible physical mechanism involved is discussed. The results show that there is a high positive corre1ation between the autumn rainfall anomaly over South China and the previous April latent heat flux anomaly in the western North Pacific (15°-30°N, 150°-170°E). When the prophase April latent heat flux in the key area is higher (lower) than normal, South China would receive more (less) than normal rainfall during the subsequent autumn. It is found that the high latent heat flux in the key area is due to the cyclonic wind shear in the western North Pacific. Northeasterly anomalies north of the anomalous cyclone enhance the wind speed,which would cause a cooling in heat content. The associated westerly anomalies south of the anomalous cyclone lead to the occurrence of anomalous warm heat content near the date line. After that, the anomalous warm heat content is transported eastward through the warming Kelvin Wave effect. Correspondingly, the anomalous cold heat content migrates westward accompanied by the Rossby wave. When the Rossby wave reaches the western tropical Pacific, it motivates the anomalous Philippine Sea anticyclone. It is conductive to more water vapor being transported towards South China and thus more rainfall appears over southern China during autumn.This research suggests a potential signal for predicting the autumn precipitation over South China two seasons in advance.