春季中国东海黑潮区大气热源异常对中国东部降水的影响

The spring atmospheric heat source over the East China Sea Kuroshio area and its impact on precipitation in Eastern China

采用ERA-interim逐日再分析数据集与中国东部389个站逐日降水资料,通过相关和合成分析讨论了不同时间尺度上,春季中国东海黑潮区上空大气热源异常对东亚大气环流和中国东部降水的影响。观测分析表明,春季中国东海黑潮区上空为一显著的大气热源,大气对该热源的响应在不同时间尺度上表现出不同的形式。在较长时间的季节和年际尺度上,春季中国东海黑潮区大气热源增强时,可在大气对流层低层强迫出偏南气流,同期春季及后期夏季西太平洋副热带高压增强并西伸,相比于热源低值年西北太平洋副热带地区为一反气旋式异常环流所控制,中国长江中下游以南地区降水增多;反之亦然。与年际和季节时间尺度不同,在较短的天气时间尺度上,中国东海黑潮区上空大气热源增强可在其下方强迫出气旋式异常环流。大气热源的增强与中国东部对流层低层气旋式异常环流的东移有关,相应地在中国东部地区出现了显著的降水增多。

In this paper, the impact of atmospheric heat source over the East China Sea Kuroshio area in spring on the atmos- pheric circulation and precipitation at the different time scales are investigated in terms of the ERA-interim daily reanalysis and in-situ precipitation. Observations show that there is a marked heat source over the Kuroshio area in the East China Sea, to which the atmospheric responses differ at the different time scales. On the seasonal and inter-annual time scales, southerly wind anomalies in the lower troposphere is associated with an enhanced atmospheric heat source over the Kuroshio in the East China Sea. At the same time, the northwestern Pacific subtropical high is also abnormally enhanced with its position extending west- ward during the spring and the late summer. In this situation the northwestern Pacific subtropical regions are mainly dominated by an anomaly anticyclonic circulation and precipitation abnormally increases over the southern China south of the middle-lower reaches of the Yangtze River, and vice versa. In contrast with the seasonal and inter-annual time scales, an enhanced atmos- pheric heat source over the East China Sea Kuroshio area can excite an anomaly cyclonic circulation in the lower troposphere on the synoptic time scale and its short-term variation is closely related to an eastward-moving anomaly cyclonic circulation at the lower troposphere and associated with abnormal precipitation over eastern China.