海表温度差异对1998及2016年8月西北太平洋热带气旋生成频数的影响

Influence of sea surface temperature difference on the tropical cyclone genesis number in the Western North Pacific in August 1998 and August 2016

基于1970—2016年Hadley中心海温资料、NCEP/NCAR再分析资料和ECHAM4模式,研究了各海盆海表温度异常(SSTA)对1998和2016年这两个超级厄尔尼诺衰减年8月西北太平洋热带气旋(TC)生成及大尺度环流变化的可能影响。结果表明,热带印度洋和大西洋在1998与2016年几乎相反的SSTA型态是导致TC生成频数显著差异的主要原因之一,而热带和北太平洋SSTA在1998与2016年均分别在珠江三角洲和日本以南形成气旋性环流。1998年8月热带印度洋和大西洋SSTA产生的西北太平洋反气旋环流响应强于太平洋SSTA产生的气旋性环流异常,使西北太平洋受异常反气旋控制,减少TC的生成。2016年在三个大洋SSTA共同作用下,西北太平洋受异常气旋控制导致TC生成频数偏多。太平洋经向SSTA模在北半球副热带强迫出东西反向的跷跷板形势,在西北太平洋对流层产生的响应与实际变化相反,因此太平洋经向模对西北太平洋TC生成没有正的贡献。

Based on the Hadley Center sea surface temperature data, NCEP/NCAR reanalysis data from 1970 to2016 and numerical modeling simulation(ECHAM4), the possible effects of sea surface temperature anomalies(SSTA) in 1998 and 2016, which are the super El Ni?o attenuation years, on tropical cyclone(TC) formation and large-scale circulation in the Western North Pacific in August were studied. It is suggested that the SSTA, which was almost opposite in the tropical Indian Ocean and the Atlantic Ocean in 1998 and 2016, is one of the main reasons for the significant difference in the TC genesis number. Tropical and North Pacific SSTA can exert low pressure cyclonic circulation in the Pearl River Delta and south of Japan respectively in August 1998 and August2016. The anomalous anti-cyclonic response of the tropical Indian Ocean and Atlantic SSTA in 1998 was stronger than the cyclonic anomaly generated by the Pacific SSTA. Therefore, the Western North Pacific Ocean is subject to anti-cyclonic circulation, which makes the TC genesis number less. In 2016, under the combined action of three oceans, the anomalous cyclone in the Western North Pacific led to more TC genesis number. The Pacific meridional mode structure forced an east-west overturning circulation anomaly in the subtropical North Pacific,and the response over the Western Pacific Ocean was opposite to that observed. Therefore, the Pacific meridional model has no positive contribution to the TC genesis number in the Western North Pacific.