On the Weakened Relationship between Spring Arctic Oscillation and Following Summer Tropical Cyclone Frequency over the Western North Pacific:A Comparison between 1968–1986 and 1989–2007  

作　　者：CAO Xi CHEN Shangfeng CHEN Guanghua CHEN Wen WU Renguang 

机构地区：[1]Center for Monsoon System Research,Institute of Atmospheric Physics,Chinese Academy of Sciences

出　　处：《Advances in Atmospheric Sciences》2015年第10期1319-1328,共10页大气科学进展（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.41461164005,41275001 and 41230527)

摘　　要：This study documents a weakening of the relationship between the spring Arctic Oscillation （AO） and the following summer tropical cyclone （TC） formation frequency over the eastern part （150°-180°E） of the western North Pacific （WNP）. The relationship is strong and statistically significant during 1968-1986, but becomes weak during 1989-2007. The spring AO- related SST, atmospheric dynamic, and thermodynamic conditions are compared between the two epochs to understand the possible reasons for the change in the relationship. Results indicate that the spring AO leads to an E1 Nifio-like SST anomaly, lower-level anomalous cyclonic circulation, upper-level anomalous anticyclonic circulation, enhanced ascending motion, and a positive midlevel relative humidity anomaly in the tropical western-central Pacific during 1968-1986, whereas the AOrelated anomalies in the above quantities are weak during 1989-2007. Hence, the large-scale dynamic and thermodynamic anomalies are more favorable for TC formation over the eastern WNP during 1968-1986 than during 1989-2007.This study documents a weakening of the relationship between the spring Arctic Oscillation （AO） and the following summer tropical cyclone （TC） formation frequency over the eastern part （150°-180°E） of the western North Pacific （WNP）. The relationship is strong and statistically significant during 1968-1986, but becomes weak during 1989-2007. The spring AO- related SST, atmospheric dynamic, and thermodynamic conditions are compared between the two epochs to understand the possible reasons for the change in the relationship. Results indicate that the spring AO leads to an E1 Nifio-like SST anomaly, lower-level anomalous cyclonic circulation, upper-level anomalous anticyclonic circulation, enhanced ascending motion, and a positive midlevel relative humidity anomaly in the tropical western-central Pacific during 1968-1986, whereas the AOrelated anomalies in the above quantities are weak during 1989-2007. Hence, the large-scale dynamic and thermodynamic anomalies are more favorable for TC formation over the eastern WNP during 1968-1986 than during 1989-2007.

关 键 词：spring Arctic Oscillation summer tropical cyclone western North Pacific SST 

分 类 号：P732[天文地球—海洋科学]