Interannual Weakening of the Tropical Pacific Walker Circulation Due to Strong Tropical Volcanism  

作　　者：Jiapeng MIAO Tao WANG Huijun WANG Jianqi SUN 

机构地区：[1]Nansen-Zhu International Research Center, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China [2]Joint Laboratory for Climate and Environmental Change, Chengdu University of lnformation Technology, Chengdu 610225, China [3]Key Laboratory of Meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing 210044, China [4]Climate Change Research Center, Chinese Academy of Sciences, Beijing 100029, China [5]University of Chinese Academy of Sciences, Beijing 100049, China

出　　处：《Advances in Atmospheric Sciences》2018年第6期645-658,共14页大气科学进展（英文版）

基　　金：supported by the National Key R&D Program of China(Grant No.2016YFA0600701);the National Natural Science Foundation of China(Grant Nos.41661144005,41575086 and 41320104007);the CAS–PKU Joint Research Program

摘　　要：In order to examine the response of the tropical Pacific Walker circulation（PWC） to strong tropical volcanic eruptions（SVEs）, we analyzed a three-member long-term simulation performed with Had CM3, and carried out four additional CAM4 experiments. We found that the PWC shows a significant interannual weakening after SVEs. The cooling effect from SVEs is able to cool the entire tropics. However, cooling over the Maritime Continent is stronger than that over the central-eastern tropical Pacific. Thus, non-uniform zonal temperature anomalies can be seen following SVEs. As a result, the sea level pressure gradient between the tropical Pacific and the Maritime Continent is reduced, which weakens trade winds over the tropical Pacific. Therefore, the PWC is weakened during this period. At the same time, due to the cooling subtropical and midlatitude Pacific, the Intertropical Convergence Zone（ITCZ） and South Pacific convergence zone（SPCZ） are weakened and shift to the equator. These changes also contribute to the weakened PWC. Meanwhile, through the positive Bjerknes feedback, weakened trade winds cause El Nino-like SST anomalies over the tropical Pacific, which in turn further influence the PWC. Therefore, the PWC significantly weakens after SVEs. The CAM4 experiments further confirm the influences from surface cooling over the Maritime Continent and subtropical/midlatitude Pacific on the PWC. Moreover, they indicate that the stronger cooling over the Maritime Continent plays a dominant role in weakening the PWC after SVEs. In the observations,a weakened PWC and a related El Nino-like SST pattern can be found following SVEs.In order to examine the response of the tropical Pacific Walker circulation（PWC） to strong tropical volcanic eruptions（SVEs）, we analyzed a three-member long-term simulation performed with Had CM3, and carried out four additional CAM4 experiments. We found that the PWC shows a significant interannual weakening after SVEs. The cooling effect from SVEs is able to cool the entire tropics. However, cooling over the Maritime Continent is stronger than that over the central-eastern tropical Pacific. Thus, non-uniform zonal temperature anomalies can be seen following SVEs. As a result, the sea level pressure gradient between the tropical Pacific and the Maritime Continent is reduced, which weakens trade winds over the tropical Pacific. Therefore, the PWC is weakened during this period. At the same time, due to the cooling subtropical and midlatitude Pacific, the Intertropical Convergence Zone（ITCZ） and South Pacific convergence zone（SPCZ） are weakened and shift to the equator. These changes also contribute to the weakened PWC. Meanwhile, through the positive Bjerknes feedback, weakened trade winds cause El Nino-like SST anomalies over the tropical Pacific, which in turn further influence the PWC. Therefore, the PWC significantly weakens after SVEs. The CAM4 experiments further confirm the influences from surface cooling over the Maritime Continent and subtropical/midlatitude Pacific on the PWC. Moreover, they indicate that the stronger cooling over the Maritime Continent plays a dominant role in weakening the PWC after SVEs. In the observations,a weakened PWC and a related El Nino-like SST pattern can be found following SVEs.

关 键 词：Pacific Walker circulation strong tropical volcanic eruptions cooling effect trade winds 

分 类 号：P317[天文地球—固体地球物理学] P731.27[天文地球—地球物理学]