This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/joc.6231 Combined impact of tropical central-eastern Pacific and North Atlantic SST on precipitation variation in monsoon transitional zone over China during August-September Combined impact of TCEP and NA SST on MTZ precipitation variaition Wei Zhao 1, 2 , Wen Chen 1, 2 , Shangfeng Chen 1, 2, * , Shuai-Lei Yao 3 , and Debashis Nath 1 1 Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100190, China 2 College of Earth Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 3 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China *Contact: chenshangfeng@mail.iap.ac.cn Abstract Previous studies suggested that sea surface temperature (SST) anomalies in the tropical central-eastern Pacific (TCEP) and tropical Northern Atlantic (TNA) both have significant impacts on the interannual variation of precipitation over the monsoon transitional zone (MTZ) in China during August-September. This study further reveals that the relationship between TCEP (TNA) SST and MTZ precipitation during August-September is strongly modulated by the sign of the TNA (TCEP) SST. When TCEP and TNA SST anomalies have the same-sign, connections of the TCEP and TNA SST with the MTZ precipitation are unclear. By contrast, TCEP and TNA SST changes both have a significant relation with the MTZ precipitation when they have the opposite-sign. During the same-sign years, the anticyclonic (cyclonic) anomaly over the western North Pacific generated by the TCEP SST cooling (warming) is weakened by the cyclonic (anticyclonic) anomaly triggered by the TNA SST cooling (warming). Thus, connections of the MTZ precipitation with the TCEP and TNA SST are weak. However, during the opposite-sign years, the anticyclonic anomalies over the This article is protected by copyright. All rights reserved.