基于数值试验的南海越赤道气流与夏季赤道中东太平洋海温异常的关系研究

Study on the Relationship between the Cross-Equatorial Flow Over the South China Sea and the Summer SST Anomalies in the Equatorial Middle East Pacific Based on Numerical Experiments

摘要: 本文利用1979~2020年HadISST月平均海表面温度(Sea surface temperature, SST)资料，驱动改进的NCAR CAM5大气环流模式进行长时间积分试验所得结果，与ERA5再分析资料进行比较，进一步分析验证了夏季赤道中东太平洋海表面温度异常(Sea surface temperature anomalies, SSTA)对南海(South China Sea, SCS)低空越赤道气流(Cross-Equatorial Flow, CEF)强度的影响，研究表明：数值试验结果与观测分析结果较为一致，即夏季赤道中东太平洋SSTA对同期SCS CEF (SCEF)强度变化产生重要影响，存在显著正相关。当夏季赤道中东太平洋SSTA偏暖时，引起Walker环流及东亚局地Hadley环流异常偏弱，对应澳大利亚北部及热带西太平洋海洋性大陆海平面气压(Sea level pressure, SLP)异常上升，北太平洋SLP异常下降，西太平洋南北向气压梯度增加，故SCEF易增强；反之亦然。

Abstract: In this paper, a long-term integral test is carried out with the improved NCAR CAM5 atmospheric general circulation model by the monthly sea surface temperature (SST) data of HadISST in 1979~2020, which further verifies the influence of the summer SST anomalies (SSTA) in the equatorial Middle East Pacific on the intensity of the low-altitude Cross-Equatorial Flow (CEF) over the South China Sea (SCS) in summer compared with the ERA5 reanalysis data. The results show that: Numerical test results are consistent with the observational results, that is, the SSTA in the equatorial Middle East Pacific in summer has a significant positive influence on the SCS CEF (SCEF) intensity in the same period. When the summer equatorial Middle Eastern Pacific SSTA becomes warmer, it will cause the Walker circulation and the East Asian local Hadley circulation to be abnormally weaker, moreover, the corresponding Sea level pressures (SLP) in northern Australia and the tropical western Pacific Ocean rise abnormally, while the trend is reversed in the North Pacific Ocean, which lead to an increase in the north-south pressure gradient over the western Pacific, thus the SCEF is enhanced as well, and vice versa.