Interannual variation of the low-level atmospheric eddy kinetic energy over the South China Sea and its relationship with the tropical cyclone formation number

• 1、Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction, College of Ocean and Meteorology, Guangdong Ocean University, Zhanjiang 524088

Abstract：Eddy kinetic energy (EKE) is one key dynamic parameter to characterize atmospheric circulations and synoptic-scale disturbance activities. Investigation of the distribution and variability of atmospheric EKE and related energy conversion components over the South China Sea (SCS) can help us to better understand the dynamics of the SCS monsoon and tropical cyclone (TC) formation in this region. We present our investigation on the interannual variations of low-level (850-hPa) atmospheric EKE over the SCS in this study. Both northern and southern SCS experienced prominent interannual variation in the 850-hPa EKE during their most active EKE months. The energy processes for generation and maintenance of the EKE were analyzed based on the EKE tendency equation. Results suggested that the barotropic energy conversion (BEC) term made the largest contribution to the interannual variation of the EKE over both northern and southern SCS. The interannual variation of the BEC over the southern SCS was mainly modulated by the El Ni?o-Southern Oscillation (ENSO) and had a close anti-correlated relationship with the sea surface temperature (SST) in the eastern equatorial Pacific. In contrast, the interannual variation of the BEC over the northern SCS was identified to be closely associated with the zonal SST gradient between the central equatorial Pacific and northern Indian Ocean. The atmospheric circulation anomalies in responses to SST anomalies enhanced the zonal wind shear over the SCS, giving rise to more BEC. The interannual variation of the BEC over the southern SCS was positively correlated with the TC formation number, with more (less) TCs formed during enhanced (suppressed) BEC years. However, the correlation between the BEC and TC formation number over the northern SCS was not significant, which may be due to the offsetting effects on TC formation by the cooling (warming) of the local SST during enhanced (suppressed) BEC years. These results could improve our understanding of the behaviors and causes of interannual variation in the low-level atmospheric EKE and its relationship with interannual variation of the TC formation number over the SCS. The results highlighted the differences in the regional climate variability between the northern SCS and the southern SCS. ?????

keywords： South China Sea regional climate interannual variation atmopsheric eddy kinrtic energy tropical cyclone genesis barotropical energy conversion

点击查看论文中文信息

点击收起