Modulation of Typhoon-Induced Sea Surface Cooling by Preexisting Eddies in the South China Sea

Abstract

The interactions between mesoscale eddies and typhoons are important for understanding the oceanic environment, but large variance is identified in each case because of the complex underlying dynamics. Fifteen-year datasets of typhoon tracks and eddy tracks in the South China Sea (SCS) are employed to comprehensively determine the influence of preexisting eddies on typhoon-induced sea surface cooling (SSC). Typhoons with high wind speeds and slow translation speeds induce large SSC in summer and autumn, when more than 80% of typhoons occur during a year. The relative locations of typhoons and eddies are used to classify their distributions, and four groups are identified, with typhoons traversing to the left or right of cyclonic or anticyclonic eddies. Generally, cyclonic eddies (CEs) located to the right of a typhoon track can result in a large cooling core, but anticyclonic eddies (AEs) can interrupt the cooling band along the right side of typhoon tracks. The recovery from typhoon-induced SSC takes longer than 15 days, though preexisting AEs can induce a rapid rebound after reaching the minimum sea surface temperature (SST). In addition, the dependence of SSCs on a typhoon’s features, such as wind speed and translation speed, are amplified (reduced) by CEs (AEs). The enhancement of typhoon-induced local SSC by CEs is counterbalanced by the suppression of SSC by AEs; thus, the overall impacts of CEs and AEs on typhoon-induced local SSC are relatively weak in the SCS.