Ocean and heat flux features on the warm water and eddy during rapid intensification of typhoons in the Northwestern Pacific

Northwestern Pacific is well known for the generation and intensification of the strong typhoons especially along the warm eddies. A series of field experiments using research vessel with ocean robots have been carried out to observe air-sea parameters to investigate total heat flux from the ocean to tropical cyclones over the years. Wave gliders, argo buoy and other instruments have been used to measure air-sea parameters over the warm eddy during TC intensification. In 2022 super typhoons have been generated over the northern latitudes on the warm SST condition, while super typhoon Mindulle in 2021 was generated and got intensified during the propagation over the warm and cold eddies.

Latent heat flux over warm eddies was also estimated based upon ocean-heat parameters during rapid intensification and near rapid intensification of typhoons. The latent heat flux is much less as 200-300 W/m2 due to less specific humidity difference by near saturation at air observed sensors from instruments equipped on the wave glider. This suggests that other process such as spray effect needs to be introduced to explain a huge heat flux needed for tropical cyclone to get intensified over the eddy.

One of the noticeable features is abrupt change of OHC in the warm eddy through cooling of warm water by super typhoon Mindulle. The ocean heat flux (OHC) over the warm eddies ranges from 126 to near 0 KJ/cm2 with category 2 to 5. The minimum OHC of about 0 KJ/cm2 occurs where dynamic sea surface anomaly (ssha) is over 0.2 m, which indicates that a huge ocean heat energy moves to air, if vertical mixing is assumed to be small.

Total heat fluxes were estimated from observed data during phases of rapid intensification, super typhoon, and within radius of maximum wind of about 50 km off the track of typhoon Mindulle. The huge heat flux than before seems to appear from analysis, indicating spray and rainfall driven effect from analysis. Various data are used for comparison between data. This study was partially supported from 'Study on Northwestern Pacific Warming and Genesis and Rapid Intensification of Typhoon', funded by the Ministry of Oceans and Fisheries (20220566)).