11:00 AM - 1:00 PM
[ACG33-P13] Quantification of SST cooling induced by Typhoons Faxai (2019) and Hagibis (2019)
Keywords:Typhoon, SST, Cooling parameter, Ocean model, Typhoon characteristics, Ocean conditions
This study focused on the cooling parameter (Co), a non-dimensional number that theoretically indicates the amount of SST cooling during the passage of a typhoon, proposed by Miyamoto et al. (2017). Based on the results of ocean model, we attempt to evaluate typhoon-induced SST cooling quantitatively, separating the impacts of typhoon characteristics from the impacts of ocean conditions using the Co.
The average decrease in SST due to the effects of strong winds associated with the typhoons differed in Faxai (0.9℃) and Hagibis (1.5℃) shown by the ocean model. The average Co value was 1.6 for Faxai and 3.6 for Hagibis, indicating that SST was more easily cooled by Hagibis than by Faxai, consistent with the observations and the ocean model. The impact of ocean conditions on SST cooling by Hagibis was 2.6 times larger than that for Faxai, indicating that it is difficult to cool SST in the ocean under Hagibis than Faxai. However, the impact of Hagibis’s characteristics was 4.8 times larger than the impact of Faxai’s characteristics, indicative of more SST cooling by Hagibis. In particular, among Hagibis’s characteristics, the size in the horizontal direction had the most efficient effect on SST cooling. Although Co does not estimate the effects of advection of ocean water, we suggest that Co is a useful indicator for estimating the SST decrease caused by a typhoon.