Quantification and attribution of ocean cooling induced by the passages of typhoons Faxai (2019) and Hagibis (2019) over the same region using a high‐resolution ocean model and cooling parameters

Abstract

This study quantitatively evaluated the typhoon‐induced sea surface temperature (SST) cooling caused by typhoons Faxai (2019) and Hagibis (2019) using a high‐resolution ocean model and the cooling parameter (Co). Faxai and Hagibis both passed over the ocean south of the eastern part of the Japanese main island, but the associated average SST decreases differed. Faxai produced a decrease of less than 2°C, whereas Hagibis produced a decrease of more than 2°C. 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. The impact of ocean conditions on the typhoon‐induced SST cooling by Hagibis was 2.6 times larger than the impact by Faxai, indicating that the ocean before Hagibis passes is less hard to cool ocean than Faxai. In short, it is important for ocean cooling not only ocean conditions but also typhoon characteristics because in fact, Hagibis cooled the ocean more than Faxai. In addition, the impact of Hagibis's characteristics on the typhoon‐induced SST cooling was 4.8 times larger than the impact of Faxai's characteristics. Thus, SST was more likely to cool by typhoon characteristics in the case of Hagibis. In particular, among Hagibis's characteristics, typhoon size in the horizontal direction had the most efficient effect on SST cooling. Although Co does not consider the effects of the advection of ocean water, we suggest that Co is a practical indicator for estimating SST cooling caused by a typhoon and comparing factors of typhoon‐induced SST cooling in multiple cases.

Buffering Effect of Atmosphere–Ocean Coupling on Intensity Changes of Tropical Cyclones Under a Changing Climate

“…However, the mean UOHC along each track from the initial time in the CNTL simulations was 51, 29, 20, and 83 kJ cm −2 for Trami, Faxai, Hagibis, and Haishen, respectively (Table S2 in Supporting Information ). As shown by previous observational and modeling studies (e.g., D’Asaro et al., 2014; Iida et al., 2023), not only ocean conditions but also typhoon characteristics such as the storm size and translation speed (hereafter, S) are important for typhoon‐induced SST‐cooling. Following D’Asaro et al.…”

“…Trami was a typical slow‐moving storm with a large eye (Figure 3j in Kanada, Aiki, Tsuboki, and Takayabu (2021) and Hirano et al. (2022)), whereas Faxai was a typical compact, fast‐moving storm (Iida et al., 2023). In general, a large, slow‐moving (compact, fast‐moving storm) storm induces greater (smaller) SST‐cooling.…”

“…By utilizing S0, we can easily identify a potentially destructive TC that strengthens greatly under global warming from a TC with significant resilience against global warming. In the present study, we defined storm size as RMW, because high SST inside the RMW is important for the TC intensification (Kanada, Tsujino, et al., 2017; Rai et al., 2016); however, there are other size definitions that can be impact on the storm‐induced SST‐cooling (Iida et al., 2023; Lin et al., 2021). Furthermore, the amount of storm‐induced SST‐cooling is also influenced by ocean stratification (Miyamoto et al., 2017).…”