Tropical cyclone-induced sea surface cooling over the Yellow Sea and Bohai Sea in the 2019 Pacific typhoon season

Shallow water response and feedback to tropical cyclones (TCs; known as typhoons in the northwest Pacific) play an important role in modulating TCs' landfall intensity. In the 2019 Pacific typhoon season, four TCs, i.e., Danas in July, Lekima in August, Lingling in September and Mitag in October, traversed and influenced the vast shallow waters of the Yellow Sea (YS) and the Bohai Sea (BS). Based on satellite and in situ buoy observed sea surface temperature (SST) datasets and numerical experiments, in this study, we examined and contrasted the SST responses of the YS and BS shallow waters to these four TCs. Compared to the other three TCs, Lekima with relatively weaker intensity, induced the largest (up to 5.5 degrees C) and most widespread SST cooling over the whole YS basin, which was attributed to the most stratified and sharpest thermal structure in August based on numerical experiments. The model results also suggest an SST cooling limitation in the condition the whole shallow water column has been well mixed. The buoy observations indicate that more than 80% of the TC-induced SST cooling occurred ahead of the TC eye centre approaching. The TC also contributes significantly to the SST seasonal cycle of coastal waters by disrupting the seasonal SST evolution in several hours and lasting for tens of days.

Automated summary

This study examines and contrasts the sea surface temperature (SST) responses of the shallow waters of the Yellow Sea and the Bohai Sea to four tropical cyclones in the 2019 Pacific typhoon season. Lekima, with relatively weaker intensity, induced the largest and most widespread SST cooling over the Yellow Sea basin, attributed to the stratified and sharp thermal structure in August. The buoy observations show that over 80% of the TC-induced SST cooling occurred ahead of the TC eye center approaching, and the TC contributes significantly to the SST seasonal cycle of coastal waters by disrupting the seasonal SST evolution lasting for tens of days.