Numerical simulation of cold wave-induced surges in Zhejiang offshore from 2013 to 2023

Cold waves are a common meteorological phenomenon in the winter seasons, which often induce water surges that further threaten offshore safety. Zhejiang offshore is a typical region that frequently suffers from cold waves. Hence, understanding the characteristics and mechanisms of cold wave-induced surges in Zhejiang offshore is of great importance. Based on the Regional Ocean Modeling System, we simulate a total of 35 cold wave events and analyze their associated surges in Zhejiang offshore in the winter seasons from 2013 to 2023. The regional maximum surges induced by these cold wave events range between 0.23 and 1.02 m. According to the spatial pattern, the surges induced by the 35 cold wave events can be classified into three categories, which are characterized by high values in Hangzhou Bay, Taizhou-Wenzhou offshore, and nearly the entire coastal region of Zhejiang, respectively. Moreover, both the Kelvin wave and Ekman transport contribute to the surges induced by cold waves. Through a comparison with control experiments, it is found that the Kelvin wave is the dominant factor, which contributes more than 75 % to the surges, whereas the contribution of Ekman transport is less than 25 %.