2 University of Chinese Academy of Sciences, Beijing 100049, China;
3 Laboratory for Ocean and Climate Dynamics, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;
4 North China Sea Marine Forecasting center of State Oceanic Administration, Qingdao 266061, China
The northern East China Sea (NECS), which mainly includes the Bohai Sea and the northern Yellow Sea, is a typical semi-enclosed shallow body of water bounded to the north and west by China and to the east by Korea (Mo et al., 2016), as shown in Fig. 1. In winter, cold air masses form over the ocean east of Novaya Zemlya, west of Novaya Zemlya or south of Iceland, which invade the NECS along three tracks: the north track, the northwest track and the west track (Ding and Krishnamurti, 1987). This is the so-called cold wave. Cold waves, including cold-air outbreaks, represent one of the most extreme meteorological systems and occur much more frequently than typhoons in high-latitude waters. They are often accompanied by strong winds exceeding Beaufort scale 6 (10.8–13.8 m/s) or even 8 (17.2–20.7 m/s). The NECS responds vigorously to the passage of cold waves, including significant sealevel rise and large waves that have a serious impact on human life and shipping. However, because of the complexity and changeability of the weather systems, there is still a lack of systematic studies on the growth of wind wave frequency spectra caused by cold waves.
With the ongoing development of numerical simulations, great progress has been made in simulation studies of ocean waves. Some researchers in China have used numerical models to simulate the wind waves induced by cold waves for case analysis or hindcasting verification (Pan et al., 1992; Zheng et al., 2010; Liu et al., 2013; Yao et al., 2013). These results have verified the applicability and promoted the practical application of prediction models. In addition, frequency spectrum analysis, as a standard procedure, has been widely used to analyze and predict wind-generated ocean waves since it was first introduced in wind wave studies around 1950. Most of the common measures of wind waves, such as significant wave height and average period, are conveniently related to the frequency spectrum moments. Hence, as the observations of cold wavegenerated spectra are lacking, this study investigates the growth properties of the one-dimensional energy spectrum of cold wave-generated waves in the NECS with the aid of a third-generation wave model.