Chinese Journal of Oceanology and Limnology   2018, Vol. 36 issue(5): 1509-1526     PDF       
http://dx.doi.org/10.1007/s00343-018-7265-8
Institute of Oceanology, Chinese Academy of Sciences
0

Article Information

MO Dongxue(莫冬雪), HOU Yijun(侯一筠), LIU Yahao(刘亚豪), LI Jian(李健)
Study on the growth of wind wave frequency spectra generated by cold waves in the northern East China Sea
Chinese Journal of Oceanology and Limnology, 36(5): 1509-1526
http://dx.doi.org/10.1007/s00343-018-7265-8

Article History

Received Sep. 15, 2017
accepted in principle Oct. 9, 2017
accepted for publication Oct. 16, 2017
Study on the growth of wind wave frequency spectra generated by cold waves in the northern East China Sea
MO Dongxue(莫冬雪)1,2, HOU Yijun(侯一筠)1,2,3, LIU Yahao(刘亚豪)1, LI Jian(李健)4     
1 Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;
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
Abstract: The growth of frequency spectra and spectral parameters of wind waves generated by cold waves, a kind of severe weather system, in the northern East China Sea is studied in this paper. Based on a third-generation wave action model (the Simulating WAves Nearshore model), simulations were developed to analyze the spatiotemporal characteristics of wind waves and to output spectral data. It is shown that the cold wave-induced spectra can be well described by the modified Joint North Sea Wave Project spectral form. The growth of wave spectra is comprehensively reflected by the evolution of the three characteristic parameters:peak frequency, spectral peak and wave energy. Besides, the approximations of dependences between spectral parameters and the three types of universal induced factors are obtained with the least squares method and compared systematically. Fetch and peak frequency turn out to be suitable parameters to describe the spectral parameters, while the dependences on the inverse wave age vary in different sea areas. In general, the derived relationships improve on results from previous studies for better practical application of the wind wave frequency spectrum in the northern East China Sea.
Keywords: cold wave     frequency spectra     wind wave parameters     Simulating WAves Nearshore (SWAN)     northern East China Sea    
1 INTRODUCTION

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.

Figure 1 Location and topography of the northern East China Sea The black dashed lines are the dividing lines between the Bohai Sea, northern Yellow Sea and southern Yellow Sea. Wave measurements were made at buoys B1, B2 and B3 (filled blue squares for case in 2015) (Section 2). Five sites were chosen (filled red triangles) for further research (Sections 3 and 4).

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.