X. San Liang

By X. San Liang and Lan Wang

The cyclogenesis of typhoons has been a continuing challenge in dynamic meteorology. In this study, we use a recently developed methodology, namely, multiscale window transform (MWT), together with the MWT-based localized multiscale energy and vorticity analysis and the theory of canonical transfer, to investigate the formation, maintenance, and decay of the typhoon Damrey, a rarely seen tropical storm of higher-latitude origin. The atmospheric fields are first reconstructed onto three scale subspaces or scale windows: large-scale window, tropical cyclone-scale window, and cumulus convection-scale window. On the cyclone-scale window, Damrey is found right along the edge of the subtropical high. It is generated due to a strong barotropic instability in the lower troposphere, but its subsequent rapid amplification is, however, related to a baroclinic instability in the upper troposphere. Damrey begins to decay before landfall, right over East China Sea at the mouth of Yangtze River, where a strong inverse cascade center resides and transfers the cyclone-scale energy backward to the large-scale window.

Part of the book: Coastal Environment, Disaster, and Infrastructure

By X. San Liang

Coastal-trapped waves (CTWs) are a class of subinertial signals in the weather frequency band that play a pivotal role in coastal air-sea interaction. However, this important topic seems to be missing in the heated debate in recent years on coastal environmental change and protection. In this chapter, a brief but self-contained introduction of the CTW theory is presented, in the hope of providing a reference for investigators in the relevant fields. Also presented is a numerical scheme for computing the wave properties. As a demonstration, we have conducted a preliminary study of the CTWs for a section across the Subei Bank in the Yellow Sea. By the results, all the computed slow modes, including a bottom-intensified one, seem to be slowing down since two decades ago. They have particularly slowed down in the event when a strong El Niño is followed by a strong La Niña, such as in the 97–98 and 09–10 El Niño events.

Part of the book: Coastal Environment, Disaster, and Infrastructure

By X. San Liang and Yineng Rong

Nuclear pollution has become a new form and perhaps more harmful type of pollution that obsesses coastal regions; it has been of increasing concern after the disastrous Fukushima nuclear leak on March 11, 2011. In order to assess the impact of the Fukushima accident on the East China Sea (ECS), a highly resolved model is set up to simulate the evolution of the 137Cs concentration. Different from previous studies in this regard, here we take into account the radionuclides originally existing in the ocean. It is found that the radionuclides from the Fukushima leak do have reached ECS, though with a concentration far below the harmful level. The major waterways that inlet the radionuclides are Taiwan Strait and the waterway east of Taiwan. The radioactive material tends to accumulate in the ECS until reaching its peak in 2019; afterward, the outflux through Tokara Strait and Tsushima exceeds the influx through the two southern waterways, and the material resumes in 2021 to its original state. The concentration is neither homogeneously nor stationarily distributed; for example, usually in summer, there is a high center over the Subei Bank in the Yellow Sea. This study is expected, should a similar accident happen again, to help decide where to monitor the ocean, and, hopefully, how to get the pollution under control.

Part of the book: Coastal Environment, Disaster, and Infrastructure

By Jianyu Hu, X. San Liang and Hongyang Lin

Upwelling is an important oceanographic phenomenon that brings cooler and nutrient-rich water upward to the surface, facilitating the growth of phytoplankton and other primary producers, which results in high levels of primary productivity and hence fishery production. This chapter presents a review of recent studies on six major upwelling regions along the China coasts, with a focus on the eastern and southeastern coasts of mainland China, based on in situ measurements, satellite observations and numerical simulations. These upwelling regions result primarily from the summer monsoon winds, though other mechanisms, such as river discharge, baroclinicity, topography, tides, and the presence of mean current, may also be in play. In this review, their impacts on local biogeochemical processes are briefly summarized. Also discussed are their possible responses to the globally changing climate.

Part of the book: Coastal Environment, Disaster, and Infrastructure

By X. San Liang, Minghai Huang, Hui Wu and Yihe Wang

An important hydrographic phenomenon in the Yellow Sea is the surface cold patches (SCP) in warm seasons, among which the most conspicuous are the Shandong SCP, Subei SCP, and Mokpo SCP. Previous studies based on monthly mean fields propose that these patches result from the collaboration of tidal mixing and tidal induced upwelling. While this is true for patches like the Shandong SCP, the monthly mean tidal mixing and upwelling alone cannot explain all their formations. In this study, through a detailed analysis of their patterns over a spring-neap tidal cycle, it is found that the Subei and Mokpo SCPs show distinct spring-neap variations. During the neap tide phase, strong stratification is established, and hence the cold patches in these two areas may be greatly weakened or even suppressed, while during the spring tide phase, the surface temperature reaches its minimum. That is to say, for these two SCPs, besides the well-accepted mechanisms, the effect of spring-neap tidal variation must be taken into account.

Part of the book: Coastal Environment, Disaster, and Infrastructure