Study of Meteorological Tsunamis Generated in the Yellow Sea

Abstract

Meteorological tsunamis (meteotsunami) are known to be generated by an atmospheric pressure disturbance coincident with a density current which can be evolved by the intrusion of a cold air mass under a warm one due to their different density. On the 31st of March, 2007 and the 5th of May, 2008, meteorological tsunamis occurred in the Yellow Sea and caused losses of life and property in the western coastal region of Korea. However, it has been difficult to understand the detailed process with respect to the occurrence and travel of the air pressure jumps, which are a main source of the meteotsunami, since there was no observations recorded in the middle of the Yellow Sea. In this study, the generation mechanism and the path of the air pressure jump and its resultant meteorological tsunami in the Yellow Sea were investigated by various data analysis and numerical simulation. For the investigation, the weather charts constructed by Korea Meteorological Administration (KMA) and the infrared images of Multifunctional Transport Satellite (MTSAT) were analyzed, and the observed atmospheric pressure data recorded by Automatic Weather Stations (AWS) of KMA and the tidal stations of Korea Hydrographic and Oceanograpgic Administration (KHOA) were applied to this analysis. The analyzed results showed that the polar jet stream, which flows mainly from west to east and meanders north and south in the atmosphere of the Earth, had an effect on the occurrence and travel of the abrupt air pressure disturbances (i.e., pressure jump), when a cold air mass, which is shed from the polar jet stream due to centrifugal force of its meandering, encountered a local warm air mass. Also, it was confirmed that the atmospheric pressure jump propagated towards the Korean Peninsula through two different routes and generated the meteorological tsunami on the 31st of March, 2007. In order to verify the relation between the atmospheric pressure jump and the meteorological tsunami, numerical simulation of the meteorological tsunami event observed on 31 March 2007 was performed by using the nonlinear shallow-water equation model. For the simulation, the analyzed pressure jump data was applied as an input data. The results of the simulation were compared with the observed data obtained from the tidal records of Yeonggwang. The comparison showed that the computed tsunami wave period and maximum water elevation agreed reasonably with those of the observations. As a result, the agreement indicates that the generation mechanism and path of air pressure jump data analyzed in this study have reasonable validity.