Study On Mathematical Model Of Tide In Zhejiang Offshore Area

This article analyses the character of Zhejiang offshore tide simply By 22 groups of absolute autoptical tide data and the quoted co-tidal and co-range charts of four main tides which are based on autoptical tide data. After that, a numerical model about Zhejiang shore tide is established by mike21 (HD) program. After validating the good agreement between simulated results and observed ones, the planar hydrodynamic flow of this ocean area is analysed in detail. Then co-tidal and co-range chart of each main tide is drew based on the computational result. It can be found that each co-tidal and co-range chart that is based on the simulated result is suitable to the co-tidal and co-range chart that is deduced from autoptical data, besides, the modle co-tidal and co-range chart can perfect the co-tidal and co-range chart from autoptical data where autoptical data is too hard to get.With co-tidal and co-range charts that depend on the computational result, this text analyses semidiurnal tide and diurnal tide in detail, including the swing value and distributing rule of each tide and their moving directions and rule. There are mainly some founds as follow. In searched place, semidiurnal tide is in the highest flight absolutely, so their swing direction of change can represent the swing change rule of Zhejiang tide. Tide swing get bigger from east to west in Zhejiang sea, near to Zhoushan sea, it gets less, but near to Hangzhou gulf, it becomes to get more again. In each bay, for example, Hangzhou gulf, Sanmen bay, Yueqing bay, Wenzhou bay, tide swing is bigger, when semidiurnal tides move from the open sea to offing, they first get the high tide in the mouth of Samen bay, then bifurcate to two branches, one goes along the northwest direction and the other goes along southwest. And it can be easily found that the moving direction of diurnal tides is obviously different from semidiurnal tides. Diurnal tides move from northeast to southwest, near to Huangze ocean, they bifurcate to two branches, one goes toward Hangzhou gulf, and the other goes toward the south of Zhejiang seaboard, semidiurnal tides spread more quickly in the south than in the north of Zhejiang seaboard. Diurnal tides spread more slowly in Zhoushan and Hangzhou gulf ocean areas, when more quickly in other ocean areas.This model can forecasts each hour tide elevation of any area in Zhejiang offshore area through several simple processes, so it owns some practicability to a certain extent. And it can be found that the forecasted tide elevation value is more accurate in an open sea than it is in a place which is close to land.