Calculation of current in the Taiwan Strait during summer Ⅱ.Three-dimensional semidiagnostic and prognostic calculations

The semidiagnostic and prognostic models are used to compute the current in the Taiwan Strait with wind and hydragraphic data collected during August,1984 and September 1-6,1988.This calculation can be divided into two stages,i.e.(1) the adjustable stage;(2) prognostic calculation.The computed result shows that the density and velocity fields etc.have been adjusted when t=2.5 d,namely the solution of semidiagr(ostic calculation is obtained,and the quasi-steady state solution have been reached after about 40 d.Comparing the results of diagnostic calculation with those of semidiagnostic and prognostic calculations indicates that they agree qualitatively.For example,they all have the foVowing common features:(1) there is a persistent northward flow with a volume transport of 0.8×10⁶m³/s through the Taiwan Strait in summer;(2) the current near the western coast of Taiwan is stronger than that in other regions;(3) the upwelling occurs near the Fujian coast and so on.However,there is a quantitative difference between them as follows.For example,the horimntal velocity near the western coast of Taiwan and the upwelling speed near the Fujian coast both are underestimated in the diagnostic calculation,because the data used in which is smoothed,and they both are intensified in the solutions of semidiagnostic and prognostic calculations.For example,the maximum velocity near the western coast of Taiwan at t=0 d(diagnostic),2.5 d(semidiagnostic) and 300 d(prognostic) is 59.1,62.1 and 62.0 ctn/s,respectively.From the above rnmparison we see it is quite necessary that a semidiagnostic model be used to compute the currents when the data have been smoothed.