Deduce The Eddy Viscosity Of South China Sea Using Adjoint Assimilation

The eddy viscosity, to some extent, indicates the dynamical mechanisms of ocean internal motions, therefore, the intensity variations of the eddy mixing can be deduced from the vertical profile of the eddy viscosity parameter and some other messages about the effect of wind force field to this parameter can be acquired. Accordingly, how to calculate and attain the profile of eddy viscosity parameter out of the phenomenon of ocean motions and some other necessary environment conditions is the main purpose of the thesis. Unfortunately, ocean observations are sparse and noisy. We have to resort to certain data simulation methods and choose an effective model which accords with the physical facts to calculate the eddy viscosity parameter. Adjoint assimilation technique is the main methods in the thesis.Ocean observations are assimilated into the one-dimension Ekman dynamic model by using the adjoint assimilation technique and the skills of resolving the counter-problems on physics, and the parameter of the model can be optimized. In this way, the internal messages of ocean, the vertical distribution of the eddy viscosity parameter, are expected to be found out in order to the further study on the internal dynamic mechanism of the ocean motions. An identical twin experiment is discussed first in which the observations are created by the dynamic model. The field measurements from the 250k ACDP located Wenchang flat roof in South China Sea and real time wind force are analyzed. The unknown vertical eddy viscosity distribution is deduced from the data. To quest for the viscosity developing process with the variations of the wind field, two simulations with two different time intervals are tried.Firstly, the eddy viscosity parameter is regarded as the function of space only and pay attention to the variations in depth. It appears that the viscosity alters graduallyvertically between the scope of 10^-3 -10^-2m²/s . Viscosity responds accordinglyafter the wind force changes. Secondly, the eddy viscosity parameter is regarded as the function both of space and time and the aim is to obtain the developing process of the parameter. It appears that the parameter vertical profile has a small adjustment of1(T4 - 1(T3 according to the variations of the wind field. It increases when wind fieldis strong or decreases when wind field is weak, however, there exits time interval before the adjustment appears.