Study Of The Seasonal And Interannual Characteristics Of The Upper Layer Circulation And The Predictability Of The Flow In The Strong-current Region In The South China Sea

The South China Sea (SCS) circulation system is characterized of muti-temporal and spatial scales and seasonal reversals. Its dynamic and thermodynamic processes play a critical role in transporting energy and substances as well as in driving the processes of marine biology, marine chemistry and marine geology in the SCS. Therefore, the study of the upper circulation in the SCS is of great importance. This paper mainly analyzes anomalous characteristics of the ocean circulation in the SCS during El Nino events, and determines the predictability of the upper flow in the mainstream region, then achieves the numerical simulation of the upper circulation in the SCS.Using the MV-EOF and the stream function, we analyze the upper circulation in the SCS based on the monthly CORA reanalysis data from1986-2008. In stead of using the results from the MV-EOF directly, we take the positive time coefficients of the first two modes, which have real physical meaning, and restructure them into a new mode. Comparing to the previous, this method is more intuitive and easier to operate, more importantly it can be used directly to analyze the seasonal and interannual variability of the upper circulation in the SCS.We design a Lagrangian tracking with dynamic criteria, it can extend the application area of the Lagrangian tracking. The dynamic criteria can be applied in the region of sudden flow change as well as the region of stable flow. Based on the Lagrangian tracking, tracks the diurnal variations of the SCS circulation among the tracking results based on three assimilation datasets:CORA、HYCOM and AIPO, we compare to point out the advantage of each dataset in the simulation with dynamic criteria. Then we extract the higher prediction values from the three models and reform into a comprehensive flow field, by which we can improve the tracking ability in strong-current region. Based on the original POM ocean model, we set up an orthogonal curvilinear coordinate of a high-resolution POM model, covering the SCS and the western Pacific Ocean. This design achieves the numerical simulation of the upper circulation in the SCS. Comparing to the observations and previous studies, we find that the POM model with the boundary conditions used in this study can well simulate the circulation structure and its time evolution in seasonal and interannual scale in the SCS.