Effect of stratification on current hydrodynamics over Louisiana shelf during Hurricane Katrina

作     者：Mohammad Nabi Allahdadi Chunyan Li Mohammad Nabi Allahdadi;Chunyan Li

作者机构：Department of Oceanography and Coastal Sciences College of the Coast and Environment Louisiana State University Baton Rouge 70803 USA 

出 版 物：《Water Science and Engineering》 (水科学与水工程（英文版）)

年 卷 期：2017年第10卷第2期

页      面：154-165页

核心收录：

学科分类：07[理学] 0707[理学-海洋科学] 070601[理学-气象学] 0815[工学-水利工程] 0706[理学-大气科学] 0813[工学-建筑学] 0824[工学-船舶与海洋工程] 0814[工学-土木工程] 

基　　金：supported by grants from Louisiana's Coastal Protection and Restoration Authority(CPRA) the Stennis Space Center,the Lake Pontchartrain Basin Foundation,the National Science Foundation(Grants No.OCE-0554674,DEB-0833225,OCE-1140268,and OCE-1140307) the Hypoxia Project of NOAA(Grant No.NA06NPS4780197) the Shanghai Universities First-Class Disciplines Project the Shanghai Ocean University International Center for Marine Studies 

主　　题：Hurricane Katrina Louisiana shelf Hydrodynamics Baroclinic and barotropic models Stratification 

摘      要：Numerical experiments were conducted using the finite volume community ocean model(FVCOM) to study the impact of the initial density stratification on simulated currents over the Louisiana shelf during Hurricane Katrina. Model results for two simulation scenarios, including an initially stratified shelf and an initially non-stratified shelf, were examined. Comparison of two simulations for two-dimensional(2D) currents,the time series of current speed, and variations of cross-shore currents across different sections showed that the smallest differences between simulated currents for these two scenarios occurred over highly mixed regions within 1 radius of maximum wind(RMW) under the hurricane.For areas farther from the mixed zone, differences increased, reaching the maximum values off Terrebonne Bay. These large discrepancies correspond to significant differences between calculated vertical eddy viscosities for the two scenarios. The differences were addressed based on the contradictory behavior of turbulence in a stratified fluid, as compared to a non-stratified fluid. Incorporation of this behavior in the MellorYamada turbulent closure model established a Richardson number-based stability function that was used for estimation of the vertical eddy viscosity from the turbulent energy and macroscale. The results of this study demonstrate the necessity for inclusion of shelf stratification when circulation modeling is conducted using three-dimensional(3D) baroclinic models. To achieve high-accuracy currents, the parameters associated with the turbulence closures should be calibrated with field measurements of currents at different depths.