LAUSR

ABSTRACT Allahdadi, M.N. and Li, C., 2018. Numerical simulation of Louisiana shelf circulation under Hurricane Katrina. The response of currents on the Louisiana shelf to Hurricane Katrina was studied using the 3-D Finite Volume Community Ocean Model (FVCOM). The study area encompassed the Louisiana shelf covering both sides of the Mississippi River's Birdsfoot Delta. The model was forced by a wind field prepared by combining the Hurricane Research Division Wind Analysis System data for the hurricane with background winds outside of the hurricane's influence from National Centers for Environmental Prediction (NCEP)/North American Regional Reanalysis (NARR). Current and water-level data recorded at Wave-Current-Surge Information System (WAVCIS) stations over the inner shelf provided a unique opportunity to examine shelf hydrodynamics in response to Katrina. Model performance was evaluated by examining water-column stratification under different scenarios and using a range of parameters of the Mellor-Yamada level 2.5 turbulence closures for vertical eddy viscosity. This resulted in a set of appropriate closure parameters for the response of a shallow shelf to a hurricane. Simulated near-surface currents followed the overall pattern of hurricane wind structure over the outer shelf and to some extent over the inner shelf; however, currents over the shallow Louisiana shelf were affected by coastal geometry. Investigation of bottom currents showed a possible baroclinic response over both the inner and outer shelves. Over the Louisiana shelf, this was similar to the baroclinic response of stratified shallow waters for regions outside of the radius of maximum wind (Rmw), as identified in previous studies. A part of this baroclinic response can be explained by the horizontal baroclinic pressure gradient that resulted from the inhomogeneous hurricane-induced surface cooling.