George Halliwell , Nick Shay Rosenstiel School of Marine and Atmospheric Science

Evaluation of the Simulated Ocean Response to Hurricane Ivan in Comparison to High-Quality Ocean Observations George Halliwell, Nick Shay Rosenstiel School of Marine and Atmospheric Science University of Miami, Miami, FL William Teague Naval Research Laboratory, Stennis Space Center, MS

Improve ocean model response to TC forcing in a complex oceanographic environment Improve coupled TC prediction models Especially intensity forecasts Improve hindcasts of the ocean response during and after individual storms e.g., oil and gas industry Improve our scientific understanding of the ocean response to TC forcing GOALS

Ocean models still require evaluation and improvement of TC response Requires high-quality observations Requirements Accurate initialization Ocean features (currents, warm- and cold-core eddies) Vertical T, S, density structure Ocean Heat Content (OHC) distribution Improve air-sea flux parameterizations Improve vertical mixing Ocean Model Improvement

Evaluate HYbrid Coordinate Ocean Model (HYCOM) against high-quality ocean observations Future ocean component of HWRF model Uncoupled ocean response simulations Isolate ocean model sensitivity given constant forcing Will complement evaluation of the coupled HWRF model Initial Focus - Hurricane Ivan (Sept. 2004) Initial OHC distribution important to SST response High-quality ADCP velocity moorings Naval Research Laboratory SEED project APPROACH

Observed SST Response to Ivan Microwave satellite (Remote Sensing Systems) AVHRR (Walker et al, 2005)

Ivan Intensity

Gulf of Mexico domain 10 Sept. to 6 Oct. 2004 Initial and boundary conditions Ocean nowcast-forecast system Alternative to feature-based analysis Several products available or under development Global Ocean Data Assimilation Experiment (GODAE) Test the U. S. Navy system Under development by NOPP consortium Couples HYCOM to the NCODA assimilation system Hurricane Ivan Simulations (1)

Forcing Navy 0.5-degree NOGAPS atmospheric model Wind speed blended with higher resolution fields obtained from the NOAA/HRD HWIND product Wind stress calculated using Powell cd Hurricane Ivan Simulations (2)

Importance of accurate initialization Evaluate ocean data assimilative hindcast U.S. Navy ocean nowcast-forecast system (HYCOM-NCODA) Sensitivity to vertical mixing parameterization K-Profile Parameterization (KPP) Mellor-Yamada level 2.5 closure (MY) Goddard Institute for Space Studies (GISS) Ocean current response ADCP moorings in north-central Gulf of Mexico Ivan Analysis

SSH, 10 Sept. 2004

Simulated SST Response to Ivan

SST (C) Before and After Ivan

Depth-Time Temperature Variability

SST Change, 10 to 17 Sept.

SST (C) After Ivan

SEED Moorings and Ivan Path 9

u v 0 150

Summary • Accurate initialization of the Loop Current, detached warm eddy, and two cold eddies by an ocean nowcast product was critically important to the Ivan ocean response simulations • Cannot forget cold ocean features • Response is sensitive to vertical mixing parameterization • Three-dimensional dynamical processes are important • Good qualitative comparison between observed and simulated currents at SEED moorings • Simulated near-inertial currents decay too rapidly • Ocean model improvement will require high-quality three-dimensional ocean observations

George Halliwell , Nick Shay Rosenstiel School of Marine and Atmospheric Science