1. 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

2. GOALS 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

3. Ocean Model Improvement 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

4. APPROACH 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

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

6. Ivan Intensity

7. Hurricane Ivan Simulations (1) 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

8. Hurricane Ivan Simulations (2) 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 c d

9. Ivan Analysis 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

10. SSH, 10 Sept. 2004

11. Simulated SST Response to Ivan

12. SST (C) Before and After Ivan

13. Depth-Time Temperature Variability

14. Ivan Analysis 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

15. SST Change, 10 to 17 Sept.

16. SST (C) After Ivan Micro- wave Satellite AVHRR Satellite GISS Sim. MY Sim. KPP Sim. Northern Cyclone (coldest T) 24.9~2322.922.821.3 Southern Cyclone (coldest T) 24.6~2221.122.218.8 Anticyclone (avg. T, 26-28N, 88-89.5W) 28.0~2829.4 29.2

17. Ivan Analysis 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

18. SEED Moorings and Ivan Path 9

20. uv 0 150

21. 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