evaluation of the simulated ocean response to hurricane ivan in comparison to high-quality ocean...
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Evaluation of the Simulated Ocean Response to Hurricane Ivan in
Comparison to High-Quality Ocean Observations
Evaluation of the Simulated Ocean Response to Hurricane Ivan in
Comparison to High-Quality Ocean Observations
George Halliwell, Nick ShayRosenstiel School of Marine and Atmospheric Science
University of Miami, Miami, FL
William TeagueNaval Research Laboratory, Stennis Space Center, MS
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
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
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
Observed SST Response to Ivan
Microwave satellite(Remote Sensing Systems)
AVHRR (Walker et al, 2005)
Ivan Intensity
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
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 cd
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
SSH, 10 Sept. 2004
Simulated SST Response to Ivan
SST (C) Before and After Ivan
Depth-Time Temperature Variability
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
SST Change, 10 to 17 Sept.
SST (C) After Ivan
Micro-wave
Satellite
AVHRR
Satellite
GISS
Sim.
MY
Sim.
KPP
Sim.
Northern
Cyclone
(coldest T)
24.9 ~23 22.9 22.8 21.3
Southern
Cyclone
(coldest T)
24.6 ~22 21.1 22.2 18.8
Anticyclone
(avg. T, 26-28N, 88-89.5W)
28.0 ~28 29.4 29.4 29.2
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
SEED Moorings and Ivan Path
9
u v0
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