65th IHC Booklet/Program (pdf - 4.9MB) - Office of the Federal ...

Improving Ocean Model Performance in Coupled Hurricane Forecasts through Improved
Initialization
George R. Halliwell 1 , Lynn K. Shay 2 , Debra Willey 3 , Jodi Brewster 2 , Benjamin Jaimes 2 , Gustavo
Goni 1
(George.Halliwell@noaa.gov)
1 Physical Oceanography Division, NOAA, Atlantic Oceanographic and Meteorological
Laboratory
2 Division of Meteorology and Physical Oceanography, RSMAS, University of Miami
3 Cooperative Institute of Marine and Atmospheric Studies, University of Miami
4 NOAA, Atlantic Oceanographic and Meteorological Laboratory
The goal of the Shay-Halliwell JHT project is to improve the performance of ocean models
for coupled hurricane forecasting. This goal will be achieved by improving the accuracy of ocean
model initialization and improving ocean model physics and numerics. Based on our prior work,
forecast SST depends so strongly on initialization accuracy that evaluation of ocean model
upgrades cannot be reliably performed until significant initialization improvements are made.
Candidate products that can be used to initialize ocean models include several real-time dataassimilative
ocean analyses along with synthetic upper-ocean temperature-salinity analyses
derived from satellite observations (altimetry and SST). Unfortunately, evaluation and
identification of optimum initialization products has been hindered by the relative lack of threedimensional
synoptic observations of the ocean in comparison to the atmosphere.
An unprecedented set of ocean observations was collected in the eastern Gulf of Mexico
during spring and summer 2010 in response to the Deepwater Horizon oil spill. Nine synoptic
surveys from a NOAA P-3 hurricane research aircraft were conducted by NOAA and
UM/RSMAS between 8 May and 9 July, deploying AXBTs, AXCTDs, and AXCPs.
NOAA/AOML and other institutions conducted extensive in-situ surveys of upper-ocean
temperature, salinity, and currents on cruises. NOAA/AOML produced satellite-derived products
(e.g. SST, SSH, surface currents) and also deployed surface drifters to provide surface
measurements and track Lagrangian trajectories. An extensive set of moored observations was
collected by the Minerals Management Service. This unprecedented regional dataset will enable
a high-quality evaluation of potential ocean initialization products to be performed in a
dynamically active region.
In this presentation, six different products are evaluated, including three HYCOM analyses
(Navy 0.08° global, Navy 0.04° GoM, NOAA/NCEP Atlantic RTOFS) and three other model
types (NRL IASNFC NCOM, NCSU SABGOM ROMS, and NOAA/NOS NGOM POM).
Evaluation of these products through comparison to P-3 profiles and AOML cruise observations
demonstrates that the Navy HYCOM products consistently display the smallest bias and RMS
errors relative to observations. In contrast, the NOAA/EMC RTOFS HYCOM displayed the
largest bias and RMS errors as a result of known code problems. This problem has negatively
impacted development of the HYCOM-HWRF coupled forecast model that uses RTOFS to
provide initial fields. Fortunately, this problem should be cured when the planned transition of
RTOFS HYCOM to the Navy global HYCOM system at EMC occurs during 2011. As of this
writing, the Navy global HYCOM system produces the smallest bias and RMS errors compared
to observations in the eastern Gulf of Mexico.
Poster Session – Page 15