| Air-Sea Stability Effects on the 10 m Winds Over the Global Ocean: Evaluations of Air-Sea Flux Algorithms |
09 APR 2008 |
15 pages |
| Authors:
Ahmet B. Kara; Alan J. Wallcraft; Mark A. Bourassa; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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 | Spatial and temporal variability of the impact of air-sea stratification on the differences between satellite-derived 10 m equivalent neutral wind speeds and stability-dependent (e.g., in situ) 10 m wind speeds are quantitatively examined over the global ocean. The influences of stability are compared with three air-sea flux algorithms, Coupled Ocean-Atmosphere Response Experiment (version 3.0), Bourassa-Vincent-Wood, and Liu-Katsaros-Businger. Analyses are first presented at many individual buoy locations and then are extended ... |
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| Value of Bulk Heat Flux Parameterizations for Ocean SST Prediction |
MAR 2008 |
20 pages |
| Authors:
Alan J. Wallcraft; A. B. Kara; Harley E. Hurlburt; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Bulk heat flux parameterization is an increasingly popular technique for forcing non-coupled ocean models. If sea surface temperature (SST) from the model is colder (warmer) than observed, then the net heat flux will be higher (lower) than observed; thus bulk parameterizations tend to keep model SST close to observational SST on long time scales. However, bulk parameterizations imply neither strong damping of SST variability nor strong relaxation to near-surface (e.g., ... |
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| Performance of Mixed Layer Models in Simulating SST in the Equatorial Pacific Ocean |
23 FEB 2008 |
17 pages |
| Authors:
Birol Kara; Alan J. Wallcraft; Paul J. Martin; Eric P. Chassignet; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| This paper examines the ability of three ocean mixed layer submodels to depict inter-annual variations of sea surface temperature (SST) in a global configuration of the HYbrid Coordinate Ocean Model (HYCOM). The mixed layer submodels are (1) the K-Profile Parameterization (KPP), (2) the NASA Goddard Institute for Space Studies (GISS) turbulence closure, and (3) the Mellor-Yamada Level 2.5 (MY) turbulence closure. Accuracy of SSTs from the submodels is investigated during ... |
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| Performance of Mixed Layer Models in the Mediterranean Sea |
2008 |
12 pages |
| Authors:
A. B. Kara; Alan J. Wallcraft; Harley E. Hurlburt; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS
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| Wind Stress Drag Coefficient over the Global Ocean |
01 DEC 2007 |
10 pages |
| Authors:
Ahmet B. Kara; Alan J. Wallcraft; E. J. Metzger; Harley E. Hurlburt; Chris Fairall; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Interannual and climatological variations of wind stress drag coefficient are examined over the global ocean from 1998 to 2004. Here CD is calculated using high temporal resolution (3- and 6-hourly) surface atmospheric variables from two datasets: 1 )the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) and 2) the Navy Operational Global Atmospheric Prediction System. The stability-dependent CD algorithm applied to both datasets gives almost identical values over ... |
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| 1/32 Degree Real-Time Global Ocean Prediction and Value-Added Over 1/16 Degree Resolution |
30 JUL 2007 |
26 pages |
| Authors:
Jay Shriver; Harley E. Hurlburt; Ole M. Smedstad; Alan J. Wallcraft; Robert C. Rhodes; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| A 1/32 degree global ocean nowcast/forecast system has been developed by the Naval Research Laboratory at the Stennis Space Center. It started running at the Naval Oceanographic Office in near real-time on 1 Nov. 2003 and has been running daily in real-time since I Mar. 2005. It became an operational system on 6 March 2006, replacing the existing 1/16 degree system which ceased operation on 12 March 2006. Both systems ... |
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| Global Ocean Prediction Using HYCOM |
JUL 2007 |
6 pages |
| Authors:
Alan J. Wallcraft; Eric P. Chassignet; James A. Cummings; Harley E. Hurlburt; E. J. Metzger; Ole M. Smedstad; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| In the third year of this project, fully-global eddy-resolving simulations have been performed using the HYCOM at 1/12-deg resolution. HYCOM is isopycnal in the open, stratified ocean, but makes a dynamically smooth transition to a terrain-following coordinate in shallow water and to pressure coordinates in the mixed layer and/or unstratified regions via the layered continuity equation. This approach incorporates the disadvantages of these three distinct vertical coordinate types into one ... |
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| The HYCOM (HYbrid Coordinate Ocean Model) Data Assimilative System |
JUN 2007 |
25 pages |
| Authors:
Eric P. Chassignet; Harley E. Hulburt; Ole M. Smedstad; George R. Halliwell; Patrick J. Hogan; Alan J. Wallcraft; Remy Baraille; Rainer Bleck; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| This article provides an overview of the effort centered on the HYbrid Coordinate Ocean Model (HYCOM) to develop an eddy-resolving. real-time global and basin-scale ocean hindcast, nowcast, and prediction system in the context of the Global Ocean Data Assimilation Experiment (GODAE). The main characteristics of HYCOM are first presented. followed by a description and assessment of the present near real-time Atlantic forecasting system. Regional/coastal applications are also discussed since an ... |
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| Wind Speed Variability over the Marmara Sea |
APR 2007 |
2 pages |
| Authors:
Ahmet B. Kara; Alan J. Wallcraft; Ewa Jarosz; Mark Bourassa; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Between 2000 and 2006, wind speed measurements were collected over the Marmara Sea by the SeaWinds scatterometer on the QuikSCAT satellite at a spatial resolution of 0.25 x 0.25 degrees. Relatively small interannual variability was noted in monthly mean wind speeds. Typically. wind speed during the summer was weaker by approximately 2 m/s than that observed in winter. This remotely sensed wind data set is intended for various air-sea interaction ... |
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| Application of Creeping Sea-Fill Methodology to the Wind Speed over the Caspian Sea |
APR 2007 |
2 pages |
| Authors:
Murat Gunduz; Ahmet B. Kara; Alan J. Wallcraft; E. J. Metzger; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Numerical weather prediction (NWP) products include possible errors near coastal regions. The effects of such errors on near-surface wind speed, which is one of the critical variables for coastal applications, are investigated over the Caspian Sea. For this purpose, a creeping sea-fill methodology developed by Kara, Wallcraft, and Hurlburt was applied to the coarse resolution (1.125 degrees x 1.125 degrees) wind speed data obtained from the European Centre for Medium-Range ... |
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| A Correction for Land Contamination of Atmospheric Variables near Land-Sea Boundaries |
APR 2007 |
17 pages |
| Authors:
A. B. Kara; Alan J. Wallcraft; Harley E. Hurlburt; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Ocean models need over-ocean atmospheric forcing. However, such forcing is not necessarily provided near the land-sea boundary because (1) the atmospheric model grid used for forcing is frequently much coarser than the ocean model grid, and (2) some of the atmospheric model grid over the ocean includes land values near coastal regions. This paper presents a creeping sea-fill methodology to reduce the improper representation of scalar atmospheric forcing variables near ... |
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| Assessment of Data Assimilative Ocean Models in the Gulf of Mexico Using Ocean Color |
09 JUN 2006 |
15 pages |
| Authors:
Eric P. Chassignet; Harley E. Hurlburt; Ole M. Smedstad; Charlie N. Barron; Dong S. Ko; Robert C. Rhodes; Jay F. Shriver; Alan J. Wallcraft; Robert A. Arnone; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| This paper illustrates the value of SeaWiFS ocean color imagery in assessing the ability of three data-assimilative ocean models (configured in five prediction systems) to map mesoscale variability in the Gulf of Mexico (i.e., the Loop Current and associated warm and cold eddies) and in helping to diagnose specific strengths and weaknesses of the systems. In addition, the study clearly illustrates that biological responses of the surface waters are strongly ... |
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| Global Ocean Prediction Using HYCOM |
JUN 2006 |
6 pages |
| Authors:
E. J. Metzger; Harley E. Hurlburt; Alan J. Wallcraft; James A. Cummings; Eric P. Chassignet; Ole M. Smedstad; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| One important aspect of ocean model design is the choice of the vertical coordinate system. Traditional ocean models use a single coordinate type to represent the vertical, but model comparison exercises performed in Europe (DYnamics of North Atlantic MOdels (DYNAMO)) and in the United States (Data Assimilation and Model Evaluation Experiment (DAMEE)) have shown that none of the three main vertical coordinates presently in use (depth [z-levels], density [isopycnal layers], ... |
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| Generalized Vertical Coordinates for Eddy-Resolving Global and Coastal Ocean Forecasts |
MAR 2006 |
13 pages |
| Authors:
Eric P. Chassignet; Harley E. Hurlburt; Ole M. Smedstad; George R. Halliwell; Alan J. Wallcraft; E. J. Metzger; Brian O. Blanton; Carlos Lozano; Desiraju B. Rao; Patrick J. Hogan; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Numerical modeling studies over the past several decades have demonstrated progress both in model architecture and in the use of rapidly advancing computational resources. Perhaps the most notable aspect of this progression has been the evolution from simulations on coarse-resolution horizontal and vertical grids that outline basins of simplified geometry and bathymetry and that are forced by idealized surface fluxes, to fine-resolution simulations that incorporate realistic coastline definition and bottom ... |
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| Ocean Prediction with the Hybrid Coordinate Ocean Model (HYCOM) |
2006 |
18 pages |
| Authors:
Eric P. Chassignet; Harley E. Hurlburt; Ole M. Smedstad; George R. Halliwell; Patrick J. Hogan; Alan J. Wallcraft; Rainer Bleck; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| This chapter provides an overview of the effort centered on the HYbrid Coordinate Ocean Model (HYCOM) to develop an eddy-resolving, real-time global and basin-scale ocean prediction system in the context of the Global Ocean Data Assimilation Experiment (GODAE). The long-term goal is an eddy-resolving, fully global ocean prediction system with data assimilation based on HYCOM to be transitioned to the Naval Oceanographic Office at 1/12 degree equatorial resolution in 2007 ... |
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| Global Ocean Prediction Using HYCOM |
JUN 2005 |
5 pages |
| Authors:
Alan J. Wallcraft; E. J. Metzger; Harley E. Hurlburt; Eric P. Chassignet; Zulema D. Garraffo; Ole M. Smedstad; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| The Hybrid Coordinate Ocean Model (HYCOM) is isopycnal in the open, stratified ocean, but uses the layered continuity equation to make a dynamically smooth transition to a terrain-following coordinate in shallow coastal regions, and to z-level coordinates in the mixed layer and/or unstratified seas. The hybrid coordinate extends the geographic range of applicability of traditional isopycnic coordinate circulation models toward shallow coastal seas and unstratified parts of the world ocean. ... |
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| Convergence of Laplacian Diffusion Versus Resolution of an Ocean Model |
APR 2005 |
5 pages |
| Authors:
Alan J. Wallcraft; A. B. Kara; Harley E. Hurlburt; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| This paper presents a convergence study for second order finite difference Laplacian diffusion used in ocean models. For demonstration, ocean model simulations are performed over a rectangular domain, based on the North Pacific subtropical gyre region with grid resolution between 1/2 deg. and 1/32 deg. and with horizontal eddy viscosity coefficient (A(sub H)) ranging from 8000 to 30 m2s-1. A range of A(sub H) which is appropriate for useful model ... |
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| 1/25 deg Atlantic Ocean Simulation Using HYCOM |
2005 |
5 pages |
| Authors:
Alan J. Wallcraft; Harley E. Hurlburt ;Tamara L. Townsend ;Eric P. Chassignet; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| Traditional ocean models use a single coordinate type to represent the vertical, but no single approach is optimal for the global ocean. Isopycnal (density tracking) layers are best in the deep stratified ocean, z-levels (constant fixed depths) provide high vertical resolution in the mixed layer, and ?-levels (terrain-following) are often the best choice in coastal regions. The HYbrid Coordinate Ocean Model (HYCOM) combines all three approaches by dynamically choosing the ... |
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| Stability-Dependent Exchange Coefficients for Air-Sea Fluxes |
27 OCT 2004 |
16 pages |
| Authors:
A. B. Kara; Harley E. Hurlburt; Alan J. Wallcraft; NAVAL RESEARCH LAB STENNIS SPACE CENTER MS OCEANOGRAPHY DIV
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| This study introduces exchange coefficients for wind stress (C(sub D)), latent heat flux (C(sub L), and sensible heat flux (C(sub S)) over the global ocean. They are obtained from the state-of-the-art Coupled Ocean-Atmosphere Response Experiment (COARE) bulk algorithm (version 3.0). Using the exchange coefficients from this bulk scheme, C(sub D), C(sub L), and C(sub s) are then expressed as simple polynomial functions of air-sea temperature difference (T(sub a)-T(sub s)) where ... |
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