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R. M. Clancy
and
LCDR W. D. Sadler

Abstract

Fleet Numerical Oceanography Center (FLENUMOCEANCEN) is the navy's real-time prediction center for global-scale and open-ocean regional-scale oceanographic products, having filled this role for over 25 years. FLENUMOCEANCEN provides operational oceanographic services to U.S. and allied naval forces, other components of the Department of Defense, and a wide variety of civilian interests with output from sophisticated ocean models. These models are highly automated and most are linked closely to atmospheric models.

Thermal structure and circulation models provide a representation of the three-dimensional mass and current structure on global coarse-resolution grids and regional eddy-resolving grids. Primary attention is focused on nowcasting ocean thennal structure using optimum interpolation analysis of ship, buoy, hathy, and satellite data. In addition, ocean feature models and synthetic subsurface data are used in conjunction with surface front and eddy locations, inferred primarily from satellite imagery, to provide a sharper subsurface depiction of the ocean mesoscale, which is generally unresolved by the available in situ data. Mixed-layer and circulation models are also employed to improve the thermal structure nowcasts, provide thermal structure forecasts, and produce ocean current forecasts.

Sea-ice models predict the thickness, concentration, and drift of ice in the Arctic basin and marginal seas, with surface winds and heat fluxes as their primary input. These models include ice dynamics and thermodynamics, and are updated from subjective analyses of ice concentration.

Wave models predict directional ocean wave energy spectra from only wind input, simply carrying the spectra forward in time from day to day without any updating from oceanographic observations. A variety of more familiar products, such as significant wave height and primary wave direction and period, are derived from the spectra.

This article gives an overview of FLENUMOCEANCEN ocean-modeling capabilities and identifies goals for the future.

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R. M. Clancy
,
J. E. Kaitala
, and
L. F. Zambresky

The Spectral Ocean Wave Model (SOWM) has been an operational product at Fleet Numerical Oceanography Center since the mid 1970s; the Global Spectral Ocean Wave Model (GSOWM) was developed to replace it. An operational test of GSOWM, using buoy, ocean-weather-station, and ship-reported wave-height data for verification, was conducted during the winter of 1984/85 by several components of the Naval Oceanography Command. This test indicated that GSOWM was superior to SOWM and that both models exhibited root-mean-square significant-wave-height errors on the order of 1 m. Wave-height errors deduced from the ship observations were comparable to those calculated from the buoy data. The GSOWM scatter index, determined from the buoy and ocean-weather-station data and defined as the standard deviation of the model-predicted wave-height error divided by the mean observed wave height, averaged 0.34.

As a result of the study reported here, GSOWM replaced SOWM as the U.S. Navy's operational wave model in June of 1985. Examples of GSOWM output, illustrating both the capabilities and shortcomings of the model, are presented.

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R. M. Clancy
,
J. M. Harding
,
K. D. Pollak
, and
P. May

Abstract

Global-scale analyses of ocean thermal structure produced operationally at the U.S. Navy's Fleet Numerical Oceanography Center are verified, along with an ocean thermal climatology, against unassimilated bathythermograph (bathy), satellite multichannel sea surface temperature (MCSST), and ship sea surface temperature (SST) data. Verification statistics are calculated from the three types of data for February–April of 1988 and February–April of 1990 in nine verification areas covering most of the open ocean in the Northern Hemisphere. The analyzed thermal fields were produced by version 1.0 of the Optimum Thermal Interpolation System (OTIS 1.0) in 1988, but by an upgraded version of this model, referred to as OTIS 1.1, in 1990. OTIS 1.1 employs exactly the same analysis methodology as OTIS 1.0. The principal difference is that OTIS 1.1 has twice the spatial resolution of OTIS 1.0 and consequently uses smaller spatial decorrelation scales and noise-to-signal ratios. As a result, OTIS 1.1 is able to represent more horizontal detail in the ocean thermal fields than its predecessor.

Verification statistics for the SST fields derived from bathy and MCSST data are consistent with each other, showing similar trends and error levels. These data indicate that the analyzed SST fields are more accurate in 1990 than in 1988, and generally more accurate than climatology for both years. Verification statistics for the SST fields derived from ship data are inconsistent with those derived from the bathy and MCSST data, and show much higher error levels indicative of observational noise.

Verification of the subsurface thermal fields with bathy data clearly show improvements in the accuracy of the analyzed thermal fields between 1988 and 1990, even though the number of hathy observations available for assimilation into the analysis is less in 1990 than in 1988. The analyzed subsurface thermal structure is also generally more accurate than climatology, particularly in 1990, indicating that the OTIS model makes effective use of the bathy data. Errors are much larger in the western halves of the midiatitude ocean basins than in the eastern halves, primarily as a result of the strong and unresolved fronts and eddies associated with the western boundary currents. Prominent subsurface maxima in the error profiles for both the analysis and climatology, probably a result of unresolved thermocline variability, are present in all five tropical verification areas.

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R. M. Clancy
,
J. D. Thompson
,
H. E. Hurlburt
, and
J. D. Lee

Abstract

A time-dependent, two-dimensional numerical model is constructed by coupling a four-layer atmosphere to a two-layer ocean through fluxes of heat and momentum. Idealized experiments are performed to investigate the oceanic response to sea breeze forcing, changes induced in the sea breeze by coastal upwelling, and air-sea feedback during periods of active coastal upwelling. This problem is motivated by the fact that the time scale of the coastal upwelling response is short compared to most oceanic response times and is comparable to the sea breeze time scale.

When forced with a longshore wind stress, the model ocean reproduces several features commonly observed in coastal upwelling regimes, including an equatorward surface jet, a poleward undercurrent, and a region of low sea surface temperatures near the coast. For the cases considered here, the sea breeze contributes significantly to the mean longshore wind stress and, consequently, plays a role in driving the coastal upwelling circulation. It also substantially increases the kinetic energy of the nearshore ocean by forcing inertial oscillations and internal gravity waves with a diurnal period.

When the sea surface temperature is held constant and the land temperature is varied diurnally, the model atmosphere cyclically reproduces a realistic simulation of the sea breeze-land breeze circulation which includes such features as the sea breeze forerunner and the sea breeze front. However, a rapid decrease in sea surface temperature near the coast characteristic of coastal upwelling produces important alterations of the sea breeze-land breeze circulation. Low-level cooling of the atmosphere over the cold water leads ultimately to the formation of a shallower, sharper, faster and longer lasting sea breeze front that penetrates more than twice as far inland than it would without the upwelling. In general, the cold water causes an increase in the low-level sea breeze intensity landward of ∼6 km inland but a decrease seaward of this point. The cold water decreases the land-sea thermal contrast at night and weakens the low-level land breeze everywhere.

Since the cold water in the upwelling zone perturbs the atmosphere on a horizontal scale that is small compared to the internal radius of deformation for the atmosphere, the increase in the longshore geostrophic wind it induces near the coast is small. Furthermore, the reduction in low-level sea breeze amplitude over the cold water compensates the effect of slightly increased mean longshore wind such that the change in mean longshore wind stress is negligible. Thus, although the sea breeze affects the upwelling and the upwelling affects the sea breeze, the air-sea feedback loop to the coastal upwelling process is exceedingly weak.

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S. Solomon
,
R. R. Garcia
,
J. J. Olivero
,
R. M. Bevilacqua
,
P. R. Schwartz
,
R. T. Clancy
, and
D. O. Muhleman

Abstract

Two-dimensional model calculations of the photochemistry and transport of carbon monoxide in the stratosphere, mesosphere, and lower thermosphere are presented. Results are compared to available observations at midlatitudes, where both observation and theory suggest that mesospheric CO abundances are larger on average in winter than in summer. The calculations also indicate that extremely large densities of CO should be found in the polar night mesosphere and upper stratosphere, but at present no high-latitude data are available for direct comparison. However, it is suggested that such a latitudinal distribution implies that the midlatitude region can exhibit unusually large abundances of CO under conditions of large-scale planetary wave activity. Two midlatitude observations during late January 1982 am shown to be consistent with this possibility.

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