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A bulk turbulence-closure mixed layer model is generalized to allow prediction of very deep polar sea mixing. The model includes unsteady three- component turbulent kinetic energy budgets. In addition to terms for shear production, pressure redistribution, and dissipation, special attention is devoted to realistic treatment of thermobaric enhancement of buoyancy flux and to Coriolis effect on turbulence. The model is initialized and verified with CTD data taken by R/V Valdivia in the Greenland Sea during winter 1993-1994. Model simulations show (1) mixed layer deepening is significantly enhanced when the thermal expansion coefficient's increase with pressure is included; (2) entrainment rate is sensitive to the direction of wind stress because of Coriolis; and (3) the predicted mixed layer depth evolution agrees qualitatively with the observations. Results demonstrate the importance of water column initial conditions, accurate representation of strong surface cooling events, and inclusion of the thermobaric effect on buoyancy, to determine the depth of mixing and ultimately the heat and salt flux into the deep ocean. Since coupling of the ocean to the atmosphere through deep mixed layers in polar regions is fundamental to our climate system, it is important that regional and global models be developed that incorporate realistic representation of this coupling, http://archive.org/details/deepmixedlayeren00ston, Lieutenant Commander, United States Navy, Approved for public release; distribution is unlimited.

Skillful long-range forecasts of acoustic variables have the potential to be very useful in planning Navy undersea warfare operations. Our study assessed the potential to predict sonic layer depth (SLD) in the western north Pacific at lead times of one to several months. We conducted correlations between SLD and remote climate system variables, and identified a high potential for skillful long-range forecasts of SLD in the western north Pacific using sea surface temperature in equatorial and south Pacific as predictors. We used tercile matching and composite analysis forecast (CAF) methods to develop hindcasts and forecasts of SLD based on SST predictors at lead times of one to four months. Our forecast verification metrics show that the resulting long lead probabilistic forecasts are a clear improvement over presently available long term mean climatology products. We also used conditional compositing techniques to create mean and environmental threshold probability products based on the long lead forecasts. Our results indicate that the support of USW operations by the Navy meteorology and oceanography community could be improved by the use of advanced climate data sets, climate analysis, and long-range forecasting methods., http://archive.org/details/longrangetmosphe109454516, US Navy (USN) author., Approved for public release; distribution is unlimited.

The rapid Arctic sea ice decline since the 1970s has propelled the United States into a state of urgency for updating its defense plan as Arctic and non-Arctic nations alike are taking an interest in the newfound natural resources of an ice-declining Arctic. In line with the National Security Presidential Directive-66, we quantify the amount of anomalous sea ice variability (aSIV) that anomalous atmospheric forcing parameters explain using partial covariance analysis. A one-system approach where the NPS Model sea ice parameters are the direct output of the atmospheric forcing parameters input is employed. Atmospheric forcing fields of 2-m temperature, downward shortwave and longwave fluxes, 10-m zonal and meridional winds and stresses, are from the European Centre for Medium-Range Weather Forecasts Reanalysis-15 and Operational Products. Locations of interest are the Central Arctic seas, and locations along the Northwest Passage (NWP) and the Northern Sea Route (NSR). Results show that the atmospheric parameter having the largest influence on aSIV is anomalous surface air temperature. This occurs during the cooling months and averages 4-39% of aSAT contribution to aSIV in the Central Arctic, 9-16% along the NWP, and 11-25% along the NSR. Results also suggest that atmospheric forcing alone does not explain all of aSIV., http://archive.org/details/towardquantifyin109455416, US Air Force (USAF) author, Approved for public release; distribution is unlimited.

In this thesis, the performance and accuracy of explicit, semiimplicit, and Hybrid EulerianLagrangian SemiImplicit (HELSI) timeintegration methods used in atmospheric modeling are examined. Four test cases are analyzed: A density current, an inertial gravity wave, a rising thermal bubble, and a hydrostatic mountain wave. Strict attention is paid to computational time, stability criteria, and accuracy. The project aims to show increased efficiency using the HELSI method over fully semiimplicit methods, which, in turn, should be better than the splitexplicit methods currently used in mesoscale models such as WRF, COAMPS, and the German LM model. This increase in efficiency allows for valuable computational resources to be used for other purposes, such as improved data assimilation, increased spatial resolution, or more detailed physics., http://archive.org/details/performanceofhyb109453309, US Air Force (USAF) author

The rapid Arctic sea ice decline since the 1970s has propelled the United States into a state of urgency for updating its defense plan as Arctic and non-Arctic nations alike are taking an interest in the newfound natural resources of an ice-declining Arctic. In line with the National Security Presidential Directive-66, we quantify the amount of anomalous sea ice variability (aSIV) that anomalous atmospheric forcing parameters explain using partial covariance analysis. A one-system approach where the NPS Model sea ice parameters are the direct output of the atmospheric forcing parameters input is employed. Atmospheric forcing fields of 2-m temperature, downward shortwave and longwave fluxes, 10-m zonal and meridional winds and stresses, are from the European Centre for Medium-Range Weather Forecasts Reanalysis-15 and Operational Products. Locations of interest are the Central Arctic seas, and locations along the Northwest Passage (NWP) and the Northern Sea Route (NSR). Results show that the atmospheric parameter having the largest influence on aSIV is anomalous surface air temperature. This occurs during the cooling months and averages 4-39% of aSAT contribution to aSIV in the Central Arctic, 9-16% along the NWP, and 11-25% along the NSR. Results also suggest that atmospheric forcing alone does not explain all of aSIV.

Skillful long-range forecasts of acoustic variables have the potential to be very useful in planning Navy undersea warfare operations. Our study assessed the potential to predict sonic layer depth (SLD) in the western north Pacific at lead times of one to several months. We conducted correlations between SLD and remote climate system variables, and identified a high potential for skillful long-range forecasts of SLD in the western north Pacific using sea surface temperature in equatorial and south Pacific as predictors. We used tercile matching and composite analysis forecast (CAF) methods to develop hindcasts and forecasts of SLD based on SST predictors at lead times of one to four months. Our forecast verification metrics show that the resulting long lead probabilistic forecasts are a clear improvement over presently available long term mean climatology products. We also used conditional compositing techniques to create mean and environmental threshold probability products based on the long lead forecasts. Our results indicate that the support of USW operations by the Navy meteorology and oceanography community could be improved by the use of advanced climate data sets, climate analysis, and long-range forecasting methods.

In this thesis, the performance and accuracy of explicit, semiimplicit, and Hybrid EulerianLagrangian SemiImplicit (HELSI) timeintegration methods used in atmospheric modeling are examined. Four test cases are analyzed: A density current, an inertial gravity wave, a rising thermal bubble, and a hydrostatic mountain wave. Strict attention is paid to computational time, stability criteria, and accuracy. The project aims to show increased efficiency using the HELSI method over fully semiimplicit methods, which, in turn, should be better than the splitexplicit methods currently used in mesoscale models such as WRF, COAMPS, and the German LM model. This increase in efficiency allows for valuable computational resources to be used for other purposes, such as improved data assimilation, increased spatial resolution, or more detailed physics.

The theory of oceanic convection and entrainment has been developed mainly in horizontally homogeneous regimes, yet large-scale spatial variability is known to control the sites and intensity of deep convection. Wintertime Greenland Sea conditions were selected to simulate convection and quantify the interplay between local forcing and large-scale gradients. Here circulation and preconditioning produce horizontal gradients in the stratification; some of the resulting stratification conducive to the formation of thermobaric convective instabilities. A large eddy simulation (LES) model modified to include large-scale horizontal density gradients was used to study the effects of the gradients on turbulence. Horizontal turbulent kinetic energy (IKE) and scalar variances increased compared to simulations with no large-scale gradient. The additional horizontal IKE is created at scales larger than the convective plume scale. A mean horizontal circulation develops in response to the large-scale overturning. The balance between convection and overturning increases stratification in the lower region of the mixed layer, and plumes may undergo slantwise convection.

The theory of oceanic convection and entrainment has been developed mainly in horizontally homogeneous regimes, yet large-scale spatial variability is known to control the sites and intensity of deep convection. Wintertime Greenland Sea conditions were selected to simulate convection and quantify the interplay between local forcing and large-scale gradients. Here circulation and preconditioning produce horizontal gradients in the stratification; some of the resulting stratification conducive to the formation of thermobaric convective instabilities. A large eddy simulation (LES) model modified to include large- scale horizontal density gradients was used to study the effects of the gradients on turbulence. Horizontal turbulent kinetic energy (IKE) and scalar variances increased compared to simulations with no large-scale gradient. The additional horizontal IKE is created at scales larger than the convective plume scale. A mean horizontal circulation develops in response to the large-scale overturning. The balance between convection and overturning increases stratification in the lower region of the mixed layer, and plumes may undergo slantwise convection.

A bulk turbulence-closure mixed layer model is generalized to allow prediction of very deep polar sea mixing. The model includes unsteady three-component turbulent kinetic energy budgets. In addition to terms for shear production, pressure redistribution, and dissipation, special attention is devoted to realistic treatment of thermobaric enhancement of buoyancy flux and to Coriolis effect on turbulence. The model is initialized and verified with CTD data taken by R/V Valdivia in the Greenland Sea during winter 1993-1994. Model simulations show (1) mixed layer deepening is significantly enhanced when the thermal expansion coefficient's increase with pressure is included; (2) entrainment rate is sensitive to the direction of wind stress because of Coriolis; and (3) the predicted mixed layer depth evolution agrees qualitatively with the observations. Results demonstrate the importance of water column initial conditions, accurate representation of strong surface cooling events, and inclusion of the thermobaric effect on buoyancy, to determine the depth of mixing and ultimately the heat and salt flux into the deep ocean. Since coupling of the ocean to the atmosphere through deep mixed layers in polar regions is fundamental to our climate system, it is important that regional and global models be developed that incorporate realistic representation of this coupling.

A bulk turbulence-closure mixed layer model is generalized to allow prediction of very deep polar sea mixing. The model includes unsteady three- component turbulent kinetic energy budgets. In addition to terms for shear production, pressure redistribution, and dissipation, special attention is devoted to realistic treatment of thermobaric enhancement of buoyancy flux and to Coriolis effect on turbulence. The model is initialized and verified with CTD data taken by R/V Valdivia in the Greenland Sea during winter 1993-1994. Model simulations show (1) mixed layer deepening is significantly enhanced when the thermal expansion coefficient's increase with pressure is included; (2) entrainment rate is sensitive to the direction of wind stress because of Coriolis; and (3) the predicted mixed layer depth evolution agrees qualitatively with the observations. Results demonstrate the importance of water column initial conditions, accurate representation of strong surface cooling events, and inclusion of the thermobaric effect on buoyancy, to determine the depth of mixing and ultimately the heat and salt flux into the deep ocean. Since coupling of the ocean to the atmosphere through deep mixed layers in polar regions is fundamental to our climate system, it is important that regional and global models be developed that incorporate realistic representation of this coupling

The theory of oceanic convection and entrainment has been developed mainly in horizontally homogeneous regimes, yet large-scale spatial variability is known to control the sites and intensity of deep convection. Wintertime Greenland Sea conditions were selected to simulate convection and quantify the interplay between local forcing and large-scale gradients. Here circulation and preconditioning produce horizontal gradients in the stratification; some of the resulting stratification conducive to the formation of thermobaric convective instabilities. A large eddy simulation (LES) model modified to include large- scale horizontal density gradients was used to study the effects of the gradients on turbulence. Horizontal turbulent kinetic energy (IKE) and scalar variances increased compared to simulations with no large-scale gradient. The additional horizontal IKE is created at scales larger than the convective plume scale. A mean horizontal circulation develops in response to the large-scale overturning. The balance between convection and overturning increases stratification in the lower region of the mixed layer, and plumes may undergo slantwise convection., http://archive.org/details/entrainmentdetra1094539421, US Navy (USN) author