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- Author or Editor: Frank Wells x
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Abstract
The interface or air–sea flux component of the Coupled Ocean–Atmosphere Response Experiment (COARE) of the Tropical Ocean Global Atmosphere (TOGA) research program and its subsequent impact on studies of air–sea interaction are described. The field work specific to the interface component was planned to improve understanding of air–sea interaction in the Tropics by improving the methodology of flux measurements and by collecting a comprehensive set of observations with coverage of a broad range of time and space scales. The strategies adopted for COARE, particularly the on-site intercomparisons, postexperiment studies of instrument performance, and bulk flux algorithm development, ensured the compilation of very high quality data for the basic near-surface meteorological variables and air–sea fluxes. The success in meeting the goals of improved air–sea heat and freshwater fluxes was verified by closure of the ocean heat and freshwater budgets to within 10 W m−2 and 20%, respectively. These results confirm that accurate in situ observations of air–sea fluxes can be obtained during extensive measurement campaigns, and have established the foundation for current plans for global, long-term oceanic observations of surface meteorology and air–sea fluxes. At the same time, some uncertainties remained after COARE, which must be addressed in future studies of air–sea interaction.
Abstract
The interface or air–sea flux component of the Coupled Ocean–Atmosphere Response Experiment (COARE) of the Tropical Ocean Global Atmosphere (TOGA) research program and its subsequent impact on studies of air–sea interaction are described. The field work specific to the interface component was planned to improve understanding of air–sea interaction in the Tropics by improving the methodology of flux measurements and by collecting a comprehensive set of observations with coverage of a broad range of time and space scales. The strategies adopted for COARE, particularly the on-site intercomparisons, postexperiment studies of instrument performance, and bulk flux algorithm development, ensured the compilation of very high quality data for the basic near-surface meteorological variables and air–sea fluxes. The success in meeting the goals of improved air–sea heat and freshwater fluxes was verified by closure of the ocean heat and freshwater budgets to within 10 W m−2 and 20%, respectively. These results confirm that accurate in situ observations of air–sea fluxes can be obtained during extensive measurement campaigns, and have established the foundation for current plans for global, long-term oceanic observations of surface meteorology and air–sea fluxes. At the same time, some uncertainties remained after COARE, which must be addressed in future studies of air–sea interaction.
Abstract
The Keweenaw Current, observed along the coast of the Keweenaw Peninsula in Lake Superior during July 1973, was simulated using a 3D, nonorthogonal coordinate transformation, primitive equation coastal ocean model. The model domain covered the entire lake with a high resolution of 250–600 m in the cross-shelf direction and 4–6 km in the alongshelf direction along the peninsula. The model was initialized using the monthly averaged temperature field observed in June 1973 and was run prognostically with synoptic wind forcing plus monthly averaged heat flux. Good agreement was found between model-predicted and observed currents at buoy stations near Eagle Harbor. Comparison of the model results with and without inclusion of heat flux suggested that combined wind and heat fluxes played a key role in the intensification of the Keweenaw Current during summer months. The model-predicted relatively strong near-inertial oscillations occurred episodically under conditions of a clockwise-rotating wind. These oscillations intensified at the surface, were weak near the coast, and increased significantly offshore.
Abstract
The Keweenaw Current, observed along the coast of the Keweenaw Peninsula in Lake Superior during July 1973, was simulated using a 3D, nonorthogonal coordinate transformation, primitive equation coastal ocean model. The model domain covered the entire lake with a high resolution of 250–600 m in the cross-shelf direction and 4–6 km in the alongshelf direction along the peninsula. The model was initialized using the monthly averaged temperature field observed in June 1973 and was run prognostically with synoptic wind forcing plus monthly averaged heat flux. Good agreement was found between model-predicted and observed currents at buoy stations near Eagle Harbor. Comparison of the model results with and without inclusion of heat flux suggested that combined wind and heat fluxes played a key role in the intensification of the Keweenaw Current during summer months. The model-predicted relatively strong near-inertial oscillations occurred episodically under conditions of a clockwise-rotating wind. These oscillations intensified at the surface, were weak near the coast, and increased significantly offshore.
Abstract
The formation and evolution of the Keweenaw Current in Lake Superior were examined using a nonorthogonal-coordinate primitive equation numerical model. The model was initialized by the monthly averaged temperaturefield observed in June and September 1973 and run prognostically under different forcing conditions with and without winds. As a Rossby adjustment problem, the model predicted the formation of a well-defined coastal current jet within an inertial period of 16.4 h after the current field adjusted to the initial temperature field. The magnitude and direction of this current jet varied with the cross-shelf temperature gradient and wind velocity. It tended to intensify during northeastward (downwelling favorable) winds, and to lessen, or even reverse, during southwestward to northwestward (upwelling favorable) or southeastward (downwelling favorable) winds. In a case with strong stratification and without external atmospheric forcings, a well-defined clockwise warm-core eddy formed near the northeastern coast of the Keweenaw Peninsula as a result of baroclinic instability. A warm-core eddy was detected recently from satellite surface temperature images, the shape and location of which were very similar to those of the model-predicted eddy. The energy budget analysis suggested that the eddy kinetic energy grew exponentially over a timescale of 7 days. Growth was due to a rapid energy transfer from available eddy potential energy. The subsequent decline of the eddy kinetic energy was the result of turbulent diffusion, transfer from the eddy kinetic energy to mean kinetic energy, and outward net energy flux.
Abstract
The formation and evolution of the Keweenaw Current in Lake Superior were examined using a nonorthogonal-coordinate primitive equation numerical model. The model was initialized by the monthly averaged temperaturefield observed in June and September 1973 and run prognostically under different forcing conditions with and without winds. As a Rossby adjustment problem, the model predicted the formation of a well-defined coastal current jet within an inertial period of 16.4 h after the current field adjusted to the initial temperature field. The magnitude and direction of this current jet varied with the cross-shelf temperature gradient and wind velocity. It tended to intensify during northeastward (downwelling favorable) winds, and to lessen, or even reverse, during southwestward to northwestward (upwelling favorable) or southeastward (downwelling favorable) winds. In a case with strong stratification and without external atmospheric forcings, a well-defined clockwise warm-core eddy formed near the northeastern coast of the Keweenaw Peninsula as a result of baroclinic instability. A warm-core eddy was detected recently from satellite surface temperature images, the shape and location of which were very similar to those of the model-predicted eddy. The energy budget analysis suggested that the eddy kinetic energy grew exponentially over a timescale of 7 days. Growth was due to a rapid energy transfer from available eddy potential energy. The subsequent decline of the eddy kinetic energy was the result of turbulent diffusion, transfer from the eddy kinetic energy to mean kinetic energy, and outward net energy flux.
Abstract
The Joint Typhoon Warning Center (JTWC), a specialized component of the Naval Oceanography Command Center, Guam, is the busiest tropical cyclone warning center in the world. Its area of responsibility encompasses four broad oceanic areas of tropical cyclone activity stretching from the international date line to the east coast of Africa, in both hemispheres. Our paper discusses the challenges imposed on the center as a result of its vast multibasin area of responsibility, the products the center produces, its warning philosophy, observational networks, analysis and forecast schemes, and the military aspects of the operation. Because of the multibasin, dual-hemisphere responsibility, there is no off-season. The challenges of information and time management, analysis and forecast improvement, expansion of meteorological understanding, and enhancement of the warning process are discussed. Current methods used to meet these challenges are presented. In addition, the paper gives a brief overview of JTWC's colorful history, with emphasis on the aircraft reconnaissance era and the evolution of satellite reconnaissance. The joint Navy-Air Force Operations Evaulation to assess the impact of the loss of aircraft reconnaissance and the Office of Naval Research Tropical Cyclone Motion-90 Experiment are briefly discussed. Finally, the paper takes a cursory look at JTWC's postanalysis program, which includes the Annual Tropical Cyclone Report; training, qualification, and certification programs; and technique development to improve tropical cyclone analysis and forecasting.
Abstract
The Joint Typhoon Warning Center (JTWC), a specialized component of the Naval Oceanography Command Center, Guam, is the busiest tropical cyclone warning center in the world. Its area of responsibility encompasses four broad oceanic areas of tropical cyclone activity stretching from the international date line to the east coast of Africa, in both hemispheres. Our paper discusses the challenges imposed on the center as a result of its vast multibasin area of responsibility, the products the center produces, its warning philosophy, observational networks, analysis and forecast schemes, and the military aspects of the operation. Because of the multibasin, dual-hemisphere responsibility, there is no off-season. The challenges of information and time management, analysis and forecast improvement, expansion of meteorological understanding, and enhancement of the warning process are discussed. Current methods used to meet these challenges are presented. In addition, the paper gives a brief overview of JTWC's colorful history, with emphasis on the aircraft reconnaissance era and the evolution of satellite reconnaissance. The joint Navy-Air Force Operations Evaulation to assess the impact of the loss of aircraft reconnaissance and the Office of Naval Research Tropical Cyclone Motion-90 Experiment are briefly discussed. Finally, the paper takes a cursory look at JTWC's postanalysis program, which includes the Annual Tropical Cyclone Report; training, qualification, and certification programs; and technique development to improve tropical cyclone analysis and forecasting.
The history of meteorology has taught us that weather analysis and prediction usually advances by a series of small, progressive studies. Occasionally, however, a special body of work can accelerate this process. When that work pertains to high-impact weather events that can affect large populations, it is especially notable. In this paper we review the contributions by Vernon F. Dvorak, whose innovations using satellite observations of cloud patterns fundamentally enhanced the ability to monitor tropical cyclones on a global scale. We discuss how his original technique has progressed, and the ways in which new spaceborne instruments are being employed to complement Dvorak's original visions.
The history of meteorology has taught us that weather analysis and prediction usually advances by a series of small, progressive studies. Occasionally, however, a special body of work can accelerate this process. When that work pertains to high-impact weather events that can affect large populations, it is especially notable. In this paper we review the contributions by Vernon F. Dvorak, whose innovations using satellite observations of cloud patterns fundamentally enhanced the ability to monitor tropical cyclones on a global scale. We discuss how his original technique has progressed, and the ways in which new spaceborne instruments are being employed to complement Dvorak's original visions.
