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Ira Sprague Bowen (1898–1973) was a prominent astrophysicist during the twentieth century. In his impressive oeuvre of work over the 50-year span (1920–70), there appears a lone contribution to the geophysical sciences on the subject of evaporation and conduction from water surfaces. This theoretical development led to an expression for the ratio of heat conduction to evaporative flux at the air–water interface, labeled the Bowen ratio by Harald Sverdrup in the early 1940s. The circumstances that led to this contribution are examined with attention to the character of education and research at the California Institute of Technology during the 1920s. Bowen was unaware of the important precedent work in meteorology and fluid dynamics that is also reviewed.
Ira Sprague Bowen (1898–1973) was a prominent astrophysicist during the twentieth century. In his impressive oeuvre of work over the 50-year span (1920–70), there appears a lone contribution to the geophysical sciences on the subject of evaporation and conduction from water surfaces. This theoretical development led to an expression for the ratio of heat conduction to evaporative flux at the air–water interface, labeled the Bowen ratio by Harald Sverdrup in the early 1940s. The circumstances that led to this contribution are examined with attention to the character of education and research at the California Institute of Technology during the 1920s. Bowen was unaware of the important precedent work in meteorology and fluid dynamics that is also reviewed.
In response to the needs of the ocean traders and military shipping during the nineteenth century, Matthew Maury (1806–73) and Wladimir Köppen (1846–1940) worked in tandem to create wind charts for the World Ocean. In the early part of the century, Maury organized and supervised the production of the Wind and Current Charts for all navigable seas. In the latter part of the century, Köppen simplified these charts by use of a synoptically innovative stratification of the data, and these analyses became centerpieces of the Segelhandbiicher (Sail Handbooks) produced by the German Marine Observatory (Seewarte).
The charts produced by each of these men are examined in an effort to clarify their separate but unique contributions. Maury and Köppen were complementary in their approach to marine meteorology: Maury possessed organizational skills and an empirical approach to science, while Köppen was more academic and interested in the basic sciences. Köppen's exceptional background in both physics and biology was instrumental to his success in simplifying Maury's charts. These appealing synoptic charts served Bergeron in his quest for a global understanding of air masses and ultimately gave Köppen a viewpoint on climatology that embraced the entire world.
In response to the needs of the ocean traders and military shipping during the nineteenth century, Matthew Maury (1806–73) and Wladimir Köppen (1846–1940) worked in tandem to create wind charts for the World Ocean. In the early part of the century, Maury organized and supervised the production of the Wind and Current Charts for all navigable seas. In the latter part of the century, Köppen simplified these charts by use of a synoptically innovative stratification of the data, and these analyses became centerpieces of the Segelhandbiicher (Sail Handbooks) produced by the German Marine Observatory (Seewarte).
The charts produced by each of these men are examined in an effort to clarify their separate but unique contributions. Maury and Köppen were complementary in their approach to marine meteorology: Maury possessed organizational skills and an empirical approach to science, while Köppen was more academic and interested in the basic sciences. Köppen's exceptional background in both physics and biology was instrumental to his success in simplifying Maury's charts. These appealing synoptic charts served Bergeron in his quest for a global understanding of air masses and ultimately gave Köppen a viewpoint on climatology that embraced the entire world.
The California Institute of Technology (Cal Tech) established a course of study in meteorology in 1933. It was intimately tied to the upsurge of activity in commercial and military aviation that occurred in the period between the world wars. The tragic crash of the airship U.S.S. Akron provided the stimulus for including meteorology as a subprogram in the aeronautics department at Cal Tech. Theodore von Kármán, head of the department and director of the school's Guggenheim Aeronautics Laboratory, masterminded the design of the program and geared it toward the solution of practical problems using the principles of dynamic meteorology. One of his doctoral students, Irving Krick, was groomed to develop the program.
Robert Millikan, head of the institute, fostered an approach to science that encouraged the faculty to consult and work with industry. In this environment, Krick established links with aviation, motion picture studios, and public utilities that would set the stage for the research thrust in meteorology. The program was primarily designed for training at the master's degree level, and a significant number of the graduates became entrepreneurs in meteorology. Based on letters of reminiscence and oral histories from some of these consulting meteorologists, it has been concluded that the Millikan/von Karman philosophy of science played an important part in directing the meteorologists into the private sector.
Following World War II, Lee DuBridge replaced Millikan as head of the institute. DuBridge's efforts were directed toward making the small elite school scientifically competitive in the changed conditions of a postwar world. In this climate, the merging of private business with academic work fell into disfavor. Without champions such as Millikan and von Karman, the meteorology program was unable to survive.
The California Institute of Technology (Cal Tech) established a course of study in meteorology in 1933. It was intimately tied to the upsurge of activity in commercial and military aviation that occurred in the period between the world wars. The tragic crash of the airship U.S.S. Akron provided the stimulus for including meteorology as a subprogram in the aeronautics department at Cal Tech. Theodore von Kármán, head of the department and director of the school's Guggenheim Aeronautics Laboratory, masterminded the design of the program and geared it toward the solution of practical problems using the principles of dynamic meteorology. One of his doctoral students, Irving Krick, was groomed to develop the program.
Robert Millikan, head of the institute, fostered an approach to science that encouraged the faculty to consult and work with industry. In this environment, Krick established links with aviation, motion picture studios, and public utilities that would set the stage for the research thrust in meteorology. The program was primarily designed for training at the master's degree level, and a significant number of the graduates became entrepreneurs in meteorology. Based on letters of reminiscence and oral histories from some of these consulting meteorologists, it has been concluded that the Millikan/von Karman philosophy of science played an important part in directing the meteorologists into the private sector.
Following World War II, Lee DuBridge replaced Millikan as head of the institute. DuBridge's efforts were directed toward making the small elite school scientifically competitive in the changed conditions of a postwar world. In this climate, the merging of private business with academic work fell into disfavor. Without champions such as Millikan and von Karman, the meteorology program was unable to survive.
Carl-Gustaf Rossby (1898–1957) was chosen to head the first U.S. program in modern meteorology at the Massachusetts Institute of Technology (MIT) in 1928. The steps that led to this appointment are briefly reviewed as well as the academic environment at MIT in the early 1930s. It has been argued that Rossby's development as a research scientist was closely tied to his connection with oceanographers at the Woods Hole Oceanographic Institution. His work on geostrophic adjustment, an outgrowth of his research on the Gulf Stream, was marked by bold simplification of the governing dynamical equations. This allowed him to capture the essence of adjustments between pressure and velocity in unbalanced geophysical flow. His work on the adjustment problem is summarized and related to earlier work by Ekman and Margules.
Carl-Gustaf Rossby (1898–1957) was chosen to head the first U.S. program in modern meteorology at the Massachusetts Institute of Technology (MIT) in 1928. The steps that led to this appointment are briefly reviewed as well as the academic environment at MIT in the early 1930s. It has been argued that Rossby's development as a research scientist was closely tied to his connection with oceanographers at the Woods Hole Oceanographic Institution. His work on geostrophic adjustment, an outgrowth of his research on the Gulf Stream, was marked by bold simplification of the governing dynamical equations. This allowed him to capture the essence of adjustments between pressure and velocity in unbalanced geophysical flow. His work on the adjustment problem is summarized and related to earlier work by Ekman and Margules.
Out of the nearly 6000 U.S. military officers who were trained to be weather forecasters during World War II, there were approximately 100 women. They were recruited into the Women Accepted for Volunteer Emergency Service (WAVES) by the U.S. Navy and underwent training with the military men in the so-called cadet program. Letters of reminiscence from six WAVES forecasters are combined with official navy correspondence, archival information from universities, and newspaper articles of the period to reconstruct the recruitment, training, duty assignments, and postwar careers of these women.
With limited information, an effort has also been made to document the training of civilian women in the cadet program, and to estimate the number of women who served as forecasters in foreign countries during the war. The status of women in meteorology prior to the United States' entry into the war is examined as a backdrop to the study. Principal results of the study are as follows:
Out of the nearly 6000 U.S. military officers who were trained to be weather forecasters during World War II, there were approximately 100 women. They were recruited into the Women Accepted for Volunteer Emergency Service (WAVES) by the U.S. Navy and underwent training with the military men in the so-called cadet program. Letters of reminiscence from six WAVES forecasters are combined with official navy correspondence, archival information from universities, and newspaper articles of the period to reconstruct the recruitment, training, duty assignments, and postwar careers of these women.
With limited information, an effort has also been made to document the training of civilian women in the cadet program, and to estimate the number of women who served as forecasters in foreign countries during the war. The status of women in meteorology prior to the United States' entry into the war is examined as a backdrop to the study. Principal results of the study are as follows:
Abstract
A data assimilation strategy based on feedback control has been developed for the geophysical sciences—a strategy that uses model output to control the behavior of the dynamical system. Whereas optimal tracking through feedback control had its early history in application to vehicle trajectories in space science, the methodology has been adapted to geophysical dynamics by forcing the trajectory of a deterministic model to follow observations in accord with observation accuracy. Fundamentally, this offline (where it is assumed that the observations in a given assimilation window are all given) approach is based on Pontryagin’s minimum principle (PMP) where a least squares fit of idealized path to dynamic law follows from Hamiltonian mechanics. This utilitarian process optimally determines a forcing function that depends on the state (the feedback component) and the observations. It follows that this optimal forcing accounts for the model error. From this model error, a correction to the one-step transition matrix is constructed. The above theory and technique is illustrated using the linear Burgers’ equation that transfers energy from the large scale to the small scale.
Abstract
A data assimilation strategy based on feedback control has been developed for the geophysical sciences—a strategy that uses model output to control the behavior of the dynamical system. Whereas optimal tracking through feedback control had its early history in application to vehicle trajectories in space science, the methodology has been adapted to geophysical dynamics by forcing the trajectory of a deterministic model to follow observations in accord with observation accuracy. Fundamentally, this offline (where it is assumed that the observations in a given assimilation window are all given) approach is based on Pontryagin’s minimum principle (PMP) where a least squares fit of idealized path to dynamic law follows from Hamiltonian mechanics. This utilitarian process optimally determines a forcing function that depends on the state (the feedback component) and the observations. It follows that this optimal forcing accounts for the model error. From this model error, a correction to the one-step transition matrix is constructed. The above theory and technique is illustrated using the linear Burgers’ equation that transfers energy from the large scale to the small scale.
Abstract
No abstract available.
Abstract
No abstract available.
Abstract
A case of squall line generation in the National Severe Storms Laboratory (NSSL) network has been examined with the intention of capturing synoptic-scale influences. A telescopic analysis approach was used whereby observations from both synoptic and mesoscale networks were combined.
The squall line formed in the warm air behind the surface position of the cold front. Large-scale circulation was responsible for creating a shallow layer (∼1-km thick) of convectively unstable air immediately above this front. Horizontal gradient of low-level moisture, pronounced low-level wind shear, and surface convergence were the large-scale factors that combined to produce the unstable region.
Mesoscale analysis showed that vertical velocity in the low levels exhibited a persistent small-scale variation prior to convective activity. The horizontal variation in vertical velocity was ultimately responsible for creating a favored position within the mesonetwork.
Conservation of potential temperature and specific humidity is examined as well as the relative importance of horizontal and vertical advection.
Abstract
A case of squall line generation in the National Severe Storms Laboratory (NSSL) network has been examined with the intention of capturing synoptic-scale influences. A telescopic analysis approach was used whereby observations from both synoptic and mesoscale networks were combined.
The squall line formed in the warm air behind the surface position of the cold front. Large-scale circulation was responsible for creating a shallow layer (∼1-km thick) of convectively unstable air immediately above this front. Horizontal gradient of low-level moisture, pronounced low-level wind shear, and surface convergence were the large-scale factors that combined to produce the unstable region.
Mesoscale analysis showed that vertical velocity in the low levels exhibited a persistent small-scale variation prior to convective activity. The horizontal variation in vertical velocity was ultimately responsible for creating a favored position within the mesonetwork.
Conservation of potential temperature and specific humidity is examined as well as the relative importance of horizontal and vertical advection.
Abstract
Comparisons between geopotential analyses derived from rawinsondes (RAOB) and the VISSR Atmospheric Sounder (VAS) generally exhibit differences that are ultimately related to the horizontal density and placement of the respective observations and the vertical resolution inherent in the instruments. In order to overcome some of the inconsistencies that appear, two strategies have been developed which allow the analyses to communicate through the derived variable, geostrophic potential vorticity. The first incorporates the statistics of RAOB derived potential vorticity into the VAS vorticity analysis. This is accomplished by making a least-squares adjustment to VAS while constraining it to have first and second moments identical to the RAOB analysis. The other approach makes mutual least-squares adjustments to RAOB and VAS vorticity analyses subject to the dynamic constraint that forecast and hindcast of potential vorticity to the time midway between analyses are equal. The forecast and hindcast are made from a two-parameter baroclinic model. In both procedures, the heights are recovered from adjusted vorticities by inverting the elliptic operators that relate height to vorticity.
Data from the GOES-East satellite at 1430 GMT 6 March 1982 are used along with rawinsonde data at 1200 GMT to test the schemes. The statistical adjustment approach makes synoptically meaningful adjustments to the VAS analysis over the Gulf of Mexico and Gulf coast region, but fails to correct the obvious discrepancies over the continental United States. The dynamic scheme succeeds in making meaningful adjustments over both the Gulf of Mexico and the continent which result in improved vertical motion fields.
Abstract
Comparisons between geopotential analyses derived from rawinsondes (RAOB) and the VISSR Atmospheric Sounder (VAS) generally exhibit differences that are ultimately related to the horizontal density and placement of the respective observations and the vertical resolution inherent in the instruments. In order to overcome some of the inconsistencies that appear, two strategies have been developed which allow the analyses to communicate through the derived variable, geostrophic potential vorticity. The first incorporates the statistics of RAOB derived potential vorticity into the VAS vorticity analysis. This is accomplished by making a least-squares adjustment to VAS while constraining it to have first and second moments identical to the RAOB analysis. The other approach makes mutual least-squares adjustments to RAOB and VAS vorticity analyses subject to the dynamic constraint that forecast and hindcast of potential vorticity to the time midway between analyses are equal. The forecast and hindcast are made from a two-parameter baroclinic model. In both procedures, the heights are recovered from adjusted vorticities by inverting the elliptic operators that relate height to vorticity.
Data from the GOES-East satellite at 1430 GMT 6 March 1982 are used along with rawinsonde data at 1200 GMT to test the schemes. The statistical adjustment approach makes synoptically meaningful adjustments to the VAS analysis over the Gulf of Mexico and Gulf coast region, but fails to correct the obvious discrepancies over the continental United States. The dynamic scheme succeeds in making meaningful adjustments over both the Gulf of Mexico and the continent which result in improved vertical motion fields.
During February and March 1988, a limited field experiment was conducted over the Gulf of Mexico to gather data on two phenomena: air mass modification over the Loop Current, and return flow characteristics of modified polar air returning to the southern shores of the United States. Six-hourly radiosondes, special Cross- Chain LORAN (Long-Range Aid to Navigation) Atmospheric Sounding System (CLASS) soundings, and three P-3 flights including dropwindsondes and Airborne Expendable Bathythermograph (AXBT) measurements were taken. The experiment objectives and the data are described.
During February and March 1988, a limited field experiment was conducted over the Gulf of Mexico to gather data on two phenomena: air mass modification over the Loop Current, and return flow characteristics of modified polar air returning to the southern shores of the United States. Six-hourly radiosondes, special Cross- Chain LORAN (Long-Range Aid to Navigation) Atmospheric Sounding System (CLASS) soundings, and three P-3 flights including dropwindsondes and Airborne Expendable Bathythermograph (AXBT) measurements were taken. The experiment objectives and the data are described.
