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- Author or Editor: Tetsuya T. Fujita x
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Abstract
Because of poor coverage by synoptic stations, the tropical circulation over the eastern Pacific has not been known too well. As a result of photographic experiments, using the geosynchronous ATS-I satellite, fields of cloud motion over the eastern equatorial Pacific were mapped in detail on a number of days in September 1967. It was found that a large-scale flow from the Southern Hemisphere recurves after crossing the equator to form an anticyclone centered around 10N. Dynamical characteristics of this type of anticyclone were investigated by estimating the vorticity dissipating force from computed values of divergence and vorticity of low-cloud velocities determined from successive ATS-I pictures. The vorticity dissipating force seems to be related closely to the sea-surface temperature which would reduce the frictional coupling between the low-level atmosphere and the underlying sea surface. It was found that the anticyclone in its development stage results in a discontinuity of the intertropical band of cloudiness, before it travels westward with an active cloud band along its leading edge. Based upon evidence found through case studies, a model of an equatorial anticyclone is proposed in this paper. Numerical computations of cross-equatorial trajectories were performed by using the divergence-vorticity relationships and the vorticity dissipating force, which were obtained through numerical analyses. This paper thus presents an initial step toward the further development of tropical synoptic meteorology, which is expected during the next few years as a result of photographic experiments using the ATS-I and III.
Abstract
Because of poor coverage by synoptic stations, the tropical circulation over the eastern Pacific has not been known too well. As a result of photographic experiments, using the geosynchronous ATS-I satellite, fields of cloud motion over the eastern equatorial Pacific were mapped in detail on a number of days in September 1967. It was found that a large-scale flow from the Southern Hemisphere recurves after crossing the equator to form an anticyclone centered around 10N. Dynamical characteristics of this type of anticyclone were investigated by estimating the vorticity dissipating force from computed values of divergence and vorticity of low-cloud velocities determined from successive ATS-I pictures. The vorticity dissipating force seems to be related closely to the sea-surface temperature which would reduce the frictional coupling between the low-level atmosphere and the underlying sea surface. It was found that the anticyclone in its development stage results in a discontinuity of the intertropical band of cloudiness, before it travels westward with an active cloud band along its leading edge. Based upon evidence found through case studies, a model of an equatorial anticyclone is proposed in this paper. Numerical computations of cross-equatorial trajectories were performed by using the divergence-vorticity relationships and the vorticity dissipating force, which were obtained through numerical analyses. This paper thus presents an initial step toward the further development of tropical synoptic meteorology, which is expected during the next few years as a result of photographic experiments using the ATS-I and III.
Abstract
An extensive aerial survey was made over a large portion of the area affected by the outbreak of tornadoes on Palm Sunday on Apr. 11, 1965. The destruction from the tornadoes extended over parts of six Midwestern States. Aerial and ground damage surveys were combined with eyewitness reports to determine the exact location and time of each tornado occurrence and its path. Radar pictures of the squall line clouds were used to verify the direction and speed of the tornado-producing clouds. Almost simultaneously with the first tornado touchdown in eastern Iowa, TIROS IX took pictures of the Midwest United States that showed a large tongue of cloud-free dry air behind the cold front. The vertical structure of the cold dome is discussed in connection with its role in the development of the tornadoes.
Two predictive parameters, namely, the best lifted index (BLI) and material differential advection (MDA) were developed and evaluated with data gathered on this outbreak of tornadoes.
The wind speed of a tornado in relation to its parent tornado cyclone is discussed in terms of an anemometer trace showing a peak gust speed of 151 mi hr–1. An indirect wind-speed estimate was also attempted by examining characteristic cycloidal marks left on the fields along the tornado paths. The ground speeds computed ranged from 166 to 180 mi hr–1 for one tornado.
Abstract
An extensive aerial survey was made over a large portion of the area affected by the outbreak of tornadoes on Palm Sunday on Apr. 11, 1965. The destruction from the tornadoes extended over parts of six Midwestern States. Aerial and ground damage surveys were combined with eyewitness reports to determine the exact location and time of each tornado occurrence and its path. Radar pictures of the squall line clouds were used to verify the direction and speed of the tornado-producing clouds. Almost simultaneously with the first tornado touchdown in eastern Iowa, TIROS IX took pictures of the Midwest United States that showed a large tongue of cloud-free dry air behind the cold front. The vertical structure of the cold dome is discussed in connection with its role in the development of the tornadoes.
Two predictive parameters, namely, the best lifted index (BLI) and material differential advection (MDA) were developed and evaluated with data gathered on this outbreak of tornadoes.
The wind speed of a tornado in relation to its parent tornado cyclone is discussed in terms of an anemometer trace showing a peak gust speed of 151 mi hr–1. An indirect wind-speed estimate was also attempted by examining characteristic cycloidal marks left on the fields along the tornado paths. The ground speeds computed ranged from 166 to 180 mi hr–1 for one tornado.
Abstract
Hurricane Gladys, 17 October 1968, is studied with data collected by Aollo 7 manned spacecraft, ESSA's especially instrumented aircraft, weather search radar, the ATS-III and ESSA 7 satellites, and conventional weather networks. This is the feast time data from all of these observing tools have been used to study the structure and dynamics of a hurricane. Techniques used in computing and integrating the various types of data are described and illustrated.
A dominant feature of this immature hurricane was a large cloud which provided a major link between the low- and high-level circulations of the storm. Evidence is presented to suggest this type of cloud and its attendant circulation are features representative of tropical cyclones passing from the tropical storm to the hurricane stage.
Abstract
Hurricane Gladys, 17 October 1968, is studied with data collected by Aollo 7 manned spacecraft, ESSA's especially instrumented aircraft, weather search radar, the ATS-III and ESSA 7 satellites, and conventional weather networks. This is the feast time data from all of these observing tools have been used to study the structure and dynamics of a hurricane. Techniques used in computing and integrating the various types of data are described and illustrated.
A dominant feature of this immature hurricane was a large cloud which provided a major link between the low- and high-level circulations of the storm. Evidence is presented to suggest this type of cloud and its attendant circulation are features representative of tropical cyclones passing from the tropical storm to the hurricane stage.
