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Abstract
The computation of θ E , the pseudo-quivalent potential temperature, ordinarily omits the contribution due to specific heats of water vapor. This may he an acceptable practice for temperate-latitude usages but a questionable one when applied in the tropics where lower layers, rich in moisture, may he several; degrees warmer and the vertical gradient larger when this factor is included.
An inexpensive method of computing θ E to include the beat capacities of water substance is presented aid the results compared with those derived from several tephigrams which ignore this contribution.
Abstract
The computation of θ E , the pseudo-quivalent potential temperature, ordinarily omits the contribution due to specific heats of water vapor. This may he an acceptable practice for temperate-latitude usages but a questionable one when applied in the tropics where lower layers, rich in moisture, may he several; degrees warmer and the vertical gradient larger when this factor is included.
An inexpensive method of computing θ E to include the beat capacities of water substance is presented aid the results compared with those derived from several tephigrams which ignore this contribution.
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Abstract
Two sources of kona-storm development in the eastern Pacific are studied, together with factors leading to storm intensification. Vertical structure of this subtropical cyclone is considered in terms of sounding data from Hawaiian stations during the storms of February and March 1951.
The kona cyclone initially possesses cold-core characteristics, with winds and rainfall amounts increasing with distance from the low-pressure center and reaching a maxima at a radius of 200 to 500 mi. However, with intensification, this cyclone may develop warm-core properties, with rainfall and wind profiles bearing marked resemblance to those of the tropical cyclone.
Abstract
Two sources of kona-storm development in the eastern Pacific are studied, together with factors leading to storm intensification. Vertical structure of this subtropical cyclone is considered in terms of sounding data from Hawaiian stations during the storms of February and March 1951.
The kona cyclone initially possesses cold-core characteristics, with winds and rainfall amounts increasing with distance from the low-pressure center and reaching a maxima at a radius of 200 to 500 mi. However, with intensification, this cyclone may develop warm-core properties, with rainfall and wind profiles bearing marked resemblance to those of the tropical cyclone.
In August 1951 an unusual airplane reconnaissance of a mature typhoon succeeded in collecting extensive data from the eye and adjacent rain area of the storm. The eye, which was clear except for a low stratocumulus undercast, was circular, 40 miles in diameter, and had a central pressure at the surface of 26.43 inches (895 mb) with a sizable pressure gradient from the center to edge of the eye. Walls of nimbostratus surrounding the eye rose like a huge coliseum to a height of 35,000 feet. Two eye soundings from the surface to 17,000 feet were made, the first at midday, the second in late afternoon. These revealed exceptionally warm temperatures, more than 16° C at 17,000 feet, with lapse rates essentially isothermal from the surface to 10,000 feet. Marked cooling occurred between these two soundings in the layer 7,000–10,000 feet. Horizontally, temperature varied little at 800 feet; at 9,000 feet, however, the eye center was nearly 8 C° warmer, and at 18,000 feet 18 C° warmer than the adjacent rain area. At 9,000 feet, significant temperature gradients were confined primarily to the eye, while at 18,000 feet they were concentrated in the rain area.
In August 1951 an unusual airplane reconnaissance of a mature typhoon succeeded in collecting extensive data from the eye and adjacent rain area of the storm. The eye, which was clear except for a low stratocumulus undercast, was circular, 40 miles in diameter, and had a central pressure at the surface of 26.43 inches (895 mb) with a sizable pressure gradient from the center to edge of the eye. Walls of nimbostratus surrounding the eye rose like a huge coliseum to a height of 35,000 feet. Two eye soundings from the surface to 17,000 feet were made, the first at midday, the second in late afternoon. These revealed exceptionally warm temperatures, more than 16° C at 17,000 feet, with lapse rates essentially isothermal from the surface to 10,000 feet. Marked cooling occurred between these two soundings in the layer 7,000–10,000 feet. Horizontally, temperature varied little at 800 feet; at 9,000 feet, however, the eye center was nearly 8 C° warmer, and at 18,000 feet 18 C° warmer than the adjacent rain area. At 9,000 feet, significant temperature gradients were confined primarily to the eye, while at 18,000 feet they were concentrated in the rain area.
The intertropical convergence zone near Panama is studied in light of meteorograph soundings, winds-aloft, and microanalyses of surface reports. When pronounced this phenomenon consists of a relatively narrow zone of cyclonic wind shear. This is frequently associated with a cold-core trough whose slope in the vertical is of cold-front proportions. Its cloud system is characterized primarily by widespread altostratus with convective activity usually quite variable in amount and intensity. Wavelike perturbations which sometimes appear along this line of convergence are found to be important in connection with cyclogenesis.
The intertropical convergence zone near Panama is studied in light of meteorograph soundings, winds-aloft, and microanalyses of surface reports. When pronounced this phenomenon consists of a relatively narrow zone of cyclonic wind shear. This is frequently associated with a cold-core trough whose slope in the vertical is of cold-front proportions. Its cloud system is characterized primarily by widespread altostratus with convective activity usually quite variable in amount and intensity. Wavelike perturbations which sometimes appear along this line of convergence are found to be important in connection with cyclogenesis.
The relation between the slope of tropical low pressure axes and the tendency for such lows to deepen or fill has been studied during investigations carried on separately in the Atlantic and in the Pacific ocean areas. The preliminary conclusions drawn from each of the two studies differ considerably and are reviewed herein. Limitations upon the use of vertical wind shear computations in determining the slope of such pressure axes are discussed. Questions are raised regarding the assumption in such computations that the vertical shear of the observed wind is a good approximation of the shear of the geostrophic components. Illustrations are given of the fallacies of reasoning that may result from such an assumption in connection with tropical cyclones.
The relation between the slope of tropical low pressure axes and the tendency for such lows to deepen or fill has been studied during investigations carried on separately in the Atlantic and in the Pacific ocean areas. The preliminary conclusions drawn from each of the two studies differ considerably and are reviewed herein. Limitations upon the use of vertical wind shear computations in determining the slope of such pressure axes are discussed. Questions are raised regarding the assumption in such computations that the vertical shear of the observed wind is a good approximation of the shear of the geostrophic components. Illustrations are given of the fallacies of reasoning that may result from such an assumption in connection with tropical cyclones.
Abstract
In convective clouds jet aircraft encounter icing at air temperatures lower than −60° C. It may be reasoned that this results from (1) the melting of frozen droplets due to dynamic or frictional heating in the quasi-potential flow around the air foil; (2) the impact of precipitation consisting of ice spheres with liquid water cores; (3) the possibility that raindrops are carried upward by vertical currents so rapidly that the water temperature remains higher than the spontaneous nucleation temperature (−40° C.) while the air temperature is much lower; or (4) the possibility that the spontaneous nucleation temperature is pressure dependent or otherwise variable. This paper investigates the third of these possibilities and finds that the difference in temperature of liquid water and air at 12 km. can be no more than a few degrees except in the case of very large drops carried through deep layers of cloud by intense steady-state updrafts of the kind associated with hail-producing thunderstorms.
Abstract
In convective clouds jet aircraft encounter icing at air temperatures lower than −60° C. It may be reasoned that this results from (1) the melting of frozen droplets due to dynamic or frictional heating in the quasi-potential flow around the air foil; (2) the impact of precipitation consisting of ice spheres with liquid water cores; (3) the possibility that raindrops are carried upward by vertical currents so rapidly that the water temperature remains higher than the spontaneous nucleation temperature (−40° C.) while the air temperature is much lower; or (4) the possibility that the spontaneous nucleation temperature is pressure dependent or otherwise variable. This paper investigates the third of these possibilities and finds that the difference in temperature of liquid water and air at 12 km. can be no more than a few degrees except in the case of very large drops carried through deep layers of cloud by intense steady-state updrafts of the kind associated with hail-producing thunderstorms.
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