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Abstract
Diagnostic and modeling results reveal that atmospheric heating typically acts to intensify extratropical cyclones. In addition, both the Petterssen–Sutcliffe and Zwack–Okossi development equations reveal that this relationship depends on the proportionality that exists between surface geostrophic vorticity tendency and the negative of the horizontal Laplacian of atmospheric heating. Because of this Laplacian relationship, the impact of a heating field with a given magnitude and vertical distribution depends on its horizontal distribution. This paper will show how horizontal heating distributions that differ by relatively small amounts over their entire extent can yield vorticity tendency responses that could contribute to either development or decay of an underlying cyclone.
Abstract
Diagnostic and modeling results reveal that atmospheric heating typically acts to intensify extratropical cyclones. In addition, both the Petterssen–Sutcliffe and Zwack–Okossi development equations reveal that this relationship depends on the proportionality that exists between surface geostrophic vorticity tendency and the negative of the horizontal Laplacian of atmospheric heating. Because of this Laplacian relationship, the impact of a heating field with a given magnitude and vertical distribution depends on its horizontal distribution. This paper will show how horizontal heating distributions that differ by relatively small amounts over their entire extent can yield vorticity tendency responses that could contribute to either development or decay of an underlying cyclone.
Abstract
Seven years of temperature observations from Cape Canaveral, Florida, are used for a detailed examination of the vertical temperature structure. In the troposphere, temperature variations increase with time; in the stratosphere 12-hour temperature changes are greatest and 24-hour changes are least, showing the diurnal temperature control. In the troposphere, temperature variations are greatest in winter, least in summer; the reverse is true in the stratosphere. The smallest annual median temperature range, 3.6C, occurs at 13 km altitude. Stratospheric temperatures over Cape Canaveral are warmest in early spring, coinciding with the maximum ozone concentration of early spring, with only 2–3 months elapsing between the warmest and coldest temperatures of the year. Cape Canaveral summer temperatures compare closely to the mean summer temperatures of other tropical maritime areas, as shown by earlier studies.
Three years of temperature data, at 23 stations from Eureka to Amundsen-Scott, are used to establish a global profile of summer and winter tropopause heights. In the equatorial belt, temperatures in the lower stratosphere are coldest in January and warmest in July, both north and south of the equator. The temperature distribution indicates that the tropopause is generally higher in winter than in summer in all latitudes. The lowering of the summer tropopause occurs with an increase of water vapor in the lower troposphere. From Buffalo to Albrook, somewhere in the 12–18 km region, a temperature belt is found that is warmer than the annual average at that attitude in winter, and colder than the annual average in summer. Another region with seasonal temperature reversals is indicated above 32 km.
Abstract
Seven years of temperature observations from Cape Canaveral, Florida, are used for a detailed examination of the vertical temperature structure. In the troposphere, temperature variations increase with time; in the stratosphere 12-hour temperature changes are greatest and 24-hour changes are least, showing the diurnal temperature control. In the troposphere, temperature variations are greatest in winter, least in summer; the reverse is true in the stratosphere. The smallest annual median temperature range, 3.6C, occurs at 13 km altitude. Stratospheric temperatures over Cape Canaveral are warmest in early spring, coinciding with the maximum ozone concentration of early spring, with only 2–3 months elapsing between the warmest and coldest temperatures of the year. Cape Canaveral summer temperatures compare closely to the mean summer temperatures of other tropical maritime areas, as shown by earlier studies.
Three years of temperature data, at 23 stations from Eureka to Amundsen-Scott, are used to establish a global profile of summer and winter tropopause heights. In the equatorial belt, temperatures in the lower stratosphere are coldest in January and warmest in July, both north and south of the equator. The temperature distribution indicates that the tropopause is generally higher in winter than in summer in all latitudes. The lowering of the summer tropopause occurs with an increase of water vapor in the lower troposphere. From Buffalo to Albrook, somewhere in the 12–18 km region, a temperature belt is found that is warmer than the annual average at that attitude in winter, and colder than the annual average in summer. Another region with seasonal temperature reversals is indicated above 32 km.
Abstract
A pole-to-pole study of density deviations near the 80th meridian west is presented from the surface to 31 km altitude. Density deviations are greatest at the surface, and under extreme conditions may range from 1.0 to 2.0 kg m−2. Density decreases almost exponentially with altitude and occasionally falls below 0.01 kg m−3 at 31 km. Density deviations decrease from the surface to an isopycnic layer, which varies in height from 6 km in polar regions to 12 km at the equator. Above this isopycnic layer, density variations increase with altitude to a maximum density deviation layer. This maximum density deviation layer occurs along the base of the summer tropopause and is approximately the center of the tropospheric wind maximum. The maximum density deviation layer is parallel to, and 50 per cent higher in altitude than the lower isopycnic layer. A weaker, second isopycnic layer is shown above and parallel to the maximum density deviation layer; this second isopycnic layer is found in tropical regions and near the south pole. Because of large seasonal and latitudinal variations in atmospheric density, no single standard atmosphere can present density data adequate for high speed vehicle operations on a global basis.
Abstract
A pole-to-pole study of density deviations near the 80th meridian west is presented from the surface to 31 km altitude. Density deviations are greatest at the surface, and under extreme conditions may range from 1.0 to 2.0 kg m−2. Density decreases almost exponentially with altitude and occasionally falls below 0.01 kg m−3 at 31 km. Density deviations decrease from the surface to an isopycnic layer, which varies in height from 6 km in polar regions to 12 km at the equator. Above this isopycnic layer, density variations increase with altitude to a maximum density deviation layer. This maximum density deviation layer occurs along the base of the summer tropopause and is approximately the center of the tropospheric wind maximum. The maximum density deviation layer is parallel to, and 50 per cent higher in altitude than the lower isopycnic layer. A weaker, second isopycnic layer is shown above and parallel to the maximum density deviation layer; this second isopycnic layer is found in tropical regions and near the south pole. Because of large seasonal and latitudinal variations in atmospheric density, no single standard atmosphere can present density data adequate for high speed vehicle operations on a global basis.
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A procedure is introduced which allows estimation of the net influence of subgrid-scale thermodynamic processes on large-scale available potential energy. A numerical example representing the average energetics over North America for March, 1962 suggests that “net” subgrid-scale generation greatly exceeds the average grid-scale generation, with positive contributions occurring in the low and middle troposphere.
Abstract
A procedure is introduced which allows estimation of the net influence of subgrid-scale thermodynamic processes on large-scale available potential energy. A numerical example representing the average energetics over North America for March, 1962 suggests that “net” subgrid-scale generation greatly exceeds the average grid-scale generation, with positive contributions occurring in the low and middle troposphere.
Abstract
Analysis of three cloud seeding experiments over areas of Australia suggests that results varied with cloud-top temperature; when cumulus and similar clouds had top temperatures ≲−10C rainfall was increased by seeding, but when the cloud tops were warmer rainfall was decreased.
Abstract
Analysis of three cloud seeding experiments over areas of Australia suggests that results varied with cloud-top temperature; when cumulus and similar clouds had top temperatures ≲−10C rainfall was increased by seeding, but when the cloud tops were warmer rainfall was decreased.
Abstract
The presence of melting snow in a radar beam produces a highly enhanced return which can lead to large errors in estimates of areal surface rainfall made with radar. This paper describes an algorithm for use in real time to detect the presence of bright bands in conventional (non-Doppler) weather rádar data. The algorithm derives values for the characteristic parameters of height and intensity of the bright band which can then be used to calculate a correction. Detection relies on the fact that the bright band causes a peak in the apparent rainfall rate measured by the radar at a range dependent on its height above the radar and the elevation of the radar beam.
Analysis of about 270 hours of data collected over a period of five months shows that the algorithm is reliable. It detects the bright-band effect when it occurs and there is sufficient precipitation present and does not raise any false alarms. When the precipitation is patchy it is able to identify the bright band correctly but not with enough confidence to apply a correction. When a correction is applied the “error” is reduced by approximately 50% on average.
Abstract
The presence of melting snow in a radar beam produces a highly enhanced return which can lead to large errors in estimates of areal surface rainfall made with radar. This paper describes an algorithm for use in real time to detect the presence of bright bands in conventional (non-Doppler) weather rádar data. The algorithm derives values for the characteristic parameters of height and intensity of the bright band which can then be used to calculate a correction. Detection relies on the fact that the bright band causes a peak in the apparent rainfall rate measured by the radar at a range dependent on its height above the radar and the elevation of the radar beam.
Analysis of about 270 hours of data collected over a period of five months shows that the algorithm is reliable. It detects the bright-band effect when it occurs and there is sufficient precipitation present and does not raise any false alarms. When the precipitation is patchy it is able to identify the bright band correctly but not with enough confidence to apply a correction. When a correction is applied the “error” is reduced by approximately 50% on average.
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