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- Author or Editor: Francis J. Merceret x
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Abstract
Extensive flight tests during GATE showed hot-film anemometry to be a useful tool for the airborne measurement of atmospheric turbulence in clear air and in subcloud rain, but not within clouds. Root-mean-square noise values lower than 0.08 ms−1 for velocity and 0.03°C for temperature were obtained over the scale range of 50 m to 4 cm at altitudes from 16 to 2000 m. Spectra of U′, W′ and θ were obtained over the same range with roughly 1 dB accuracy. Dissipation rates could be determined to within ±30%. Cross-component contamination was too large to permit reliable cross spectra to be obtained. It is suggested that an upgraded system could significantly reduce such contamination and improve the overall accuracy and signal-to-noise ratio.
Abstract
Extensive flight tests during GATE showed hot-film anemometry to be a useful tool for the airborne measurement of atmospheric turbulence in clear air and in subcloud rain, but not within clouds. Root-mean-square noise values lower than 0.08 ms−1 for velocity and 0.03°C for temperature were obtained over the scale range of 50 m to 4 cm at altitudes from 16 to 2000 m. Spectra of U′, W′ and θ were obtained over the same range with roughly 1 dB accuracy. Dissipation rates could be determined to within ±30%. Cross-component contamination was too large to permit reliable cross spectra to be obtained. It is suggested that an upgraded system could significantly reduce such contamination and improve the overall accuracy and signal-to-noise ratio.
Abstract
Conventional techniques for determining which features of hurricanes govern their distribution of kinetic energy dissipation rate (ε) fail to yield significant correlations because of the high random variability of ε. Spectral analysis of the time series of the logarithm of ε, however, shows several distinct features which may be tentatively identified with specific aspects of the storm circulation. In particular, cloud-scale, cloud-cluster-scale and rainband-scale peaks occur in the power spectrum of log10ε.
Abstract
Conventional techniques for determining which features of hurricanes govern their distribution of kinetic energy dissipation rate (ε) fail to yield significant correlations because of the high random variability of ε. Spectral analysis of the time series of the logarithm of ε, however, shows several distinct features which may be tentatively identified with specific aspects of the storm circulation. In particular, cloud-scale, cloud-cluster-scale and rainband-scale peaks occur in the power spectrum of log10ε.
Abstract
Airborne foil impactor measurements in Atlantic Hurricane Ginger (1971) show a raindrop size spectrum which is well represented by an exponential relation of the Marshall-Palmer type. No difference was observed between the spectral characteristics of the rainbands and those of the eyewall, but some dependence of the slope-rainfall rate relation on rainwater content was noted.
Abstract
Airborne foil impactor measurements in Atlantic Hurricane Ginger (1971) show a raindrop size spectrum which is well represented by an exponential relation of the Marshall-Palmer type. No difference was observed between the spectral characteristics of the rainbands and those of the eyewall, but some dependence of the slope-rainfall rate relation on rainwater content was noted.
Abstract
Fluctuations of temperature, horizontal velocity and vertical velocity were measured at scales from 50 m to 5 cm with airborne hot-film anemometers at altitudes of 150 and 900 m in clear air, and in subcloud air with and without rainfall. Although nearly inertial subrange spectral behavior was often present at scales smaller than 20 m, significant regions existed where inertial behavior did not appear until scales smaller than a few meters were reached. The energy dissipation rate varied intermittently by two orders of magnitude or more over scales ranging from 100 m to several kilometers. High Reynolds number intermittency effects were observed in the temperature spectra. In an anomalous region, here called a “dry hole,” the microstructure of the velocity and temperature fields was radically different from that of the surrounding environment. Spectral intensity decreased by an order of magnitude and spectral shape was definitely non-inertial. Despite these changes, the probability distribution of the energy dissipation seemed to remain close to log-normal as did the distribution in the surroundings.
Abstract
Fluctuations of temperature, horizontal velocity and vertical velocity were measured at scales from 50 m to 5 cm with airborne hot-film anemometers at altitudes of 150 and 900 m in clear air, and in subcloud air with and without rainfall. Although nearly inertial subrange spectral behavior was often present at scales smaller than 20 m, significant regions existed where inertial behavior did not appear until scales smaller than a few meters were reached. The energy dissipation rate varied intermittently by two orders of magnitude or more over scales ranging from 100 m to several kilometers. High Reynolds number intermittency effects were observed in the temperature spectra. In an anomalous region, here called a “dry hole,” the microstructure of the velocity and temperature fields was radically different from that of the surrounding environment. Spectral intensity decreased by an order of magnitude and spectral shape was definitely non-inertial. Despite these changes, the probability distribution of the energy dissipation seemed to remain close to log-normal as did the distribution in the surroundings.
Abstract
The statistical distribution of the magnitude of the vector wind change over 0.25-, 0.5-, 1-, and 2-h periods based on central Florida data from November 1999 through August 2001 is presented. The distributions of the 2-h u and υ wind-component changes are also presented for comparison. The wind changes at altitudes from 500 to 3000 m were measured using the Eastern Range network of five 915-MHz Doppler radar wind profilers. Quality-controlled profiles were produced every 15 min for up to 60 gates, each representing 101 m in altitude over the range from 130 to 6089 m. Five levels, each constituting three consecutive gates, were selected for analysis because of their significance to aerodynamic loads during the space-shuttle-ascent roll maneuver. The distribution of the magnitude of the vector wind change is found to be lognormal, consistent with earlier work in the midtroposphere. The parameters of the distribution vary with time lag, season, and altitude. The component wind changes are symmetrically distributed, with near-zero means, but the kurtosis coefficient is larger than that of a Gaussian distribution.
Abstract
The statistical distribution of the magnitude of the vector wind change over 0.25-, 0.5-, 1-, and 2-h periods based on central Florida data from November 1999 through August 2001 is presented. The distributions of the 2-h u and υ wind-component changes are also presented for comparison. The wind changes at altitudes from 500 to 3000 m were measured using the Eastern Range network of five 915-MHz Doppler radar wind profilers. Quality-controlled profiles were produced every 15 min for up to 60 gates, each representing 101 m in altitude over the range from 130 to 6089 m. Five levels, each constituting three consecutive gates, were selected for analysis because of their significance to aerodynamic loads during the space-shuttle-ascent roll maneuver. The distribution of the magnitude of the vector wind change is found to be lognormal, consistent with earlier work in the midtroposphere. The parameters of the distribution vary with time lag, season, and altitude. The component wind changes are symmetrically distributed, with near-zero means, but the kurtosis coefficient is larger than that of a Gaussian distribution.
Abstract
Microscale horizontal velocity fluctuation measurements in Hurricane Caroline (1975) show that except in the eye, turbulent energy dissipation does not vary systematically with wind speed or altitude. Inertial subrange-shaped spectra are found below cloud base and slightly above it. At higher altitudes, some deviation from that shape may occur. The amount of energy dissipated within the body of the storm is slightly larger than that dissipated at the surface in accord with earlier estimates by residuals. The dissipation is highly intermittent with a log-normal cumulative probability distribution.
Abstract
Microscale horizontal velocity fluctuation measurements in Hurricane Caroline (1975) show that except in the eye, turbulent energy dissipation does not vary systematically with wind speed or altitude. Inertial subrange-shaped spectra are found below cloud base and slightly above it. At higher altitudes, some deviation from that shape may occur. The amount of energy dissipated within the body of the storm is slightly larger than that dissipated at the surface in accord with earlier estimates by residuals. The dissipation is highly intermittent with a log-normal cumulative probability distribution.
Abstract
No abstract available.
Abstract
No abstract available.
