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- Author or Editor: Francis J. Merceret x
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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.
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The effective vertical resolution of the Kennedy Space Center 50-MHz Doppler radar wind profiler is determined using vertical wavenumber spectra and temporal coherence. The resolution ranges from being Nyquist limited at 300 m to as coarse as 900 m. The average resolution is about 500 m.
Abstract
The effective vertical resolution of the Kennedy Space Center 50-MHz Doppler radar wind profiler is determined using vertical wavenumber spectra and temporal coherence. The resolution ranges from being Nyquist limited at 300 m to as coarse as 900 m. The average resolution is about 500 m.
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Low-level flight data from a small cloud-free area along the periphery of Hurricane Eloise (1975) reveal the existence of a well-mixed boundary layer which is capped by a near-isothermal layer. The isothermal layer is probably created by the combined effect of subsiding air and surface-induced turbulence.
Abstract
Low-level flight data from a small cloud-free area along the periphery of Hurricane Eloise (1975) reveal the existence of a well-mixed boundary layer which is capped by a near-isothermal layer. The isothermal layer is probably created by the combined effect of subsiding air and surface-induced turbulence.
Abstract
Velocity spectra obtained from a hot-film anemometer and a gust probe on board the NOAA DC-6 (39C) during a research mission into Hurricane Eloise 1975 are compared at common frequencies. The spectra compare reasonably well, thus justifying some confidence in measurements acquired from the individual instruments.
Abstract
Velocity spectra obtained from a hot-film anemometer and a gust probe on board the NOAA DC-6 (39C) during a research mission into Hurricane Eloise 1975 are compared at common frequencies. The spectra compare reasonably well, thus justifying some confidence in measurements acquired from the individual instruments.
Abstract
The National Hurricane Research Laboratory has developed and flight tested a new airborne liquid water meter for cloud physics measurements. The sensor is maintained at constant temperature rather than at constant current, and the operating temperature is held well below the in-situ boiling point. These two changes from previous instruments, such as the popular Johnson-Williams meter, permit accurate response over a wider range of drop sizes and finer spatial resolution. Flight tests on NOAA Research Flight Facility aircraft showed the new unit to be more sensitive, more stable, and more rapidly responding than the J-W and Levine instruments presently on board.
Abstract
The National Hurricane Research Laboratory has developed and flight tested a new airborne liquid water meter for cloud physics measurements. The sensor is maintained at constant temperature rather than at constant current, and the operating temperature is held well below the in-situ boiling point. These two changes from previous instruments, such as the popular Johnson-Williams meter, permit accurate response over a wider range of drop sizes and finer spatial resolution. Flight tests on NOAA Research Flight Facility aircraft showed the new unit to be more sensitive, more stable, and more rapidly responding than the J-W and Levine instruments presently on board.
Abstract
A system for recording data from a large network of tipping bucket raingages on digital tape cassettes has been developed for the Florida Area Cumulus Experiment (FACE). This system is substantially less expensive than those previously available when large members of gages are needed. Field tests during June, July and August 1978 in South Florida showed the system to be accurate and reliable.
Abstract
A system for recording data from a large network of tipping bucket raingages on digital tape cassettes has been developed for the Florida Area Cumulus Experiment (FACE). This system is substantially less expensive than those previously available when large members of gages are needed. Field tests during June, July and August 1978 in South Florida showed the system to be accurate and reliable.
Abstract
An automated cloud-edge detection algorithm was developed and extensively tested. The algorithm uses in situ cloud physics data measured by a research aircraft coupled with ground-based weather radar measurements to determine whether the aircraft is in or out of cloud. Cloud edges are determined when the in/out state changes, subject to a hysteresis constraint. The hysteresis constraint prevents isolated transient cloud puffs or data dropouts from being identified as cloud boundaries. The algorithm was verified by detailed manual examination of the dataset in comparison to the results from application of the automated algorithm.
Abstract
An automated cloud-edge detection algorithm was developed and extensively tested. The algorithm uses in situ cloud physics data measured by a research aircraft coupled with ground-based weather radar measurements to determine whether the aircraft is in or out of cloud. Cloud edges are determined when the in/out state changes, subject to a hysteresis constraint. The hysteresis constraint prevents isolated transient cloud puffs or data dropouts from being identified as cloud boundaries. The algorithm was verified by detailed manual examination of the dataset in comparison to the results from application of the automated algorithm.
Abstract
In the presence of 3D turbulence, peak horizontal velocity estimates from an idealized Doppler profiler are found to be positively biased due to an incomplete specification of the vertical velocity field. The magnitude of the bias was estimated by assuming that the vertical and horizontal velocities can be separated into average and perturbation values and that the vertical and horizontal velocity perturbations are normally distributed. Under these assumptions, properties of the type-I extreme value distribution for maxima, known as the Gumbel distribution, can be used to obtain an analytical solution of the bias. The bias depends on geometric properties of the profiler configuration, the variance in the horizontal velocity, and the unresolved variance in the vertical velocity. When these variances are normalized by the average horizontal velocity, the bias can be mapped as a simple function of the normalized variances.
Abstract
In the presence of 3D turbulence, peak horizontal velocity estimates from an idealized Doppler profiler are found to be positively biased due to an incomplete specification of the vertical velocity field. The magnitude of the bias was estimated by assuming that the vertical and horizontal velocities can be separated into average and perturbation values and that the vertical and horizontal velocity perturbations are normally distributed. Under these assumptions, properties of the type-I extreme value distribution for maxima, known as the Gumbel distribution, can be used to obtain an analytical solution of the bias. The bias depends on geometric properties of the profiler configuration, the variance in the horizontal velocity, and the unresolved variance in the vertical velocity. When these variances are normalized by the average horizontal velocity, the bias can be mapped as a simple function of the normalized variances.
