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- Author or Editor: John D. Marwitz x
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Abstract
The 1977–78 Sierra Cooperative Pilot Project (SCPP) field season offered an opportunity for comparing several Particle Measuring Systems (PMS) probes. During that winter the University of Wyoming's King Air aircraft was instrumented with 1D cloud, 2D cloud and 2D precipitation probes. Data from the three probes were analyzed from several flights in stable oregraphic storms. Various temperature levels (and hence, hydrometeor habits) above and below 0°C were flown in order to compare the data for water drops and for different ice crystal habits. It was found that all three probes agree quite well when sampling water drops of any size; however, when sampling ice crystals the probes agreed only at sizes larger than about 1 mm.
Abstract
The 1977–78 Sierra Cooperative Pilot Project (SCPP) field season offered an opportunity for comparing several Particle Measuring Systems (PMS) probes. During that winter the University of Wyoming's King Air aircraft was instrumented with 1D cloud, 2D cloud and 2D precipitation probes. Data from the three probes were analyzed from several flights in stable oregraphic storms. Various temperature levels (and hence, hydrometeor habits) above and below 0°C were flown in order to compare the data for water drops and for different ice crystal habits. It was found that all three probes agree quite well when sampling water drops of any size; however, when sampling ice crystals the probes agreed only at sizes larger than about 1 mm.
Abstract
Synthetic dual-Doppler (SDD) is a single-Doppler analysis technique that combines measurements from two different times, provided the viewing angle changes significantly. In this study, the viability of the SDD technique is investigated through comparisons with dual-Doppler analyses. Three case studies are used for the comparisons: a mature gust front, a supercell thunderstorm, and a developing squall line. An attempt to internally establish the efficacy of SDD analyses is made by examining the temporal correlation of the single-Doppler reflectivity fields and by comparing wind fields derived from similar synthetic analyses.
Results indicate that the SDD technique may be practical for the estimation of mean velocity fields of certain quasi-steady phenomena. The similarity of the SDD and conventional dual-Doppler results were found to be sensitive to the time between the two volume scans used in the SDD analyses, the angle subtended by the event, and the radii of influence of the Cressman weighting function used for the interpolation of the data.
Abstract
Synthetic dual-Doppler (SDD) is a single-Doppler analysis technique that combines measurements from two different times, provided the viewing angle changes significantly. In this study, the viability of the SDD technique is investigated through comparisons with dual-Doppler analyses. Three case studies are used for the comparisons: a mature gust front, a supercell thunderstorm, and a developing squall line. An attempt to internally establish the efficacy of SDD analyses is made by examining the temporal correlation of the single-Doppler reflectivity fields and by comparing wind fields derived from similar synthetic analyses.
Results indicate that the SDD technique may be practical for the estimation of mean velocity fields of certain quasi-steady phenomena. The similarity of the SDD and conventional dual-Doppler results were found to be sensitive to the time between the two volume scans used in the SDD analyses, the angle subtended by the event, and the radii of influence of the Cressman weighting function used for the interpolation of the data.
Abstract
A method for the analysis of single-Doppler radar data called band-velocity-processing (BVP) is presented. The BVP method was designed to exploit the two-dimensional nature of banded precipitation systems with crossband length scales of 5–50 km. The BVP method offers improved horizontal (crossband) resolution over existing volume scan methods (VAD/VVP), plus the ability to extract band-perpendicular vertical cross sections from a single volume scan. The BVP analysis yields a more complete kinematic structure than RHI analyses, providing estimates for both horizontal wind components, both horizontal divergence components, the shearing deformation, and the vertical shear vector. The bias and variance errors for the BVP method are shown to be acceptably small.
The application of the BVP method to a narrow cold frontal rainband reveals several important kinematic features. The mesoscale structure of the low-level jet ahead of the narrow cold frontal rainband is examined. The band relative flow field exhibits a closed helical circulation cell at the front of the band.
Abstract
A method for the analysis of single-Doppler radar data called band-velocity-processing (BVP) is presented. The BVP method was designed to exploit the two-dimensional nature of banded precipitation systems with crossband length scales of 5–50 km. The BVP method offers improved horizontal (crossband) resolution over existing volume scan methods (VAD/VVP), plus the ability to extract band-perpendicular vertical cross sections from a single volume scan. The BVP analysis yields a more complete kinematic structure than RHI analyses, providing estimates for both horizontal wind components, both horizontal divergence components, the shearing deformation, and the vertical shear vector. The bias and variance errors for the BVP method are shown to be acceptably small.
The application of the BVP method to a narrow cold frontal rainband reveals several important kinematic features. The mesoscale structure of the low-level jet ahead of the narrow cold frontal rainband is examined. The band relative flow field exhibits a closed helical circulation cell at the front of the band.
Abstract
A remote-sensing technique called TRACIR (tracking air with circular-polarization radar) was developed recently for studying air-parcel trajectories in clouds. The technique uses a dual-circular-polarization radar to detect microwave chaff fibers that serve as tracers of the air motion. The radar is able to detect the chaff inside clouds and precipitation by measuring the circular-depolarization ratio, which is much higher for chaff than for hydrometeors. Chaff concentrations are also estimated by the technique, thus permitting turbulent diffusion in clouds to be examined. Demonstrations of TRACIR's capabilities are presented for three cases in which chaff was used to simulate the movement of cloud-seeding nuclei in clouds and precipitation. In two cases involving airborne chaff releases, the gradual drift and diffusion of chaff in a stratiform cloud are contrasted with its abrupt transport and dispersion in a convective cloud. In the third case study, the technique successfully detected a plume of chaff released from the ground in a snowstorm. In each case the radar data provided three-dimensional visualizations of the extent of the chaff region and maps of the chaff concentration with excellent spatial and temporal resolution.
Abstract
A remote-sensing technique called TRACIR (tracking air with circular-polarization radar) was developed recently for studying air-parcel trajectories in clouds. The technique uses a dual-circular-polarization radar to detect microwave chaff fibers that serve as tracers of the air motion. The radar is able to detect the chaff inside clouds and precipitation by measuring the circular-depolarization ratio, which is much higher for chaff than for hydrometeors. Chaff concentrations are also estimated by the technique, thus permitting turbulent diffusion in clouds to be examined. Demonstrations of TRACIR's capabilities are presented for three cases in which chaff was used to simulate the movement of cloud-seeding nuclei in clouds and precipitation. In two cases involving airborne chaff releases, the gradual drift and diffusion of chaff in a stratiform cloud are contrasted with its abrupt transport and dispersion in a convective cloud. In the third case study, the technique successfully detected a plume of chaff released from the ground in a snowstorm. In each case the radar data provided three-dimensional visualizations of the extent of the chaff region and maps of the chaff concentration with excellent spatial and temporal resolution.
