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<br />generate a fast echo. The existence of high updraft speeds, as detected by both the aircraft platfonn
<br />and the radar, implies short transit times of the droplets upward through the clouds and adds credibility
<br />to thes(~ observations. The radar data further indicate that if a cloud can grow above the -10oC level
<br />before generating an echo, then it will probably grow to much greater final altitudes than one that
<br />generates a first echo at temperature levels warmer than freezing. This may result from updrafts that
<br />rise free of the load of precipitation-size drops in transit to the higher altitudes and then are enhanced
<br />owing to the release of latent heat of fusion derived from the larger amounts of supercooled liquid water
<br />transported to the higher altitudes, where a high rate of heat input from accelerated freezing is relatively
<br />more effective in maintaining convection.
<br />
<br />L6pez. R. E., R. F. Reinking, J. Hallett, and J. Jordan, 1982: 5-cm radar echoes and their microphysical
<br />significance in Florida cumuli. Preprints, Conference on Cloud Physics, Chicago, IL, November 15-18.
<br />1982. American Meteorological Society, Boston, MA, 183-186.
<br />
<br />No abstract.
<br />
<br />Martner, B. E., J. D. Marwitz, and R. A. Kropfli, 1992: Radar observations of transport and diffusion in clouds
<br />and precipitation using TRACIR. Journal of Atmospheric and Oceanic Technology. 9:226-241.
<br />
<br />A remote-sensing technique called TRACIR (tracking air with circular-polarization radar) was developed
<br />recently for studying air-parcel trajectories in clouds. The technique uses a dual-circular-polarization
<br />radar to detect microwave chaff fibers that serve as tracers of the air motion. The radar is able to detect
<br />the chaff inside clouds and precipitation by measuring the circular-depolarization ratio, which is much
<br />higher for chaff than for hydrometeors. Chaff concentrations are also estimated by the technique, thus
<br />pennitting turbulent diffusion in clouds to be examined. Demonstrations of TRACIR's capabilities are
<br />presented for three cases in which chaff was used to simulate the movement of cloud-seeding nuclei in
<br />clouds and precipitation. In two cases involving airborne chaff releases, the gradual drift and diffusion
<br />of chaff in a stratifonn cloud are contrasted with its abrupt transport and dispersion in a convective
<br />cloud. In the third case study, the technique successfully detected a plume of chaff released from the
<br />ground in a snowstonn. In each case, the radar data provided three-dimensional visualizations of the
<br />extent of the chaff region and maps of the chaff concentration with excellent spatial and temporal
<br />resolution.
<br />
<br />Martner, B. E., 1990: Radar observations of transport and diffusion of chaff in a stratus cloud. Preprints,
<br />9th Symposium on Turbulence and Diffusion, Roskilde, Denmark, April 30-May 3, 1990.
<br />American Meteorological Society, Boston, MA, 115-118.
<br />
<br />No abstract.
<br />
<br />Martner, B. E., and J. D. Marwitz, 1990: Transport and diffusion of chaff in a convective cloud. Preprints,
<br />Conference on Cloud Physics. San Francisco, CA, July 23-27. 1990. American Meteorological Society,
<br />Boston, MA, 722-729.
<br />
<br />No abstract.
<br />
<br />I
<br />Meitfn, R. J., R. A. Brown, and J. G. Meitfn. 1991: Comparison of airborne dual-Doppler and
<br />airborne/ground-based dual-Doppler analyses of North Dakota thunderstonns. Preprints,
<br />25th International Conference on Radar Meteorology, Paris, France, June 24-28, 1991. American
<br />Meteorological Society, Boston, MA, 474-477.
<br />
<br />No abstract.
<br />
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