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- Author or Editor: Guy G. Goyer x
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Abstract
Radar echo tops of individual cells, integrated over their duration above 7.6 km, are used to define an overall storm magnitude, a growth factor after seeding, and an average seeding rate. The growth factor is then plotted as a function of the average seeding rate for 23 seeded cells and 23 randomly selected non-seeded cells. The results show an appreciable decrease not only in the range of growth factors but also in the average growth factor as the average seeding rate is increased.
Time-integrated values of other radar measures, such as reflectivity and echo coverage, that can be better related to precipitation intensity than echo tops, are suggested as more accurate and sensitive measures of the effects of cloud seeding on the radar characteristics of convective storms.
Abstract
Radar echo tops of individual cells, integrated over their duration above 7.6 km, are used to define an overall storm magnitude, a growth factor after seeding, and an average seeding rate. The growth factor is then plotted as a function of the average seeding rate for 23 seeded cells and 23 randomly selected non-seeded cells. The results show an appreciable decrease not only in the range of growth factors but also in the average growth factor as the average seeding rate is increased.
Time-integrated values of other radar measures, such as reflectivity and echo coverage, that can be better related to precipitation intensity than echo tops, are suggested as more accurate and sensitive measures of the effects of cloud seeding on the radar characteristics of convective storms.
Abstract
The method of analysis and display of airborne infrared radiometer data is presented. The method involves recording, enhancing, digitizing, filtering, compressing, calibrating and displaying on contour radiation temperature maps, the ground temperatures measured with a Texas Instrument RS-310 scanning radiometer and a Barnes PRT-6 starring radiometer.
The method is applied to the analysis of a hailswath near Fort Morgan, Colo., on 13 June 1972.
Final conclusions on the research and operational uses of this technique for the analysis of hailswaths are presented.
Abstract
The method of analysis and display of airborne infrared radiometer data is presented. The method involves recording, enhancing, digitizing, filtering, compressing, calibrating and displaying on contour radiation temperature maps, the ground temperatures measured with a Texas Instrument RS-310 scanning radiometer and a Barnes PRT-6 starring radiometer.
The method is applied to the analysis of a hailswath near Fort Morgan, Colo., on 13 June 1972.
Final conclusions on the research and operational uses of this technique for the analysis of hailswaths are presented.
Abstract
A cloud of small supercooled water droplets was subjected to shock waves of reproducible intensity in the laboratory. Nucleation of freezing occurred only when the gas driving the shock waves was cooled to −37C or below by adiabatic expansion and subsequently mixed with the droplet-bearing air. Passage of the shock wave did not produce nucleation of the cloud. Results of a numerical model of a lightning discharge show, in the pressure wave from a lightning discharge, that the degree of cooling by adiabatic expansion is probably too small to produce ice crystals by homogeneous nucleation.
Abstract
A cloud of small supercooled water droplets was subjected to shock waves of reproducible intensity in the laboratory. Nucleation of freezing occurred only when the gas driving the shock waves was cooled to −37C or below by adiabatic expansion and subsequently mixed with the droplet-bearing air. Passage of the shock wave did not produce nucleation of the cloud. Results of a numerical model of a lightning discharge show, in the pressure wave from a lightning discharge, that the degree of cooling by adiabatic expansion is probably too small to produce ice crystals by homogeneous nucleation.
Abstract
The effect of explosively generated shock waves on ice cubes has been investigated in the laboratory. Impact tests on cubes previously exposed to shock demonstrate that the action of the latter weakens the cubes, the effect being markedly greater when the latter contain a water column. The phenomenon observed is discussed in terms of the theory of shock waves; the weakening of the ice cubes appears to be plausible on the basis of shock-induced cavitations within the water columns inside them. Insofar as ice cubes containing a water column very crudely simulate hailstones, the results observed suggest the possibility that explosive shock waves might similarly weaken actual hailstones. Thus, rocketborne explosive charges could conceivably be a practical way of reducing damage from hailstorms.
Abstract
The effect of explosively generated shock waves on ice cubes has been investigated in the laboratory. Impact tests on cubes previously exposed to shock demonstrate that the action of the latter weakens the cubes, the effect being markedly greater when the latter contain a water column. The phenomenon observed is discussed in terms of the theory of shock waves; the weakening of the ice cubes appears to be plausible on the basis of shock-induced cavitations within the water columns inside them. Insofar as ice cubes containing a water column very crudely simulate hailstones, the results observed suggest the possibility that explosive shock waves might similarly weaken actual hailstones. Thus, rocketborne explosive charges could conceivably be a practical way of reducing damage from hailstorms.
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Recent advances in the technology of the optical radar (lidar) are reviewed. Its use as a remote probe for the study of atmospheric parameters, such as water vapor, density, temperature and aerosols at altitudes above 10 km is discussed. The lidar data on the reflectivity of the 20 km sulfate layer is used to determine the most likely size distribution of the particulates in that layer.
Recent advances in the technology of the optical radar (lidar) are reviewed. Its use as a remote probe for the study of atmospheric parameters, such as water vapor, density, temperature and aerosols at altitudes above 10 km is discussed. The lidar data on the reflectivity of the 20 km sulfate layer is used to determine the most likely size distribution of the particulates in that layer.
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Weathereord, a 40-grain detonating fuse containing about 20 per cent of silver iodide, has been evaluated as a cloud seeding nuclei generator in the laboratory, in the field, and in aircraft cloud seeding. Comparative data on the output efficiencies of several types of silver iodide generators are presented and show that, as a dispersal system, Weathercord provides in unit time and unit volume the highest concentration of nuclei available from any known source. The tests in supercooled logs at Yellowstone National Park and two test cases of the seeding from aircraft of orographic cumuli are also described. Although of a preliminary nature these field tests suggest the effectiveness of the large concentrations of AgI nuclei, generated by Weathercord, in modifying relatively thin supercooled clouds.
Abstract
Weathereord, a 40-grain detonating fuse containing about 20 per cent of silver iodide, has been evaluated as a cloud seeding nuclei generator in the laboratory, in the field, and in aircraft cloud seeding. Comparative data on the output efficiencies of several types of silver iodide generators are presented and show that, as a dispersal system, Weathercord provides in unit time and unit volume the highest concentration of nuclei available from any known source. The tests in supercooled logs at Yellowstone National Park and two test cases of the seeding from aircraft of orographic cumuli are also described. Although of a preliminary nature these field tests suggest the effectiveness of the large concentrations of AgI nuclei, generated by Weathercord, in modifying relatively thin supercooled clouds.
Abstract
A calorimetric method for measuring the liquid water content of hailstones has been developed. When parameters such as the radiative losses of the system and the changes in heat capacity of the apparatus are eliminated by performing all measurements under identical conditions, the temperature drop is linearly related to the mass of ice melted. For equal masses the temperature drop is smaller if water is present, and there is a linear relationship between the changes in temperature drop and the amount of water present. The water content of hailstones can then be determined from a calibration plot of the changes in temperature drop as a function of the water content of ice.
Abstract
A calorimetric method for measuring the liquid water content of hailstones has been developed. When parameters such as the radiative losses of the system and the changes in heat capacity of the apparatus are eliminated by performing all measurements under identical conditions, the temperature drop is linearly related to the mass of ice melted. For equal masses the temperature drop is smaller if water is present, and there is a linear relationship between the changes in temperature drop and the amount of water present. The water content of hailstones can then be determined from a calibration plot of the changes in temperature drop as a function of the water content of ice.
