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- Author or Editor: W. L. Woodley x
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Abstract
Documentation during January and February 2000 of the structure of severe convective storms in Mendoza, Argentina, with a cloud-physics jet aircraft penetrating the major feeder clouds from cloud base to the −45°C isotherm level is reported. Complementary radar, satellite, and radiosonde measurements are incorporated into the study. The main research goal was the description of the microphysical evolution of the convective feeders of the hailstorms from cloud base to the anvil in an attempt to gain insights into the microphysical evolution of the clouds that are associated with the high frequency of large hail in the region. The aircraft penetrated preferentially the tops of young growing elements, which were typically the major feeders to severe hailstorms, producing hail that is large (>3 cm) in size. Cloud bases typically were at 6°–14°C, with typical base updrafts of 4–7 m s−1. The cloud updrafts increased with height, exceeding 25 m s−1 at heights ≥7 km and, on occasion, 40 m s−1 at heights >8 km. Thermal buoyancies of 5°–8°C were measured in the convective towers at heights of 8–10 km. The vertical wind shear was weak below 6 km but increased strongly above that level as the west winds cleared the Andes barrier, which averages 6.1 km to the west of Mendoza. The clouds had very little coalescence and contained no detectable precipitation-sized particles >100 μm at temperatures >−15°C. Nearly adiabatic cloud water with most cloud water still not converted into precipitation-sized hydrometeors (>100 μm in diameter) was found in cloud filaments within the strongest updrafts up to the level of homogeneous freezing, reaching 4 g m−3 at −38°C in one cloud before vanishing abruptly at colder temperatures. Graupel >1 mm appeared at the tops of growing new towers at temperatures <−27°C, in agreement with radar first-echo heights of about 8 km.
Abstract
Documentation during January and February 2000 of the structure of severe convective storms in Mendoza, Argentina, with a cloud-physics jet aircraft penetrating the major feeder clouds from cloud base to the −45°C isotherm level is reported. Complementary radar, satellite, and radiosonde measurements are incorporated into the study. The main research goal was the description of the microphysical evolution of the convective feeders of the hailstorms from cloud base to the anvil in an attempt to gain insights into the microphysical evolution of the clouds that are associated with the high frequency of large hail in the region. The aircraft penetrated preferentially the tops of young growing elements, which were typically the major feeders to severe hailstorms, producing hail that is large (>3 cm) in size. Cloud bases typically were at 6°–14°C, with typical base updrafts of 4–7 m s−1. The cloud updrafts increased with height, exceeding 25 m s−1 at heights ≥7 km and, on occasion, 40 m s−1 at heights >8 km. Thermal buoyancies of 5°–8°C were measured in the convective towers at heights of 8–10 km. The vertical wind shear was weak below 6 km but increased strongly above that level as the west winds cleared the Andes barrier, which averages 6.1 km to the west of Mendoza. The clouds had very little coalescence and contained no detectable precipitation-sized particles >100 μm at temperatures >−15°C. Nearly adiabatic cloud water with most cloud water still not converted into precipitation-sized hydrometeors (>100 μm in diameter) was found in cloud filaments within the strongest updrafts up to the level of homogeneous freezing, reaching 4 g m−3 at −38°C in one cloud before vanishing abruptly at colder temperatures. Graupel >1 mm appeared at the tops of growing new towers at temperatures <−27°C, in agreement with radar first-echo heights of about 8 km.
Abstract
The Florida Area Cumulus Experiment (FACE) was a two-stage program dedicated to assessing the potential of “dynamic seeding” for enhancing convective rainfall in a fixed target area. FACE-1 (1970–76) was an exploratory cloud seeding experiment that produced substantial indications of a positive treatment effect on rain at the ground, and FACE-2 (1978–80) was a confirmatory experiment that did not confirm the treatment effect results of FACE-1.
This article presents some new analyses of both the FACE-1 and FACE-2 data in an effort to better understand the role of meteorological and treatment factors on rainfall in the days selected for experimentation in Florida. The analyses rely upon a guided exploratory linear modeling of the natural target area rainfall and the potential treatment effects. In particular, a conceptual model of natural Florida rainfall is utilized to guide the construction of the exploratory linear model. After the form of the model is selected it is fitted to both the FACE-1 and the FACE-2 data sets in an attempt to reassess the effects of treatment.
Two approaches are taken to assessing the treatment effects in FACE-1 and in FACF-2: cross-comparison and cross-validation. Both techniques suggest a positive treatment effect in each stage of FACE (i.e., 30–45% in FACE-1 and 10–15% in FACF-2). However, the conventional 0.05 unadjusted statistical level of support is only present in the FACE-1 data. The question of whether FACE-1 results were different from FACE-2 is unresolved. These results continue to emphasize the need to better account for the natural convective precipitation processes in south Florida prior to conducting a cloud seeding project.
Abstract
The Florida Area Cumulus Experiment (FACE) was a two-stage program dedicated to assessing the potential of “dynamic seeding” for enhancing convective rainfall in a fixed target area. FACE-1 (1970–76) was an exploratory cloud seeding experiment that produced substantial indications of a positive treatment effect on rain at the ground, and FACE-2 (1978–80) was a confirmatory experiment that did not confirm the treatment effect results of FACE-1.
This article presents some new analyses of both the FACE-1 and FACE-2 data in an effort to better understand the role of meteorological and treatment factors on rainfall in the days selected for experimentation in Florida. The analyses rely upon a guided exploratory linear modeling of the natural target area rainfall and the potential treatment effects. In particular, a conceptual model of natural Florida rainfall is utilized to guide the construction of the exploratory linear model. After the form of the model is selected it is fitted to both the FACE-1 and the FACE-2 data sets in an attempt to reassess the effects of treatment.
Two approaches are taken to assessing the treatment effects in FACE-1 and in FACF-2: cross-comparison and cross-validation. Both techniques suggest a positive treatment effect in each stage of FACE (i.e., 30–45% in FACE-1 and 10–15% in FACF-2). However, the conventional 0.05 unadjusted statistical level of support is only present in the FACE-1 data. The question of whether FACE-1 results were different from FACE-2 is unresolved. These results continue to emphasize the need to better account for the natural convective precipitation processes in south Florida prior to conducting a cloud seeding project.
Abstract
No abstract available.
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No abstract available.
Abstract
The development, testing and use of an airborne pyrotechnic cloud seeding system is described. Pyrotechnic flares producing 50 gm of silver iodide smoke each were developed by two industrial corporations and laboratory tested for nucleation effectiveness in the Colorado State University cloud chamber. A delivery rack and firing system were developed, under ESSA supervision, and installed on its B-57 jet aircraft. Night flight tests were made of reliability, burn time and flare trajectory.
The flare system was used in a Florida cumulus seeding experiment in May 1968 conducted jointly by ESSA and the Naval Research Laboratory, with the participation of the U.S. Air Force, the University of Miami Radar Laboratory, and Meteorology Research, Inc. A randomized seeding scheme was used on 19 supercooled cumuli, of which 14 were seeded and 5 were studied identically as controls. Of the 14 seeded clouds, 13 grew explosively. Seeded clouds grew 11,400 ft higher than the controls, with the difference significant at better than the 0.5% level. Rainfall from seeded and control clouds was compared by means of calibrated ground radars. Large increases in rainfall were found from seeded clouds, but at a significance level ranging from 5–20% depending on the statistical test used. A single successful repeat of the experiment could result in rainfall differences significant at the 3% level with the most stringent test.
Abstract
The development, testing and use of an airborne pyrotechnic cloud seeding system is described. Pyrotechnic flares producing 50 gm of silver iodide smoke each were developed by two industrial corporations and laboratory tested for nucleation effectiveness in the Colorado State University cloud chamber. A delivery rack and firing system were developed, under ESSA supervision, and installed on its B-57 jet aircraft. Night flight tests were made of reliability, burn time and flare trajectory.
The flare system was used in a Florida cumulus seeding experiment in May 1968 conducted jointly by ESSA and the Naval Research Laboratory, with the participation of the U.S. Air Force, the University of Miami Radar Laboratory, and Meteorology Research, Inc. A randomized seeding scheme was used on 19 supercooled cumuli, of which 14 were seeded and 5 were studied identically as controls. Of the 14 seeded clouds, 13 grew explosively. Seeded clouds grew 11,400 ft higher than the controls, with the difference significant at better than the 0.5% level. Rainfall from seeded and control clouds was compared by means of calibrated ground radars. Large increases in rainfall were found from seeded clouds, but at a significance level ranging from 5–20% depending on the statistical test used. A single successful repeat of the experiment could result in rainfall differences significant at the 3% level with the most stringent test.
