Ice Evolution within Seeded and Nonseeded Florida Cumuli

Sax, Robert I.; Thomas, Jack; Bonebrake, Marilyn; Hallett, John

doi:10.1175/1520-0450(1979)018<0203:iewsan>2.0.co;2

Cited by 23 publications

(6 citation statements)

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“…3) Increase in the number of crystals and decrease in cloud liquid water following seeding of convective clouds. These observations were reported in FACE [Florida Area Cumulus Experiment] (Sax et al, 1979) and in the HIPLEX measurements (Issac et al, 1977). Although this finding follows our concepts as to how seeding should work, the fact that it has been difficult to verify this physical sequence in convective clouds indicates that we do not yet fully understand the dimensions of this finding.…”

Section: A Look At the Information Basementioning

confidence: 58%

meeting review

1981

Bulletin of the American Meteorological Society

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Section: A Look At the Information Basementioning

confidence: 58%

meeting review

1981

Bulletin of the American Meteorological Society

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“…Note that the latent heat released by the deposition of supercooled water enhances the convective cloud development further because this heat release can lead to stronger updrafts and higher cloud tops. These factors accelerate the Bergeron and collision-coalescence processes to form large-size precipitation particles after seeding of the AgI, thereby increasing the precipitation (Simpson and Woodley, 1971;Sax et al, 1979;Woodley et al, 1982;Rosenfeld and Woodley, 1989;Bruintjes, 1999).…”

Section: Analysis Of Cloud Microphysical Properties From Aircraft Obs...mentioning

confidence: 99%

“…Hence, researchers have focused mostly on the changes of cloud-top height and surface precipitation but not on the detailed physical processes. Therefore, the dynamic seeding mechanism still lacks the verification through directly-observed data (Sax et al, 1979;Hallet, 1981;Woodley et al, 1982;Orville, 1996). Due to the complex structural characteristics of mixed convective-stratiform clouds (Lawson et al, 2015;Lin et al, 2019), there have been few studies related to the response of different cloud parts after seeding, such as the convective and stratiform parts, as well as the presence or absence of dynamic seeding effects.…”

Section: Introductionmentioning

confidence: 99%

Macro- and Micro-physical Characteristics of Different Parts of Mixed Convective-stratiform Clouds and Differences in Their Responses to Seeding

Li¹,

Zhao

et al. 2022

Adv. Atmos. Sci.

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This study investigates the cloud macro- and micro-physical characteristics in the convective and stratiform regions and their different responses to the seeding for mixed convective-stratiform clouds that occurred in Shandong province on 21 May 2018, based on the observations from the aircraft, the Suomi National Polar-Orbiting Partnership (NPP) satellite, and the high-resolution Himawari-8 (H8) satellite. The aircraft observations show that convection was deeper and radar echoes were significantly enhanced with higher tops in response to seeding in the convective region. This is linked with the conversion of supercooled liquid droplets to ice crystals with released latent heat, resulting in strengthened updrafts, enhanced radar echoes, higher cloud tops, and more and larger precipitation particles. In contrast, in the stratiform cloud region, after the Silver Iodide (AgI) seeding, the radar echoes become significantly weaker at heights close to the seeding layer, with the echo tops lowered by 1.4–1.7 km. In addition, a hollow structure appears at the height of 6.2–7.8 km with a depth of about 1.6 km and a diameter of about 5.5 km, and features such as icing seeding tracks appear. These suggest that the transformation between droplets and ice particles was accelerated by the seeding in the stratiform part. The NPP and H8 satellites also show that convective activity was stronger in the convective region after seeding; while in the stratiform region, a cloud seeding track with a width of 1–3 km appears 10 km downstream of the seeding layer 15 minutes after the AgI seeding, which moves along the wind direction as width increases.

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“…(iv) FACE-2 FACE-2 was carried out during the summers of , 1979, and 1980(Woodley et al 1983. Whereas FACE-1 was an exploratory experiment, FACE-2 was designed and conducted as a confirmatory experiment.…”

Section: (Iii) Face-1mentioning

confidence: 99%

“…The physical support for the dynamic-mode seeding conceptual model comes from such studies as 1) the microphysical study by Sax et al (1979) that showed that clouds seeded with silver iodide contained more ice than their unseeded counterparts; 2) the theoretical study by Lamb et al (1981) that indicated that dynamic seeding should work best in clouds that contain rain drops; 3) the radar studies by Gagin et al (1985) and Gagin et al (1986) specified the relationship between maximum echo heights and the rain volumes produced by individual convective cells and showed that an increase in cell-top height nearly doubles its rain production; 4) the radar study by Rosenfeld and Woodley (1993) that suggested that seed convective cells merge with neighboring cells more frequently than unseeded convective cells; 5) the exploratory analyses of Woodley and Rosenfeld (1996) that suggested that the apparent effects of seeding were larger in clouds with cloud-base temperatures > 15°C, which they attributed to the greater likelihood that rain drops would be present in vigorous updrafts above the freezing level because of more active condensation-coalescence processes; 6) the microphysical study by Rosenfeld and Woodley (1997) that suggested that the initial response of the cloud to dynamic seeding is greatest in clouds that contain supercooled rain drops; 7) the microphysical studies by Sudhikoses et al (1998) and Rosenfeld et al (1999) that indicated that the supercooled liquid water content depletes faster in seeded clouds than in unseeded clouds; and 8) the microphysical study by Woodley and Rosenfeld (2000) that suggested that seeding appears to result in the production of ice in invigorated updraft regions with a concomitant decrease in the cloud water. The numerical model experiments of seeding cold convective clouds with ice nuclei by Reisen et al (1996) showed, on the other hand, that seeding effectiveness was greatest in extreme continental clouds, in which collision-coalescence played only a minor role, and decreased as the clouds became less continental in character until it was only marginally effective for maritime clouds.…”

Section: B Physical Evidencementioning

confidence: 99%

A Critical Assessment of Glaciogenic Seeding of Convective Clouds for Rainfall Enhancement

Silverman¹

2001

Bull. Amer. Meteor. Soc.

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The scientific evidence for enhancing rainfall from convective clouds by static-mode and dynamic-mode seeding with glaciogenic agents is examined and critically assessed. The assessment uses, as a measure of proof of concept, the criteria for success of any cloud seeding activity that was recommended in the Scientific Background for the 1998 AMS Policy Statement on Planned and Inadvertent Weather Modification, criteria that require both statistical and physical evidence. Based on a rigorous examination of the accumulated results of the numerous experimental tests of the staticmode and dynamic-mode seeding concepts conducted over the past four decades, it has been found that they have not yet provided either the statistical or physical evidence required to establish their scientific validity. Thus, the conclusion of several high-level reviews of weather modification conducted by the Advisory Committee on Weather Control, the National Academy of Sciences, and the Weather Modification Advisory Board during the period from 1957 to 1978 that cloud seeding was promising, unproven, and worth pursuing is still valid today. The research and experiments related to the static-mode and dynamic-mode seeding concepts, especially those conducted since 1978, provided physical insights about some important cold-cloud precipitation development mechanisms and the possible effect of glaciogenic seeding on them. Exploratory, post hoc analyses of some of the experiments have suggested positive effects of seeding under restricted meteorological conditions, at extended times after seeding and, in general, for reasons not contemplated in the guiding conceptual seeding models; however, these exploratory results have never been confirmed through subsequent experimentation. New experiments are needed to resolve the uncertainties, inconsistencies, and deficiencies in the statistical and physical evidence in support of static-mode and dynamic-mode seeding of convective clouds obtained thus far. Considering the statistically positive result of hygroscopic flare seeding of cold convective clouds in South Africa and its replication in Mexico, and of hygroscopic particle seeding of warm convective clouds in Thailand, efforts to obtain the physical evidence required to place the hygroscopic seeding concept on a secure scientific foundation is, perhaps, a more immediate and higher-priority investment. Future experiments on glaciogenic seeding of convective clouds, indeed any cloud seeding technique, should feature well-defined physical-statistical tests of the seeding concepts, in accordance with the proof-of-concept criteria, in order to establish their scientific validity. People with water interests at stake who are investing in operational glaciogenic cloud seeding projects for precipitation enhancement should be aware of the inherent risks of applying an unproven cloud seeding technology and provide a means of evaluation that allows for an assessment of the scientific integrity and cost effectiveness of the operational seeding projects. Those ...

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Ice Evolution within Seeded and Nonseeded Florida Cumuli

Cited by 23 publications

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Macro- and Micro-physical Characteristics of Different Parts of Mixed Convective-stratiform Clouds and Differences in Their Responses to Seeding

A Critical Assessment of Glaciogenic Seeding of Convective Clouds for Rainfall Enhancement

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