scholarly journals Precipitation Enhancement—A Scientific Challenge

1986 ◽  
Vol 43 ◽  
pp. 1-6 ◽  
Author(s):  
Roscoe R. Braham
Keyword(s):  
Cloud Seeding ◽  
Weather Modification ◽  
Scientific Challenge ◽  
Precipitation Enhancement

Abstract Schaefer's 1946 cloud seeding experiment initiated a quest for weather modification techniques. Progress has been slow; but there are several reasons for believing that useful precipitation augmentation may be possible.

scholarly journals Review of Advances in Precipitation Enhancement Research

2019 ◽  
Vol 100 (8) ◽  
pp. 1465-1480 ◽  
Author(s):  
Andrea I. Flossmann ◽  
Michael Manton ◽  
Ali Abshaev ◽  
Roelof Bruintjes ◽  
Masataka Murakami ◽  
...  
Keyword(s):  
Convective Cloud ◽  
Cloud Seeding ◽  
Weather Modification ◽  
Catchment Scale ◽  
Cloud Systems ◽  
The Past ◽  
Expert Team ◽  
Orographic Cloud ◽  
Water Catchment ◽  
Precipitation Enhancement

AbstractThis paper provides a summary of the assessment report of the World Meteorological Organization (WMO) Expert Team on Weather Modification that discusses recent progress on precipitation enhancement research. The progress has been underpinned by advances in our understanding of cloud processes and interactions between clouds and their environment, which, in turn, have been enabled by substantial developments in technical capabilities to both observe and simulate clouds from the microphysical to the mesoscale. We focus on the two cloud types most commonly seeded in the past: winter orographic cloud systems and convective cloud systems. A key issue for cloud seeding is the extension from cloud-scale research to water catchment–scale impacts on precipitation on the ground. Consequently, the requirements for the design, implementation, and evaluation of a catchment-scale precipitation enhancement campaign are discussed. The paper concludes by indicating the most important gaps in our knowledge. Some recommendations regarding the most urgent research topics are given to stimulate further research.

scholarly journals Satellite-Retrieved Microstructure of AgI Seeding Tracks in Supercooled Layer Clouds

2005 ◽  
Vol 44 (6) ◽  
pp. 760-767 ◽  
Author(s):  
Daniel Rosenfeld ◽  
Xing Yu ◽  
Jin Dai
Keyword(s):  
Spatial Relations ◽  
Central China ◽  
Cloud Seeding ◽  
Weather Modification ◽  
Fall Velocity ◽  
Cloud Tops ◽  
Visible Reflectance ◽  
Precipitation Enhancement ◽  
Cloud Top Temperature ◽  
Observation Period

Abstract NOAA Advanced Very High Resolution Radiometer (AVHRR) images revealed conspicuous tracks of glaciated cloud in thick supercooled layer clouds over central China. These tracks were identified as being artificially produced by cloud-seeding operations at the −10°C isotherm, less than 1 km below cloud tops, aimed at precipitation enhancement, by means of AgI acetone generators. The cloud composition was deduced by retrieving the cloud-top effective radius (re) and analyzing its spatial relations with cloud-top temperatures and with the visible reflectance. Cloud-top temperature varied between −13° and −17°C. The glaciation became apparent at cloud tops about 22 min after seeding. The glaciated tops sank and formed a channel in the supercooled layer cloud. The rate of sinking of about 40 cm s−1 is compatible with the fall velocity of ice crystals that are likely to form at these conditions. A thin line of new water clouds formed in the middle of the channel of the seeded track between 38 and 63 min after seeding, probably as a result of rising motions induced by the released latent heat of freezing. These clouds disappeared in the more mature segments of the seeded track, which continued to expand throughout the observation period of more than 80 min. Eventually the seeding tracks started to dissipate by expansion of the ambient cloud tops inward from the sides. Using the brightness temperature difference between 10.8 and 12.0 μm allowed for observation of the seeding signature deep in the clouds, even when it was obscured under thin supercooled layer clouds. This is the third and most detailed report of effects of advertent cloud seeding for precipitation enhancement being detected and analyzed based on satellite observations. It opens new possibilities of using satellites for directing and monitoring weather modification experiments and operations.

scholarly journals Evaluation of the Wyoming Weather Modification Pilot Project (WWMPP) Using Two Approaches: Traditional Statistics and Ensemble Modeling

2018 ◽  
Vol 57 (11) ◽  
pp. 2639-2660 ◽  
Author(s):  
Roy M. Rasmussen ◽  
Sarah A. Tessendorf ◽  
Lulin Xue ◽  
Courtney Weeks ◽  
Kyoko Ikeda ◽  
...  
Keyword(s):  
Null Hypothesis ◽  
Initial Conditions ◽  
Pilot Project ◽  
Physical Experiment ◽  
Annual Precipitation ◽  
Ensemble Modeling ◽  
Cloud Seeding ◽  
Weather Modification ◽  
Mountain Ranges ◽  
The Impact

AbstractThe Wyoming Weather Modification Pilot Project randomized cloud seeding experiment was a crossover statistical experiment conducted over two mountain ranges in eastern Wyoming and lasted for 6 years (2008–13). The goal of the experiment was to determine if cloud seeding of orographic barriers could increase snowfall and snowpack. The experimental design included triply redundant snow gauges deployed in a target–control configuration, covariate snow gauges to account for precipitation variability, and ground-based seeding with silver iodide (AgI). The outcomes of this experiment are evaluated with the statistical–physical experiment design and with ensemble modeling. The root regression ratio (RRR) applied to 118 experimental units provided insufficient statistical evidence (p value of 0.28) to reject the null hypothesis that there was no effect from ground-based cloud seeding. Ensemble modeling estimates of the impact of ground-based seeding provide an alternate evaluation of the 6-yr experiment. The results of the model ensemble approach with and without seeding estimated a mean enhancement of precipitation of 5%, with an inner-quartile range of 3%–7%. Estimating the impact on annual precipitation over these mountain ranges requires results from another study that indicated that approximately 30% of the annual precipitation results from clouds identified as seedable within the seeding experiment. Thus the seeding impact is on the order of 1.5% of the annual precipitation, compared to 1% for the statistical–physical experiment, which was not sufficient to reject the null hypothesis. These results provide an estimate of the impact of ground-based cloud seeding in the Sierra Madre and Medicine Bow Mountains in Wyoming that accounts for uncertainties in both initial conditions and model physics.

Precipitation enhancement by cloud seeding using the shell structured TiO2/NaCl aerosol as revealed by new model for cloud seeding experiments

2018 ◽  
Vol 212 ◽  
pp. 202-212 ◽  
Author(s):  
Miloš Lompar ◽  
Mladjen Ćurić ◽  
Djordje Romanic ◽  
Linda Zou ◽  
Haoran Liang
Keyword(s):  
Cloud Seeding ◽  
New Model ◽  
Precipitation Enhancement

scholarly journals Charged Particle (Negative Ion)-Based Cloud Seeding and Rain Enhancement Trial Design and Implementation

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1644
Author(s):  
Wei Zheng ◽  
Fengming Xue ◽  
Ming Zhang ◽  
Qiqi Wu ◽  
Zhou Yang ◽  
...  
Keyword(s):  
Large Scale ◽  
Evaluation Method ◽  
Water Shortage ◽  
Northwest China ◽  
Negative Ion ◽  
Cloud Seeding ◽  
Weather Modification ◽  
Solid Carbon Dioxide ◽  
Design And Implementation ◽  
Hygroscopic Salts

China has been suffering from water shortage for a long time. Weather modification and rainfall enhancement via cloud seeding has been proved to be effective to alleviate the problem. Current cloud seeding methods mostly rely on solid carbon dioxide and chemicals such as silver iodide and hygroscopic salts, which may have negative impacts on the environment and are expensive to operate. Lab experiments have proved the efficiency of ion-based cloud seeding compared with traditional methods. Moreover, it is also more environmentally friendly and more economical to operate at a large scale. Thus, it is necessary to carry out a field experiment to further investigate the characteristics and feasibility of the method. This paper provides the design and implementation of the ion-based cloud seeding and rain enhancement trial currently running in Northwest China. It introduces the basic principle of the trial and the devices developed for it, as well as the installation of the bases and the evaluation method design for the trial.

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