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 Review of Wintertime Orographic Cloud Seeding

1986 ◽  
Vol 43 ◽  
pp. 87-104 ◽  
Author(s):  
Robert D. Elliott
Keyword(s):  
Scientific Literature ◽  
Doppler Radar ◽  
Cloud Seeding ◽  
Weather Modification ◽  
The Past ◽  
Orographic Clouds ◽  
The 1960S ◽  
Orographic Cloud ◽  
Microwave Radiometers ◽  
Seeding Effects

Abstract This review provides a sketchy background of orographic weather modification activities prior to the 1960s, followed by a more critical review of major orographic projects carried out and reported in the scientific literature during the past 25 years. In the earlier of these major projects, evaluation of results had been based largely upon comparisons of seeded and nonseeded precipitation experimental units stratified by various sounding-derived parameters in an attempt to amplify the physical significance of the seeding effects within various sub-types of orographic clouds. The later major projects are still underway with no final evaluations having been presented. However, a wealth of significant data analyses have been reported that provide important insights into the various natural and seeding precipitation mechanisms. Much of this is attributable to the new observational tools in use, which include airborne and ground microphysical sensors, doppler radar, and microwave radiometers.

Wintertime Orographic Cloud Seeding—A Review

2019 ◽  
Vol 58 (10) ◽  
pp. 2117-2140 ◽  
Author(s):  
Robert M. Rauber ◽  
Bart Geerts ◽  
Lulin Xue ◽  
Jeffrey French ◽  
Katja Friedrich ◽  
...  
Keyword(s):  
Supercooled Water ◽  
Mountain Range ◽  
Target Area ◽  
Cloud Seeding ◽  
Cloud Systems ◽  
The Past ◽  
Precipitation Efficiency ◽  
Focus On Results ◽  
Orographic Cloud ◽  
Modern Instrumentation

AbstractThis paper reviews research conducted over the last six decades to understand and quantify the efficacy of wintertime orographic cloud seeding to increase winter snowpack and water supplies within a mountain basin. The fundamental hypothesis underlying cloud seeding as a method to enhance precipitation from wintertime orographic cloud systems is that a cloud’s natural precipitation efficiency can be enhanced by converting supercooled water to ice upstream and over a mountain range in such a manner that newly created ice particles can grow and fall to the ground as additional snow on a specified target area. The review summarizes the results of physical, statistical, and modeling studies aimed at evaluating this underlying hypothesis, with a focus on results from more recent experiments that take advantage of modern instrumentation and advanced computation capabilities. Recent advances in assessment and operations are also reviewed, and recommendations for future experiments, based on the successes and failures of experiments of the past, are given.

scholarly journals Quantifying snowfall from orographic cloud seeding

2020 ◽  
Vol 117 (10) ◽  
pp. 5190-5195 ◽  
Author(s):  
Katja Friedrich ◽  
Kyoko Ikeda ◽  
Sarah A. Tessendorf ◽  
Jeffrey R. French ◽  
Robert M. Rauber ◽  
...  
Keyword(s):  
Climate Change ◽  
Population Growth ◽  
Arid Regions ◽  
Temporal Evolution ◽  
Cloud Seeding ◽  
Cloud Systems ◽  
Physically Based ◽  
Statistical Approaches ◽  
Orographic Cloud ◽  
Precipitation Gauge

Climate change and population growth have increased demand for water in arid regions. For over half a century, cloud seeding has been evaluated as a technology to increase water supply; statistical approaches have compared seeded to nonseeded events through precipitation gauge analyses. Here, a physically based approach to quantify snowfall from cloud seeding in mountain cloud systems is presented. Areas of precipitation unambiguously attributed to cloud seeding are isolated from natural precipitation (<1 mm h−1). Spatial and temporal evolution of precipitation generated by cloud seeding is then quantified using radar observations and snow gauge measurements. This study uses the approach of combining radar technology and precipitation gauge measurements to quantify the spatial and temporal evolution of snowfall generated from glaciogenic cloud seeding of winter mountain cloud systems and its spatial and temporal evolution. The results represent a critical step toward quantifying cloud seeding impact. For the cases presented, precipitation gauges measured increases between 0.05 and 0.3 mm as precipitation generated by cloud seeding passed over the instruments. The total amount of water generated by cloud seeding ranged from 1.2 × 105 m3 (100 ac ft) for 20 min of cloud seeding, 2.4 × 105 m3 (196 ac ft) for 86 min of seeding to 3.4 x 105 m3 (275 ac ft) for 24 min of cloud seeding.

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 Evaluating Winter Orographic Cloud Seeding: Design of the Wyoming Weather Modification Pilot Project (WWMPP)

2014 ◽  
Vol 53 (2) ◽  
pp. 282-299 ◽  
Author(s):  
Daniel Breed ◽  
Roy Rasmussen ◽  
Courtney Weeks ◽  
Bruce Boe ◽  
Terry Deshler
Keyword(s):  
Sample Size ◽  
Statistical Significance ◽  
Pilot Project ◽  
Cloud Seeding ◽  
Weather Modification ◽  
South Central ◽  
Design Choice ◽  
Wide Range ◽  
Orographic Cloud ◽  
Size Estimates

AbstractAn overview of the Wyoming Weather Modification Pilot Project (WWMPP) is presented. This project, funded by the State of Wyoming, is designed to evaluate the effectiveness of cloud seeding with silver iodide in the Medicine Bow and Sierra Madre Ranges of south-central Wyoming. The statistical evaluation is based on a randomized crossover design for the two barriers. The description of the experimental design includes the rationale behind the design choice, the criteria for case selection, facilities for operations and evaluation, and the statistical analysis approach. Initial estimates of the number of cases needed for statistical significance used historical Snow Telemetry (SNOTEL) data (1987–2006), prior to the beginning of the randomized seeding experiment. Refined estimates were calculated using high-resolution precipitation data collected during the initial seasons of the project (2007–10). Comparing the sample size estimates from these two data sources, the initial estimates are reduced to 236 (110) for detecting a 10% (15%) change. The sample size estimates are highly dependent on the assumed effect of seeding, on the correlations between the two target barriers and between the target and control sites, and on the variance of the response variable, namely precipitation. In addition to the statistical experiment, a wide range of physical studies and ancillary analyses are being planned and conducted.

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.

International responses to weather modification

1975 ◽  
Vol 29 (3) ◽  
pp. 805-826 ◽  
Author(s):  
Edith Brown Weiss
Keyword(s):  
International Cooperation ◽  
New Technology ◽  
International Community ◽  
Weather Modification ◽  
Weather System ◽  
The Past ◽  
Time Horizons ◽  
Weather And Climate ◽  
Potential Problems ◽  
Do So

In the past few decades we have been improving our understanding of the weather system and exploring ways to modify it. Over sixty countries have experimented with modifying the weather. The new technology of weather and climate modification will raise important political problems which will demand new responses from the international community. Whether states will be able to establish the cooperative measures necessary to develop and manage new technology depends upon whether there are sufficient incentives to do so. This article analyzes the historical patterns of international cooperation in meteorology, and then plots against several time horizons projected developments and capabilities in weather modification technology and the potential problems emerging from using the technology. It derives a tentative picture of the responsibilities demanded, compares the likely responses with those needed, and assesses whether they will be adequate for the problems projected.

scholarly journals Randomized convective cloud seeding experiment in extended areas in Cuba (EXPAREX)

2011 ◽  
Vol 26 (4) ◽  
pp. 515-528 ◽  
Author(s):  
Daniel Martinez-Castro ◽  
Carlos A Pérez-Sanchez ◽  
Boris P Koloskov ◽  
Victor V. Korneev ◽  
Victor V Petrov ◽  
...  
Keyword(s):  
Experimental Design ◽  
Rainy Season ◽  
Convective Cloud ◽  
General Description ◽  
Cloud Seeding ◽  
Design Procedures ◽  
Successful Experiment ◽  
Randomization Scheme ◽  
Confirmatory Phase

The Randomized Convective Cloud Seeding Experiment in Extended Areas (EXPerimento aleatorizado de siembra de nubes en AReas EXtensas, EXPAREX) is being implemented in Camagüey, Cuba and adjacent regions from August 2005 as the continuation of a previous successful experiment (PCMAT), held in the period 1982-1990. The first season of the experiment was exploratory and was focused on upgrading facilities, equipment and software, including an An-26 instrumented aircraft and the 10-cm MRL-5 weather radar. It was aimed at implementing methodologies and testing the application of the experimental design, excluding the randomization scheme, which was scheduled to be started in the second experimental year, in the rainy season of 2006. The field operations of the confirmatory phase started only in October, 2006, when seven experimental units, treated under a randomized scheme, were qualified. In the 2007 experiment, 13 more experimental units were processed. The general description, experimental design, procedures and characterization of the first two experimental seasons of the confirmatory phase of EXPAREX are presented in this work. Is it shown that the experimental clouds processed in the first two seasons of the experiment have similar characteristics to the PCMAT clouds, so that the conclusions of previous physical research are applicable.

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.

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