The South African rainfall enhancement programme: 1997-2001

Terblanche, Deon; Mittermaier, Marion; Burger, Roelof; Waal, K; Ncipha, Xolile

doi:10.4314/wsa.v31i3.5218

Cited by 4 publications

(3 citation statements)

References 7 publications

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“…Similarly, Silverman and Sukarnjanaset (2000) found that the methodology of seeding individual mixed-phase clouds is unlikely to be economically viable. Further studies by Terblanche et al (2005) and Shippey et al (2004) also concluded that more efficient ways to deliver seeding material into clouds would be required to achieve impacts at catchment scales.…”

Section: Economic Issuesmentioning

confidence: 99%

Review of Advances in Precipitation Enhancement Research

Flossmann

Manton

Abshaev³

et al. 2019

Bulletin of the American Meteorological Society

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This 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.

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Section: Economic Issuesmentioning

confidence: 99%

Review of Advances in Precipitation Enhancement Research

Flossmann

Manton

Abshaev³

et al. 2019

Bulletin of the American Meteorological Society

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“…They derived quantitative measurements of seeding aerosol dispersion and dilution rates at multiple levels to demonstrate the effectiveness of cloud base seeding for both rainfall enhancement and hail suppression purposes. Consolidating the outcomes of the South African Rainfall Enhancement Program, Terblanche, et al [38] compiled a radar-based storm climatology over a 10,000 km 2 seeding target area using thresholds of 15 min and 30 dBZ for storm lifetime and radar reflectivity, respectively. They found that seeded storms produce approximately twice as much radar-estimated rainfall as the control (unseeded) storms.…”

Section: Introductionmentioning

confidence: 99%

The UAE Cloud Seeding Program: A Statistical and Physical Evaluation

Hosari¹,

Mandous²,

Wehbe³

et al. 2021

Atmosphere

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Operational cloud seeding programs have been increasingly deployed in several countries to augment natural rainfall amounts, particularly over water-scarce and arid regions. However, evaluating operational programs by quantifying seeding impacts remains a challenging task subject to complex uncertainties. In this study, we investigate seeding impacts using both long-term rain gauge records and event-based weather radar retrievals within the framework of the United Arab Emirates (UAE) National Center of Meteorology’s operational cloud seeding program. First, seasonal rain gauge records are inter-compared between unseeded (1981–2002) and seeded (2003–2019) periods, after which a posteriori target/control regression is developed to decouple natural and seeded rainfall time series. Next, trend analyses and change point detection are carried out over the July-October seeding periods using the modified Mann-Kendall (mMK) test and the Cumulative Sum (CUSUM) method, respectively. Results indicate an average increase of 23% in annual surface rainfall over the seeded target area, along with statistically significant change points detected during 2011 with decreasing/increasing rainfall trends for pre-/post-change point periods, respectively. Alternatively, rain gauge records over the control (non-seeded) area show non-significant change points. In line with the gauge-based statistical findings, a physical analysis using an archive of seeded (65) and unseeded (87) storms shows enhancements in radar-based storm properties within 15–25 min of seeding. The largest increases are recorded in storm volume (159%), area cover (72%), and lifetime (65%). The work provides new insights for assessing long-term seeding impacts and has significant implications for policy- and decision-making related to cloud seeding research and operational programs in arid regions.

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“…Therefore, the North Dakota Atmospheric Resource Board started the Polarimetric Cloud Analysis and Seeding Test (POLCAST) research program in 2006, to determine effectiveness of hygroscopic cloud seeding in North Dakota. While hygroscopic cloud seeding in South Africa, Mexico City and Thailand (Mather et al 1997;Terblanche 2005) had positive statistical results, it is important to determine if North Dakota is similarly conducive before implementing such operations. Furthermore, these new statistically-positive results did not fully account for potential multiplicity in the analyses (Silverman 2003), so the POLCAST program included a randomized seeding experiment.…”

Section: Introductionmentioning

confidence: 99%

Suitability of North Dakota for Conducting Effective Hygroscopic Seeding

Delene

2016

JournalWeaMod

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One goal of the Polarimetric Cloud Analysis and Seeding Test (POLCAST) project is to determine if North Dakota clouds created by surface-base convection are suitable for treatment with hygroscopic flares to enhance surface rainfall amounts. The suitability evaluation examines the processes involved in the hygroscopic seeding conceptual model to determine how supportive North Dakota's environment is to conducting an effective rain enhancement program. POLCAST field measurements are used to determine if important environmental factors support an increase in cloud precipitation efficiency from hygroscopic seeding. Current scientific theories and modeling results indicate that the most important environmental factors are cloud condensation nuclei (CCN) concentrations, droplet size distribution, and cloud base temperature and height. North Dakota's high CCN concentration supports the conclusion that releasing large hygroscopic particles at cloud base produces more collector droplets which increases precipitation efficiency. North Dakota's cloud base temperatures and several kilometer thick clouds indicates that ice phase hydrometeors are important in the precipitation formation process. Hence, increases in precipitation efficiency is not a simple warm rain process but involves more graupel production in the cold cloud region. North Dakota's low cloud base heights indicate that increases in precipitation would increase rain at the surface. All environmental factors examined indicate North Dakota's suitability for conducting hygroscopic seeding to enhance precipitation; however, some cloud processes are impossible to fully evaluate with the current POLCAST data set. A complete aerosol/cloud physics data set would provide a valuable resource for further understanding physical processes and help in constructing a more accurate regional precipitation forecast model. Development, validation, and use of a precipitation forecast model with a known uncertainty would be an effective method for determining precipitation increases from hygroscopic seeding.

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The South African rainfall enhancement programme: 1997-2001

Cited by 4 publications

References 7 publications

Review of Advances in Precipitation Enhancement Research

Review of Advances in Precipitation Enhancement Research

The UAE Cloud Seeding Program: A Statistical and Physical Evaluation

Suitability of North Dakota for Conducting Effective Hygroscopic Seeding

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