Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study
<p>An airborne cloud seeding experiment was conducted over the eastern coast of Zhejiang, China, on 4 September 2016 during a major international event held in Hangzhou. In an attempt to reduce the likelihood of rainfall onset, a major airborne experiment for weather modification took place by...
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doaj-c04a4fff60b34f7b89c2d33a8b8a78e02020-11-25T01:11:16ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-12-0119149671497710.5194/acp-19-14967-2019Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility studyF. Wang0F. Wang1Z. Li2Z. Li3Q. Jiang4G. Wang5S. Jia6J. Duan7Y. Zhou8Key Laboratory for Cloud Physics, Chinese Academy of Meteorological Sciences, Beijing, 100081, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, ChinaDepartment of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20742, USANational Meteorological Center, Beijing, 100081, ChinaState Key Laboratory of Severe Weather, Chinese Academy of Meteorological Science, Beijing, 100081, ChinaChina Huayun Group, Beijing, 100081, ChinaKey Laboratory for Cloud Physics, Chinese Academy of Meteorological Sciences, Beijing, 100081, ChinaKey Laboratory for Cloud Physics, Chinese Academy of Meteorological Sciences, Beijing, 100081, China<p>An airborne cloud seeding experiment was conducted over the eastern coast of Zhejiang, China, on 4 September 2016 during a major international event held in Hangzhou. In an attempt to reduce the likelihood of rainfall onset, a major airborne experiment for weather modification took place by seeding hygroscopic agents to warm clouds to reduce cloud droplet size. The effectiveness of seeding is examined, mainly for stratiform clouds with patchy small convective cells. A radar-domain-index (RDI) algorithm was proposed to analyze the seeding effect. The threshold strategy and the tracking radar echo by correlation (TREC) technique was applied in the domain selection. Factors analyzed include echo reflectivity parameters such as the mean and maximum echo intensity, the anomaly percentage of the grid number of effective echoes, the fractional contribution to the total reflectivities, and the vertically integrated liquid (VIL) water content during and after the seeding process. About 12 min after seeding ended, the composite reflectivity of seeded clouds decreased to a minimum (< 10 dBz) and the VIL of seeded clouds was <span class="inline-formula">∼0.2</span> kg m<span class="inline-formula"><sup>−3</sup></span>. The echo top height dropped to <span class="inline-formula">∼3.5</span> km, and the surface echoes were also weakened. By contrast, there was no significant variation in these echo parameters for the surrounding non-seeded clouds. The seeded cell appeared to have the shortest life cycle, as revealed by applying the cloud-cluster tracking method. The airborne Cloud Droplet Probe (CDP) measured cloud number concentration, effective diameter, and liquid water content, which gradually increased after the start of cloud seeding. This is probably caused by the hygroscopic growth of agent particles and collision–coalescence of small cloud droplets. However, these parameters sampled at <span class="inline-formula">∼40</span> min after seeding decreased significantly, which is probably due to the excessive seeding agents generating a competition for cloud water and thus suppressing cloud development and precipitation. Overall, the physical phenomenon was captured in this study, but a more quantitative in-depth analysis of the underlying principle is needed.</p>https://www.atmos-chem-phys.net/19/14967/2019/acp-19-14967-2019.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
F. Wang F. Wang Z. Li Z. Li Q. Jiang G. Wang S. Jia J. Duan Y. Zhou |
spellingShingle |
F. Wang F. Wang Z. Li Z. Li Q. Jiang G. Wang S. Jia J. Duan Y. Zhou Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study Atmospheric Chemistry and Physics |
author_facet |
F. Wang F. Wang Z. Li Z. Li Q. Jiang G. Wang S. Jia J. Duan Y. Zhou |
author_sort |
F. Wang |
title |
Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study |
title_short |
Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study |
title_full |
Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study |
title_fullStr |
Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study |
title_full_unstemmed |
Evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study |
title_sort |
evaluation of hygroscopic cloud seeding in liquid-water clouds: a feasibility study |
publisher |
Copernicus Publications |
series |
Atmospheric Chemistry and Physics |
issn |
1680-7316 1680-7324 |
publishDate |
2019-12-01 |
description |
<p>An airborne cloud seeding experiment was conducted over
the eastern coast of Zhejiang, China, on 4 September 2016 during a major
international event held in Hangzhou. In an attempt to reduce the likelihood
of rainfall onset, a major airborne experiment for weather modification took
place by seeding hygroscopic agents to warm clouds to reduce cloud droplet
size. The effectiveness of seeding is examined, mainly for stratiform clouds
with patchy small convective cells. A radar-domain-index (RDI) algorithm was
proposed to analyze the seeding effect. The threshold strategy and the
tracking radar echo by correlation (TREC) technique was applied in the
domain selection. Factors analyzed include echo reflectivity parameters such
as the mean and maximum echo intensity, the anomaly percentage of the grid
number of effective echoes, the fractional contribution to the total
reflectivities, and the vertically integrated liquid (VIL) water content during
and after the seeding process. About 12 min after seeding ended, the
composite reflectivity of seeded clouds decreased to a minimum (< 10 dBz) and the VIL of seeded clouds was <span class="inline-formula">∼0.2</span> kg m<span class="inline-formula"><sup>−3</sup></span>. The echo
top height dropped to <span class="inline-formula">∼3.5</span> km, and the surface echoes were
also weakened. By contrast, there was no significant variation in these echo
parameters for the surrounding non-seeded clouds. The seeded cell appeared
to have the shortest life cycle, as revealed by applying the cloud-cluster
tracking method. The airborne Cloud Droplet Probe (CDP) measured cloud
number concentration, effective diameter, and liquid water content, which gradually
increased after the start of cloud seeding. This is probably caused by the
hygroscopic growth of agent particles and collision–coalescence of small
cloud droplets. However, these parameters sampled at <span class="inline-formula">∼40</span> min
after seeding decreased significantly, which is probably due to the
excessive seeding agents generating a competition for cloud water and thus
suppressing cloud development and precipitation. Overall, the physical
phenomenon was captured in this study, but a more quantitative in-depth
analysis of the underlying principle is needed.</p> |
url |
https://www.atmos-chem-phys.net/19/14967/2019/acp-19-14967-2019.pdf |
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