Abstract
Abstract. 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 ∼0.2 kg m−3. The echo
top height dropped to ∼3.5 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 ∼40 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.
Reference49 articles.
1. Albrecht, B. A.: Aerosols, cloud microphysics, and fractional cloudiness,
Science, 245, 1227–1231, 1989.
2. Belyaeva, M., Drofa, A., and Ivanov, V.: Efficiency of stimulating
precipitation from convective clouds using salt powders, Izvestiya,
Atmospheric and Oceanic Physics, 49, 154–161, 2013.
3. Bowen, E.: A new method of stimulating convective clouds to produce rain and
hail, Q. J. Roy. Meteor. Soc., 78, 37–45,
1952.
4. Bruintjes, R.: Similarities between the effects of hygroscopic seeding and
anthropogenic pollution on clouds, 8th WMO Scientific Conference on Weather
Modification, Casablanca, Morocco, 2003.
5. China Meteorological Data Service Center: Hourly rainfall, radar and radiosonde data, available at:
http://data.cma.cn/en, last access: 4 December 2019.
Cited by
11 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献