Based on our hypothesis that the concentration of particulate matters will decrease when it rains, we investigated cloud seeding as a measure to alleviate severe air pollution problem. Trough some investigations, we want to determine whether cloud seeding can be effective solution to air pollution problem.

Cloud seeding

Cloud seeding is a type of weather modification that aims to change the amount or type of precipitation that falls from clouds by dispersing substances into the air that serve as cloud condensation or ice nuclear, which alter the microphysical processes within the cloud.

Process

1. An aircraft injects silver iodide or other substances into the atmosphere.

2. The chemicals mimic the particles that serve as surfaces for condensation that creates water droplets

3. Once the condensation creates water droplets that are large enough, the rain will fall.

Cloud seeding experiments in Korea

1. Korea Meteorological Administration, cloud seeding experiment in West Sea (2019. 1. 25.)

After dispersing cloud seeds, rainfall particles develop and detect rainfall in parts of the ground.
No rainfall detected due to dry atmosphere in the ground.
No inland rainfall, meaningful effects of fine dust reduction cannot be confirmed.

2. Ministry of science and ICT, cloud seeding experiment using TR-60 (2019. 04. 25)

Unmanned Air Vehicle
The concentration of large cloud particles increased 3.8 times and the average particle size increased 25μm after spraying cloud seeds.
Observation of 0.5mm rainfall mixed with natural precipitation in Boseong and Gwangyang after spraying cloud seeds

Picture 1 TR-60

Paper : An assessment of the effectiveness of cloud seeding
as a measure of air quality improvement in the Seoul metropoltian area

: This paper deals with PM10 mass concentration and seedability of the clouds in Seoul to assess the effectiveness of cloud seeding. It is related to our analysis of particulate matter and precipitation in 2019 and 2020 in Seoul.

1. Results

1) Tendency of PM10 mass concentration in Seoul

Figure 1 Annually averaged PM10 mass concentration in Seoul between 1995 and 2017 (Ministry of Environment, 2018) (a) and 2D histogram of relative occurrence frequency per each PM10 bin versus year for the 9 years (2010~2018) measurement at KMA Seoul station (b).

2) Correlation of PM10 mass concentration and meteorological variables related to seedability of the clouds

Figure 2 2D histogram of relative occurrence frequency of PM10 mass concentration versus relative occurrence frequency of cloud amount for the 9 years (2010~2018) measurement at KMA Seoul station

Figure 3 PM10 mass concentration versus T-TD for the 9 years (2010~2018) measurement at KMA Seoul station.

Figure 4 PM10 mass concentration versus liquid water path (LWP) (a) and ice water path (IWP) (b) for the 9 years (2010~2018) reanalyzed data of ECMWF ERA5.

Figure 1 indicates that PM10 mass concentration in Seoul teds to decreases annually, but frequency of high concentration cases tends to increase relatively.
Figure 2 indicates that as PM10 mass concentration increases, cloud amount decreases. It is because the difference between temperature and dew point temperature tends to increase, shown by figure 3.
Also, figure 4 indicates that as PM10 mass concentration increases, liquid water path, and ice water path decrease.

2. Conclusion

It is important cloud amountSuch finding suggests that cloud seeding becomes less feasible as air pollution becomes more severe in the Seoul metropolitan area, at least in a statistical sense.