The Blanket Effect is intended for others to learn about weather modification and its related subjects in an easy to understand way. Started in 2005, this blog is a work in progress as the technology advances

February 26, 2008

Clearing Fog in South Korea

(note: We feature this excerpt from a report about South Korea's WM research activities)

Weather Modification Experiments in [South] Korea

Sung-Nam Oh, Ki-Ho Chang, and Myoung-Joo Lee
Remote Sensing Research Laboratory,
Meteorological Research Institute,
Korea Meteorology Administration
Seoul 156-720, South Korea


The object of cloud seeding is to increase rainfall amount on the ground by enhancing precipitation efficiency of clouds through seeding of artificially generated IN (ice Nuclei) or CCN (Cloud Condensation Nuclei) in desired areas.

Before cloud seeding and weather modification experiments, however, a comprehensive study of cloud microphysics, local and synoptic weather conditions is required to judge the feasibility of the experiments.

Recently, Meteorological Research Institute (METRI), Korea Meteorological Administration (KMA) has conducted several ground-based experiments and aircraft experiments in the past.

METRI/KMA will try to develop the techniques of Weather Modification in Korea with more scientific methods.

Fog is well known for its impact on quality of life and public safety in transportation, tourism and outdoor activities such as open-air sports. (image left from:

Despite modern systems for take-off and landing with poor visibility, aircraft-running frequency is largely reduced in the presence of fogs. For an airport like Frankfurt/Main, the economic loss per fog hour is estimated at about 250,000 euro/hr (Moeller et al., 2003).

Road traffic accidents due to fog may also be catastrophic. (image at right from:

For example, on US highways, from 1981 to 1989, more than 6000 deaths were associated with such events.

The problem is becoming more important with the increase in fog frequency associated with air pollution and climate change.

On the other hand, in certain very dry areas, fog is beneficial and supplies some of the necessary moisture to vegetation. (image at left from

Fog droplets can also be captured with nets and be used as an alternative source of freshwater. (image right of fog net collector, from

Cold Cloud Seeding

The major objective of cold cloud seeding is to enhance the precipitation into the ground to accelerate precipitation efficiency with inputting artificially AgI (silver iodide) particles into the seeding experiment target area. (image left: Silver ion reacts with iodide to form silver iodide, AgI, from

We concentrated on basic research of cloud physics for practical use of precipitation enhancement and fog dissipation and numerical model applications through the cloud seeding experiments.

To observe and analyze the change of the cloud characteristics before and after the seeding experiment, we have established the Cloud Physics Observation System (CPOS).

Warm cloud modification

Two hygroscopic-particle (mainly composed of CaCl2) (Calcium chloride) seeding experiments have been performed at the Daegwallyeong super site with 1-hour interval during about 2 hours in 16 June 2005 to dissipate the natural warm fog.

During the hours, the particle size and number concentration have been measured by the FSSP-100 (Forward Scattering Spectrometer Probe) and then visibility obtained. (image at right: example of FSSP-100 spectrometer probe, from

The seeding gives the mean 1.38-times visibility improvement during the mean 13 minutes. The fog dissipation suggests the decrease of buoyant fog droplets by their enhancement of condensation and falling due to seeding.

To dissipate the natural fog, two experiments have been performed by using a hygroscopic flare composed of mainly CaCl2 (Calcium Chloride) at the CPOS with the altitude of 842 m from mean sea level during about 2 hours in 16 June 2005. (image left example of hygroscopic flare, from North Dakota Water Commission)

The equipment primarily employed in this experiment is the FSSP-100 (FSSP) measuring the size and concentration of the fog droplets.

Two seeding experiments of hygroscopic material mainly composed of CaCl2 (Calcium Chloride) have been performed to investigate into their effect on the natural fog during the foggy hours (about 2 hours of 16 June 2005) at Deagwallyeong site.

The 13 physical cloud seeding experiments were conducted for the optimized atmospheric conditions, characterized by easterly fog flow, during the period Jan. ~ Feb. 2006, and then we found that the snow enhancement is observed for the 6 experiments using the small amount of AgI (silver iodide) when the fog exists in Gangneung. (image right of location of Gangneung, from

Wintertime cloud seeding experiments have been performed by using AgI ground-generator at the CPOS during 18 Jan. ~ 19 Feb. 2006. (image left example of silver iodide ground generator, from

Wintertime orographic cloud seeding experiments performed easterly fog flow and air temperatures below -5C .


To dissipate the fog, we have performed the two CaCl2 seeding experiments, which gives the averaged 1.38 times improved visibility during the averaged 13 min. This result suggests that this CaCl2 seeding has the potential to dissipate the fog.

The 13 physical cloud seeding experiments were conducted over the Daegwallyeong CPOS (Cloud Physical Observation System) for the easterly fog flow during the period Jan. ~ Feb. 2006, and then we found that the snow enhancement is observed for the 6 experiments using the small amount of AgI when the fog exists in Gangneung, which will be useful for the large scale water resource supply.

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