First domestic observation using LIDAR to assess

African volcanic ash in the stratosphere over the Korean Peninsula

[Figure 1] Located on the sixth floor of GIST's Dasan Building, the LIDAR laser light (green) is projected to the sky: a close-up photo of the LIDAR on the 6th floor (left) and a photo of the laser beam coming being projected toward the sky (right). The white bright part of the picture on the left is the moon.

□ The Gwangju Institute of Science and Technology (GIST) successfully used the LIDAR * laser remote sensing system to observe and analyze the distributional characteristics of African volcanic ash that has dispersed over the stratosphere (about 10 to 50 km) above the Korean peninsula.

  * LIDAR: Light Detection and Ranging. Also known as 'laser radar,' it is a remote sensing device for measuring the presence and movement of wind, dust, smoke, aerosols, and cloud particles. Visible or infrared laser beams are used as the light source.

  ∘ This study was the first observation and analysis of stratospheric aerosol using LIDAR in Korea and demonstrates that a domestic LIDAR system can be used to successfully analyze disasters, such as a volcanic eruption of Baekdu Mountain.

The volcanic ash, which is mainly in the stratosphere, acts as a major mediator of chemical reactions and serves to lower the global atmospheric temperature. For example, the volcanic eruption of Pinatubo in 1991 caused a massive volcanic ash flow into the stratosphere, lowering the average global temperature by 0.5 to 0.8 ° C.

In order to study the changes in the atmospheric environment of the earth, it is necessary to study the distribution of stratospheric aerosols, such as volcanic ash, but there has never been direct observations made over Korea.

[Figure 2] Principle of using LIDAR to observe volcanic ash. When the laser light source is sent to the atmosphere, it reaches the stratosphere. When the laser beam hits the ash, the laser light scatters and is observed by a telescope. From this observation, the date can be analyzed to determine the altitude and concentration of the ash.

Research Professor Youngmin Noh of the GIST International Environmental Research Center used atmospheric observations to confirm that volcanic ash generated from the eruption of Nabro in Eritrea on June 12, 2011, was present in the stratosphere over the Korean peninsula for six months.

  ∘ The research team then built a system capable of real-time observation of stratospheric particles by improving the detection performance of an existing multi-wavelength Raman LIDAR system and started full-scale observations from February 2011. On June 19, the first observations were made of volcanic ash from the Nabro volcanic eruption over the stratosphere.

  ∘ Observations of the ash in the stratosphere over the next 6 months showed that the volcanic ash was initially had a thickness of 2 km that was spread 15 to 17 km above the stratosphere, and then after two months had a thickness of 9 km that was spread 11 to 19 km above the stratosphere, which has since decreased over time.

  ∘ In addition, the dispersion time (half-life period) when the volcanic ash concentration from the first observational data point was reduced to half was observed to be 117 days. As a result of analysis of the volcanic ash particles, some volcanic ash was found distributed at lower temperatures due to the increase in atmospheric density.

  ∘ The research team did not know whether it was volcanic from the first observation, but it was later confirmed through reverse analysis of the atmospheric weather data and comparison with the satellite data that the air layer containing the aerosol particles came to the Korean Peninsula from the Nabro volcanic eruption.

(From left) Research Professor Youngmin Noh, Dr. Dong-Ho Shin (GIST alumnus), Professor Detlef Müller

Research Professor Youngmin Noh said, "This study shows that the LIDAR system can simultaneously observe ultra-fine dust, sandstorms, and pollen in the troposphere (0 to 10 km above sea level), as well as stratospheric ash that affects global meteorological phenomena and environmental changes. It is also possible to utilize the LIDAR system to measure the impact of a volcanic eruption around the Korean peninsula, such as in the case of an eruption of Baekdu Mountain."

This work was led by Dr. Dong-Ho Shin (corresponding author) of the National Institute of Environmental Research, Research Professor Youngmin Noh of GIST (first author), and Professor Detlef Müller of Hertfordshire University (co-author). This research was supported by the Korea Meteorological Agency and the National Research foundation. Their paper was published on January 17, 2017 in Atmospheric Environment.