16:45 〜 17:00
[MIS09-06] Development of lightning energy estimation method based on infrasound measurement
Rainfall from thunderstorms and typhoons sometimes cause large-scale disasters, especially in tropical regions such as Southeast Asia. Real-time monitoring and forecast can help minimize the damage. It is known that there is some correlation between heavy rainfall and lightning discharge activity, but until now, the relationship has mainly been investigated only with lightning frequency. If individual lightning energy can be estimated, more accurate monitoring could be possible. However, since there is no way to directly measure the conductivity of the discharge path, it is difficult to estimate the lightning energy consumed as Joule heat from electromagnetic field measurements alone.
Since sound waves are emitted by the expansion of the atmosphere as a result of Joule heating, they are thought to reflect the energy of lightning discharges more correctly than electromagnetic waves. In this study, we will focus on infrasound originated by lightning, which is expected to be a good indicator of lightning strike energy dissipation.
Using fireworks, in this study we try to estimate the quantitative relationship between the intensity of low-frequency sound waves measured at known distances and the energy dissipated in the atmosphere. The measurements were carried out at a distance of about 3 km from the fireworks at the shore of Lake Toya in Hokkaido. The maximum dissipated energy of the fireworks was about 10^6 J, which is about 1/500 of that of common lightning. We also succeeded in observing infrasound induced by lightning discharges at a distance of 4 km from the building in Hokkaido University, and used the quantitative relationship estimated by the experiment using fireworks. This method for lightning energy estimation will contribute to the monitoring of the thunderstorm activity more accurately for better prediction of rainfall in the futre.
This research was supported by Science and Technology Research Partnership for Sustainable Development (SATREPS), funded by Japan Science and Technology Agency (JST) / Japan International Cooperation Agency (JICA)."
Since sound waves are emitted by the expansion of the atmosphere as a result of Joule heating, they are thought to reflect the energy of lightning discharges more correctly than electromagnetic waves. In this study, we will focus on infrasound originated by lightning, which is expected to be a good indicator of lightning strike energy dissipation.
Using fireworks, in this study we try to estimate the quantitative relationship between the intensity of low-frequency sound waves measured at known distances and the energy dissipated in the atmosphere. The measurements were carried out at a distance of about 3 km from the fireworks at the shore of Lake Toya in Hokkaido. The maximum dissipated energy of the fireworks was about 10^6 J, which is about 1/500 of that of common lightning. We also succeeded in observing infrasound induced by lightning discharges at a distance of 4 km from the building in Hokkaido University, and used the quantitative relationship estimated by the experiment using fireworks. This method for lightning energy estimation will contribute to the monitoring of the thunderstorm activity more accurately for better prediction of rainfall in the futre.
This research was supported by Science and Technology Research Partnership for Sustainable Development (SATREPS), funded by Japan Science and Technology Agency (JST) / Japan International Cooperation Agency (JICA)."