1:45 PM - 2:00 PM
[AAS06-01] Effect of graupel growth on the increase in lightning activity preceding severe wind.
★Invited Papers
Keywords:lightning, downburst, graupel, numerical simulation
To understand the mechanism of lightning jump (LJ[1]), which is an increase in lightning activity preceding severe wind, is needed for using lightning observation data for severe wind prediction. In this study, using the SCALE[2][3][4] meteorological lightning model, which can explicitly calculate lightning activity, we conducted an idealized simulation for downbursts, a type of severe wind, to investigate the characteristics of cloud particles such as graupel and charge separation inside convective clouds that cause downbursts and preceding lightning activity.
The idealized simulation was conducted using a horizontally homogeneous convectively unstable base state based on soundings at Maebashi and Tateno for a downburst that occurred in Misato-machi, Saitama Prefecture on September 8, 1994 [5]. A 4-K warm bubble above the domain mean was placed on the southwest side of the model domain based on Guo et al. (1999)[6].
The idealized simulation resulted in four downbursts with maximum wind speeds exceeding 40 m/s associated with strong precipitation exceeding 100 mm/h during the 90-minute simulation period. Of these four downbursts, an increase in lightning frequency regarded as LJ was simulated 10 minutes before the occurrence of the second downburst. The mass of the graupel particles around the LJ was derived from the mass mixing ratio and number concentration. The particle mass of the graupel indicated that the number of heavy graupel particles was large just before the downburst, while the number of heavy graupel particles was small when the LJ occurred. The active charge separation due to the collision of graupel and snow was calculated during the LJ event. These results suggest that the coexistence of graupel, snow, and liquid water, which is suitable for charge separation, was not an unsuitable environment for the growth of large-particle graupel, such as during downburst events.
Reference
1. Williams, E. R., and Coauthors, 1999: The behavior of total lightning activity in severe Florida thunderstorms. Atmos. Res., 51 , 245–264. doi:10.1016/S0169-8095(99)00011-3
2. Nishizawa, S., Yashiro, H., Sato, Y., Miyamoto, Y. & Tomita, H. Influence of grid aspect ratio on planetary boundary layer turbulence in large-eddy simulations. Geosci. Model Dev. 8, 3393–3419 (2015).
3. Sato, Y. S. Nishizawa, H. Yashiro, Y. Miyamoto, Y. Kajikawa, & H. Tomita. Impacts of cloud microphysics on trade wind cumulus: which cloud microphysics processes contribute to the diversity in a large eddy simulation? Prog. Earth Planet. Sci. 2, (2015).
4. Sato, Y., Y. Miyamoto, and H. Tomita, 2019: Large dependency of charge distribution in a tropical cyclone inner core upon aerosol number concentration. Prog. Earth Planet. Sci., 6, 62, doi:10.1186/s40645-019-0309-7.
5. Takayama, H., H. Niino, S. Watanabe, and J. Sugaya, 1997: Downbursts in the northwestern part of Saitama Prefecture on 8 September 1994. J. Meteor. Soc. Japan, 75, 885–905, doi:10.2151/jmsj1965.75.4_885.
6. Guo, X. L., Niino, H., & Kimura, R., 1999. Numerical Modeling on a Hazardous Microburst-Producing Hailstorm. Toward Digital Earth Proceedings of the International Symposium on Digital Earth (Vol. 1, pp. 383– 398). Science Press.
The idealized simulation was conducted using a horizontally homogeneous convectively unstable base state based on soundings at Maebashi and Tateno for a downburst that occurred in Misato-machi, Saitama Prefecture on September 8, 1994 [5]. A 4-K warm bubble above the domain mean was placed on the southwest side of the model domain based on Guo et al. (1999)[6].
The idealized simulation resulted in four downbursts with maximum wind speeds exceeding 40 m/s associated with strong precipitation exceeding 100 mm/h during the 90-minute simulation period. Of these four downbursts, an increase in lightning frequency regarded as LJ was simulated 10 minutes before the occurrence of the second downburst. The mass of the graupel particles around the LJ was derived from the mass mixing ratio and number concentration. The particle mass of the graupel indicated that the number of heavy graupel particles was large just before the downburst, while the number of heavy graupel particles was small when the LJ occurred. The active charge separation due to the collision of graupel and snow was calculated during the LJ event. These results suggest that the coexistence of graupel, snow, and liquid water, which is suitable for charge separation, was not an unsuitable environment for the growth of large-particle graupel, such as during downburst events.
Reference
1. Williams, E. R., and Coauthors, 1999: The behavior of total lightning activity in severe Florida thunderstorms. Atmos. Res., 51 , 245–264. doi:10.1016/S0169-8095(99)00011-3
2. Nishizawa, S., Yashiro, H., Sato, Y., Miyamoto, Y. & Tomita, H. Influence of grid aspect ratio on planetary boundary layer turbulence in large-eddy simulations. Geosci. Model Dev. 8, 3393–3419 (2015).
3. Sato, Y. S. Nishizawa, H. Yashiro, Y. Miyamoto, Y. Kajikawa, & H. Tomita. Impacts of cloud microphysics on trade wind cumulus: which cloud microphysics processes contribute to the diversity in a large eddy simulation? Prog. Earth Planet. Sci. 2, (2015).
4. Sato, Y., Y. Miyamoto, and H. Tomita, 2019: Large dependency of charge distribution in a tropical cyclone inner core upon aerosol number concentration. Prog. Earth Planet. Sci., 6, 62, doi:10.1186/s40645-019-0309-7.
5. Takayama, H., H. Niino, S. Watanabe, and J. Sugaya, 1997: Downbursts in the northwestern part of Saitama Prefecture on 8 September 1994. J. Meteor. Soc. Japan, 75, 885–905, doi:10.2151/jmsj1965.75.4_885.
6. Guo, X. L., Niino, H., & Kimura, R., 1999. Numerical Modeling on a Hazardous Microburst-Producing Hailstorm. Toward Digital Earth Proceedings of the International Symposium on Digital Earth (Vol. 1, pp. 383– 398). Science Press.