[A-AS09] Atmospheric Chemistry

[AAS09-P23] Satellite observations on the response of the middle and upper atmospheric ozone variation to solar eclipses

*Tianliang Yang¹, Akira Mizuno^1,2, Tomoo Nagahama^1,2 (1.Graduate School of Science, Nagoya University, 2.ISEE, Nagoya University)

Keywords:Mesospheric ozone, Solar eclipse, Sateillite observation, Short-term variation

Solar eclipses can often serve as natural experiments in multiple fields on the Earth’s atmosphere since their swift change in solar radiation, thus the fast response of short-lived atmospheric tracer gas, for example, the mesospheric ozone. In the upper stratosphere and the lower mesosphere of 1 hPa to 0.02 hPa (45 km to 70 km), the daily variation of ozone is primely determined by Hydroxide(OH) resource from atmospheric vapor. However, because of the limited time-space solution observation instrument, details of the short-term response are not fully understood. In this research, the variabilities of trace gas in the upper stratosphere and lower mesosphere observed by NASA Aura satellite Microwave Limb Sounder (Aura/MLS) during solar eclipse events are mainly discussed, and analyses are conducted in aspects of solar radiation change and temporal variation. We extend the result of ozone variation during eclipses via limb-sounding observation by Imai et al, who confirmed the photolysis kinetics of the upper stratospheric and the lower mesospheric ozone during the mid-eclipse of the annular solar eclipse on 15^th January 2010. The increase seems to have a constant exponential relationship with the solar flux index, but the exponential relationship weakens before totality. The least-square fitting shows that during the solar eclipse, the averaged exponential index increases from 0.03 to 0.75 as the altitude level grows from 45 km which is consistent with the former study. However, the index decreases right before the totality at each altitude level. For example, during the solar eclipse event on December 14^th, 2020, the index decreased from 0.30 to 0.05 at 50 km - 55km (0.68 hPa and 0.46 hPa), from 0.36 to 0.10 at 55 km - 60 km (0.32 hPa and 0.21 hPa), and above 60 km, we have the index at each level from 0.54 to 0.20 at 0.14 hPa, from 0.56 to 0.45 at 0.10 hPa and from 0.75 to 0.35 as averaged results shown in 0.046 hPa and 0.021 hPa.
The possible reason for the result is that at the climax of the eclipse events, the OH generation from vapor photolysis is highly inhibited due to the drastic cutdown of the solar radiation. Besides, the Aura satellite also recorded 3 pieces of solar eclipse events over the polar region. Given the zonal scan direction of the Aura satellite and the more complicated environment there, the discussion of ozone variability during solar eclipse events shall be different.