Variation of Mesosphere Ozone and Related Constituents During Solar Eclipse on 21 June 2020 Based on WACCM-X Simulations

Abstract

The Whole Atmosphere Climate Community Model is utilized to simulate the complete process of variation in ozone and related constituent concentrations within the height range of 47–79 km (1–0.01 hPa) in the mesosphere during the annular solar eclipse on 21 June 2020. The simulated ozone vertical profile closely matches the Microwave Limb Sounder observation. Simulation results show that the largest average ozone concentration increase occurs at 66 km (0.07547 hPa), reaching 18.4%. Ozone concentration at this altitude increases by 96.0% after the eclipse obscuration reaches its maximum. The ozone increased region closely follows the trajectory of the eclipse obscuration, although its spatial extent is slightly smaller. Only regions experiencing more than 30% solar obscuration exhibited ozone increases exceeding 10%. This study quantitatively analyzes the relative contributions of different factors to ozone variations during the solar eclipse. Ozone variations are primarily driven using chemical processes rather than dynamic transport. The key chemical pathways involve ozone production through the three-body recombination ($O+O_2+M=O_3+M$), ozone photolysis, and the H-ozone reaction. Reduced solar radiation suppresses photolysis more effectively than it limits ozone production, resulting in a net increase in O₃ concentration. Meanwhile, the decreased production of H further weakens the destruction of ozone. Single-point analysis reveals that at the eclipse central location, the change in the ozone variation rate from the three-body recombination and photolysis accounts for 75.2% of the O₃ chemical variation rate change collectively. The H-ozone reaction accounts for 24.7% of the ozone chemical variation.