SMILES observations of mesospheric ozone during the solar eclipse

The Superconducting Submillimeter‐Wave Limb‐Emission Sounder (SMILES) successfully observed vertical distributions of ozone (O 3 ) concentration in the middle atmosphere during the annular solar eclipse that occurred on 15 January 2010. In the mesosphere, where the photochemical lifetime of O 3 is relatively short (approximately 100 s), altitude‐dependent changes in O 3 concentration under reduced solar radiation and their temporal variations were clearly observed as a function of the eclipse obscuration. This study reports the vertical distributions of mesospheric O 3 during a solar eclipse event and analyzes theoretically the eclipse‐induced changes. We show that simple analytical expressions for O 3 concentration, which assume that O 3 and O are in a photochemically steady state, can be used to describe the O 3 concentration under reduced solar radiation. The SMILES data obtained during the eclipse provide a unique opportunity to test our current understanding of mesospheric O 3 photochemistry.