Oxygen dayglow emissions as proxies for atomic oxygen and ozone in the mesosphere and lower thermosphere

Abstract The main goal of this study is to propose and then to justify a set of methods for retrieving the [O] and [O 3 ] altitude distributions from the observation of emissions of the excited oxygen molecules and O( 1 D ) atom at daytime in the mesosphere and lower thermosphere (MLT) region. In other words, we propose retrieving the [O] and [O 3 ] using the proxies. One of the main requirements for the proxy is that the measured value should be directly related to a variable of our interest while, at the same time, the influence of the proxies on [O 3 ] and [O( 3 P )] should be minimal. For a comprehensive analysis of different O 3 and O( 3 P ) proxies, we use a full model of electronic vibrational kinetics of excited products of O 3 and O 2 photolysis in the MLT of the Earth. Based on this model, we have tested five excited components; namely, O 2 ( b 1 Σ g + ,  v  = 0, 1, 2), O 2 ( a 1 Δ g ,  v  = 0) and O( 1 D ) as the [O 3 ] and [O( 3 P )] proxies in the MLT region. Using an analytical approach to sensitivity studies and uncertainty analysis, we have therefore developed the following methods of [O( 3 P )] and [O 3 ] retrieval, which utilise electronic-vibrational transitions from the oxygen molecule second singlet level (O 2 ( b 1 Σ g + ,  v  = 0, 1, 2). We conclude that O 2 ( b 1 Σ g + ,  v  = 2) and O 2 ( b 1 Σ g + ,  v  = 0) are preferable proxies for [O( 3 P )] retrieval in the altitude range of 90–140 km, while O 2 ( b 1 Σ g + ,  v  = 1) is the best proxy for [O 3 ] retrieval in the altitude range of 50–98 km.