Oxygen dayglow emissions as proxies for atomic oxygen and ozone in the mesosphere and lower thermosphere
Résumé
The main goal of this study is to propose and then to justify a set of methods for retrieving the [O] and [O3] altitude distributions from the observation of emissions of the excited oxygen molecules and O(1D) atom at daytime in the mesosphere and lower thermosphere (MLT) region. In other words, we propose retrieving the [O] and [O3] 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 [O3] and [O(3P)] should be minimal. For a comprehensive analysis of different O3 and O(3P) proxies, we use a full model of electronic vibrational kinetics of excited products of O3 and O2 photolysis in the MLT of the Earth. Based on this model, we have tested five excited components; namely, O2(b1Σg+, v = 0, 1, 2), O2(a1Δg , v = 0) and O(1D) as the [O3] and [O(3P)] proxies in the MLT region. Using an analytical approach to sensitivity studies and uncertainty analysis, we have therefore developed the following methods of [O(3P)] and [O3] retrieval, which utilise electronic-vibrational transitions from the oxygen molecule second singlet level (O2(b1 Σg+, v = 0, 1, 2). We conclude that O2(b1 Σg+, v = 2) and O2(b1 Σg+, v = 0) are preferable proxies for [O(3P)] retrieval in the altitude range of 90-140 km, while O2(b1 Σg+, v = 1) is the best proxy for [O3] retrieval in the altitude range of 50-98 km.