Abstract
Due to their buoyance, methane and water vapor (H2O(g)) ascend into the mesosphere where they are destroyed by chemical reactions or photolysis. In the mesosphere at 81 to 83 km, H2O(g) condenses to ice which then, due to the lack of buoyance, descends to 70 to 75 km where ice sublimates back to H2O(g). A mesospheric minicycle of water forms. In boreal summer evenings the ice layer is visually observable from the ground as noctilucent clouds (NLC). The middle mesospheric ozone maximum (MMM) forms in the wintertime at a height of 70 to 75 km. It is located between the mid-latitudes and somewhat north from the Arctic Circle, and symmetrically in the Southern Hemisphere. In the daytime solar radiation keeps the ozone concentration at a low level. During the civil and nautical twilight the intensity of the sun's rays decrease dramatically. Ozone gains from this decrease most. At high latitudes the solar radiation angle (θs) decreases more slowly than at the mid-latitudes. IR radiation has more time to photoexcite O2(1Δg) and triplet state ozone (O3*). O2(1Δg) maintains the ozone concentration and O3* spontaneously provides oxygen atoms. As a result, the amplitude of the MMM layer in terms of ozone concentration increases towards the high latitudes.
Highlights
The mesosphere is the layer between the altitudes of 50 to 55 km and 85 to 90 km above Earth’s surface
The aim of this meta-study is to provide a basic understanding of the dynamics related to mesospheric phenomena such as the formation of the MMM and noctilucent clouds (NLC)
The importance of triplet state ozone and excited oxygen molecules O2(1Δg) in the dynamics leading to the formation of the MMM layer is discussed as well
Summary
The mesosphere is the layer between the altitudes of 50 to 55 km and 85 to 90 km above Earth’s surface. The stratopause separates this layer from the stratosphere and above it the mesopause separates it from the thermosphere. The altitude of the mesopause may vary seasonally between 86 and 100 km [1]. Verniani and Viani [2] studied the atmospheric temperature at an altitude of 90 km for each month of the year in 1962. They found that a minimum temperature of 170 K is reached in May and a maximum of 207 K in November. The deep night minimum appears to occur in all seasons
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