NASA satellite observations for the first time confirmed that the Earth’s mesosphere at an altitude of 50-80 kilometers above the surface is compressed due to cooling. This effect was predicted by climate change models caused by human activity, but it was still difficult to trace a global trend over time, since the oscillations of the mesosphere also occur due to natural cycles, such as solar. This is reported in a press release on the site of the space agency. The full text of the study is published in the Journal of Atmospheric and Solar-Terrestrial Physics.
New data, including the composition of the atmosphere, pressure and temperature in the mesosphere, cover 30 years of satellite monitoring of the thickness of the mesosphere in the summer months over the polar regions of the Earth (June for the North and December for the South). These data were collected through the dimension of sunlight passing through various layers of the atmosphere. It turned out that this layer is cooled at 1-2 degrees Celsius in a decade, and the rate of thinning reaches 150-200 meters in ten years.
greenhouse gases emitted by man lead to warming the lower layers of the atmosphere (troposphere and stratosphere), but in the upper layers should lead to the opposite effect. The lower layers are dense with a large number of gases molecules, therefore, long-wavelength energy emitted by carbon dioxide is delayed here and transferred to convective processes. High layers, on the contrary, rarefied, and carbon dioxide molecules are so effectively emitting heat that most of the energy goes into space. The more carbon dioxide molecules in the mesosphere, the stronger it is cooled and decreases in thickness.
The set of previous observations confirmed the cooling of the mesosphere, but the reduction in the height was only theoretically derived. In this case, the hydrostatic compression should change the pressure distribution in the layer and lead to a slight warming slightly above the height of polar mesospheric clouds (RMS) and cooling slightly below this level. Mesospheric clouds are ice clouds that are usually observed in the summer mesosphere of high latitudes at an altitude of 82-86 kilometers at a low temperature. Recently, an increased formation of the RMS is recorded on medium and low latitudes, which also indicates the total cooling of the troposphere.
Results obtained by scientists are consistent with theoretical models predicting the reduction in the thickness of the mesosphere due to the accumulation of greenhouse gas. Cooling occurs only in the mesosphere and is not associated with the possible cooling and compression of the underlying layers. The researchers also confirmed relative warming at the height of the formation of mesosphere clouds, which is caused by hydrostatic compression due to cooling. Changes in PMC also do not correspond to the current phase of the solar cycle and are largely dependent on the dynamics of the atmosphere both within the hemisphere and from the intermetrack interactions.