Observations of the mesospheric OH structure using FTIR and LIDAR measurements

The study of the OH layer between about 80 to 95 km altitude reveals important infomation about the mesopause region. An interesting information, which can be drawn from the relaxation of chemically excited OH molecules, is the rotational temperature of this layer, which forms the boundary between mesosphere and thermosphere. Under certain circumstances, the rotational temperature of the OH molecules can be related to the ambient temperature of the air at the mesopause region. The OH molecules are formed by the reaction of O3 and H2, which leaves the OH molecules at a highly excited vibrational state. The course of the deexcitation is still subject of discussion and will be studied using a FTIR spectrometer, which is able to observe the transistions reching from the higlhy excited state to the ground state of the OH molecule. The ground state of the OH molecule can be observed by LIDAR. A method to do this will be developed in a project at the Universität Bremen in cooperation with the AWI Potsdam.

The LIDAR is out of operation. Therefor only the FTIR measurements of the excited OH molecules are continued.