Changes to the Earth System are especially evident in the upper levels of earth’s atmosphere, where they can be detected there earlier than elsewhere. Of course, this assumes that measurements are possible at such lofty levels. It is especially important to monitor airglow. Due to various chemical reactions in the atmosphere, a layer of excited-state hydroxyl (OH) and oxygen (O2) molecules about 8 kilometres thick is formed, enveloping the planet at an altitude of some 90 kilometres. As with any physical system these molecules strive to return to a lower energy level, frequently achieved by emitting radiation in the visible and infrared part of the electromagnetic spectrum. Powerful ground-based and satellite-borne spectrometers and camera systems can detect this radiation, allowing conclusions about a multitude of geophysical processes at this region of the atmosphere, which is also referred to as the mesopause.
Compared with the levels underneath, the importance of the mesopause is above all due to the fact that it is influenced by the underlying atmospheric levels as well as by extra-terrestrial effects. At this altitude level—so to speak at the threshold to outer space—dynamic, photochemical and radiative processes collectively characterize the observed variations. For example, at this altitude winter temperatures are up to 100 degrees higher than those of summer, a situation that cannot be explained by radiative processes and is primarily caused by atmospheric dynamics.
Experts from 11 countries are meeting 15.-18.Mai in Grainau for the 7th Symposium of the global Network for the Detection of Mesospheric Change, NDMC. Its programme reflects the wide-ranging science spectrum under discussion. NDMC is coordinated by DFD in partnership with CONICET, which promotes science and technology in Argentina. The NDMC anchor station is at the Schneefernerhaus Environmental Research Station, where DFD continuously runs an airglow laboratory. Data from many NDMC stations can be accessed through the World Data Center for Remote Sensing of the Atmosphere, WDC-RSAT, operated by DFD.