Upper mesosphere/ lower thermosphere temperatures from non-LTE modelling of the CRISTA 15μm measurements

摘要

The CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment measured mid-and far-infrared limb spectra during two Shuttle missions in November 1994 and August 1997 from the upper troposphere to the lower thermosphere. From the CO_2 15μm spectra temperatures in the mesosphere and lower thermosphere were derived using a non-LTE model coupled to a line-by-line radiative transfer code. CO_2 and atomic oxygen densities were calculated from the simultaneously recorded 4.3μm (CO_2) and 9.6 μm (ozone) measurements. The retrieved temperatures reveal the very low high latitude summer mesopause temperatures. Zonal structures are found at all altitudes and in the summer hemisphere as well as in the winter hemisphere. The north polar temperature distribution near the mesopause is dominated by a wave 1 structure with some wave 2 contribution. The same pattern is observed in the distribution of polar mesospheric clouds (PMC) which were detected via their thermal emission near 12 μm. The appearance of the PMCs thus verifies the temperatures obtained from the non-LTE modelling. The wave structures extend well into the thermosphere.