Alexander Kutepov

Atmospheric parameters retrieved from CRISTA measurements in the upper mesosphere and lower thermosphere

During its two missions of about one week duration each in November 1994 and in August 1997 the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment observed spectrally resolved mid- and far- infrared emissions from the earth limb in the altitude regime from the troposphere to the lower thermosphere. The measurements concentrated on high spatial resolution in all three dimensions in the lower part of the height range. At upper mesosphere/lower thermosphere altitudes global ozone concentrations during day and night, daytime carbon-dioxide densities, and atmospheric temperatures were derived using a comprehensive non-LTE model. The derived parameters compare well with other experimental data. Pronounced horizontal structures in latitude as well as in longitude are found in all parameters showing that dynamical influences are of importance also in the upper mesosphere/lower thermosphere. Carbon dioxide mixing ratios start to depart from their tropospheric values at altitudes as low as 70 - 80 km. Atmospheric temperatures of 140 K and below were retrieved near the mesopause at high northern latitudes in August. These data are supported by the simultaneous observation of polar mesospheric clouds.

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

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 CO2 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. CO2 and atomic oxygen densities were calculated from the simultaneously recorded 4.3 μm (CO2) 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 modeling. The wave structures extend well into the thermosphere.