Description: To improve our knowledge of the coupling of atmospheric circulation, composition and regional climate, and to provide the urgently needed observations of long-term changes in the middle atmosphere, the Changing-Atmosphere Infra-Red Tomography Explorer (CAIRT) is one of four mission concepts down-selected by the European Space Agency (ESA) for competitive pre-feasibility studies, vying for implementation as the next Earth Explorer satellite mission. As a Fourier transform infrared limb imager, CAIRT will observe simultaneously from the middle troposphere to the lower thermosphere at high spectral resolution and with unprecedented horizontal and vertical resolution (with a goal of 50×50×1 km globally). With this, CAIRT will provide new and critical information on (a) atmospheric gravity waves, circulation and mixing, (b) coupling with the upper atmosphere, solar variability and space weather and, (c) aerosols and pollutants in the upper troposphere and lower stratosphere. In this presentation we will give an overview of CAIRT’s science goals and the expected mission performance, based on latest results from early mission definition studies.

Description: The Changing-Atmosphere Infra-Red Tomography Explorer (CAIRT) is one of the four candidates for ESA’s Earth Explorer 11, aimed to study the coupling between atmospheric composition, circulation and climate. By exploiting its imaging capabilities, CAIRT indeed can sound the atmosphere simultaneously from the middle troposphere to the lower thermosphere at 0.2 cm〈sup〉-1〈/sup〉 spectral resolution and with horizontal sampling of 50 km along track, 50 km across track and vertical sampling of 1 km. Flying in loose formation with MetOp-SG mission allows to combine spatially resolved limb observations with horizontally resolved nadir measurements of IASI-NG and Sentinel-5 nadir spectrometers to extend limb observations down to the surface. An accurate knowledge of trace gas composition around the tropopause is particularly important to reduce significant uncertainties in projected future warming: changes in the surface air pollution and in the stratosphere-troposphere exchange may significantly affect it. Moreover quantifying the influence of stratospheric transport on near-surface tropospheric composition is important since it conditions attempts to derive emission fluxes from surface observations for important greenhouse gases. We evaluated advantages coming from the exploitation of the synergy between realistic simulations of CAIRT, IASI-NG and Sentinel 5 observations applying the rigorous approach of the two-dimensional complete data fusion. The synergistic products demonstrate a better quality in sounding both the troposphere and the Upper Troposphere - Lower Stratosphere region. Results will be shown for selected case studies involving ozone, methane and other pollutants.