The ACECHEM (Atmospheric Composition Explorer for CHEMistry and climate interaction) mission will investigate the composition of the upper troposphere and lower stratosphere, its interaction with the climate and the impact on anthropogenic activities.
Changes to the composition of the atmosphere are the primary cause of global climate change, but the processes whereby atmospheric composition and climate interact are not well understood. Existing and planned spaceborne atmospheric composition sounding missions mainly address the issues of stratospheric ozone depletion and tropospheric pollution.
However, today it is clear that improvements in our ability to predict climate change and to improve understanding of the underlying atmospheric processes will only come about as a result of an integrated approach. Thus it is essential to study the troposphere and stratosphere together as a coherent unit, and to consider simultaneously the chemical, dynamical,and radiative processes involved,and their non-linear coupling. In particular, the region around the tropopause is of paramount importance for the interactions between composition and climate and for the mixing between the atmospheric layers.
The main goal of the ACECHEM mission is therefore to investigate the composition of the upper troposphere and the lower stratosphere (UTLS), its interaction with climate, and the impact of anthropogenic activities. In particular, four scientific objectives are addressed:
The role of the UTLS region in the radiative forcing of climate and in climate-chemistry feedbacks
The importance of stratosphere-troposphere exchange in atmospheric chemistry and climate
Stratospheric change and its interactions with stratospheric chemistry and climate
- Impact of pollution on the composition of the upper troposphere
ACECHEM is the first space mission that will have the observational capabilities necessary for a focussed study of the UTLS region, and in particular of the upper troposphere, a region that is difficult to observe from space. ACECHEM will carry on a dedicated platform:
the first limb-sounding millimetre-wave spectrometer optimised specifically for upper tropospheric observations through specification of spectral bands and resolution, vertical resolution, sensitivity and tomographic measurement strategy;
the first limb-sounding mid-infrared spectrometer optimised specifically for upper tropospheric observations through specification of spectral resolution,horizontal sampling (along-and across-track)and vertical resolution;
- the first spaceborne limb-viewing cloud imager, to support tropospheric trace gas retrievals by precise determination of cloud and aerosol contamination in the spectrometers' fields of view.
ACECHEM will fly in formation with MetOp to exploit simultaneous and co-located nadir-viewing observations synergistically.
Last update: 19 October 2001