Retrieval of Global Tropospheric Methane Distributions from IASI

In poster describes a scheme that has been developed at the Rutherford Appleton Laboratory to retrieve methane distributions from the IASI instrument on METOP. IASI is an infrared nadir viewing Fourier transform spectrometer, primarily sensitive to methane in the middle to upper troposphere. Methane is an important greenhouse gas, and knowledge of its distribution, sources and sinks, and trend within the atmosphere are important for our understanding of the current atmosphere and future climate. The ability to measure information on methane from space allows global methane distributions to be derived alongside seasonal and even longer term variations in its concentration. Here, results from our version 1 methane data are described, and their quality is illustrated by comparison to models and other satellite data. In addition, the impact of clouds on the results are investigated. This is found to be a critical source of error leading to anomalously high retrieved methane value