Detection of Cloud Effects in Mipas Spectral Data and Implications for the Mipas Operational Processor

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument measures the intensity of atmospheric radiation emitted in the infra -red spectral region in five bands ranging from 685 cm to 2410 cm. Previous low spectral resolution observations of such infra-red emissions by the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) had revealed the presence of cloud effects in measured spectra. Accordingly, a cloud detection system has been designed for MIPAS and implemented in a pre-operational (prototype) processor. The first data recorded by MIPAS have confirmed the characteristic spectral behaviour of the cloud component to the signal, and revealed exciting new detail from the high spectral resolution of MIPAS. It has been possible to demonstrate successful cloud detection using the method designed before launch and it is concluded that the technique is suitable for implementation in the full operational processor. It is further shown that this cloud detection for MIPAS is necessary at low altitudes for accurate retrievals to produce accurate geophysical products at level 2. The cloud index profiles derived constitute valuable diagnostic information and could be made available in level 2 data.