Mipas Observations of Clouds and Their Effects on Level 2 Trace Gas Products

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument measures the intensity of atmospheric radiation emitted in the infra-red spectral region at high spectral resolution in five bands ranging from 685 cm to 2410 cm. Clouds affect the appearance of the measured spectra at all wavelengths which are sensitive to emission from the layer of atmosphere containing the cloud. Both low resolution (cloud continuum) and high resolution features (complicated spectral lineshapes) can be observed due to the MIPAS resolution of 0.025 cm (unapodized). This has two implications. Firstly, spectra containing clouds must be identified and flagged prior to retrievals of trace gas concentrations at level 2. Secondly, the cloud information constitutes valuable products in themselves. In this paper, the success of the cloud detection scheme is reported and the MIPAS level 2 data are examined to demonstrate the effects of the clouds and the quality of the data given cloud flagging. The results are excellent and the cloud detection method will be included in the next update of the MIPAS operational processor. The results presented also support the quality of the MIPAS reference atmospheres which are available for use by other instrument teams.