The purpose of the Algorithm Theoretical Basis Document (ATBD) is to present the algorithm and technical
details necessary to realise a processor for the retrieval of cloud properties form the Level 1b (L1B) data of
ESA instrument MIPAS on-board the ENVISAT satellite. The infrared spectra measured by MIPAS (main information
of L1B) include sufficient information to retrieve various cloud parameter. Recent publications have
already shown the large potential of the dataset ([11], [12], [5], [6]). But so far no validated and consolidated
MIPAS cloud product is available for the scientific community. Consequently the development of a cloud parameter
processor for MIPAS and the application to the time series is highly desired.
The proposed MIPAS cloud processor follows the requirements of the statement of work of the ESA-ITT
AO/1-5255/06/I-OL. Therefore the development and application of the processor is so far restricted to the first

Detailed information on the data available at:measurement period of MIPAS from July 2002 to March 2004 (spectral high resolution (HR) mode). After
2004 MIPAS is operating with slightly reduced resolution (RR-mode). A transfer of the prototype processor
for application of the RR mode has been taken into account during the algorithm development. It is desirable,
that this will be also considered in the realisation phase of the prototype processor.
Primary task of the software is to retrieve cloud properties from the MIPAS L1B spectra. This contains various
items of interest:
• the detection of cloudy spectra in the L1B data
• to classify various cloud types in the measurements (e.g. polar stratospheric clouds, liquids and ice
clouds)
• to retrieve cloud top information on height, temperature, pressure
• to retrieve profile information on cloud parameters (e.g.. extinction, ice water path or integrated limb
path quantities like volume/area density path)
• information on microphysical parameter like effective radius of the particle size distribution (PSD) or
Volume and Area densities.
The retrievability of the cloud parameters like the ones above have been investigated in a feasibility study of
the MIPclouds project

1) Spang, R., Remedios, J. J., and Barkley, M., Colour Indices for the Detection and Differentiation of Cloud Types in Infra-red Limb Emission Spectra, Adv. Space Res., 33, pp.1041-1047, 2004.
2) Spang, R., Arndt, K., Dudhia, A., Höpfner, M., Hoffmann, L., Hurley, J., Grainger, R. G., Griessbach, S., Poulsen, C., Remedios, J. J., Riese, M., Sembhi, H., Siddans, R., Waterfall, A., and Zehner, C.: Fast cloud parameter retrievals of MIPAS/Envisat, Atmos. Chem. Phys., 12, 7135-7164, doi:10.5194/acp-12-7135- 2012, 2012.
3) Sembhi, H., Remedios, J., Trent, T., Moore, D. P., Spang, R., Massie, S., and Vernier, J.-P.: MIPAS detection of cloud and aerosol particle occurrence in the UTLS with comparison to HIRDLS and CALIOP, Atmos. Meas. Tech., 5, 2537- 2553, doi:10.5194/amtd-5-2537-2012, 2012
4) Hurley, J., Dudhia, A., and Grainger, R. G.: Retrieval of macrophysical cloud parameters from MIPAS: algorithm description, Atmos. Meas. Tech., 4, 683- 704, doi:10.5194/amt-4-20 683-2011, 2011."