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Broadband_Clouds: A Tool for 2D Representation of Clouds in MIPAS/ENVISAT Scenario, Description and Applications

Elisa Castelli(1), Bianca Maria Dinelli(2), Massimo Carlotti(3), Marco Ridolfi(3), Enrico Arnone(3) and Enzo Papandrea(3)

(1) IAC-CNR, via Madonna del piano, 50019 Sesto Fiorentino (FI), Italy
(2) ISAC-CNR, via Gobetti 101, 40129 Bologna, Italy
(3) DCFI -University of Bologna, Viale Risorgimento 4, 40136 Bologna, Italy

Abstract

Clouds play a key role in the Earth's daily weather and long term climate. They represent a critical factor in regulating the Earth's atmospheric energy balance, influencing both the amount of solar radiation that reaches the ground and that is reflected back to space, and the thermal radiation trapped within the troposphere. Clouds also play an important role in many chemical processes within the atmosphere, acting as a surface for chemical reactions, providing a mechanism for the depletion of ozone or removal of aerosol particles through scavenging, and also altering the distribution of soluble and reactive species in the atmosphere through transport of air masses. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), operating on-board ENVISAT, is a limb sounding Fourier Transform spectrometer for the measurement of high-resolution gaseous emission spectra. Studies on MIPAS data have demonstrated its sensitivity to the radiation emitted from the clouds. The GMTR (Geo-fit Multi Target Retrieval) retrieval system is an open source code specifically designed for MIPAS measurements that adopts a 2D discretization of the atmosphere. The GMTR forward model has been used to create a self-standing Broad Band (BB) forward model (capable to simulate extended spectral regions). We have introduced into the BB forward model the capability to model the effects of cloud contamination into MIPAS spectra (BB_Clouds). Exploiting the 2D approach, the cloud is no longer represented as an infinite cloudy shell, but it is characterized by both a vertical and a horizontal extension. BB_Clouds has been used to assess the possibility to retrieve cloud extension and other parameters from MIPAS spectra. The developed algorithm and the results of the tests performed will be presented and discussed.