Publications (2)6.1 Total impact
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Article: MARC: A code for the retrieval of atmospheric parameters from millimeter-wave limb measurements
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ABSTRACT: A new data analysis software is presented that has been developed for the retrieval of atmospheric minor constituents from limb-sounding observations made in the millimeter and sub-millimeter spectral regions. The code, which is called MARC (Millimetre-wave Atmospheric-Retrieval Code), has been designed to analyze the observations of the MARSCHALS (Millimetre-wave Airborne Receivers for Spectroscopic CHaracterisation in Atmospheric Limb-Sounding) instrument which operates on the M-55 stratospheric aircraft. The main objective of the analysis of MARSCHALS observations will be to assess long-wave measurement capabilities for the study of the upper troposphere and lower stratosphere regions. The key questions will be the accuracy and spatial resolution that can be achieved by long-wave measurements in presence of clouds and horizontal gradients.MARC performs a global-fit multi-target retrieval, in which optimal estimation is used and errors of the forward model parameters are taken into account for the definition of the cost function minimized in the retrieval. With these features it is easy to use the variables of the problem as either forward model constant parameters or retrieved unknowns with minimum impact on the stability of the retrieval. MARC can perform a wide spectral-band analysis of the observations without a selection of the analyzed channels, and the retrieval process provides an error budget of the retrieved unknowns that includes both the forward model errors and the measurement errors. The error budget obtained in this way is smaller than that obtained when accounting a posteriori for the systematic errors. The new combination of the retrieval features makes possible an efficient and optimal exploitation of the information content of the observations.Journal of Quantitative Spectroscopy and Radiative Transfer 02/2013; · 3.19 Impact Factor -
Article: Retrieval of minor constituents in a cloudy atmosphere with remote‐sensing millimetre‐wave measurements
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ABSTRACT: The presence of clouds in remote-sensing measurements is often the cause of information loss about the minor atmospheric constituent profiles that are the goal of the measurement. Millimetre- and submillimetre-wave sounding can be used to abate the problems of cloud contamination. A quantitative assessment of this possibility is provided with the systematic simulation of the retrieval of minor atmospheric constituents in the presence of ice cirrus clouds of different density and particle size. The simulations are made for the particular case of the MARSCHALS instrument which is a heterodyne limb-sounding spectrometer that measures the atmospheric thermal emission in the millimetre- and submillimetre-wave regions operating on board a stratospheric aircraft. Four types of measuring conditions are identified: clouds that do not modify the observation, clouds that are adequately described with an atmospheric continuum absorption model, clouds for which an error is introduced when the limited vertical resolution of the sounding does not resolve the sharp discontinuity of the cloud, and clouds which require the modelling of scattering effects for a correct retrieval. When a rigorous modelling of the cloud is performed, the retrieval of minor atmospheric constituent is marginally affected by the presence of the cloud. We find that in the worst case the cloud causes a loss, with respect to clear-sky conditions, of two degrees of freedom from about 90 and of 7% of information content relative to climatological information. Copyright © 2007 Royal Meteorological SocietyQuarterly Journal of the Royal Meteorological Society 11/2007; 133(S2):163 - 170. · 2.91 Impact Factor
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2007
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The “Nello Carrara” Institute of Applied Physics
Sesto Fiorentino, Tuscany, Italy
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