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Title: The potential effect of cirrus on microwave limb sounder retrievals
Author: Bond, Stephen Thomas
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1996
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A microwave limb sounder (MLS) is an instrument used to study the composition and temperature of the atmosphere by measuring the microwave radiation that is thermally emitted by atmospheric molecules. When such measurements are made in the upper troposphere, the extinction of radiation caused by cirrus clouds may affect the quality of the results obtained. The extent to which such extinction degrades the sensitivity of MLS measurements to tropospheric parameters has been estimated using computer simulations of radiative transfer in a cloudy atmosphere. Results have been derived specifically for the proposed EOS MLS instrument due to be launched in December 2002, but are applicable to microwave limb sounding in general. To calculate the microwave emission spectrum of the atmosphere, a forward model was developed which represents the absorption properties of atmospheric molecules, and solves the equation of radiative transfer along a one-dimensional path through the atmosphere. A simple scattering model was developed using Mie theory to calculate scattering and extinction by a distribution of spherical particles, and was used to extend the capabilities of the forward model such that it was able to simulate radiative transfer through a cloudy atmosphere. A review of existing literature on the microphysical structure of cirrus clouds has been conducted, allowing the parameterisation of their size distributions and a characterisation of their crystal shapes. Cirrus is composed of ice-crystals which take a variety of non-spherical forms. Therefore in order to make use of the forward model described, a method was developed for converting the geometrical forms of the cirrus crystals into spheres of the same projected area, on the assumption that such spheres will have similar gross scattering properties to their non-spherical counterparts.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available