Correcting middle infrared cloud reflectances for atmospheric effects
Correcting middle infrared cloud reflectances for atmospheric effects
This thesis demonstrates a method for obtaining middle infrared cloud reflectances using NOAA AVHRR satellite data. These reflectances can then be used to obtain microphysical properties of clouds utilising established relationships between them. Two major aspects are addressed as part of the technique. Firstly, the correction for atmospheric effects and secondly, the ability to separate the received signal into reflected and emitted components. These aspects are of fundamental importance if middle infrared channels are to be effectively used to measure cloud properties.
A numerical, short wavelength, atmospheric model is initially constructed, tested and validated against observational data and another existing model. This model is then adapted to operate on satellite data and specifically in the middle infrared section of the electromagnetic spectrum, (approximate wavelength range of 3.5-4.0 μm.). As the received satellite signal is a mixture of reflected solar and emitted terrestrial radiation, a method is required to separate the two components in order to obtain the purely reflected contribution. This method is verified by validating the emitted component against observed, nightime radiances. Finally a sensitivity analysis is carried out on the finished model. A number of estimated or derived parameters are varied to determine output response and hence required accuracies.
This research contributes to the understanding of the data requirements for deriving middle infrared cloud reflectances. Furthermore it demonstrates the development and application of a new and tested atmospheric model to satellite data in order to obtain these reflectances. Finally, it addresses the problem of partially cloud-filled pixels and demonstrates a method which accounts for the emitted contributions to the total radiance from these pixels.
University of Southampton
1999
Duane, William John
(1999)
Correcting middle infrared cloud reflectances for atmospheric effects.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis demonstrates a method for obtaining middle infrared cloud reflectances using NOAA AVHRR satellite data. These reflectances can then be used to obtain microphysical properties of clouds utilising established relationships between them. Two major aspects are addressed as part of the technique. Firstly, the correction for atmospheric effects and secondly, the ability to separate the received signal into reflected and emitted components. These aspects are of fundamental importance if middle infrared channels are to be effectively used to measure cloud properties.
A numerical, short wavelength, atmospheric model is initially constructed, tested and validated against observational data and another existing model. This model is then adapted to operate on satellite data and specifically in the middle infrared section of the electromagnetic spectrum, (approximate wavelength range of 3.5-4.0 μm.). As the received satellite signal is a mixture of reflected solar and emitted terrestrial radiation, a method is required to separate the two components in order to obtain the purely reflected contribution. This method is verified by validating the emitted component against observed, nightime radiances. Finally a sensitivity analysis is carried out on the finished model. A number of estimated or derived parameters are varied to determine output response and hence required accuracies.
This research contributes to the understanding of the data requirements for deriving middle infrared cloud reflectances. Furthermore it demonstrates the development and application of a new and tested atmospheric model to satellite data in order to obtain these reflectances. Finally, it addresses the problem of partially cloud-filled pixels and demonstrates a method which accounts for the emitted contributions to the total radiance from these pixels.
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Published date: 1999
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Local EPrints ID: 464146
URI: http://eprints.soton.ac.uk/id/eprint/464146
PURE UUID: 0ed63d4b-a5c3-4796-96ee-783de579e5c2
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Date deposited: 04 Jul 2022 21:20
Last modified: 04 Jul 2022 21:20
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Author:
William John Duane
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