Title page for ETD etd-2047101569611961

Type of Document Dissertation
Author Villeneuve, Pierre V.
URN etd-2047101569611961
Title A Numerical Study of the Sensitivity of Cloudy-Scene Bidirectional Reflectivity Distribution Functions to Variations in Cloud Parameters
Degree PhD
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Campbell, James B. Jr.
Nelson, Douglas J.
Scott, Elaine P.
Stern, Curtis H.
Mahan, James Robert Committee Chair
  • none
Date of Defense 1996-06-28
Availability unrestricted
The goal of this research has been to characterize the sensitivity of the earth's

shortwave bidirectional reflectivity distribution function (BRDF) to variations in

cloud parameters. The BRDF is a remote sensing tool used to predict the flux

reflected from a given earth scene from a satellite-based measurement of the

reflected intensity. The BRDF is necessary in order to account for the anisotropic

nature of the shortwave radiation field. A shortwave atmospheric radiation

Monte-Carlo ray-trace model has been developed as part of this research to predict

the earth-reflected radiation field at the top of the atmosphere. This model was

developed while paying special attention to clouds including realistic

three-dimensional cloud fields characterized by fundamental physical properties.

This model was used to predict the BRDF for various cloud fields where a single

cloud parameter was varied as part of the sensitivity analysis. The results show that

the shortwave BRDF is very sensitive to changes in cloud vertical thickness and

mean cloud size. This sensitivity is also strongly dependent on the direction from

which the scene is observed. In a related analysis, a study was done of the error

associated with using a BRDF from one scene to retrieve fluxes from a second

scene. The model was also used to predict images of cloud fields for comparison

with experimental data from the Rutherford Appleton Laboratories satellite-based

Along Track Scanning Radiometer (ATSR). Finally the output from the radiation

model was integrated with the end-to-end radiative electrothermal model of a

practical earth radiation budget instrument. This integrated model was used to

predict the instrument response to scanning a realistic partly-cloudy earth scene.

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