Limb scatter measurements of high altitude cloud distributions
type: CreativeWork
description: Clouds have pivotal influence on the Earth's hydrological cycle and climate system because they are intricately involved in the dynamical, chemical, and radiative processes within the upper troposphere and lower stratosphere. Cirrus clouds occur at high altitude around the tropopause level and, despite their thin appearance and low optical thickness, they contribute to the radiative balance of the atmosphere. The processes in this region of the atmosphere have become increasingly important for a clear understanding of feedback mechanisms in the climate system. The Canadian designed and built Optical Spectrograph and Infrared Imaging System (OSIRIS) satellite instrument measures the spectrum of sunlight scattered from the Earth's atmosphere at wavelengths from the ultraviolet (280 nm) to the near infrared (810 nm). The limb scattering measurement technique allows OSIRIS to collect information on the vertical profile of atmospheric chemical and particle composition at a resolution of approximately 2km with nearly global daily coverage. In this work, a technique characterizing the distribution of cirrus cloud top occurrences from OSIRIS limb scattering radiance profiles is presented. The technique involves computing residual profiles by comparing normalized measured radiance and modelled molecular density profiles where mismatches between the two traces indicate the presence of clouds. Probability density functions of scattering residuals show the distribution is not a continuum measurement; there is a clear distinction between the cloudy and cloud-free conditions. Observations show high cloud top occurrences in the upper troposphere and lower stratosphere region above Indonesia and Central America. Results obtained using the high altitude cloud detection technique and OSIRIS measurements are compared to those by Sassen et al. (2008) who used CALIPSO nadir measurements and to those by Wang et al. (1996) who used SAGE II solar occultation measurements of cirrus clouds. …
abstract: Clouds have pivotal influence on the Earth's hydrological cycle and climate system because they are intricately involved in the dynamical, chemical, and radiative processes within the upper troposphere and lower stratosphere. Cirrus clouds occur at high altitude around the tropopause level and, despite their thin appearance and low optical thickness, they contribute to the radiative balance of the atmosphere. The processes in this region of the atmosphere have become increasingly important for a clear understanding of feedback mechanisms in the climate system. The Canadian designed and built Optical Spectrograph and Infrared Imaging System (OSIRIS) satellite instrument measures the spectrum of sunlight scattered from the Earth's atmosphere at wavelengths from the ultraviolet (280 nm) to the near infrared (810 nm). The limb scattering measurement technique allows OSIRIS to collect information on the vertical profile of atmospheric chemical and particle composition at a resolution of approximately 2km with nearly global daily coverage. In this work, a technique characterizing the distribution of cirrus cloud top occurrences from OSIRIS limb scattering radiance profiles is presented. The technique involves computing residual profiles by comparing normalized measured radiance and modelled molecular density profiles where mismatches between the two traces indicate the presence of clouds. Probability density functions of scattering residuals show the distribution is not a continuum measurement; there is a clear distinction between the cloudy and cloud-free conditions. Observations show high cloud top occurrences in the upper troposphere and lower stratosphere region above Indonesia and Central America. Results obtained using the high altitude cloud detection technique and OSIRIS measurements are compared to those by Sassen et al. (2008) who used CALIPSO nadir measurements and to those by Wang et al. (1996) who used SAGE II solar occultation measurements of cirrus clouds. …
author: Normand, Elise
language: eng
keywords: Cirrus, Clouds, OSIRIS, Occurrence Frequency
date published: 2014-06-20
date modified: 2026-07-24T04:27:16Z
provider: University of Saskatchewan
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Saskatchewan

PropertyValue
property ID: Handle
value: https://hdl.handle.net/10388/ETD-2012-10-722