Abstract
Abstract. A technique characterizing the distribution of cirrus cloud-top occurrences from the Optical Spectrograph and Infrared Imaging System (OSIRIS) limb-scattering radiance profiles is presented. The technique involves computing scattering residual profiles by comparing normalized measured radiance and modelled molecular radiance profiles where enhancements in the measured radiance indicate the presence of clouds. Probability density functions of scattering residuals show the distribution is not a continuum measurement; there is a 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 this technique with OSIRIS measurements are compared to those obtained by Sassen et al. (2008) with Cloud-Aerosol Lidar Pathfinder Satellite Observations (CALIPSO) nadir measurements and to those obtained by Wang et al. (1996) with Stratospheric Aerosol and Gas Experiment (SAGE) II solar occultation measurements.
Highlights
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 (UTLS) (Chahine, 1992; Liou, 1992; Hobbs, 1993)
We present a technique for mapping the occurrence frequency and distribution of high-altitude cirrus clouds with satellite measurements of limb-scattered sunlight
Clouds are not measured directly, Optical Spectrograph and Infrared Imaging System (OSIRIS) measurements are used in the development of a highaltitude cloud detection technique
Summary
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 (UTLS) (Chahine, 1992; Liou, 1992; Hobbs, 1993). Cirrus clouds occur at high altitude around the tropopause level and, despite their thin appearance and low optical thickness, they have an important contribution to the radiative balance of the atmosphere (Liou, 1986, 2002). The processes in this region of the atmosphere have become increasingly important for a clear understanding of feedback mechanisms in the climate system. We use measurements from the Optical Spectrograph and Infrared Imaging System (OSIRIS), a Canadian satellite instrument that measures atmospheric limb profiles of scattered solar radiation, along with a statistical approach to characterize and discriminate cloud scattering. A detailed description of the cloud detection technique is presented and the results obtained using the technique are compared to those by Sassen et al (2008), who used CloudAerosol Lidar Pathfinder Satellite Observations (CALIPSO) nadir measurements and to those by Wang et al (1996), who used Stratospheric Aerosol and Gas Experiment (SAGE) II solar occultation measurements of cirrus clouds
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