Ir Cirrus Optical Depth
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Optical Properties of Cirrus Clouds from Satellite Imagery and Radiative Transfer Calculations
Author | : Robert S. Stone |
Publisher | : |
Total Pages | : 113 |
Release | : 1987 |
Genre | : Cloud physics |
ISBN | : |
In this study, differences between narrowband near infrared (NIR) and infrared (IR) brightness temperatures are related to cloud optical depth providing a theoretical basis for determining cirrus optical properties from combined satellite images.
Understanding Satellite Cirrus Cloud Climatologies with Calibrated Lidar Optical Depths
Author | : Donald P. Wylie |
Publisher | : |
Total Pages | : 40 |
Release | : 1994 |
Genre | : |
ISBN | : |
Optical depth measurements of transmissive cirrus clouds were made using coincident lidar and satellite data to improve our interpretation of recent satellite cloud climatologies. These climatologies differ in the way they detect transmissive clouds because some use solar reflectance data (ISCCP) while other use multi-spectral infrared data (CO2 Slicing). To relate these climatologies and estimate the impact of transmissive clouds on the earth's heat budget, a relationship between visible and infrared radiation properties has to be used. We examined the popular assumption that the ratio of the visible to infrared optical depths should be 2.0 because the visible extinction cross section is twice the infrared absorption cross section when cloud particles are large compared to the wavelength.
Distribution and Radiative Forcing of Tropical Thin Cirrus Clouds
Author | : |
Publisher | : |
Total Pages | : 13 |
Release | : 2009 |
Genre | : |
ISBN | : |
To understand the radiative impact of tropical thin cirrus clouds, the frequency of occurrence and optical depths of these clouds have been derived. "Thin" cirrus clouds are defined here as being those that are not detected by the operational Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask, corresponding to an optical depth value of approximately 0.3 or smaller, but that are detectable in terms of the cirrus reflectance product based on the MODIS 1.375-micron channel. With such a definition, thin cirrus clouds were present in more than 40% of the pixels flagged as "clear sky" by the operational MODIS cloud mask algorithm. It is shown that these thin cirrus clouds are frequently observed in deep convective regions in the western Pacific. Thin cirrus optical depths were derived from the cirrus reflectance product. Regions of significant cloud fraction and large optical depths were observed in the Northern Hemisphere during the boreal spring and summer and moved southward during the boreal autumn and winter. The radiative effects of tropical thin cirrus clouds were studied on the basis of the retrieved cirrus optical depths, the atmospheric profiles derived from the Atmospheric Infrared Sounder (AIRS) observations, and a radiative transfer model in conjunction with a parameterization of ice cloud spectral optical properties. To understand how these clouds regulate the radiation field in the atmosphere, the instantaneous net fluxes at the top of the atmosphere (TOA) and at the surface were calculated. The present study shows positive and negative net forcings at the TOA and at the surface, respectively. The positive (negative) net forcing at the TOA (surface) is due to the dominance of longwave (shortwave) forcing. Both the TOA and surface forcings are in a range of 0-20 W/sq m, depending on the optical depths of thin cirrus clouds.
An Introduction to Atmospheric Radiation
Author | : K. N. Liou |
Publisher | : Elsevier |
Total Pages | : 598 |
Release | : 2002-05-09 |
Genre | : Science |
ISBN | : 0080491677 |
This Second Edition of An Introduction to Atmospheric Radiation has been extensively revised to address the fundamental study and quantitative measurement of the interactions of solar and terrestrial radiation with molecules, aerosols, and cloud particles in planetary atmospheres. It contains 70% new material, much of it stemming from the investigation of the atmospheric greenhouse effects of external radiative perturbations in climate systems, and the development of methodologies for inferring atmospheric and surface parameters by means of remote sensing. Liou's comprehensive treatment of the fundamentals of atmospheric radiation was developed for students, academics, and researchers in atmospheric sciences, remote sensing, and climate modeling. - Balanced treatment of fundamentals and applications - Includes over 170 illustrations to complement the concise description of each subject - Numerous examples and hands-on exercises at the end of each chapter
Optically Thin Cirrus Clouds Over Oceans and Possible Impact on Sea Surface Temperature of Warm Pool in Western Pacific
Author | : National Aeronautics and Space Adm Nasa |
Publisher | : Independently Published |
Total Pages | : 46 |
Release | : 2018-10-25 |
Genre | : Science |
ISBN | : 9781729223628 |
Over the convectively active tropical ocean regions, the measurement made from space in the IR and visible spectrum have revealed the presence of optically thin cirrus clouds, which are quite transparent in the visible and nearly opaque in the IR. The Nimbus-4 IR Interferometer Spectrometer (IRIS), which has a field of view (FOV) of approximately 100 km, was utilized to examine the IR optical characteristics of these cirrus clouds. From the IRIS data, it was observed that these optically thin cirrus clouds prevail extensively over the warm pool region of the equatorial western Pacific, surrounding Indonesia. It is found that the seasonal cloud cover caused by these thin cirrus clouds exceeds 50 percent near the central regions of the warm pool. For most of these clouds, the optical thickness in the IR is less than or = 2. It is deduced that the dense cold anvil clouds associated with deep convection spread extensively and are responsible for the formation of the thin cirrus clouds. This is supported by the observation that the coverage of the dense anvil clouds is an order of magnitude less than that of the thin cirrus clouds. From these observations, together with a simple radiative-convective model, it is inferred that the optically thin cirrus can provide a greenhouse effect, which can be a significant factor in maintaining the warm pool. In the absence of fluid transports, it is found that these cirrus clouds could lead to a runaway greenhouse effect. The presence of fluid transport processes, however, act to moderate this effect. Thus, if a modest 20 W/sq m energy input is considered to be available to warm the ocean, then it is found that the ocean mixed-layer of a 50-m depth will be heated by approximately 1 C in 100 days. Prabhakara, C. and Yoo, J.-M. and Dalu, G. and Kratz, P. Goddard Space Flight Center ...