Observing and Modelling the Impact of Arctic and Tropical Cirrus Clouds on Far-infrared Radiance Spectra PDF Download

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Languages : en
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Author: Elizabeth Baugher
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Languages : en
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Surface downward far-infrared (far-IR) spectra were collected from NASA's Far-Infrared Spectroscopy of the Troposphere (FIRST) instrument from August to October 2009 at an altitude of 5.4 km near the summit of Cerro Toco, Chile. This region is known for its dry, cold, and dominantly clear atmosphere, which is optimal for studying the effects, that water vapor and cirrus clouds have on the far-IR. Comparisons with Line-By-Line Discrete Ordinants Radiative Transfer model, LBLDIS, show that FIRST observes the very fine spectral structure in the far-IR with differences as small as ± 0.7% for both clear-sky and cloudy-sky simulations. Clear sky model analysis demonstrated the greatest sensitivity to atmospheric conditions is between 300 and 500 cm-1. The cloudy-sky simulations demonstrated that the far-IR radiation has minimal sensitivity to cloud particle effective radius, yet is very sensitive to cloud optical thickness at wavenumbers between 400 - 600 cm-1. In fact, cirrus optical thickness found to be inferred from the brightness temperature differences at 250 and 559.5 cm-1. Aerosols proved to reduce downwelling radiance by half that a clear-sky would emit, but had little effect on the total far-IR radiative forcing. Furthermore, these far-IR measurements open a new window to understanding the radiative impacts of various atmospheric constituents such as water vapor and clouds, and to understanding and modeling the Earth's climate and energy budget.

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Languages : en
Pages : 13

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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.

Author: Sylvia Sullivan
Publisher: John Wiley & Sons
ISBN: 1119700310
Category : Science
Languages : en
Pages : 371

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Clouds and Their Climatic Impacts Clouds are an influential and complex element of Earth’s climate system. They evolve rapidly in time and exist over small spatial scales, but also affect global radiative balance and large-scale circulations. With more powerful models and extensive observations now at our disposal, the climate impact of clouds is receiving ever more research attention. Clouds and Their Climatic Impacts: Radiation, Circulation, and Precipitation presents an overview of our current understanding on various types of clouds and cloud systems and their multifaceted role in the radiative budget, circulation patterns, and rainfall. Volume highlights include: Interactions of aerosol with both liquid and ice clouds Surface and atmospheric cloud radiative feedbacks and effects Arctic, extratropical, and tropical clouds Cloud-circulation coupling at global, meso, and micro scales Precipitation efficiency, phase, and measurements The role of machine learning in understanding clouds and climate The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.

Author: David K. Lynch
Publisher: Oxford University Press
ISBN: 0195351398
Category : Science
Languages : en
Pages : 499

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Cirrus clouds are high, thin, tropospheric clouds composed predominately of ice. In the last ten years, considerable work has shown that cirrus is widespread--more common than previously believed--and has a significant impact on climate and global change. As the next generation weather satellites are being designed, the impact of cirrus on remote sensing and the global energy budget must be recognized and accommodated. This book, the first to be devoted entirely to cirrus clouds, captures the state of knowledge of cirrus and serves as a practical handbook as well. Each chapter is based on an invited review talk presented at Cirrus, a meeting hosted by the Optical Society of America and co-sponsored by the American Geophysical Union and the American Meteorological Society. All aspects of cirrus clouds are covered, an approach that reaches into diverse fields. Topics include: the definition of cirrus, cirrus climatologies, nucleation, evolution and dissipation, mixed-phase thermodynamics, crystallinity, orientation mechanisms, dynamics, scattering, radiative transfer, in situ sampling, processes that produce or influence cirrus (and vice versa), contrails, and the influence of cirrus on climate.

Author: Daniel Y. Gezari
Publisher:
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Category : Infrared astronomy
Languages : en
Pages : 380

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Author: Alexander Marshak
Publisher: Springer Science & Business Media
ISBN: 3540239588
Category : Science
Languages : en
Pages : 688

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Developments in three-dimensional cloud radiation over the past few decades are assessed and distilled into this contributed volume. Chapters are authored by subject-matter experts who address a broad audience of graduate students, researchers, and anyone interested in cloud-radiation processes in the solar and infrared spectral regions. After two introductory chapters and a section on the fundamental physics and computational techniques, the volume extensively treats two main application areas: the impact of clouds on the Earth's radiation budget, which is an essential aspect of climate modeling; and remote observation of clouds, especially with the advanced sensors on current and future satellite missions.

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Category : Aeronautics
Languages : en
Pages : 836

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Author: Teruyuki Nakajima
Publisher: American Institute of Physics
ISBN:
Category : Science
Languages : en
Pages : 810

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All papers have been peer-reviewed. The International Radiation Symposium (IRS) is organized every four years by the International Radiation Commission (IRC) and this book presents a compilation on the current problems in atmospheric radiation, from theory and modeling to measurements and applications on weather and climate, from spectroscopy to satellite remote sensing of the many land-ocean-atmosphere components.

Author: National Aeronautics and Space Adm Nasa
Publisher: Independently Published
ISBN: 9781729223628
Category : Science
Languages : en
Pages : 46

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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 ...