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Modeling Single Scattering And Radiative Properties Of Cirrus Clouds
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Book Synopsis Modeling Single Scattering and Radiative Properties of Cirrus Clouds by :
Download or read book Modeling Single Scattering and Radiative Properties of Cirrus Clouds written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The specific objective of this research has been the development and improvement of theoretical models to simulate the effect of nonsphericity on single scattering properties of cirrus cloud particles in the visible and infrared spectral regions. First, we have shown that using a matrix inversion scheme based on a special LU factorization rather than on the standard Gaussian elimination significantly improves the numerical stability of T-matrix computations for nonabsorbing and weakly absorbing nonspherical particles. Second, we use exact T-matrix computations and the Kirchhoff approximation to show that the delta function transmission peak predicted by the GO approximation for hexagonal ice crystals is an artifact of GO completely ignoring physical optics effects and must be convolved with the Fraunhofer pattern, thereby producing a phase function component with an angular profile similar to the standard diffraction component. Third, we have used the improved T-matrix method to compute the linear depolarization ration for polydispersions of randomly oriented ice spheroids, circular cylinders, and Chebyshev particles with sizes typical of young contrails. We have shown that ice crystals with effective radii as small as several tenths of a micron can already produce 3 exceeding 0.5 at visible wavelengths.
Book Synopsis Improvements in Modeling the Microphysical and Radiative Properties of Cirrus Clouds Using the Regional Atmospheric Modeling System (RAMS). Final Report by :
Download or read book Improvements in Modeling the Microphysical and Radiative Properties of Cirrus Clouds Using the Regional Atmospheric Modeling System (RAMS). Final Report written by and published by . This book was released on 1998 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main work activity during this period was the refinement and GCM parameterization of the treatment of ice cloud radiative properties, developed for this project. The treatment has now been rigorously tested and improved, and can now be used with confidence in radiation transfer schemes. The ice Cloud radiation scheme has also proven useful in satellite remote sensing. The radiation scheme differs from others in the thermal infrared, where it is assumed that photon tunneling does not occur for real ice particles (tunneling can be viewed as a process by which photons outside a particle's area-cross section can still be absorbed). Single particle T-matrix and Mie calculations suggest that a particle's ability to capture energy through tunneling depends on surface morphology, with more tunneling the more circular (or less angular) a surface is. This assumption leads to retrievals of mean particle size which are similar to those observed in tropical cirrus by optical imaging probes, whereas retrieved sizes using Mie theory are about 1/3 those predicted by this scheme. The retrieval method requires channels in the 8--9 [mu]m and 11--12 [mu]m ranges. This assumption about tunneling, as well as treating size distributions in the radiation scheme as bimodal, allows retrievals over a broader range of mean particle size than previous schemes permitted, making such size retrievals applicable to most types of cirrus clouds.
Book Synopsis Simulation of the Extinction Efficiency, the Absorption Efficiency and the Asymmetry Factor of Ice Crystals and Relevant Applications to the Study of Cirrus Cloud Radiative Properties by : Kai Lu
Download or read book Simulation of the Extinction Efficiency, the Absorption Efficiency and the Asymmetry Factor of Ice Crystals and Relevant Applications to the Study of Cirrus Cloud Radiative Properties written by Kai Lu and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The single-scattering properties of six non-spherical ice crystals, droxtals, plates, solid columns, hollow columns, aggregates and 6-branch bullet rosettes are simulated. The anomalous diffraction theory (ADT) is applied to the simulation of the extinction efficiency and the absorption efficiency. Because the first order reflection is considered, the accuracy of the absorption efficiency increases with the increasing of the size parameter. Compared with the reference single-scattering properties from an improved geometric optics method (IGOM), the errors in the extinction and absorption efficiencies are small. In addition, the asymmetry factor is formulated within the framework of diffraction and external reflection. The asymmetry factor based on the ADT matches very well with the IGOM counterpart when the absorption is strong, but needs an improvement in the solar region. The errors in conjunction with the application of the ADT-based optical properties to the computation of atmospheric fluxes and heating rates, based on the Fu-Liou model also are investigated. Two cases, one for tropical cirrus clouds and the other for mid-latitude cirrus clouds, are designed. It is found that the errors of bulk asymmetry factor between ADT-based and IGOM-based result in an overestimation of downward infrared (IR) fluxes and upward solar fluxes, and an underestimation of upward IR fluxes and downward solar fluxes. The errors of the fluxes and heating rates based on two sets of single-scattering properties are caused mainly by the underestimation of the bulk absorption efficiency based on ADT. It is also shown that ADT-based optical properties generate more accurate radiative properties for tropical cirrus clouds than for the mid-latitude cirrus clouds. In conclusion, the ADT-based method can generate reasonably accurate single-scattering properties of ice crystals, and can result in reasonable upward IR and solar fluxes at top of atmosphere (TOA), downward IR fluxes at the surface, and net heating rates.
Book Synopsis Satellite-based Remote Sensing of Cirrus Clouds by : Zhibo Zhang
Download or read book Satellite-based Remote Sensing of Cirrus Clouds written by Zhibo Zhang and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation consists of three parts, each devoted to a particular issue of significant importance for satellite-based remote sensing of cirrus clouds. In the first part, we develop and present a fast infrared radiative transfer model on the basis of the adding-doubling principle. The model aims to facilitate the radiative transfer computations involved in hyperspectral remote sensing applications. The model is applicable to a variety of cloud conditions, including vertically inhomogeneous or multilayered clouds. It is shown that for hyperspectral applications the model is two order-of-magnitude faster than the well-known discrete ordinate transfer (DISORT) model, while maintains a similar accuracy. The second part is devoted to the investigation of uncertainties in the FSSP (Forward Scattering Spectrometer Probe) measurement of cloud extinction by small ice particles. First, the single-scattering properties of small ice particles in cirrus clouds are derived and compared to those of equivalent spheres according to various definitions. It is found that, although small ice particles in cirrus clouds are often "quasi-spherical", their scattering phase functions and asymmetry factors are significant different from those of ice spheres. Such differences may lead to substantial underestimation of cloud extinction in FSSP measurement, if small ice particles are assumed to be spheres. In the third part, we present a comparison of cirrus cloud optical thickness retrievals from two important instruments, MODIS (Moderate Resolution Imaging Spectrometer) and POLDER (Polarization and Directionality of Earth's Reflection), on board NASA's A-train satellite constellation. The comparison reveals a large difference. Several possible reasons are discussed. It is found that much of the difference is attributable to the difference between the MODIS and POLDER retrieval algorithm in the assumption of cirrus cloud bulk scattering properties. Potential implications of the difference for climate studies are investigated. An important finding is that the use of an unrealistic cirrus bulk scattering model might introduce artificial seasonal variation of cirrus optical thickness and shortwave radiative forcing into the retrieval.
Download or read book Cirrus written by David K. Lynch and published by Oxford University Press, USA. This book was released on 2002 with total page 499 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text, devoted entirely to cirrus clouds, captures the state of knowledge of cirrus clouds and serves as a practical handbook as well.
Book Synopsis Radiation and Cloud Processes in the Atmosphere by : Kuo-Nan Liou
Download or read book Radiation and Cloud Processes in the Atmosphere written by Kuo-Nan Liou and published by Oxford University Press on Demand. This book was released on 1992 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an up-to-date treatment of atmospheric science and the key roles of solar radiation and cloud layers.
Book Synopsis Study of Cloud Properties from Single-scattering, Radiative Forcing, and Retrieval Perspectives by : Yong-Keun Lee
Download or read book Study of Cloud Properties from Single-scattering, Radiative Forcing, and Retrieval Perspectives written by Yong-Keun Lee and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation reports on three different yet related topics in light scattering computation, radiative transfer simulation, and remote sensing implementation, regarding the cloud properties and the retrieval of cloud properties from satellite-based infrared radiometric measurements. First, the errors associated with the use of circular cylinders as surrogates for hexagonal columns in computing the optical properties of pristine ice crystals at infrared (8-12 [micron]) wavelengths are investigated. It is found that the differences between the results for circular cylinders and hexagonal columns are on the order of a few percent at infrared wavelengths. Second, investigated in this dissertation are the outgoing broadband longwave and window channel radiances at the top-of-atmosphere under clear-sky conditions on the basis of the data acquired by the Cloud and the Earth's Radiant Energy System (CERES) instrument onboard the NASA Terra satellite platform. Based on the comparison of the observed broadband radiances with those obtained from rigorous radiative transfer simulations, it is found that the theoretical results tend to be larger than their measured counterparts. Extensive sensitivity studies regarding the uncertainties of various parameters were carried out. Within the considered uncertainties of various factors, the computed radiances are still larger than the observed radiances if thin cirrus clouds are excluded. Thus, a potential cause for the differences could be associated with the presence of thin cirrus clouds whose visible optical thickness is smaller than approximately 0.3. Third, presented in this dissertation is an illustration of the application of hyperspectral infrared channel observations to the retrieval of the cloud properties. Specifically, the hyperspectral measurements acquired from the Atmospheric Infrared Sounder (AIRS) aboard the NASA Aqua platform are used to infer cloud top pressure, effective cloud amount, cloud thermodynamic phase, cloud optical thickness, and the effective size of cloud particles. The AIRS-based retrievals are compared with the counterparts of the operational cloud products derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). The two retrievals agree reasonably well except for the retrieved cloud effective particle size. Furthermore, the diurnal and seasonal contrasts of cloud properties are also investigated on the basis of the cloud properties retrieved from the AIRS data.
Book Synopsis Light Scattering by Ice Crystals by : Kuo-Nan Liou
Download or read book Light Scattering by Ice Crystals written by Kuo-Nan Liou and published by Cambridge University Press. This book was released on 2016-10-06 with total page 461 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume outlines the fundamentals and applications of light scattering, absorption and polarization processes involving ice crystals.
Book Synopsis Radiative Effects of Dust Aerosols, Natural Cirrus Clouds and Contrails: Broadband Optical Properties and Sensitivity Studies by : Bingqi Yi
Download or read book Radiative Effects of Dust Aerosols, Natural Cirrus Clouds and Contrails: Broadband Optical Properties and Sensitivity Studies written by Bingqi Yi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation aims to study the broadband optical properties and radiative effects of dust aerosols and ice clouds. It covers three main topics: the uncertainty of dust optical properties and radiative effects from the dust particle shape and refractive index, the influence of ice particle surface roughening on the global cloud radiative effect, and the simulations of the global contrail radiative forcing. In the first part of this dissertation, the effects of dust non-spherical shape on radiative transfer simulations are investigated. We utilize a spectral database of the single-scattering properties of tri-axial ellipsoidal dust-like aerosols and determined a suitable dust shape model. The radiance and flux differences between the spherical and ellipsoidal models are quantified, and the non-spherical effect on the net flux and heating rate is obtained over the solar spectrum. The results indicate the particle shape effect is related to the dust optical depth and surface albedo. Under certain conditions, the dust particle shape effect contributes to 30% of the net flux at the top of the atmosphere. The second part discusses how the ice surface roughening can exert influence on the global cloud radiative effect. A new broadband parameterization for ice cloud bulk scattering properties is developed using severely roughened ice particles. The effect of ice particle surface roughness is derived through simulations with the Fu-Liou and RRTMG radiative transfer codes and the Community Atmospheric Model. The global averaged net cloud radiative effect due to surface roughness is around 1.46 Wm-2. Non-negligible increase in longwave cloud radiative effect is also found. The third part is about the simulation of global contrail radiative forcing and its sensitivity studies using both offline and online modeling frameworks. Global contrail distributions from the literature and Contrail Cirrus Prediction Tool are used. The 2006 global annual averaged contrail net radiative forcing from the offline model is estimated to be 11.3 mW m^(-2), with the regional contrail radiative forcing being more than ten times stronger. Sensitivity tests show that contrail effective size, contrail layer height, the model cloud overlap assumption, and contrail optical properties are among the most important factors. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151136
Book Synopsis Proceedings of the Fifth Atmospheric Radiation Measurement (ARM) Science Team Meeting by :
Download or read book Proceedings of the Fifth Atmospheric Radiation Measurement (ARM) Science Team Meeting written by and published by . This book was released on 1995 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Cirrus written by David K. Lynch and published by Oxford University Press. This book was released on 2002-01-24 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Investigation of Thin Cirrus Cloud Optical and Microphysical Properties on the Basis of Satellite Observations and Fast Radiative Transfer Models by : Chenxi Wang
Download or read book Investigation of Thin Cirrus Cloud Optical and Microphysical Properties on the Basis of Satellite Observations and Fast Radiative Transfer Models written by Chenxi Wang and published by . This book was released on 2013 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the global investigation of optically thin cirrus cloud optical thickness [tau] and microphysical properties, such as, effective particle size (D_(eff)) and ice crystal habits (shapes), based on the global satellite observations and fast radiative transfer models (RTMs). In the first part, we develop two computationally efficient RTMs simulating satellite observations under cloudy-sky conditions in the visible/shortwave infrared (VIS/SWIR) and thermal inferred (IR) spectral regions, respectively. To mitigate the computational burden associated with absorption, thermal emission and multiple scattering, we generate pre-computed lookup tables (LUTs) using two rigorous models, i.e., the line-by-line radiative transfer model (LBLRTM) and the discrete ordinates radiative transfer model (DISORT). The second part introduces two methods (i.e., VIS/SWIR- and IR-based methods) to retrieve [tau] and D_(eff) from satellite observations in corresponding spectral regions of the two RTMs. We discuss the advantages and weakness of the two methods by estimating the impacts from different error sources on the retrievals through sensitivity studies. Finally, we develop a new method to infer the scattering phase functions of optically thin cirrus clouds in a water vapor absorption channel (1.38-[mu]m). We estimate the ice crystal habits and surface structures by comparing the inferred scattering phase functions and numerically simulated phase functions calculated using idealized habits. We find two critical features of the two retrieval methods: (1) the IR-based method is more sensitive to optically thin cirrus cloud, and (2) the VIS/SWIR-based method is more sensitive to the pre-assumed ice cloud microphysical parameterization schemes. We derive the optically thin cirrus cloud phase functions based on the two methods. We find that small column-like particles (e.g., solid columns and column-aggregates) and droxtals with rough surfaces are likely to reside in optically thin cirrus clouds. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151213
Book Synopsis Modeling of Cloud/Radiation Processes for Cirrus Cloud Formation by :
Download or read book Modeling of Cloud/Radiation Processes for Cirrus Cloud Formation written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This technical report includes five reprints and pre-prints of papers associated with the modeling of cirrus cloud and radiation processes as well as remote sensing of cloud optical and microphysical properties from an airborne spectrometer based on radiative transfer principles. The time-dependent two-dimensional cirrus model includes a second-order turbulence closure scheme, an advanced interactive radiative transfer scheme, and ice microphysics parameterization. This model is used to understand the physical processes governing the formation and evolution of cirrostratus clouds.
Author :Alexander A. Kokhanovsky Publisher :Springer Science & Business Media ISBN 13 :3642321062 Total Pages :653 pages Book Rating :4.6/5 (423 download)
Book Synopsis Light Scattering Reviews 8 by : Alexander A. Kokhanovsky
Download or read book Light Scattering Reviews 8 written by Alexander A. Kokhanovsky and published by Springer Science & Business Media. This book was released on 2013-06-12 with total page 653 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light scattering review (vol 8) is aimed at the presentation of recent advances in radiative transfer and light scattering optics. The topics to be covered include: scattering of light by irregularly shaped particles suspended in atmosphere (dust, ice crystals), light scattering by particles much larger as compared the wavelength of incident radiation, atmospheric radiative forcing, astrophysical radiative transfer, radiative transfer and optical imaging in biological media, radiative transfer of polarized light, numerical aspects of radiative transfer.
Book Synopsis Fast Processes in Large-Scale Atmospheric Models by : Yangang Liu
Download or read book Fast Processes in Large-Scale Atmospheric Models written by Yangang Liu and published by John Wiley & Sons. This book was released on 2023-12-11 with total page 483 pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving weather and climate prediction with better representation of fast processes in atmospheric models Many atmospheric processes that influence Earth’s weather and climate occur at spatiotemporal scales that are too small to be resolved in large scale models. They must be parameterized, which means approximately representing them by variables that can be resolved by model grids. Fast Processes in Large-Scale Atmospheric Models: Progress, Challenges and Opportunities explores ways to better investigate and represent multiple parameterized processes in models and thus improve their ability to make accurate climate and weather predictions. Volume highlights include: Historical development of the parameterization of fast processes in numerical models Different types of major sub-grid processes and their parameterizations Efforts to unify the treatment of individual processes and their interactions Top-down versus bottom-up approaches across multiple scales Measurement techniques, observational studies, and frameworks for model evaluation Emerging challenges, new opportunities, and future research directions 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.
Book Synopsis Proceedings of the Fourth Atmospheric Radiation Measurement (ARM) Science Team Meeting by :
Download or read book Proceedings of the Fourth Atmospheric Radiation Measurement (ARM) Science Team Meeting written by and published by . This book was released on 1994 with total page 428 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Tropical Cirrus Cloud Property Retrievals Using Misr and Modis by : Sarah M. Thomas
Download or read book Tropical Cirrus Cloud Property Retrievals Using Misr and Modis written by Sarah M. Thomas and published by . This book was released on 2002 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
