Download or read book Case Evaluations of NWP Model Ice Clouds by Comparison to Retrieved Ice Cloud Properties Using ARM Data written by Urszula J. Jambor and published by . This book was released on 2000 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Retrieval of Optical and Microphysical Properties of Ice Clouds Using Atmospheric Radiation Measurement ARM Data written by Jacqueline Anne Kinney and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The research presented here retrieves the cloud optical thickness and particle effective size of cirrus clouds using surface radiation measurements obtained during the Atmospheric Radiation Measurement (ARM) field campaign. The algorithm used is based on a method proposed by Yang et al. (2005). The research examines single-layer ice clouds in the midlatitude and polar regions. The retrieved information in the midlatitudes is then verified using retrievals from the Moderate-resolution Imaging Spectroradiometer (MODIS) onboard the Terra and Aqua satellites.
Download or read book Study of Ice Cloud Properties from Synergetic Use of Satellite Observations and Modeling Capabilities written by Yu Xie and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dissertation first investigates the single-scattering properties of inhomogeneous ice crystals containing air bubbles. Specifically, a combination of the ray-tracing technique and the Monte Carlo method is used to simulate the scattering of light by randomly oriented large hexagonal ice crystals containing spherical or spheroidal air bubbles. The effect of the air bubbles within ice crystals is to smooth the phase functions, diminish the 22° and 46° halo peaks, and reduce the backscatter in comparison with the case of bubble-free ice crystals. Cloud reflectance look-up tables were generated at the wavelengths of 0.65 um and 2.13 um to examine the impact of accounting for air bubbles in ice crystal morphology on the retrieval of ice cloud optical thickness and effective particle size. To investigate the effect of the representation of aggregates on electromagnetic scattering calculations, an algorithm is developed to efficiently specify the geometries of aggregates and to compute some of their geometric parameters such as the projected area. Based on in situ observations, aggregates are defined as clusters of hexagonal plates with a chain-like overall shape. An aggregate model is developed with 10 ensemble members, each consisting of between 4-12 hexagonal plates. The scattering properties of an individual aggregate ice particle are computed using the discrete dipole approximation or an Improved Geometric Optics Method, depending upon the size parameter. The aggregate model provides an accurate and computationally efficient way to represent all aggregates occurring within ice clouds. We developed an algorithm to determine an appropriate ice cloud model for application to satellite-based retrieval of ice cloud properties. Collocated Moderate Resolution Imaging Spectroradiometer and Multi-angle Imaging SpectroRadiometer (MISR) data are used to retrieve the optical thicknesses of ice clouds as a function of scattering angle in the nine MISR viewing directions. The difference between cloud optical thickness and its averaged value over the nine viewing angles can be used to validate the ice cloud models. Using the data obtained on 2 July 2009, an appropriate ice cloud model is determined. With the presence of all the uncertainties in the current operational satellite-based retrievals of ice cloud properties, this ice cloud model has excellent performance in terms of consistency in cloud property retrievals with the nine MISR viewing angles.
Download or read book Master s Theses Directories written by and published by . This book was released on 2002 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Education, arts and social sciences, natural and technical sciences in the United States and Canada".
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of Ice Cloud Properties Using Infrared Spectral Data written by Kevin James Garrett and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The research presented in this thesis involves the study of ice cloud microphysical and optical properties using both hyperspectral and narrowband infrared spectral data. First, ice cloud models are developed for the Infrared Atmospheric Sounding Interferometer (IASI) instrument onboard the METOP-A satellite, which provide the bulk-scattering properties of these clouds for the 8461 IASI channels between 645 and 2760 cm-1. We investigate the sensitivity of simulated brightness temperatures in this spectral region to the bulk-scattering properties of ice clouds containing individual ice crystal habits as well as for one habit distribution. The second part of this thesis describes an algorithm developed to analyze the sensitivity of simulated brightness temperatures at 8.5 and 11.0 ℗æm to changes in effective cloud temperature by adjusting cloud top height and geometric thickness in a standard tropical atmosphere. Applicability of using these channels in a bi-spectral approach to retrieve cirrus cloud effective particle size and optical thickness is assessed. Finally, the algorithm is applied to the retrieval of these ice cloud properties for a case of single-layered cirrus cloud over a tropical ocean surface using measurements from the Moderate Resolution Infrared Spectroradiometer (MODIS). Cloud top height and geometric thickness in the profile are adjusted to assess the influence of effective cloud temperature on the retrieval.
Download or read book Mixed Phase Clouds written by Constantin Andronache and published by Elsevier. This book was released on 2017-09-28 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed-Phase Clouds: Observations and Modeling presents advanced research topics on mixed-phase clouds. As the societal impacts of extreme weather and its forecasting grow, there is a continuous need to refine atmospheric observations, techniques and numerical models. Understanding the role of clouds in the atmosphere is increasingly vital for current applications, such as prediction and prevention of aircraft icing, weather modification, and the assessment of the effects of cloud phase partition in climate models. This book provides the essential information needed to address these problems with a focus on current observations, simulations and applications. Provides in-depth knowledge and simulation of mixed-phase clouds over many regions of Earth, explaining their role in weather and climate Features current research examples and case studies, including those on advanced research methods from authors with experience in both academia and the industry Discusses the latest advances in this subject area, providing the reader with access to best practices for remote sensing and numerical modeling
Download or read book Retrieval of Cloud Phase Using the Moderate Resolution Imaging Spectroradiometer Data During the Mixed Phase Arctic Cloud Experiment written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving climate model predictions over Earth's polar regions requires a comprehensive knowledge of polar cloud microphysics. Over the Arctic, there is minimal contrast between the clouds and background snow surface, making it difficult to detect clouds and retrieve their phase from space. Snow and ice cover, temperature inversions, and the predominance of mixed-phase clouds make it even more difficult to determine cloud phase. Also, since determining cloud phase is the first step toward analyzing cloud optical depth, particle size, and water content, it is vital that the phase be correct in order to obtain accurate microphysical and bulk properties. Changes in these cloud properties will, in turn, affect the Arctic climate since clouds are expected to play a critical role in the sea ice albedo feedback. In this paper, the IR trispectral technique (IRTST) is used as a starting point for a WV and 11-[micro]m brightness temperature (T11) parameterization (WVT11P) of cloud phase using MODIS data. In addition to its ability to detect mixed-phase clouds, the WVT11P also has the capability to identify thin cirrus clouds overlying mixed or liquid phase clouds (multiphase ice). Results from the Atmospheric Radiation Measurement (ARM) MODIS phase model (AMPHM) are compared to the surface-based cloud phase retrievals over the ARM North Slope of Alaska (NSA) Barrow site and to in-situ data taken from University of North Dakota Citation (CIT) aircraft which flew during the Mixed-Phase Arctic Cloud Experiment (MPACE). It will be shown that the IRTST and WVT11P combined to form the AMPHM can achieve a relative high accuracy of phase discrimination compared to the surface-based retrievals. Since it only uses MODIS WV and IR channels, the AMPHM is robust in the sense that it can be applied to daytime, twilight, and nighttime scenes with no discontinuities in the output phase.
Download or read book Final Technical Report for Ice Nuclei Relation to Aerosol Properties written by and published by . This book was released on 2012 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Clouds play an important role in weather and climate. In addition to their key role in the hydrologic cycle, clouds scatter incoming solar radiation and trap infrared radiation from the surface and lower atmosphere. Despite their importance, feedbacks involving clouds remain as one of the largest sources of uncertainty in climate models. To better simulate cloud processes requires better characterization of cloud microphysical processes, which can affect the spatial extent, optical depth and lifetime of clouds. To this end, we developed a new parameterization to be used in numerical models that describes the variation of ice nuclei (IN) number concentrations active to form ice crystals in mixed-phase (water droplets and ice crystals co-existing) cloud conditions as these depend on existing aerosol properties and temperature. The parameterization is based on data collected using the Colorado State University continuous flow diffusion chamber in aircraft and ground-based campaigns over a 14-year period, including data from the DOE-supported Mixed-Phase Arctic Cloud Experiment. The resulting relationship is shown to more accurately represent the variability of ice nuclei distributions in the atmosphere compared to currently used parameterizations based on temperature alone. When implemented in one global climate model, the new parameterization predicted more realistic annually averaged cloud water and ice distributions, and cloud radiative properties, especially for sensitive higher latitude mixed-phase cloud regions. As a test of the new global IN scheme, it was compared to independent data collected during the 2008 DOE-sponsored Indirect and Semi-Direct Aerosol Campaign (ISDAC). Good agreement with this new data set suggests the broad applicability of the new scheme for describing general (non-chemically specific) aerosol influences on IN number concentrations feeding mixed-phase Arctic stratus clouds. Finally, the parameterization was implemented into a regional cloud-resolving model to compare predictions of ice crystal concentrations and other cloud properties to those observed in two intensive case studies of Arctic stratus during ISDAC. Our implementation included development of a prognostic scheme of ice activation using the IN parameterization so that the most realistic treatment of ice nuclei, including their budget (gains and losses), was achieved. Many cloud microphysical properties and cloud persistence were faithfully reproduced, despite a tendency to under-predict (by a few to several times) ice crystal number concentrations and cloud ice mass, in agreement with some other studies. This work serves generally as the basis for improving predictive schemes for cloud ice crystal activation in cloud and climate models, and more specifically as the basis for such a scheme to be used in a Multi-scale Modeling Format (MMF) that utilizes a connected system of cloud-resolving models on a global grid in an effort to better resolve cloud processes and their influence on climate.
Download or read book Development and Testing of Parameterizations for Continental and Tropical Ice Cloud Microphysical and Radiative Properties in GCM and Mesoscale Models Final Report written by and published by . This book was released on 1997 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall purpose of this research was to exploit measurements in clouds sampled during several field programs, especially from experiments in tropical regions, in a four-component study to develop and validate cloud parameterizations for general circulation models, emphasizing ice clouds. The components were: (1) parameterization of basic properties of mid- and upper-tropospheric clouds, such as condensed water content, primarily with respect to cirrus from tropical areas; (2) the second component was to develop parameterizations which express cloud radiative properties in terms of basic cloud microphysical properties, dealing primarily with tropical oceanic cirrus clouds and continental thunderstorm anvils, but also including altocumulus clouds; (3) the third component was to validate the parameterizations through use of ground-based measurements calibrated using existing and planned in-situ measurements of cloud microphysical properties and bulk radiative properties, as well as time-resolved data collected over extended periods of time; (4) the fourth component was to implement the parameterizations in the National Center for Atmospheric Research (NCAR) community climate model (CCM) II or in the NOAA-GFDL model (by L. Donner GFDL) and to perform sensitivity studies.
Download or read book The Microphysics of Ice Clouds written by Rosemary M. Dyer and published by . This book was released on 1979 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published results of observations of crystal habits, particle sizes and numbers of ice particles in clouds are summarized and discussed. There are systematic variations with cloud type, and in some instances, with cloud age and location within a cloud system. However, the body of data available is insufficient to formulate a climatology of ice cloud microphysics. The several measurement techniques in current use are evaluated, as are some of the techniques now under consideration for future use. The particle enhancement observed on some occasions is discussed, and the various theories accounting for it presented. Finally, recommendations are made concerning future field programs and theoretical studies required before accurate predictions of the ice cloud microphysical environment can be made. (Author).
Download or read book Determining Best Estimates and Uncertainties in Cloud Microphysical Parameters from ARM Field Data written by and published by . This book was released on 2015 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: We proposed to analyze in-situ cloud data collected during ARM/ASR field campaigns to create databases of cloud microphysical properties and their uncertainties as needed for the development of improved cloud parameterizations for models and remote sensing retrievals, and for evaluation of model simulations and retrievals. In particular, we proposed to analyze data collected over the Southern Great Plains (SGP) during the Mid-latitude Continental Convective Clouds Experiment (MC3E), the Storm Peak Laboratory Cloud Property Validation Experiment (STORMVEX), the Small Particles in Cirrus (SPARTICUS) Experiment and the Routine AAF Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign, over the North Slope of Alaska during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) and the Mixed-Phase Arctic Cloud Experiment (M-PACE), and over the Tropical Western Pacific (TWP) during The Tropical Warm Pool International Cloud Experiment (TWP-ICE), to meet the following 3 objectives; derive statistical databases of single ice particle properties (aspect ratio AR, dominant habit, mass, projected area) and distributions of ice crystals (size distributions SDs, mass-dimension m-D, area-dimension A-D relations, mass-weighted fall speeds, single-scattering properties, total concentrations N, ice mass contents IWC), complete with uncertainty estimates; assess processes by which aerosols modulate cloud properties in arctic stratus and mid-latitude cumuli, and quantify aerosol's influence in context of varying meteorological and surface conditions; and determine how ice cloud microphysical, single-scattering and fall-out properties and contributions of small ice crystals to such properties vary according to location, environment, surface, meteorological and aerosol conditions, and develop parameterizations of such effects. In this report we describe the accomplishments that we made on all 3 research objectives.
Download or read book The Remote Sensing of Tropospheric Composition from Space written by John P. Burrows and published by Springer Science & Business Media. This book was released on 2011-01-15 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: The impact of anthropogenic activities on our atmospheric environment is of growing public concern and satellite-based techniques now provide an essential component of observational strategies on regional and global scales. The purpose of this book is to summarise the state of the art in the field in general, while describing both key techniques and findings in particular. It opens with an historical perspective of the field together with the basic principles of remote sensing from space. Three chapters follow on the techniques and on the solutions to the problems associated with the various spectral regions in which observations are made. The particular challenges posed by aerosols and clouds are covered in the next two chapters. Of special importance is the accuracy and reliability of remote sensing data and these issues are covered in a chapter on validation. The final section of the book is concerned with the exploitation of data, with chapters on observational aspects, which includes both individual and synergistic studies, and on the comparison of global and regional observations with chemical transport and climate models and the added value that the interaction brings to both. The book concludes with scientific needs and likely future developments in the field, and the necessary actions to be taken if we are to have the global observation system that the Earth needs in its present, deteriorating state. The appendices provide a comprehensive list of satellite instruments, global representations of some ancillary data such as fire counts and light pollution, a list of abbreviations and acronyms, and a set of colourful timelines indicating the satellite coverage of tropospheric composition in the foreseeable future. Altogether, this book will be a timely reference and overview for anyone working at the interface of environmental, atmospheric and space sciences.
Download or read book Using Radar Lidar and Radiometer Measurements to Classify Cloud Type and Study Middle Level Cloud Properties written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The project is mainly focused on the characterization of cloud macrophysical and microphysical properties, especially for mixed-phased clouds and middle level ice clouds by combining radar, lidar, and radiometer measurements available from the ACRF sites. First, an advanced mixed-phase cloud retrieval algorithm will be developed to cover all mixed-phase clouds observed at the ACRF NSA site. The algorithm will be applied to the ACRF NSA observations to generate a long-term arctic mixed-phase cloud product for model validations and arctic mixed-phase cloud processes studies. To improve the representation of arctic mixed-phase clouds in GCMs, an advanced understanding of mixed-phase cloud processes is needed. By combining retrieved mixed-phase cloud microphysical properties with in situ data and large-scale meteorological data, the project aim to better understand the generations of ice crystals in supercooled water clouds, the maintenance mechanisms of the arctic mixed-phase clouds, and their connections with large-scale dynamics. The project will try to develop a new retrieval algorithm to study more complex mixed-phase clouds observed at the ACRF SGP site. Compared with optically thin ice clouds, optically thick middle level ice clouds are less studied because of limited available tools. The project will develop a new two wavelength radar technique for optically thick ice cloud study at SGP site by combining the MMCR with the W-band radar measurements. With this new algorithm, the SGP site will have a better capability to study all ice clouds. Another area of the proposal is to generate long-term cloud type classification product for the multiple ACRF sites. The cloud type classification product will not only facilitates the generation of the integrated cloud product by applying different retrieval algorithms to different types of clouds operationally, but will also support other research to better understand cloud properties and to validate model simulations. The ultimate goal is to improve our cloud classification algorithm into a VAP.
Download or read book On the Microphysical Properties of Ice Clouds as Inferred from the Polarization of Electromagnetic Waves written by Benjamin Cole and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Uncertainties associated with the microphysical and radiative properties of ice clouds remain an active research area because of the importance these clouds have in atmospheric radiative transfer problems and the energy balance of the Earth. In this study, an adding/doubling model is used to simulate the top of atmosphere (TOA) radiance and full Stokes vector from an ice cloud at the wavelength lambda = 865 nm with many different combinations of assumed ice habits (shapes) and different degrees of ice surface roughness, and the polarized radiance at a wide range of scattering angles is derived. Simulated results are compared with polarized radiance data from the POLDER (POLarization and Directionality of the Earth's Reflectances) instrument on board the PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) satellite. Bulk ice scattering properties are obtained by using five different size distributions collected during field campaigns ranging in effective diameter from 10 micrometers to 90 micrometers. Bulk scattering properties for the MODIS Collection 5 ice cloud product are used in this study, along with properties for two mid-latitude ice cloud models, a polar/mid-latitude ice model, and a model built for ice clouds over deep convection. Solid columns and hollow columns are used as well. The polarized radiance simulation results for the moderate surface roughness level best fit the satellite measurements for all ice models, though severely roughened ice crystals do fare well in a few cases. Hollow columns are the best fit to the satellite polarization measurements, but of the ensemble ice models, the polar/mid-latitude model at an effective diameter of 90 micrometers best fits the polarized radiance measurements for the one day of PARASOL data considered. This model should be the best to simulate ice cloud properties on a global scale.
Download or read book Investigating Arctic Cloud and Radiative Properties Associated with the Large scale Climate Variability Through Observations Reanalysis and Mesoscale Modeling written by Neil P. Barton and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation examines two decades of Arctic cloud cover data and the variability in Arctic clouds with relation to changes in sea ice using observational and reanalysis data, as well as a state-of-the-art mesoscale model. Decadal length Arctic cloud cover data are examined because of the inherent differences within these measurements that have not been explored in previous research. Cloud cover data are analyzed from regions poleward of 60°N from several sources of visual surface observations including surface remotely sensed measurements at two locations, two spaced-based passive remotely sensed datasets (Advanced Very High Resolution Radiometer Polar Pathfinder extended (APPx) and Television Infrared Observation Satellite Operational Vertical Sounder (TOVS) Polar Pathfinder (TPP)), and one reanalysis dataset (European Center for Medium-Range Weather Forecasting Reanalysis (ERA-40)) are compared. The passive remotely sensed data are sensitive to surface type. Cloud amounts from the APPx and TPP decrease with increases in sea ice concentrations. In comparison to the surface remotely sensed measurements over sea ice, the APPx and TPP cloud amounts are consistently low. The ERA-40 output cloud cover not contain a sharp decrease from water to ice surfaces, and compares reasonably with the remotely sensed surface measurements over sea ice. During the northern hemisphere winter at land stations, the TPP and ERA-40 cloud amounts are similar. This is most likely a result of the ERA-40 model using TOVS irradiances as input data. The APPx and surface cloud amounts are similar during all seasons, but they are not in precise agreement with the TPP/ERA-40 values. Cloud amounts from the ERA-40 are also most similar to surface measurements in regions where radiosonde data are used as input. Cloud radiative forcing calculated from the ERA-40 output is examined with relation to sea ice concentrations using 20 years of data. The radiative effect of clouds varies linearly with sea ice concentrations during the winter and spring. This relationship is most statistically significant in the North Atlantic region, but statistically significant relationships also occurring the northern Pacific. Statistically significant correlations do not occur during the summer months. By calculating differences in cloud amount during low and high sea ice concentration summers, greater cloud cover amounts occur with decreases in sea ice in the Arctic poleward of the Pacific at the 80 percent statistical significant level. In October, clouds are varying with relation to sea ice near the sea ice edge. One-month lag relationships are calculated to examine if the cloud radiative forcing terms are changing before or after changes in sea ice concentration. Changes in the longwave radiative forcing of clouds occurs before changes in sea ice concentrations and surface temperatures in the North Atlantic region. Cloud radiative forcing, sea ice concentrations, and surface temperatures are interrelated in this region, and may be forced by the same physical mechanism. The response of Arctic clouds and surface radiative properties is examined using the polar version of the Weather Research and Forecasting (WRF) regional model over the Laptev Sea. WRF is run for four Septembers and Octobers with anomalously low and high sea ice concentrations. Differences in the surface radiative forcing, cloud radiative forcing, cloud properties and the surface heat budget are examined for the composite low and high years. In both months, there are more clouds during low sea ice years. WRF produces more low-level liquid cloud amount during years without sea ice. The increase in clouds during low sea ice years corresponds with an increase in downwelling longwave radiation, and hence longwave cloud radiative forcing. Increases in downwelling longwave radiation during low sea ice years are canceled by the increased amount of upwelling longwave radiation, which is a result of warmer surface skin temperatures. In September, the decrease in surface albedo associated with sea ice retreat/melt results in an increased net surface radiation during low sea ice years. In October, the changes in net surface radiation are not statistically significant. After the Arctic solar night begins, during times with no sea ice, large latent and sensible heat upward surface fluxes aids in the deepening of the boundary layer and preventing the formation of the typical Arctic inversion. In WRF, the increases in cloud water liquid content and downwelling longwave radiation, in low sea ice years, seems to be a result of increased open water, while the changes in the boundary layer are the result of changes in the surface radiative fluxes.
Download or read book Earth and Mineral Sciences written by and published by . This book was released on 2000-07 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:
