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Results from the Longwave Effective Cloud Fraction in the Cloudiness Intercomparison Introduction

Description: While it may seem to be a simple quantity, cloud amount is somewhat elusive. Different types of instruments placed next to each other can give different cloud amounts because they use different parts of the spectrum, have different fields of view, sampling rates, etc. Another consideration is that cloud amount depends on the physical scale under consideration. The cloud amount appropriate for comparison to a single pyrgeometer is not likely to be useful for a grid square with 100 km sides.
Date: March 18, 2005
Creator: Takara, E.E. & Ellingson, R.G.
Partner: UNT Libraries Government Documents Department

New Mexico cloud super cooled liquid water survey final report 2009.

Description: Los Alamos and Sandia National Laboratories are partners in an effort to survey the super-cooled liquid water in clouds over the state of New Mexico in a project sponsored by the New Mexico Small Business Assistance Program. This report summarizes the scientific work performed at Sandia National Laboratories during the 2009. In this second year of the project a practical methodology for estimating cloud super-cooled liquid water was created. This was accomplished through the analysis of certain MODIS sensor satellite derived cloud products and vetted parameterizations techniques. A software code was developed to analyze multiple cases automatically. The eighty-one storm events identified in the previous year effort from 2006-2007 were again the focus. Six derived MODIS products were obtained first through careful MODIS image evaluation. Both cloud and clear-sky properties from this dataset were determined over New Mexico. Sensitivity studies were performed that identified the parameters which most influenced the estimation of cloud super-cooled liquid water. Limited validation was undertaken to ensure the soundness of the cloud super-cooled estimates. Finally, a path forward was formulized to insure the successful completion of the initial scientific goals which include analyzing different of annual datasets, validation of the developed algorithm, and the creation of a user-friendly and interactive tool for estimating cloud super-cooled liquid water.
Date: February 1, 2010
Creator: Beavis, Nick; Roskovensky, John K. & Ivey, Mark D.
Partner: UNT Libraries Government Documents Department

Two-stage Framework for a Topology-Based Projection and Visualization of Classified Document Collections

Description: During the last decades, electronic textual information has become the world's largest and most important information source available. People have added a variety of daily newspapers, books, scientific and governmental publications, blogs and private messages to this wellspring of endless information and knowledge. Since neither the existing nor the new information can be read in its entirety, computers are used to extract and visualize meaningful or interesting topics and documents from this huge information clutter. In this paper, we extend, improve and combine existing individual approaches into an overall framework that supports topological analysis of high dimensional document point clouds given by the well-known tf-idf document-term weighting method. We show that traditional distance-based approaches fail in very high dimensional spaces, and we describe an improved two-stage method for topology-based projections from the original high dimensional information space to both two dimensional (2-D) and three dimensional (3-D) visualizations. To show the accuracy and usability of this framework, we compare it to methods introduced recently and apply it to complex document and patent collections.
Date: July 19, 2010
Creator: Oesterling, Patrick; Scheuermann, Gerik; Teresniak, Sven; Heyer, Gerhard; Koch, Steffen; Ertl, Thomas et al.
Partner: UNT Libraries Government Documents Department

Impingement of Cloud Droplets on a Cylinder and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method

Description: "Evaluation of the rotating multicylinder method for the measurement of droplet-size distribution, volume-median droplet size, and liquid-water content in clouds showed that small uncertainties in the basic data eliminate the distinction between different cloud droplet-size distributions and are a source of large errors in the determination of the droplet size. Calculations of the trajectories of cloud droplets in incompressible and compressible flow fields around a cylinder were performed on a mechanical analog constructed for the study of the trajectories of droplets around aerodynamic bodies" (p. 1).
Date: September 5, 1952
Creator: Brun, R. J.; Lewis, W.; Perkins, P. J. & Serafini, J. S.
Partner: UNT Libraries Government Documents Department

Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content

Description: "Flight icing-rate data obtained in a dense and abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer" (p. 1).
Date: July 11, 1951
Creator: Perkins, Porter J. & Kline, Dwight B.
Partner: UNT Libraries Government Documents Department

A meteorological measure of maximum gust velocities in clouds

Description: Report presenting analytical considerations of the energy transformations in convective-type clouds indicate that a simple function of the height of convective activity and horizontal-temperature variations could yield a measure of the gustiness in clouds. A simplified relation that may be used to forecast the maximum effective gust velocities within convective-type clouds is developed. The analysis indicates that the method might be extended to almost all cloud types.
Date: April 1948
Creator: Gringorten, I. I. & Press, H.
Partner: UNT Libraries Government Documents Department

Icing Properties of Noncyclonic Winter Stratus Clouds

Description: Note presenting measurements of the vertical distribution of liquid water concentration and drop size made in winter stratus clouds in the absence of significant cyclonic or frontal activity. The observations indicate that the clouds are formed by turbulent mixing of the lower layers of the atmosphere, resulting in a region of constant specific humidity and adiabatic lapse rates.
Date: September 1947
Creator: Lewis, William
Partner: UNT Libraries Government Documents Department

Final Report - From Measurements to Models: Cross-Comparison of Measured and Simulated Behavioral States of the Atmosphere

Description: The ARM sites and the ARM Mobile Facility (AMF) were constructed to make measurements of the atmosphere and radiation system in order to quantify deficiencies in the simulation of clouds within models and to make improvements in those models. While the measurement infrastructure of ARM is well-developed and a model parameterization testbed capability has been established, additional effort is needed to develop statistical techniques which permit the comparison of simulation output from atmospheric models with actual measurements. Our project establishes a new methodology for objectively comparing ARM measurements to the outputs of leading global climate models and reanalysis data. The quantitative basis for this comparison is provided by a statistical procedure which establishes an exhaustive set of mutually-exclusive, recurring states of the atmosphere from sets of multivariate atmospheric and cloud conditions, and then classifies multivariate measurements or simulation outputs into those states. Whether measurements and models classify the atmosphere into the same states at specific locations through time provides an unequivocal comparison result. Times and locations in both geographic and state space of model-measurement agreement and disagreement will suggest directions for the collection of additional measurements at existing sites, provide insight into the global representativeness of the current ARM sites (suggesting locations and times for use of the AMF), and provide a basis for improvement of models. Two different analyses were conducted: One, using the Parallel Climate Model, focused on an IPCC climate change scenario and clusters that characterize long-term changes in the hydrologic cycle. The other, using the GISS Model E GCM and the ARM Active Remotely Sensed Cloud Layers product, explored current climate cloud regimes in the Tropical West Pacific.
Date: October 22, 2007
Creator: Del Genio, Anthony D; Hoffman, Forrest M & Hargrove, Jr, William W
Partner: UNT Libraries Government Documents Department

Statistical Explanation of Spontaneous Freezing of Water Droplets

Description: Note presenting a theory based on the presence of small crystallization nuclei suspended in water to explain experimental results showing that on the average, small droplets can be supercooled to lower temperatures than large ones. The average behavior of the supercooled droplets is reproduced on the basis of probability theory with an assumed distribution of crystallization nuclei with respect to the temperatures at which the nuclei cause freezing.
Date: December 1950
Creator: Levine, Joseph
Partner: UNT Libraries Government Documents Department

On the Estimation of Clear-Sky Upwelling Shortwave and Longwave

Description: Previous work (Long and Ackerman 2000; Long 2004) has concentrated on estimation of the downwelling clear-sky irradiances and the calculation of the effect of clouds on the downwelling radiative energy budget. However, cloud forcing is defined for the difference between clear- and cloudy-sky net radiation, which includes the upwelling components. Thus, if we are to estimate the surface radiative cloud forcing, the means must be developed to estimate what the upwelling shortwave and longwave irradiance would be if the clouds were not present. Estimation of the upwelling longwave (LW) is particularly troublesome in that the emitted upwelling LW is a function of the total surface energy exchange including latent and sensible heat, which is related to but not necessarily always totally driven by the radiative exchange alone, but also involves the evolving soil and vegetation properties and changes in soil moisture amounts.
Date: March 18, 2005
Creator: Long, C.N.
Partner: UNT Libraries Government Documents Department

Scale Dependence of Variability in Stratiform Clouds Based on Millimeter Wave Could Radar

Description: Internal variability of stratiform clouds is manifested on grid scales ranging from cloud resolving models to general circulation models, and its accurate formulation is one of the most important tasks in improvement of model predictions. Understanding cloud variability on different scales will help to develop and improve subgrid-scale cloud parameterizations. Information about variability is also crucial when dealing with retrieval of microphysical information from observations of volume averaged reflectivity parameters, since neglecting variability can lead to substantial biases in estimation of retrieved microphysical variables. The Atmospheric Radiation Measurement Program (ARM) operates millimeter wave cloud radar (MMCR) at the ARM Climate Research Facility over the Southern Great Plains (ACRF SGP) that provides a unique opportunity to obtain continuous observations in order to address issues of cloud variability. These data contain information on spatial and/or temporal short- and long-range correlations in cloudiness, enabling scale-by-scale (scaling) analyses over a range of hundreds of meters to hundreds of kilometers. The objective of this study is to conduct an analysis based on radar reflectivity observations of clouds over the ACRF SGP site with special emphasis on boundary layer clouds, and the effect of drizzle.
Date: March 18, 2005
Creator: Kogan, Z.N.; Kogan, Y.L. & Mechem, D.B.
Partner: UNT Libraries Government Documents Department

Final Report on NPS/CIRPAS support of DOE Classic Experiment

Description: The Department of Energy conducted the Cloud-Land Surface Interaction Campaign (CLASIC) in Poncha City Oklahoma, in June 2007. The purpose of the experiment was to study the influence of different surface conditions on properties of small cumulus clouds. The Oklahoma site provided climatologically arid surface in the western part of the state, and lush green conditions in the eastern part. The summer of 2007, however, was exceptionally wet, with flooded fields and rivers flowing over their banks. This had seriously adverse effect on the experiment. CIRPAS participated in this with its instrumented Twin Otter aircraft, flight crew and scientist. The CIRPAS instruments measured temperature, dewpoint temperature, pressure, winds, aerosol particle concentrations, aerosol size distribution, cloud droplet concentration, cloud droplet size spectra, total scatter coefficients and absorption coefficients at three different wavelengths. Additionally, CIRPAS provided measurements of aircraft location, velocity and attitude. CIRPAS reduced all the data to engineering units, quality assured the data, and submitted a coherent data set to the project’s archive. The Twin Otter flew 15 sorties from the airport in Ponca City, and characterized meteorological, aerosol and cloud conditions as well as the temperature of the underlying surface in a wide variety of conditions. Conditions ranged from deep convection and thunderstorms, to totally clear sky and stable atmosphere. Some flights were coordinated with other aircraft, such as the DOE’s G-1, which was in Ponca City simultaneously doing the CHAPS mission, the NASA King Air, which used lidar to characterize underlying aerosol and clouds, and a helicopter from Duke University, which was characterizing turbulence. Other flights were coordinated with satellite overpasses, ground-based observation sites. The field campaign took place during the month of June, 2007, and all CIRPAS data had been delivered by October that same year.
Date: March 7, 2011
Creator: Jonsson, Haflidi H
Partner: UNT Libraries Government Documents Department

[Aerial Photo of Detroit Skyline]

Description: Photograph of Detroit, Michigan out of an airplane window. Dark clouds and the moon have been superimposed above the city, and the wing of the airplane is visible on the right side of the image. Narrative by Junebug Clark: This photo is the cover image of the Joe Clark book, "Detroit: God's Greatest City" Photo by: Joe Clark, HBSS. Signed by: Joe Clark, HBSS Clark PhotoFile: 7800-111
Date: 1959
Creator: Clark, Joe
Partner: UNT Libraries Special Collections

The ARM-GCSS Intercomparison Study of Single-Column Models and Cloud System Models

Description: The Single-Column Model (SCM) Working Group (WC) and the Cloud Working Group (CWG) in the Atmospheric Radiation Measurement (ARM) Program have begun a collaboration with the GEWEX Cloud System Study (GCSS) WGs. The forcing data sets derived from the special ARM radiosonde measurements made during the SCM Intensive Observation Periods (IOPs), the wealth of cloud and related data sets collected by the ARM Program, and the ARM infrastructure support of the SCM WG are of great value to GCSS. In return, GCSS brings the efforts of an international group of cloud system modelers to bear on ARM data sets and ARM-related scientific questions. The first major activity of the ARM-GCSS collaboration is a model intercomparison study involving SCMs and cloud system models (CSMs), also known as cloud-resolving or cloud-ensemble models. The SCM methodologies developed in the ARM Program have matured to the point where an intercomparison will help identify the strengths and weaknesses of various approaches. CSM simulations will bring much additional information about clouds to evaluate cloud parameterizations used in the SCMs. CSMs and SCMs have been compared successfully in previous GCSS intercomparison studies for tropical conditions. The ARM Southern Great Plains (SGP) site offers an opportunity for GCSS to test their models in continental, mid-latitude conditions. The Summer 1997 SCM IOP has been chosen since it provides a wide range of summertime weather events that will be a challenging test of these models.
Date: October 27, 1999
Creator: Cederwall, R.T.; Rodriques, D.J.; Krueger, S.K. & Randall, D.A.
Partner: UNT Libraries Government Documents Department

Cloud classification using whole-sky imager data

Description: Clouds are one of the most important moderators of the earth radiation budget and one of the least understood. The effect that clouds have on the reflection and absorption of solar and terrestrial radiation is strongly influenced by their shape, size, and composition. Physically accurate parameterization of clouds is necessary for any general circulation model (GCM) to yield meaningful results. The work presented here is part of a larger project that is aimed at producing realistic three-dimensional (3D) volume renderings of cloud scenes, thereby providing the important shape information for parameterizing GCMs. The specific goal of the current study is to develop an algorithm that automatically classifies (by cloud type) the clouds observed in the scene. This information will assist the volume rendering program in determining the shape of the cloud. Much work has been done on cloud classification using multispectral satellite images. Most of these references use some kind of texture measure to distinguish the different cloud types and some also use topological features (such as cloud/sky connectivity or total number of clouds). A wide variety of classification methods has been used, including neural networks, various types of clustering, and thresholding. The work presented here utilizes binary decision trees to distinguish the different cloud types based on cloud feature vectors.
Date: February 1, 1995
Creator: Buch, K.A. Jr. & Sun, Chen-Hui
Partner: UNT Libraries Government Documents Department

Observations and Inferred Physical Characteristics of Compact Intracloud Discharges

Description: Compact intracloud discharges (CIDS) represent a distinct class of electrical discharges that occur within intense regions of thunderstorms. They are singular discharges that produce brief (typically 3 µs in duration) broadband RF emissions that are 20 to 30 dB more powerful than radiation from all other recorded lightning processes in the HF and VHF radio spectrum. Far field electric field change recordings of CIDS consist of a single, large-amplitude bipolar pulse that begins to rise during the RF-producing phase of the CID and typically lasts for 20 µs. During the summer of 1998 we operated a 4-station array of electric field change meters in New Mexico to support FORTE satellite observations of transient RF and optical sources and to learn more about the phenomenology and physical characteristics of CIDS. Over 800 CIDS were detected and located during the campaign. The events were identified on the basis of their unique field change waveforms. CID source heights determined using the relative delays of ionospherically reflected source emissions were typically between 4 and 11 km above ground level. Events of both positive and negative polarity were observed with events' of initially- negative polarity (indicative of discharges occurring between underlying positive and overlying negative charge) occurring at slightly higher altitudes. Within CID field change waveforms the CID pulse was often followed within a few ms by one or more smaller-amplitude pulses. We associate these subsequent pulses with the initial activity of a "normal" intracloud flash, the inference being that some fraction of the time, a CID initiates an intracloud lightning flash.
Date: February 1, 1999
Creator: Argo, P.E.; Eack, K.B.; Holden, D.N.; Massey, R.S.; Shao, X.; Smith, D.A. et al.
Partner: UNT Libraries Government Documents Department

Remote sensing of thundercloud electric fields

Description: Theoretical and experimental work was performed on emission of photons from the air within and above thunderclouds and within lightning channels. Predictions were made of the telltale emissions from ionized nitrogen molecules and these emissions were recorded. The measurements will be utilized to help to understand the nature of thundercloud-produced airglow.
Date: August 1, 1997
Creator: Borovsky, J.; Buchwald, M. & Suszcynsky, D.
Partner: UNT Libraries Government Documents Department

Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method

Description: "The rotating multicylinder method for in-flight determination of liquid-water content, droplet size, and droplet-size distribution in icing clouds is described. The theory of operation, the apparatus required, the technique of obtaining data in flight, and detailed methods of calculating the results, including necessary charts and tables, are presented" (p. 1).
Date: June 29, 1953
Creator: Lewis, William; Perkins, Porter J. & Brun, Rinaldo J.
Partner: UNT Libraries Government Documents Department