Showing papers on "Cloud computing published in 1989"

C0 2 and climate: a missing feedback?

Abstract: THE potential of changes in cloud properties to modulate climate perturbations is well known1,2. Changes in cloud amount and cloud height3, cloud radiative properties4–6 and cloud condensation nuclei7 (CCN) have all been recognized as possible sources of climate feedbacks. Here we report results of simulations that indicate that the changes of state of cloud water may provide a substantial negative feedback on climate. The feedback is concen-trated in mid-latitudes and affects both the magnitude and distribu-tion of the climate change expected from increases in 'greenhouse' gases. Improved measurements and parameterizations of cloud processes are needed to quantify this process.

Fractal Statistics of Cloud Fields

Abstract: Landsat Multispectral Scanner (MSS) and Thematic Mapper (TM) data, with 80 and 30 m spatial resolution, respectively, have been employed to study the spatial structure of boundary-layer and intertropical convergence zone (ITCZ) clouds The probability distributions of cloud areas and cloud perimeters are found to approximately follow a power-law, with a different power (ie, fractal dimension) for each cloud type They are better approximated by a double power-law behavior, indicating a change in the fractal dimension at a characteristic size which depends upon cloud type The fractal dimension also changes with threshold The more intense cloud areas are found to have a higher perimeter fractal dimension, perhaps indicative of the increased turbulence at cloud top A detailed picture of the inhomogeneous spatial structure of various cloud types will contribute to a better understanding of basic cloud processes, and also has implications for the remote sensing of clouds, for their effects on remote sensing of other parameters, and for the parameterization of clouds in general circulation models, all of which rely upon plane-parallel radiative transfer algorithms

Measuring cloud properties from space: a review

Abstract: A brief review of observations of clouds using satellites highlights open issues and directions for future studies. The key one is improved treatment of the effects of small-scale spatial inhomogeneity in remote sensing data analyses and in the treatment of radiation in climate models, though studies and observations of the spectral dependence of cloud-radiation interactions are also limited. Significant progress in understanding the role of clouds in climate, especially regarding cloud-radiation budget relationships, is expected in the next several years because of an unprecedent suite of global and regional observation and analysis programs.

Retrieval of Cloud Parameters from Satellite Sounder Data: A Simulation Study

Abstract: Estimates of cloud-top pressure and effective fractional cloud cover may be retrieved from satellite infrared sounder data. This paper presents the results of a simulation study which provides some insights into the relative performance of different retrieval methods and of different combinations of spectral channels. The “minimum residual method,” a variant of a technique described previously by other authors, is presented. It is applied here to groups of HIRS-2 channels and some aspects of its performance for different combinations of channels are examined using simulated data. It is also compared with the “radiance rationing method.” Calculations suggest that the minimum residual method is comparable in performance to the radiance rationing method for high cloud but better for midlevel cloud. The relationship (and relative performance) of these methods to that used operationally to assign pressures to cloud tracers in Meteosat data is also discussed. The methods presented are for retrieving cl...

Analysis of Polar Clouds from Satellite Imagery Using Pattern Recognition and a Statistical Cloud Analysis Scheme

Abstract: The analysis of cloud cover in the polar regions from satellite data is more difficult than at other latitudes because the visible and thermal contrasts between the cloud cover and the underlying surface are frequently quite small. Pattern recognition has proven to be a useful tool in detecting and identifying several cloud types over snow and ice. Here a pattern recognition algorithm in combined with a hybrid histogram-spatial coherence (HHSC) scheme to derive cloud classification and fractional coverage, surface and cloud visible albedos and infrared brightness temperatures from multispectral AVHRR satellite imagery. The accuracy of the cloud fraction estimates were between 0.05 and 0.26, based on the mean absolute difference between the automated and manual nephanalyses of nearly 1000 training samples. The HHSC demonstrated greater accuracy at estimating cloud friction than three different threshold. methods. An important result is that the prior classification of a sample may significantly im...

The management of end-user computing

Abstract: End users can be classified into six distinct types. Each of them needs differentiated education, support, and control from the Information Systems function. To support a large number of their applications a new computing environment, “the third environment” must be developed by Information Systems (I/S) management. Close attention must also be paid by I/S management to the need to involve “functional support personnel” (end users in each functional area who spend most of their time programming and aiding other end users) in the I/S end user management process.

Automated Visibility & Cloud Cover Measurements with a Solid State Imaging System

Abstract: : This Final Report, under Contract No. F19628-84-K-0047, summarizes the development status of two computer-controlled, video-based imaging systems, their initial deployment and the preliminary application of their output data for the objective determination of cloud free paths of sight, total cloud cover, and sector visibilities. The research supporting these tasks has been a multi- year activity conducted at the Scripps Institution of Oceanography under the sponsorship of the Air Force Geophysics Laboratory. The effort has been directed toward the development of two related systems, one for the automatic assessment of total cloud cover and its related distributional statistics, and the other for the automatic determination of local sector visibilities. Both systems involve the use of similar hardware for image acquisition and manipulation, but quite different analytics and control algorithms, thus they are discussed separately in this Final Report. The development status at the conclusion of this contract interval is such that two prototype systems, the Whole Sky Imager which is used for cloud cover assessments and the Automatic Horizon Scanner which is used for visibility determinations, are built, operational in several locations, and are producing image oriented data bases appropriate for computer analysis. Preliminary analytic algorithms for the use of these data in automated processes have been developed and are undergoing refinement. (RRH)

Models of cloud chemistry

Abstract: Clouds and precipitation systems play a very important role in the transformation and redistribution of chemical species in the atmosphere. Modeling of cloud chemistry is a complicated subject not only because chemistry in clouds is very complex, but also because cloud chemical processes are highly dependent on the microphysics and dynamics of clouds. A general cloud chemistry model must take into consideration the wide range of temporal and spatial scales over which cloud microphysical and dynamical processes take place. In this paper, a review of the basic cloud chemical and microphysical processes are presented. Special emphasis is given to the interactions between chemical and microphysical processes, and to considerations which may lead to model simplifications. SO 2 and NO x chemistries are used as the main examples, a subject of interest in air pollution and acid rain research. A summary of recent modeling work is also presented. DOI: 10.1111/j.1600-0889.1989.tb00121.x

The effect of spatial resolution upon texture-based cloud field classifications

Abstract: The loss of cloud-classification accuracy as a function of spatial resolution is assessed by investigating the variation of textural measures as a function of spatial resolution. Landsat MSS imagery is progressively averaged to produce degraded imagery of 1/8-km, 1/4-km, 1/2-km, and 1-km spatial resolution, and textural measures are computed from the Gray Level Difference Vector (GLDV) approach described by Chen et al. (1989). It is found that the classification accuracies obtained using the 1/8-km spatial resolution data are similar to those obtained using the full-resolution (1/16 km) texture measures, indicating that there is no advantage in using even higher spatial resolution 30-m Landsat Thematic Mapper and 10-m SPOT imagery for cloud classification.

Apparatus and method for maximizing production of heat, gas, and electricity through the acceleration of hydrogen dissociation

Abstract: An apparatus for inducing and accelerating hydrogen dissociation in a cloud generated from feedstock fed into a chamber defined by the apparatus is provided. The apparatus includes a device for thermally stimulating the feedstock to generate the cloud, a device for localizing the cloud within the chamber, a device for electrically stimulating the localized cloud, and a device for photonically stimulating the localized cloud. A method is also provided.

Synoptic Weather Patterns Associated with the Milwaukee, Wisconsin Flash Flood of 6 August 1986

Abstract: A flash flood occurred at Milwaukee, Wisconsin on 6 August 1986 as a result of >6 in. (15.2 cm) of rain, much of it falling over a 2-h period. Several possible contributing factors to the excessive rainfall are addressed, as well as a brief overview of the radar imagery and the local National Weather Service (NWS) forecasts issued during the event. Conventional weather analyses and infrared satellite imagery are used to describe the synoptic-scale weather patterns and cloud features associated with the flash flood. The synoptic patterns are compared with a meteorological composite for heavy rain-producing weather systems associated with relatively warm-topped cloud signatures imbedded in comma-shaped cloud features, as described by Spayd (1982). This composite is referred to as a cyclonic circulation system (CCS). A comparison between the observed synoptic patterns and those predicted by the operational numerical model forecasts is also discussed. A climatological survey is performed to document ...

Imagery Randomized Block Analysis (IRBA) Applied to the Verification of Cloud Edge Detectors

Abstract: A recently developed statistical method is described for evaluating the effectiveness of numerical models. This method is applied to the verification of the effectiveness of satellite imagery cloud edge detectors. Digital satellite data are objectively modeled as cloud/no-cloud imagery using three different edge detection techniques. The imagery resulting from each technique is then quantitatively compared to a verification image through a recently developed imagery analysis method termed Imagery Randomized Block Analysis. The method also provides an agreement measure for objectively choosing a situationally effective technique among several competitors.

Two Automated Methods to Derive Probability of Precipitation Fields over Oceanic Areas from Satellite Imagery

Abstract: Two methods of deriving probability of precipitation fields (PP) over oceanic areas are presented and compared. The cloud fields are analyzed at the scale of ∼130–150 km from satellite visible and infrared imagery and collocated with ship observations of present weather. Method 1 is based on a detailed cloud classification scheme in 20 classes: a mean PP is determined for each cloud class. Method 2 assigns a PP based on cloud top temperature and mean cloud albedo only. For both methods, a normalization with respect to cloud fraction is applied. Method 1 involves more cloud field descriptors than Method 2, but the latter is simpler to implement and much faster. The PPs assigned to individual cloud fields vary between 0% and 65%. The importance of the visible sensor is clearly demonstrated, i.e., infrared-only techniques will be much less accurate. For real-time applications, the two methods provide similar results except for some specific cloud classes where maximum differences reach 13%, due to t...

The Numerical Modeling of Ice-Phase Cloud Seeding Effects in a Warm-Base Cloud: Preliminary Results

Abstract: A numerical simulation of a warm-base cloud in the southeastern United States has resulted in a vigorous cloud development, much in agreement with observations by radar and aircraft on that day (20 July 1986). The case has been rerun with all of the ice processes turned off and vigorous growth still occurs. The natural ice processes enhance the cloud cell development and produce about 12% more precipitation. Simulated cloud seeding of the natural cloud case [testing both silver iodide (Agl) and solid carbon dioxide (C02)] produces about 5% less precipitation from this large convective cloud. The same sounding is used but with decreased vapor flux, to produce a smaller warm-base cloud. Simulated cloud seeding of that cloud results in 12% increases in precipitation, illustrating that the dynamics of the cloud are important for determining the seeding results.

A Cloud Climatology for the North Pacific Area Centered at Shemya, Alaska

Abstract: : A cloud climatology data set for the North Pacific area is presented based on monthly statistics of mean cloud percent and frequency of occurrence of cloud amount for 18 grid-point locations within approximately 1000 km of Shemya, Alaska. The cloud statistics are derived from the Air Force 3D-Nephanalysis Global Cloud Archive (3D-NEPH Model) for the period 1977 to 1983. These cloud statistics, together with atmospheric temperature profiles derived from the Air Force Summarized Analysis Data Set, are used to determine estimates of cloud top heights and temperatures for representative months at the various locations.

Classification of storms based on their boundaries and cloud top temperatures using satellite imagery

Abstract: A system for interpreting and classifying severe weather patterns is presented. The system uses several image-processing and pattern-recognition techniques to detect storms in satellite cloud cover imagery. It performs several basic satellite image-interpretation tasks, i.e. cloud boundary detection, cloud top temperature and height estimation, cloud systems motion analysis, and storm classification. Some preliminary results on actual satellite images are presented. >

Infrared Cloud Scene Radiance Model

Abstract: The development and evaluation of algorithms to detect targets against cloud backgrounds requires a comprehensive understanding of the clutter properties such as the radiance distributions, textures, edge effects, etc A number of measurement programs are collecting data for this purpose However they are limited by the vast amounts of data required, and their limited resources for obtaining the data This paper will describe and show results from a first principles infrared cloud scene radiance model The work is sponsored by the Naval Surface Warfare Center (NSWC) through a Small Business Innovative Research Program (SBIR) to support IRAMMP (Infrared Analysis Modeling and Measurement Program -- formerly BMAP) as part of the Navy's Infrared Search and Track effort The model is designed to handle arbitrary viewing geometries, atmospheric conditions, and sensor parameters The output is a two dimensional (n x m pixels) scene radiance map which can be used by system designers, data takers, and analysts

Satellite cloud retrieval - Past, present, future

Abstract: Satellite cloud observation is reviewed, including past accomplishments, current problems, and possible future developments. Past and current cloud retrieval algorithms are discussed, noting efforts to overcome various problems associated with cloud retrieval. The Hybrid Bispectral Threshold Method (Minnis and Harrison, 1984), the CO2 slicing algorithm (Chahine, 1974) and the ISCCEP algorithm (Rossow et al., 1985) are considered. An error analysis is presented for the determination of reference cloud fraction from Landsat TM data. The implications of the preliminary results from the First ISCCP Regional Experiment are examined and plans for future research projects are given.