Showing papers on "Cloud computing published in 1991"

ISCCP Cloud Data Products

Abstract: The operational data collection phase of the International Satellite Cloud Climatology Project (ISCCP) began in July 1983. Since then, visible and infrared images from an international network of weather satellites have been routinely processed to produce a global cloud climatology. This report outlines the key steps in the data processing, describes the main features of the data products, and indicates how to obtain these data. We illustrate some early results of this analysis.

The Polarization Lidar Technique for Cloud Research: A Review and Current Assessment

Abstract: The development of the polarization lidar technique is reviewed, and the current capabilities and limitations of the technique for the cloud research are discussed. At present, polarization lidar is a key component of climate-research programs designed to characterize the properties of cirrus clouds and is an integral part of multiple remote-sensor studies of mixed-phase cloud systems such as winter mountain storms, making it possible to discriminate between cloud phases and to identify some particle types and orientations. Recent theoretical approaches involving ice crystal ray-tracing and cloud microphysical-model simulations are expected to increase the utility of the polarization lidar technique.

Response of the National Center for Atmospheric Research community climate model to improvements in the representation of clouds

Abstract: A new parameterization for the shortwave radiative properties of water clouds and the European Centre for Medium-range Weather Forecasts (ECMWF) cloud prediction scheme have both been included in the National Center for Atmospheric Research (NCAR) community climate model. The techniques employed to treat the contribution by water vapor absorption to the cloud radiative properties, the overlaps between cloud layers, and the spectral dependence of the properties are described, and comparisons are made with a more detailed radiation code. Only minor adjustments were necessary to implement the cloud prediction scheme. Results from a suite of integrations are used to examine the effect on model simulations. There are improvements in the model's temperature structure and in the radiation budget and cloud radiative forcing when compared with results from the Earth Radiation Budget Experiment. It is shown that the changes in the cloud distribution over the subtropical oceans induce changes not only in the surface radiative fluxes but also in the surface turbulent fluxes, through modifications to the boundary layer stability. The turbulent fluxes change in such a way as to maintain the cloud. While the cloud distributions in these areas appear realistic, it is argued that important physical processes are ignored by the model and that a more comprehensive formulation of the cloudy boundary layer is required.

Analysis of Global Cloud Imagery from Multiple Satellites

Abstract: Synoptic images of the global cloud field have been created from infrared measurements taken aboard tour geostationary and two polar-orbiting platforms simultaneously observing the earth. A series of spatial and temporal interpolations together with data reliability criteria are used to composite data from the individual satellites into synoptic images of the global cloud pattern. The composite Global Cloud Imagery (GCI) have a horizontal resolution of about half a degree and a temporal resolution of 3 h, providing an unprecedented view of the earth's cloud field. Each composite image represents a nearly instantaneous snapshot of the global cloud pattern. Collectively, the composite imagery resolve, on a global basis, most of the variability associated with organized convection, including several harmonies of the diurnal cycle. The dense and 3-dimensional nature of the GCI make them a formidable volume of information to treat in a practical and efficient manner. To facilitate analysis of global c...

The Earth Observing System Data and Information System

Abstract: The system is described in terms of the broad context of scientific cooperation and research which are facilitated by the architecture designed and the nature of the generated data. The Earth Observing System Data and Information System (EOSDIS) is composed of earth-science and applications data systems which archive global-change data and distribute the information to system users. Several archive centers catalogue selected Pathfinder data sets and generate new data products (such as maps of sea ice, cloud studies, etc.) with consistent calibration of all data. The schedule of three versions of EOSDIS is discussed with reference to the system architecture, programmatic plans, and data policy. The critical issue for EOSDIS is international cooperation to sponsor an infrastructure of global change data of this magnitude for public benefit and scientific research.

Studies concerning the empirical relationship of cloud shade to point cloudiness (Romania)

Abstract: This paper analyses the accuracy of three simple relationships of cloud shade (CS) to point cloudiness (PC). 1740 pairs of monthly average values (CS, PC) from twenty-nine weather stations of Romania were used. The following statistical indicators of accuracy were used: the mean bias error, the mean absolute error and the root mean square error. Also, a bootstraping technique provided a general way to evaluate the confidence and significance associated with each of the statistical indicators of accuracy. The paper deals with the accuracy of the empirical relationships when applied in other areas and time intervals than the ones where the relations were determined.

Windage-gauging method and apparatus for hunters

Abstract: A wind gauge includes silica particles dispensed from their container as a floating cloud which is carried along by ambient wind and thus illustrates wind speed and direction. The particulate media may also include a mixture of silica particles and thermoplastic color-pigmented particles, so that the floating cloud is colored and thus more easily visible. The particles may also embody a scent and be used to form a scent trail as they are carried along by the wind and as they gradually settle out of the air.

A neural network approach to cloud detection in AVHRR images

Abstract: The problem of identifying clouds and fog areas from advanced very high resolution radiometer (AVHRR) images using a neural network approach is used. The backpropagation paradigm was used to train many different architectural configurations of the neural network to classify the cloud content of an 8*8-pixel window in an image into five categories (ranging from 100% cloudy to 0% cloudy). The results indicate a large range in the performance of the different architectures. The most successful architectural configuration was used to create cloud masks for a series of AVHRR images. The cloud masks generated compared favorably with a trained analyst and other automated techniques. >

Fault-Tolerant Computing Systems

Abstract: A concept of responsive computer systems is presented. The emerging responsive systems demand fault-tolerant and real-time performance in parallel and distributed computing environments. A new design framework for responsive systems is introduced. It is based on a fundamental problem of consensus. Then, a new measure of responsiveness for specifying fault tolerance and real-time requirements is described. Next, the design methodologies for fault-tolerant, real-time and responsive systems are discussed, and novel techniques for introducing redundancy for improved performance and dependability are illustrated.

Landsat Observations of Fractal Cloud Structure

Abstract: LANDSAT Thematic Mapper (TM) data, with 30m spatial resolution, has been employed to study the spatial structure of boundary-layer and ITCZ clouds. Statistical parameters characterizing the cloud size, shape, and spacing have been determined. The probability distributions of cloud areas and cloud perimeters are found to be approximately power-law, with the power related to the fractal dimension. Stratocumulus clouds conform to a single power more closely than do fair weather cumulus, which exhibit a clear change in the fractal dimension at a diameter of about 0.5 km. The fractal dimension also changes with the reflectivity threshold. As the threshold is raised from cloud base to cloud top, the perimeter fractal dimension increases, perhaps indicative of the increased turbulence at cloud top. The distribution of nearest-neighbor spacings between cloud centers is shown to deviate from that expected for independendy distributed centers due to cloud clustering. The cloud spacing distribution is better approximated by a Levy flight. Results of this study are being used to develop statistical simulations of broken cloud fields. Properties of the associated radiation fields will then be computed by Monte Carlo methods.

Illinois precipitation research : a focus on cloud and precipitation modification

Abstract: At the heart of the 40-year atmospheric research endeavors of the Illinois State Water Survey have been studies to understand precipitation processes in order to learn how precipitation is modified purposefully and accidentally, and to measure the physical and socioeconomic consequences of cloud and precipitation modification. Major field and laboratory activities of past years are briefly treated as a basis for describing the key findings of the past ten years. Recent studies of inadvertent and purposeful cloud and rain modification and their effects are emphasized, including a 1989 field project conducted in Illinois and key findings from an on-going exploratory experiment addressing cloud and rain modification. Results are encouraging for the use of dynamic seeding on summer cumuliform clouds of the Midwest. Typical in-cloud results at −10°C reveal multiple updrafts that tend to be filled with large amounts of supercooled drizzle and raindrops. Natural ice production is vigorous, and initial concentrat...

Solar Radiative Fluxes for Realistic Extended Broken Cloud Fields above Reflecting Surfaces

Abstract: Structural properties and solar radiative fluxes for broken, inhomogeneous cloud fields (primarily fairweather cumulus) are examined from the point. of view of sub--grid parameterization for global climate models (GCMs). AVHRR satellite visible and infrared radiances (256x256 kIn images) display almost identical one and two-dimensional wavenumber spectra. For scales greater than ",4 km, radiance spectra follow k-1 to k-5/3 where k is wavenumber (at scales greater than ",40 kIn, radiance spectra for stratocumulus and stratocumulus of open polygonal cells behave as white noise). At scales between ",4 Ion and ",2 km, spectra follow ",k-4. Aircraft observations of cloud microphysics and temperature, however, .suggest that these fields follow closely Kolmogorov's classic k-5/3 law down to at least ",120 m. The dramatic scaling change in radiance fields may, ther~rore, be due to horizontal variation in the vertical integral of liquid water content. Based on the empirical data, a phenomonological scaling cloud field model which produces three different forms of a cloud field is developed and demonstrated. The cloud fields produced by this model are used ultimately in a three-dimensional atmospheric Monte Carlo photon transport model which is developed and validated. Also, two methods of including an underlying reflecting surface are developed and validated. Using the models mentioned above, fluxes for various scaling, random,

Classification of Cloud Types Based on Spatial Textural Measures Using Noaa-Avhrr Data

Abstract: The United States Navy has a requirement for real time cloud analysis and classification as part of a nowcasting capability. The use of texture me asures in addition to standard Advanced Very High Resolution Radiometer (AVHRR) channel radiances is explored to provide an improved cloud analysis. Nowcasting delivers a very short term (2 to 4 hours) weather forecast for operational use. Therefore, speed and accuracy of computation are both critical. This research effort resulted in the development of multi-spectral textural cloud type detection algorithm. Several statistical textural measures were investigated in order to select the most appropriate subset of textures suitable for cloud classification. The algorithm was tested on a NOAA-AVHRR data set over the Pacific ocean near the coast of California.

Neural Network Methodologies and Their Potential Application to Cloud Pattern Recognition.

Abstract: : Six artificial neural network models are explored as potential methodologies for the automated interpretation of satellite cloud images. The Multi-layer Perceptron Network is chosen to be the most applicable to the image interpretation problem. A complete, mathematical description of the methodology is presented. The neural network's classification capability is demonstrated using simple geometric patterns and alphabetic characters. A more complex test using GOES infrared imagery shows that the neural network can distinguish 53 of 54 large-scale cloud patterns. An architecture for a complete, automated cloud feature recognition system is proposed.

The Simulation of Cloud Seeding Effects using Numerical Cloud Models

Abstract: One of the technological and scientific developments helping to quantify cloud results is cloud models which, in some instances, require nearly as much computing power as the larger scale climate and general circulation models of the atmosphere. Cloud seeding simulations have been conducted in multi-dimensional, time-dependent cloud models over the past 10 to 15 years, and are increasing in frequency now as computers are more able to handle the task. This presentation will review some of the results obtained. The cloud models are sets of nonlinear partial differential quations, representing the conservation of mass, momentum, and energy. All phases of water are considered. The models treat all types of clouds, from severe convection with hail to gentle upslope motion stratus clouds with snow and light rain, on to non-precipitating clouds. The ice processes are emphasized in both field operations and modeling. Cloud seeding is simulated by changing the initiation and number of ice crystals in the cloud. The most realistic way to make this change is via the simulation of seeding agents, such as silver iodide or solid carbon dioxide, and their interactions with supercooled liquid water and water vapor. The results of the modeling have indicated support for the basic hypotheses of cloud seeding and have shown quantitatively the signals to be expected from the seeding.

An Interactive System for Analysis of Global Cloud Imagery

Abstract: Synoptic images of the global cloud pattern composited from six contemporaneous satellites provide an unprecedented view of the global cloud field. Having horizontal resolution of about 0.5 deg and temporal resolution of 3 h, the global cloud imagery (GCI) resolves most of the variability of organized convection, including several harmonics of the diurnal cycle. Although the GCI has these attractive features, the dense and 3D nature of that data make it a formidable volume of information to treat in a practical and efficient manner. An interactive image-analysis system (IAS) has been developed to investigate the space-time variability of global cloud behavior. In the IAS, data, hardware, and software are integrated into a single system providing a variety of space-time covariance analyses in a menu-driven format. Owing to its customized architecture and certain homogeneous properties of the GCI, the IAS calculates such quantities effectively. Many covariance statistics are derived from 3D data with interactive speed, allowing the user to interrogate the archive iteratively in a single session. The 3D nature of those analyses and the speed with which they are performed distinguish the IAS from conventional image processing of 2D data.

Inadvertent modification of atmospheric electricity

Abstract: Human activities on different scales of space and time cause a change in electrical state of the atmosphere or cloud electrification. Ionization and nuclei introduced into the atmosphere by human activities may contribute to such modification. Urbanization, desertification and air pollution, which modify cloud electrification characteristics, can influence the evolution of precipitation and dynamics of clouds.

A surface-based cloud observing system

Abstract: The paper describes a surface-based system, called the Cloud Observing System (COS), that was developed for measurements of the dynamical and thermodynamical properties of clouds and of their interaction with the large-scale environment, by combining several remote sensors and in situ systems. The atmospheric parameters that will be measured by COS include precipitation, the velocity and direction of wind, the cloud liquid water, the low-level winds and turbulence structure, integrated liquid and vapor quantities, the temperature and water profiles, the cloud radiance and the cloud base temperature, irradiances at the surface, the low-level temperature profile, the cloud-base height, and the cloud fraction; video cameras will provide visual records of clouds.

Cloud seeding in California: an evaluation of the rainshadow effect of weather modification projects

Abstract: Much of the early scientific information on cloud seeding and downwind influences was based on single experiments, programs extending over a season, or project durations of a few years. Today, some cloud seeding projects have been operating for thirty years or more; and these long-term programs provide an improved data base for assessing the spatial influences of cloud seeding activities. The purpose of this paper is to test the hypothesis that cloud seeding in on e locale results in the creation of a rainshadow effect, that is precipitation deprivation downwind from the target are a of the cloud seeding activity. Two long-term cloud seeding projects in California are analyzed.

Processing of Cloud Databases for the Development of an Automated Global Cloud Climatology

Abstract: : This study describes data sources, data processing activities, compression, prediction, and blending of cloud databases being utilized in the development of an automated fast retrieval global cloud climatology. Correlation of sky cover over a sky dome from up-looking whole sky photos and from down- viewing satellite data is demonstrated. An updated documentation of a whole sky photo database and documentation of two geographic databases optimized for use on small PCs are also provided. Several FORTRAN subroutines pertinent to cloud data processing are listed in the Appendix.