Showing papers on "Cloud computing published in 1988"
01 Jan 1988
TL;DR: The general aspects for obtaining a consistent parameterization scheme, including prediction of cloud water content, are discussed in this article, where various basic formulations are discussed individually and in conjunction; a specific approach is presented as a concrete application.
Abstract: The general aspects for obtaining a consistent parameterization scheme, including prediction of cloud water content, are discussed. Regardless of whether the condensation is convective or stratiform, the basic problem is to deduce formulations for the partitioning of converging vapor in a grid box between i) a change of the existing cloud mass, ii) a change of cloud volume and iii) a change of the vapor content of the box. The parameterizations of the processes responsible for this partitioning become different, primarily depending on whether the condensation is convective or stratiform. Those various basic formulations are discussed individually and in conjunction; a specific approach is presented as a concrete application. A brief discussion is devoted to special features related to stratocumulus and to cirrus clouds that appear to require attention in addition to the overall formulations.
177 citations
TL;DR: In this paper, a model for the scavenging of aerosol particles has been coupled with the two-dimensional form of the convective cloud model of Clark and Collaborators, which is then used to simulate a convective warm cloud for the meteorological situation which existed at 1100 LST 12 July 1985 over Hawaii; assuming an aerosol size distribution of maritime number concentration and of mixed composition with (NH4)2SO4 as the soluble compound.
Abstract: Our model for the scavenging of aerosol particles has been coupled with the two-dimensional form of the convective cloud model of Clark and Collaborators. The combined model was then used to simulate a convective warm cloud for the meteorological situation which existed at 1100 LST 12 July 1985 over Hawaii; assuming an aerosol size distribution of maritime number concentration and of mixed composition with (NH4)2SO4 as the soluble compound. A shallow model cloud developed 26 min after the onset of convection leading to moderate rain which began after 45 min and ended after 60 min. Various parameters which characterize the dynamics and micophysics of the cloud, as well as the scavenging mechanism taking place inside and below the cloud were computed during the cloud development. The computation showed that: 1) the scavenged aerosol mass became redistributed inside the cloud water as the cloud grew, whereby the main aerosol mass scavenged always remained associated with the main water mass in the c...
80 citations
TL;DR: In this paper, the mixing ratio of the cloud's condensed water is predicted as a new prognostic variable, which does not fully interact with the radiation schemes, but the aim is to predict the cloud optical properties.
37 citations
TL;DR: In this paper, the spatial distributions of gray levels (cloud reflectivities) are determined for LANDSAT Multispectral Scanner digital data using the Spatial Gray Level Co-Occurrence Matrix method.
Abstract: Statistical measures of the spatial distributions of gray levels (cloud reflectivities) are determined for LANDSAT Multispectral Scanner digital data Textural properties for twelve stratocumulus cloud fields, seven cumulus fields, and two cirrus fields are examined using the Spatial Gray Level Co-Occurrence Matrix method The co-occurrence statistics are computed for pixel separations ranging from 57 m to 29 km and at angles of 0°, 45°, 90° and 135° Nine different textual measures are used to define the cloud field spatial relationships However, the measures of contrast and correlation appear to be most useful in distinguishing cloud structure Cloud field macrotexture describes general cloud field characteristics at distances greater than the size of typical cloud elements It is determined from the spatial asymptotic values of the texture measures The slope of the texture curves at small distances provides a measure of the microtexture of individual cloud cells Cloud fields composed primar
31 citations
TL;DR: In this article, the performance of a cloud layer model in estimating solar radiation was examined for different intervals (1 to 6 h) between cloud observations for two Canadian and three European stations.
16 citations
Journal Article•
13 citations
TL;DR: In this article, a model referred to as the cloudy sky geometry (CSG) model is proposed for the description of the geometric characteristics of clouds in the sky, where clouds are modeled on a modification of the parallel relationships among upright vertical cylinders of variable diameter and height.
12 citations
TL;DR: In this article, the internal dynamics of an illuminated dust cloud of finite optical thickness is investigated, and the dependence of the radiation pressure on the optical depth makes the individual particles oscillate, in one dimension, around the accelerated centre of gravity of the cloud.
Abstract: The internal dynamics of an illuminated dust cloud of finite optical thickness is investigated. The dependence of the radiation pressure on the optical depth makes the individual particles oscillate, in one dimension, around the accelerated centre of gravity of the cloud. The cloud moves as an entity, irrespectively of the velocity dispersion of the particles and their efficiency for radiation pressure. If the optical depth does not change, i.e. if the cloud does not expand laterally, its lifetime is unlimited. A contraction caused by energy dissipation in mechanical collissions between the dust particles is expected.
The range of particle sizes which can be transported by such a “coherent cloud” is estimated, as well as the acceleration of the whole cloud. The structure of the cloud in real space and in velocity space is investigated. A comparison with the “striae” observed in the dust tails of great comets shows that the parent clouds of these striae may have been of the kind considered.
9 citations
TL;DR: This work states that the complementary nature of the bird's eye and worm's eye views of a multilayered cloud scene and the distinct and complementary advantages of high-quality cloud texture/type retrieval from the surface and aircraft and excellent spatial and temporal coverage by satellites have prompted proposals for cloud climatologies combining conventional and satellite retrievals.
Abstract: Cloud cover over the Earth is measurable using several techniques, including a trained observer, some automated ground-based system, or an aircraft or a space platform. These three views of the three-dimensional cloud scene differ in a number of ways. The surface-observing system is generally fairly close to the clouds ( 1000 km). The complementary nature of the bird's eye and worm's eye views of a multilayered cloud scene and the distinct and complementary advantages of high-quality cloud texture/type retrieval from the surface and aircraft and excellent spatial and temporal coverage by satellites have prompted proposals for cloud climatologies combining conventional and satellite retrievals. This requires careful study of the nature of conventional (surface-based) cloud observation techniques.
01 Jan 1988
TL;DR: In this paper, a review of recent field studies of cloud microphysics in a hill cap cloud and in growing cumulus clouds is presented, and the implications of the results for cloud chemical processes are discussed.
Abstract: In this paper a review is presented of recent field studies of cloud microphysics in a hill cap cloud and in growing cumulus clouds. In each case the implications of the results for cloud chemical processes are discussed. In particular it is suggested that the entrainment of dry air into the cloud from the free troposphere may reduce the lifetime of individual droplets to values considerably below that of the cloud and may introduce extra oxidant which may substantially increase the sulphate production. A new model of cloud microphysics and chemistry in a growing cumulus cloud is presented to quantify the magnitude of this effect.
TL;DR: In this paper, the authors discuss the general characteristics of daily nonrandom cloudiness and illustrate the use of satellite imagery to resolve nonrandom patterns over portions of the Rocky Mountain region of the United States.
01 Sep 1988
TL;DR: In this paper, an existing ship track detection algorithm is examined and improvements are developed and evaluated, which works well in areas with uniform cloud cover which contain well defined ship track cloud lines, but it begins to break down in regions with no ship tracks, cloud free areas and regions of transition from one cloud regime to another.
Abstract: : Anomalous cloud lines produced by stack exhaust from ships in the North Pacific Ocean basin are analyzed. These cloud lines or 'ship tracks' are observed most clearly in the channel 3 near-infrared satellite imagery obtained from the NOAA-9 AVHRR sensor. The ship tracks are produced as hot exhaust gases are expelled into the atmosphere creating an aerosol concentration higher than background areas. These aerosols serve as cloud condensation nuclei (CCN) and cause a shift in the cloud droplet distribution to a higher concentration of smaller droplets. Channel 3 AVHRR data are sensitive to cloud droplet size and show these ship tracks as an increase in radiance. An existing ship track detection algorithm is examined and improvements are developed and evaluated. The existing algorithm works well in areas with uniform cloud cover which contain well defined ship track cloud lines. However, it begins to break down in areas with no ship tracks, cloud free areas and regions of transition from one cloud regime to another. An improved algorithm is developed which is able to improve the analysis in these problem areas. Comparison of this algorithm with the original algorithm shows a twofold increase in the percentage of valid ship tracks detected. Neither algorithm is capable of fully representing all the ship track pixels in given image but the feasibility of this type of analysis is clearly shown. The detection algorithm is also adapted to evaluate large scale areas of data as a precursor to the development of a ship track cloud climatology for the North Pacific Ocean. While computer processing time becomes a limitation, some ability is shown for the analysis of large scale areas.
01 Jan 1988
01 Jan 1988
TL;DR: The purpose of the CIDOS-88 Executive Summary is to expeditiously inform the entire DoD cloud impacts community, i.e., decision makers, systems developers, program managers, and environmental researchers as mentioned in this paper.
Abstract: : The purpose of this Executive Summary is to expeditiously inform the entire DoD cloud impacts community, i.e., decision makers, systems developers, program managers, and environmental researchers, of the purpose, presentations, discussions, and conclusions of CIDOS-88. The following summaries are included: (1) cloud impacts on surveillance, studies and analysis, and the post-attack environment; (2) high energy laser cloud interactions; (3) cirrus clouds and lidar detection of clouds; and (4) cloud modeling, prediction, data bases.
24 Aug 1988
TL;DR: In this article, an average optical depth for the cloud is first calculated by use of LOWTRAN6 with specified aerosol optical properties, and then combined with a multiple scattering model which uses a two stream approximation.
Abstract: The presence of clouds affects most infrared (IR) military sensors. Foreground clouds degrade or occult target signatures and background clouds clutter a scene. Models used to assess or predict system performance must include important features of clouds: absorption, single and multiple scattering, thermal emission, partial transmission and spatial non-uniformity. Exact models which account for the details of cloud microphysics require large computation times and inputs which are difficult to obtain. Aerodyne has developed an approximate model which produces realistic cloud scenes in a reasonable amount of computer time. An average optical depth for the cloud is first calculated by use of LOWTRAN6 with specified aerosol optical properties. These properties are combined with a multiple scattering model which uses a two stream approximation. This model assumes that 1) the cloud layer is a parallel plane and infinite, 2) there is a constant single scattering albedo which may be wavelength dependent, 3) there is local thermodynamic equilibrium between particles and atmospheric gases, and 4) there is a uniform cloud temperature and emissivity. The result is an average cloud radiance spectrum along a specified line-of-sight. The line-of-sight may be up-looking or down-looking, and up to two cloud layers may be present. Spatial non-uniformities are incorporated by use of a cloud texture model based on a 1/f spectral shaping of spatial variations. The final scene including the effect of the atmospheric path from the cloud to the observer is in-band integrated and recorded as a grid of radiances with an associated depth map for use in a target/background interface model.
25 Jan 1988
TL;DR: A class of cloud detection algorithms that are well suited for implementations that provide ultrafast information about current cloud conditions and can generate information in less than five seconds after the sensor data are received are described.
Abstract: This paper describes a class of cloud detection algorithms that are well suited for implementations that provide ultrafast information about current cloud conditions. The algorithms can work on a variety of sensor data including data from satellites, radars and all-sky cameras. Using currently available VLSI technology, the algorithm implementations can generate information in less than five seconds after the sensor data are received.
Journal Article•
01 Jan 1988
TL;DR: In this article, a review of recent field studies of cloud microphysics in a hill cap cloud and in growing cumulus clouds is presented, and the implications of the results for cloud chemical processes are discussed.
Abstract: In this paper a review is presented of recent field studies of cloud microphysics in a hill cap cloud and in growing cumulus clouds. In each case the implications of the results for cloud chemical processes are discussed. In particular it is suggested that the entrainment of dry air into the cloud from the free troposphere may reduce the lifetime of individual droplets to values considerably below that of the cloud and may introduce extra oxidant which may substantially increase the sulphate production. A new model of cloud microphysics and chemistry in a growing cumulus cloud is presented to quantify the magnitude of this effect.
25 Jan 1988
TL;DR: This paper describes how a technique using metric (Euclidean distance) statistical methods is applied in the detection and subsequent verification of cloud fields.
Abstract: A primary goal of satellite cloud analysis is to objectively detect the presence of a cloud field and to identify its spatial structure. Several different classical non-metric algorithms ex-ist which, to varying degrees, approach this goal. This paper describes how a technique using metric (Euclidean distance) statistical methods is applied in the detection and subsequent verification of cloud fields. To quantitatively and objectively determine the effectiveness of several different cloud detec-tion algorithms, an inferential metric statistical technique is applied. This method, termed Multi-Response Blocking Pro-cedures (MRBP), compares the results of the detection algo-rithms with a verification data set, resulting in a measure of agreement and a level of significance. The MRBP results are presented and discussed.
12 Sep 1988