Showing papers on "Cloud computing published in 1999"

Grids as production computing environments: the engineering aspects of NASA's Information Power Grid

Abstract: Information Power Grid (IPG) is the name of NASA's project to build a fully distributed computing and data management environment-a Grid. The IPG project has near, medium, and long-term goals that represent a continuum of engineering, development, and research topics. The overall goal is to provide the NASA scientific and engineering communities a substantial increase in their ability to solve problems that depend on use of large-scale and/or dispersed resources: aggregated computing, diverse data archives, laboratory instruments and engineering test facilities, and human collaborators. The approach involves infrastructure and services than can locate, aggregate, integrate, and manage resources from across the NASA enterprise. An important aspect of IPG is to produce a common view of these resources, and at the same time provide for distributed management and local control. In addition to addressing the overall goal of enhanced science and engineering, there is a potential important side effect. With a large collection of resources that have common use interfaces and a common management approach, the potential exists for a considerable pool of computing capability that could relatively easily, for example, be called on in extraordinary situations such as crisis response.

Clouds as Seen by Satellite Sounders (3I) and Imagers (ISCCP). Part I: Evaluation of Cloud Parameters

Abstract: The improved initialization inversion (3I) algorithms convert TIROS-N Operational Vertical Sounder observations from the National Oceanic and Atmospheric Administration (NOAA) polar-orbiting environmental satellites into atmospheric temperature and water vapor profiles, together with cloud and surface properties. Their relatively good spectral resolution and coverage make IR sounders a very useful tool for the determination of cloud properties both day and night. The iterative process of detailed comparisons between cloud parameters obtained from this global dataset, which is available in the framework of the NOAA–National Aeronautics and Space Administration Pathfinder Program, with time–space-collocated observations of clouds from the recently reprocessed International Satellite Cloud Climatology Project (ISCCP) dataset has led to an improved 3I cloud analysis scheme based on a weighted-χ2 method described in the second article of this series. This process also provides a first evaluation of th...

Cloud Cover in the ECMWF Reanalysis

Abstract: Data from reanalyses recently carried out by several climate and numerical weather prediction centers will find a variety of applications in different branches of atmospheric science. A careful evaluation of the many aspects of these datasets is a prerequisite for their successful use. This paper describes the implementation of a fully prognostic cloud scheme into the ECMWF reanalysis system and provides a first assessment of the simulation of cloud cover by comparing it with monthly mean cloud cover derived from satellite observations in the context of the International Satellite Cloud Climatology Project for the years 1983–90. Special emphasis is put on the major cloud regimes and their intra- and interannual variation. The main deficiencies identified are an underestimation of extratropical cloud cover over the oceans by 10%–15%, an overestimation of trade wind cumulus cover by about 10%–15%, an underestimation of stratocumulus off the west coasts of the subtropical continents by 15%, and an u...

Realizing the performance potential of the virtual interface architecture

Abstract: The Virtual Interface (VI) Architecture provides pr otected userlevel communication with high delivered bandwidth a nd low permessage latency, particularly for small messages. The VI Architecture attempts to reduce latency by eliminat ing user/kernel transitions on routine data transfers and by allowi ng direct use of user memory for network buffering. This results in significantly lower latencies than those achieved by network prot ocols such as TCP/IP and UDP. In this paper we examine the low-le vel performance of two VI implementations, one implemen ted in hardware, the other implemented in device driver so ftware. Using a set of low-level benchmarks, we measure bandwidth , la ency, and processor utilization as a function of message siz for the GigaNet cLAN and Tandem ServerNet VI implementation s. We report that both VI implementations offer significa nt performance advantage relative to the corresponding UDP impleme ntation on the same hardware. We also investigate the problem s associated with delivering this performance to distributed app lications running on clustered multiprocessor workstations. Using an existing MPI library implemented using UDP as a bas eline, we explore several performance and implementation issu es that arise when adapting this library to use VI instead of UDP . Among these issues are memory registration costs, polling vs. blocking, reliability of delivery, and memory-to-memory copyi ng. By eliminating explicit acknowledgements, reducing mem ory-tomemory copying, and choosing the most appropriate synchronization primitives, we reduced the message l tency seen by user applications by an average of 55% across al l message sizes. We also identify several areas that offer t h potential for further performance enhancement.

Cloud base height and weather characterization, visualization and prediction based on satellite meteorological observation

Abstract: A method exploits the spectral signature of cloud bases in microwave moisture sounder data to determine cloud base heights. This signature requires the accurate specification of cloud top height, which in a preferred embodiment, comes from the analysis of data provided by an electro-optical sensor (EO) such as the Advanced Very High Resolution Radiometer (AVHRR) instrument flown on operational NOAA satellites. The method includes a receiving step in which satellite EO (visible through infrared) and microwave radiance data of a view of the earth's atmosphere is received. The view has both location and time information. In a determining step, cloud top height is determined based on the EO and infrared radiance data. Moisture profiles of the view are retrieved in a retrieving step based on the microwave radiance data. Subsequently, in a determining step, cloud base heights of clouds in the view are determined using cloud top heights as a constraint in the retrieval of moisture profiles with tile microwave data. With the cloud base height information, three dimensional models of the clouds may be constructed based on the cloud top heights, cloud base heights and moisture data which may be used for weather visualization and prediction.

Comparison of Mechanisms of Cloud-Climate Feedbacks in GCMs

Abstract: International model comparisons of cloud-climate feedbacks have typically been restricted to assessing only the radiative effect of changes in clouds and have not attempted to explain the mechanisms for differences in cloud feedbacks. This paper uses different versions of the U.K. Meteorological Office GCM run at the Hadley Centre to illustrate the usefulness of a detailed comparison of microphysical cloud properties in understanding cloud feedback mechanisms and their effect on the regional distribution of the predicted warming in simulations of climate change. The inclusion of interactive cloud radiative properties explains much of the difference in the spatial patterns of cloud feedback and leads to a marked difference in the response of the large-scale circulation and in the resulting meridional gradient of surface temperature changes. In the model versions that include interactive radiative properties, the strength of the related feedback is determined by the water path of the cloud in the c...

Combined Satellite- and Surface-Based Observations of Clouds

Abstract: A new method for combining satellite and surface-based cloud observations into a self-consistent three-dimensional field is presented. This method derives the probabilities of the cloud states, which are most consistent with all of the observations and assumptions concerning the nature and relative uncertainties of the observations. It is applied to a three-layer atmosphere using monthly satellite- and surface-based cloud observations. The reconstructions of the observed fields usually lead to modifications of the surface-observed low cloud amount of less than 0.008 fractional cloud cover. Over the ocean the satellite-view low cloud amounts are usually decreased by between 0.06 and 0.12 for most of the middle latitudes and southeastern tropical Pacific. Over land the adjustments in the satellite low cloud amounts are generally smaller. The method leads to increases in satellite high cover of between 0.03 and 0.09 over most regions, and increases in middle cloud cover of up to around 0.03 over the...

Level 1 Cloud Detection Algorithm Theoretical Basis

Abstract: This Algorithm Basis (ATB) document describes the algorithms used to retrieve the Radiometic Camera-by-camera Cloud Mask (RCCM) within the MISR level 1B2 Geo-rectified Radiance Product.

Dynamical Structure of the Zodiacal Cloud

Abstract: Advances in infrared astronomy and computing power have made detailed study of the structure of the zodiacal cloud possible. An extremely complex cloud has been revealed, quite distinct from the smooth, rotationally symmetric structure assumed prior to the launch of IRAS. The relative contribution of cometary and asteroidal material to the cloud as a whole remains a subject for debate. However, the existence of discrete structures within the cloud, such as the dust bands associated with the Hirayama asteroid families and the Earth’s resonant ring, serve as dynamical constraints on the possible sources for the cloud.

Cumulus Cloud Formulations for Longwave Radiation Calculations

Abstract: Longwave radiative transfer under broken cloud conditions is often treated as a problem in cloud bulk geometry, especially for cumulus clouds, because individual clouds are nearly black. However, climate models ignore cloud geometry and estimate the effects of broken cumulus clouds as the cloud amount weighted average of clear and black cloud overcast conditions (i.e., the black plate approximation). To overcome the simplicity of the black plate approximation, the authors developed a more generalized form of cloud geometrical effects on the effective cloud fraction. Following previous work, this form includes parameters that allow a more precise specification of cloud size and spatial distributions. The sensitivity of the generalized form to the variation in cloud size and spatial distributions is discussed in relation to others. Model calculations show that cloud bulk geometrical shapes, aspect ratio, size distribution, and side inclination angle are the primary factors significantly affecting t...

Mining Classification Knowledge Based on Cloud Models

Abstract: Data classification is an important research topic in the field of data mining and knowledge discovery There have been many data classification methods studied, including decision-tree method, statistical methods, neural networks, rough sets, etc In this paper, we present a new mathematical representation of qualitative concepts-Cloud Models With the new models, mapping between quantities and qualities becomes much easier and interchangeable Based on the cloud models, a novel qualitative strategy for data classification in large relational databases is proposed Then, the algorithms for classification are developed, such as cloud generation, complexity reduction, identifying interacting attributes, etc Finally, we perform experiments on a challenging medical diagnosis domain, acute abdominal pain The results show the advantages of the model in the process of knowledge discovery

Some Bulk Properties of Cumulus Ensembles Simulated by a Cloud-Resolving Model.Part I: Cloud Root Properties

Abstract: To provide a basis for developing an improved cloud model for use in cumulus parameterization (CMCP), a two-dimensional cloud-resolving model is used to simulate the bulk properties of cloud roots. Two idealized experiments are presented: one is based on an undisturbed trade wind situation and the other is based on a disturbed tropical situation. The simulated data are analyzed through extensive trajectory analysis to trace the thermodynamic properties and buoyancy of ascending air back into the subcloud layer. Particular efforts are placed on finding the relations between cloud root properties and large-scale variables that are valid for both deep and shallow clouds. It is found that the air below cloud base (in cloud roots) is usually moister than its environment and typically becomes saturated at levels closer to or below the mixed-layer top. Moreover, no matter at which levels cloud roots become saturated, they have very small buoyancy near the level of the mixed-layer top. Based on these two...

Cloud cover observed simultaneously from FOLDER and METEOSAT

Abstract: The POLDER instrument that was aboard the Japanese ADEOS platform between August 1996 and June 1997. is designed to the global observations of the polarisation and directionality of the sun-light reflected by the Earth-atmosphere system. The cloud detection from POLDER takes advantage of the original capabilities of the instrument (spectral polarisation and directionality). This cloud detection scheme uses 5 threshold tests based on pressure, reflectance, polarised reflectance and spectral variability. The results of the POLDER cloud detection scheme are compared to those of the LMD dynamical clustering method applied to visible and infrared METEOSAT data and local spatial variability of these two parameters. Special focus is given to the detection capabilities of the two kind of measurements for cloud situations such as small cumulus, thin cirrus and multilayered cloud cover. Results of this comparison would give some insight on the behaviour of the International Satellite Cloud Climatology Project (ISCCP) cloud detection scheme built mainly from visible and infrared measurements.

Spatial characteristics of the tropical cloud systems: comparison between model simulation and satellite observations

Abstract: A Lagrangian cloud classification algorithm is applied to the cloud fields in the tropical Pacificsimulated by a high-resolution regional atmospheric model. The purpose of this work is toassess the model’s ability to reproduce the observed spatial characteristics of the tropical cloudsystems. The cloud systems are broadly grouped into three categories: deep clouds, mid-levelclouds and low clouds. The deep clouds are further divided into mesoscale convective systemsand non-mesoscale convective systems. It is shown that the model is able to simulate the totalcloud cover for each category reasonably well. However, when the cloud cover is broken downinto contributions from cloud systems of different sizes, it is shown that the simulated cloudsize distribution is biased toward large cloud systems, with contribution from relatively smallcloud systems significantly under-represented in the model for both deep and mid-level clouds.The number distribution and area contribution to the cloud cover from mesoscale convectivesystems are very well simulated compared to the satellite observations, so are low clouds aswell. The dependence of the cloud physical properties on cloud scale is examined. It is foundthat cloud liquid water path, rainfall, and ocean surface sensible and latent heat fluxes have aclear dependence on cloud types and scale. This is of particular interest to studies of the cloudeffects on surface energy budget and hydrological cycle. The diurnal variation of the cloudpopulation and area is also examined. The model exhibits a varying degree of success in simulatingthe diurnal variation of the cloud number and area. The observed early morning maximumcloud cover in deep convective cloud systems is qualitatively simulated. However, the afternoonsecondary maximum is missing in the model simulation. The diurnal variation of the tropospherictemperature is well reproduced by the model while simulation of the diurnal variationof the moisture field is poor. The implication of this comparison between model simulation andobservations on cloud parameterization is discussed. DOI: 10.1034/j.1600-0870.1999.00026.x

Investigations of cloud layer base and top heights from 95 GHz radar reflectivity data

Abstract: Cloud radars operating at millimeter wavelengths have proven to be invaluable for studying the 3-dimensional distribution of stratiform clouds. An improved knowledge of the occurrence of multiple cloud layers as well as of heights of their upper and lower boundaries is important for the determination of radiative fluxes with a higher accuracy. In this study measurements with the 95 GHz radar of GKSS Research Centre, Geesthacht, are used to determine base and top heights of layers of different cloud types. However, an accurate retrieval of cloud boundaries by remote sensors is not obvious, e.g., it is known that simultaneous measurements of the radar and backscatter lidars often show significant differences in cloud base heights. Reasons for inaccuracies in the determination of cloud boundary heights are discussed. Possibilities for corrections are illustrated that will finally lead to more reliable cloud boundary statistics necessary to improve radiative transfer calculations within large-scale weather forecasting and climate models.

Cloud Predictions Diagnosed from Global Weather Model Forecasts

Abstract: Observed cloud characteristics, such as cloud cover, type, and base and top altitude, are of interest to the U.S. Air Force operational community for mission support. Predictions of such cloud characteristics are useful in support of a variety of mission activities. In this paper, a model output statistics approach to diagnosing these cloud characteristics from a forecast field generated by a mesoscale numerical weather prediction model is presented. Cloud characteristics information obtained from the air force RTNEPH cloud analysis supplied the cloud predictands, and forecast fields from the MM5 mesoscale numerical weather prediction model provided the weather variable predictors. Multiple linear regression (MLR) and multiple discriminant analysis (MDA) were used to develop the predictand–predictor relationships using 10 days of twice-daily cloud analyses and corresponding forecasts over a theater-scale grid. The consequent relationships were then applied to subsequent gridded forecast fields to...

Object-Oriented Technology and Computing Systems Re-Engineering

Abstract: Description: This book delivers the latest developments in object technology and their impact in computing systems re-engineering. Object-oriented programming is here shown to provide support for constructing large scale systems that are cheaply built and with reusable components, adaptable to changing requirements and use efficient and cost-effective techniques. the UK and the USA here record their research and development work on the industrial techniques and structured object-oriented methodologies in forward and reverse engineering of computing systems. This book takes stock of progress of that work showing its promise and feasibility, and how its structured technology can overcome the limitations of forward engineering methods used in industry. Forward methods are focused in the domain of reverse engineering to implement a high level of specification for existing software.-Delivers the latest developments in object technology and their impact in computing systems re-engineering-Provides support for constructing large scale systems that are cheaply built and with reusable components, adaptable to changing requirements and use efficient and cost-effective techniques-Contains the content of the first UK Colloquium on Object Technology and Systems Re-Engineering held at Oxford University in 1998 Contents: Toward an object-oriented design methodology for hybrid systems Design patterns and their role in formal object-oriented development Devising coexistence strategies for objects with legacy systems Object-oriented model for expert systems implementation Re-engineering requirements specifications for re-use Object-oriented development of X-ray spectrometer software Pre-processing COBOL programs for reverse engineering Agent oriented programming language Fair objects Systems of systems as communicating structures Suitability of CORBA as a heterogeneous distributed platform Using O-O design to enhance procedural software Reengineering procedural software to object-oriented software using design transformations and resource usage matrix.

Single-column models, arm observations, and GCM cloud-radiation schemes

Abstract: Among the most serious sources of uncertainty in current general circulation models (GCMs) is the treatment of clouds and cloud-radiation interactions. We have used a single-column model (SCM) diagnostically to evaluate parameterizations against observations from the Atmospheric Radiation Measurement (ARM) Program. We find that schemes with explicit cloud water budgets and interactive radiative properties are potentially capable of matching observational data closely. In our SCM, using an interactive cloud droplet radius decreases the cloud optical thickness and cloud infrared emittance of high clouds, which acts to increase the downwelling surface shortwave flux and the outgoing longwave radiation. However, it is difficult to evaluate the realism of the vertical distribution of model-produced cloud extinction, cloud emittance, cloud liquid water content and effective cloud droplet radius until high-quality observations of these quantities become more widely available. We also find that in the SCM, cloud parameterizations often underestimate the observed cloud amount, and that ARM observations indicate the presence of clouds while the corresponding maximum relative humidity is less than 80%. This implies that the underlying concept of a critical gridpoint relative humidity of about 80% for cloud formation, as used in many GCM cloud parameterizations, may need to be re-examined.

Towards a Scalable Metacomputing Storage Service

Abstract: We describe a prototypical storage service through which we are addressing some of the open storage issues in wide-area distributed high-performance computing. We discuss some of the relevant topics such as latency-tolerance, hierarchical storage integration, and legacy and commercial application support. Existing high-performance computing environments are either ad-hoc or focus narrowly on the simple clienserver case. The storage service which we are developing as part of the DISCWorld metacomputing infrastructure, will provide high-performance access to a global “cloud”, of storage resources in a manner which is scalable, secure, adaptive and portable requiring no application or operating system modifications. Our system design provides flexible, modular and user-extensible access to arbitrary storage mechanisms and on-demand data generation and transformations. We describe our current prototype's status, some performance analysis, other related research and our future plans for the system.

Validation of cloud parameter retrieval methods with objective ground based measurements

Abstract: To understand and model the radiative transport in a cloudy atmosphere information on the cloud height and optical thickness is indispensable. Therefore retrieval techniques for cloud parameters are developed for the AVHRR, ATSR and the future MSG. Mainly synoptic observations are used for validation despite their subjective nature and varying quality. To validate advanced cloud parameter retrieval methods objective physical measurements are necessary. At KNMI retrieval methods of cloud fraction, cloud top temperature, optical thickness and LWP from AVHRR observations are developed. Much effort is put in building an infrastructure for validation. The retrieval methods are validated with a two-year data set from the KNMI Cloud Detection System (CDS). Detailed analysis is performed with observations from the CLARA-campaigns, when a number of advanced remote sensing and in-situ instruments were added to the CDS. The collocated lidar, radar, microwave radiometer and aircraft measurements from the CLARA data set allow for the evaluation of the assumptions in cloud parameter retrieval methods. Furthermore, the study presented here shows that combining measurements from lidar, radar and AVHRR provide information on cloud properties that cannot be retrieved from any of these instruments alone.

An Evaluation of the Xu-Randall Cloud Fraction Parameterization Using ASTEX Data

Abstract: A dearth of detailed cloud observations has encouraged large-scale modelers to utilize methods that employ cloud resolving models (CRMs) to evaluate the utility of cloud parameterizations. However, cloud radars are now making detailed observations of clouds. In this paper, we use such observations to evaluate a parameterization based on CRM results. Herein we examine a particular cloud parameterization developed by Xu and Randall (1996). Unlike cloud parameterizations involving probability distribution functions (PDFs), which require knowledge of the higher order moments of the subgrid variables, the Xu and Randall (1996) technique depends only upon the large-scale relative humidity (RH), the saturation water vapor mixing ratio, and cloud and ice water mixing ratios. “Largescale” refers to space and time scales resolved by a large-scale model, such as a global numerical weather prediction (NWP) model or a global climate model. A large-scale quantity typically represents a spatial average over a 250 km by 250 km area and, under quiescent conditions, a time variation on the order of 3 hours. Herein, we apply the Xu and Randall (1996) stratus cloud parameterization to Atlantic Stratocumulus Transition Experiment (ASTEX) observations of the RH field obtained from sounding data and liquid water content (LWC) profiles derived from a combination of the liquid water path (LWP) measured by a Microwave Radiometer (MWR), and reflectivity Z from a millimeter wavelength cloud radar. The parameterized cloud fraction is then compared with observed cloud fraction profiles determined from cloud radar measurements.

Neural network system for cloud classification from satellite images

Abstract: Highly accurate, automated cloud detection and classification methods are essential for processing multispectral meteorological satellite in an operational environment and providing data for meteorological and climatological studies. They help to discover hazardous meteorological phenomena such as hail storms developing on tops of clouds, hurricanes and cyclones. Weather prediction and rainfall estimation systems are enhanced substantially by having access to information about cloud cover distribution and being able to trace changes in meteorological conditions. This paper reports on a research project, sponsored by the British Natural Resources Institute, to investigate the problem of cloud feature extraction, detection and classification. The paper presents a novel architecture and implementation of a hybrid two-stage neural network system for cloud detection and classification from satellite imagery.

Errata To A Study Of Cloud Classification With Neural Networks Using Spectral And Textural Features

Abstract: Manuscript received March 1, 1999. B. Tian, M. A. Shaikh, and M. R. Azimi-Sadjadi are with the Department of Electrical Engineering, Colorado State University, Fort Collins, CO 80523 USA. T. H. Vonder Haar and D. L. Reinke are with the Cooperative Institute for Research in the Atmosphere (CIRA), Colorado State University, Fort Collins, CO 80523 USA. Publisher Item Identifier S 1045-9227(99)05313-8. 1B. Tian, M. A. Shaikh, M. R. Azimi-Sadjadi, T. H. Vonder Haar, and D. L. Reinke,IEEE Trans. Neural Networks , vol. 10, pp. 138–151, Jan. 1999. (a)

The real time calculation of cloud motion in infrared image sequences using mathematical morphology operations

Abstract: The real time calculation of local cloud motion may be useful in aiding the discrimination of small targets from backgrounds by infrared search and track systems. While the apparent motion of clouds in image sequences can be considered to be optical flow, the standard methods of optical flow calculation are not suited to real time calculation of cloud motion. In this paper a method is presented for estimating the local apparent cloud motion based on mathematical morphology operations. The method is illustrated with a 1D analogue of a moving cloud mass. The extension to 2D images is straight forward.

Comparisons of cloud cover estimates and cloud fraction profiles from ARM's cloud-detecting instruments and GOES-8 data

Abstract: The DOE's Atmospheric Radiation Measurement (ARM) Program employs both upward- and downward-looking remote-sensing instruments to measure the horizontal and vertical distributions of clouds across its Southern Great Plains (SGP) site. No single instrument is capable of completely determining these distributions over the scales of interest to ARM's Single Column Modeling (SCM) and Instantaneous Radiative Flux (IRF) groups; these groups embody the primary strategies through which ARM expects to achieve its objectives of developing and testing cloud formation parameterizations (USDOE, 1996). Collectively, however, the data from ARM's cloud-detecting instruments offer the potential for such a three-dimensional characterization. Data intercomparisons, like the ones illustrated in this paper, are steps in this direction. Examples of some initial comparisons, involving satellite, millimeter cloud radar, whole sky imager and ceilometer data, are provided herein. that many of the lessons learned can later be adapted to cloud data at the Boundary and Extended Facilities. Principally, we are concerned about: (1) the accuracy of various estimates of cloud properties at a single point, or within a thin vertical column, above the CF over time, and (2) the accuracy of various estimates of cloud properties over the Cloud and Radiation Testbed (CART) site, which can then be reducedmore » to single, representative profiles over time. In the former case, the results are usable in the IRF and SCM strategies; in the latter case, they satisfy SCM needs specifically. The Whole Sky Imager (WSI) and ceilometer data used in one study were collected at the SGP CF between October 1 and December 31, 1996 (Shields, et. al., 1990). This three-month period, corresponding to the first set of WSI data released by ARM's Experiment Center, was sufficiently long to reveal important trends (Rodriguez, 1998).« less