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...

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.

Abstract: A scheme for detecting cloud-affected radiances is described. the method is used to determine the probability of cloud-free conditions given the observations and the prior knowledge we have about the atmosphere from a numerical weather prediction (NWP) model. This is achieved using a likelihood method. It combines the strengths of some alternative methods (e.g. comparison of infra-red and microwave channels sounding the lower troposphere and comparison of infra-red window channels with sea surface temperature) in a powerful and flexible method. It is powerful because it uses different types of information simultaneously. It is flexible because it makes no assumption about which instrument is being processed, or what type of prior information (NWP, climatology etc.) is used. Therefore, it can readily be extended to new situations and data types (e.g. Advanced TIROS Operational Vertical Sounder (ATOVS)). It is suitable for use on general cloud-detection problems, using combined microwave and infra-red data. It has been tested using TIROS Operational Vertical Sounder (TOVS) radiances. the new method has been compared with an alternative cloud-detection method tailored specifically for TOVS and has been developed to a level of robustness adequate for operational use. the new method gave very similar results to the alternative method, especially over the ocean. the differences that did occur have been investigated by comparing with cloud information derived from the Advanced Very High Resolution Radiometer (AVHRR). Both the alternative method and the new scheme were found to have deficiencies when dealing with very low cloud. Some cloud missed by the existing scheme is identified by the new scheme. Over land, cloud detection is more difficult. the two schemes disagree more often, but validation using AVHRR is also more difficult because of increased surface heterogeneity and more variable emissivity and surface temperature errors. the new method is therefore shown to perform at least as well as an alternative method in operational use, whilst gaining the flexibility required for future systems. the implications for ATOVS are discussed.

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...

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.

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.

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...

Abstract: The understanding and the confusion resulting from any scientific metaphor thus have to be considered when it is used. For example, a common chemical metaphor for the electron distribution about an atom is a cloud. Some of the entailments of this metaphor are apt, such as the diffuse nature of a cloud. Others, such as the ability of a cloud to evaporate, are not appropriate.

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...

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...

Abstract: We show two-dimensional numerical simulations of the gravitational collapse of rotating gas clouds. We assume the polytropic equation of state, P = Kργ, to take account of the temperature change during the collapse. Our numerical simulations have two model parameters, β and γ, which specify the initial rotation velocity and polytropic index, respectively. We show three models, β = 1.0, 0.5, and 0.2, for each γ, which is taken to be 0.8, 0.9, 0.95, 1.05, 1.1, or 1.2. These 18 models are compared with previously reported isothermal models (γ = 1). In each model a rotating cylindrical cloud initially in equilibrium fragments periodically because of the growth of a velocity perturbation and forms cloud cores. The cloud core becomes a dynamically collapsing gaseous disk whose central density (ρc) increases with time (t) in proportion to ρc ∝ (t - t0)-2. This collapse is qualitatively similar in density and velocity distributions to the runaway collapse of a rotating isothermal cloud. The surface density of the disk, Σ, is proportional to the power of the radial distance, Σ(r) ∝ r1-2γ, in the envelope. Models with γ > 1 have geometrically thick disks (aspect ratio rd/zd 2), while those with γ 10). While the former disks are stable, the latter disks are unstable against fragmentation if we adopt the Toomre stability criterion for a thin gaseous disk. Our numerical simulations also show the growth of a rotationally supported disk by radial accretion in a period t > t0 for models with γ > 1. The accretion phase starts at a stage in which the central density is still finite. The central density at the beginning of the accretion phase is lower when β and γ are larger. Our models with γ 1 are applicable to star formation in primordial clouds in which the temperature increase during the collapse is due to less efficient cooling.

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

Abstract: Assimilation of satellite data can enhance the ability of a mesoscale modeling system to produce accurate short-term forecasts of clouds and precipitation, but only if there is a mechanism for the satellite-derived information to propagate coherently from the analysis into the forecast period. In situations where stratiform cloud cover inhibits surface heating, assimilation of visible image data can be beneficial for analyses, but those data present particular challenges for application to numerical forecasts. To address the forecast problem, a method to adjust the humidity field and the radiative parameterization of a model was developed such that satellite retrievals of cloud properties have an impact that extends well into the forecast. The adjustment directs the model’s cloud diagnosis and radiation algorithms to produce results that agree with satellite retrievals valid at the forecast initiation time. Experiments showed a high level of fidelity between a short-term forecast made with this m...

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.

Abstract: The interstellar cloud surrounding the solar system regulates the galactic environment of the Sun and constrains the physical characteristics of the interplanetary medium. This paper compares interstellar dust grain properties observed within the solar system with dust properties inferred from observations of the cloud surrounding the solar system. Properties of diffuse clouds in the solar vicinity are discussed to gain insight into the properties of the diffuse cloud complex flowing past the Sun. Evidence is presented for changes in the galactic environment of the Sun within the next 10$^4$--10$^6$ years. The combined history of changes in the interstellar environment of the Sun, and solar activity cycles, will be recorded in the variability of the ratio of large- to medium-sized interstellar dust grains deposited onto geologically inert surfaces. Combining data from lunar core samples in the inner and outer solar system will assist in disentangling these two effects.

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.

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

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.

Abstract: Ship-based measurements in June 1994 provided information about ship-track clouds and associated atmospheric environment observed from below cloud levels that provide a perspective different from satellite and aircraft measurements. Surface measurements of latent and sensible heat fluxes, sea surface temperatures, and meteorological profiles with free and tethered balloons provided necessary input conditions for models of ship-track formation and maintenance. Remote sensing measurements showed a coupling of ship plume dynamics and entrainment into overlaying clouds. Morphological and dynamic effects were observed on clouds unique to the ship tracks. These morphological changes included lower cloud bases early in the ship-track formation, evidence of raised cloud bases in more mature tracks, sometimes higher cloud tops, thin cloud-free regions paralleling the tracks, and often stronger radar returns. The ship-based lidar aerosol measurements revealed that ship plumes often interacted with the over...

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.

Abstract: Preliminary results of laboratory observations of the scattered light on cloud droplets at an interface between the cloud and clear air are presented. Results suggest a weak dependence 'of the absolute value of the brightness gradient (related to the gradient of droplet concentration and liquid water content) at the interface on the interface orientation and turbulence level. There is an evidence of anisotropy (vertical direction preferred) of filaments created in the process of turbulent mixing.

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.

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.

Abstract: The work described in this paper is concerned with the analysis of AVHRR data which visually exhibit ship trail clouds. The aim was to devise an automatic means of identifying these features. The existence of ship trail clouds has been known for some time, though the exact mechanism for their formation is not yet fully understood. They are normally associated with low-level stratus and stratocumulus cloud and are thought to be caused by the presence of condensation nuclei emanating from the ship exhaust funnel. Given the right conditions, these trails can be easily seen in both visible and infrared imagery and under calm conditions they can exist for several days. Edge-detection analysis was found to be unsatisfactory for identification purposes and hence a neural approach was adopted. The neural analysis was shown to be very promising. Application of a neural network trained on four images resulted in the detection of the presence of most of the trails in the dataset on which it was trained. Just as impo...

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.