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1

Cloud base height survey based on stereo image  

NASA Astrophysics Data System (ADS)

Cloud observation is an important factor for weather application and change of cloud base height plays a vital role in development of future weather system. Aim at requirement of cloud observation, a method on survey of cloud base height (CBH) is proposed based on stereo image. The main contents include image match and calculation of CBH which makes use of forward intersection of photogrammetry. It overcomes discontinuity, strong subjectivity and qualitative analysis of traditional eye observation. By application of National Day's weather safeguard, it tests that method of stereo imaging surveying is a way of direct measurement with better precision and is possible in technology also.

Li, Guosheng; Lin, Zongjian; Ma, Shuqing; Zhi, Xiaodong

2011-04-01

2

Behavior of cloud base height from ceilometer measurements  

NASA Astrophysics Data System (ADS)

Given the importance of clouds in the climate, and the difficulty in determining their behavior and their contribution to climate change, there is a need for improvement of methods for automatic and continuous description of cloud characteristics. Ceilometers constitute a priori a reliable instrumental method for sounding the atmosphere and describing cloudiness, specifically cloud base height (CBH), cloud cover, and even cloud vertical structure. In the present study, the behavior of CBH at different time scales has been investigated at Girona (Spain) including a statistical analysis of the frequency distributions of CBH. The study covers four years (2007-2010) of high resolution (both in time and in the vertical direction) ceilometer measurements. At this location, ceilometer measurements reveal a seasonal cycle, with important differences between "extreme" seasons (winter and summer) and the "transition" seasons (spring and autumn). Summer months in general and July in particular behave quite differently than other periods in the year, both regarding the presence of clouds (with a minimum cloud occurrence of about 20-30%) and the distribution of CBH (with more than 25% of clouds having CBH around 1400 m and 80% of clouds with CBH lower than 3000 m). The distributions of CBH are explained on the basis of some atmospheric situations that generate clouds, in particular conditions that produce the large number of low level clouds found.

Costa-Surós, M.; Calbó, J.; González, J. A.; Martin-Vide, J.

2013-06-01

3

Cloud Base Height and Effective Cloud Emissivity Retrieval with Ground-Based Infrared Interferometer  

NASA Astrophysics Data System (ADS)

Based on ground-based Atmospheric Emitted Radiance Interferometer (AERI) observations in Shouxian, Anhui province, China, the cloud base height (CBH) and effective cloud emissivity are retrieved by using the minimum root-mean-square difference method. This method was originally developed for satellite remote sensing. The high-temporal-resolution retrieval results can depict the trivial variations of the zenith clouds continuously. The retrieval results are evaluated by comparing them with observations by the cloud radar. The comparison shows that the retrieval bias is smaller for the middle and low clouds, especially for opaque clouds. When two layers of clouds exist, the retrieval results reflect the weighting radiative contribution of the multi-layer cloud. The retrieval accuracy is affected by uncertainties of the AERI radiances and sounding profiles, in which the role of uncertainty in the temperature profile is dominant.

Pan, L.; Lu, D.

2012-12-01

4

Experimental optoelectronic model of ceilometer for cloud base height measurement  

NASA Astrophysics Data System (ADS)

Experimental determination of cloud base height (CBH) by a passive monostatic method by means of opto-electronic ceilometer model was carried out. The model of a ceilometer is two black-and-white CCD-cameras having closest sighting lines. Focal lengths for optical systems of used television cameras were selected for the possibility of measuring the CBH from 50 to 1500 m. Obtained by cameras the pictures with different scale images of selected for measure of cloudiness fragments are digitized on computer and are processed. The algorithm for determining the CBH using the proposed model of ceilometer is described and results of experimental measurements are shown.

Zuev, S. V.; Krasnenko, N. P.

2009-02-01

5

Automated cloud base height determination from high resolution Landsat data - A Hough transform approach  

NASA Technical Reports Server (NTRS)

A direct method for determining the cloud base height derived from the displacement of the shadow from the cloud, and the solar azimuth and zenith angle is presented. Cumulus cloud scenes over land from Landsat MSS imagery are considered. The clouds are first matched with the corresponding shadows; the pixel distance of a reference point in the cloud is computed from the corresponding reference point in the shadow; and then the solar zenith angle is used to compute the cloud base height. Observations indicate that the cloud base height appears to be size-dependent with larger clouds generally associated with higher cloud bases and that clouds within the same size range and within the same scene region are approximately of the same height.

Sengupta, S. K.; Berendes, T.; Welch, R. M.; Navar, M.; Wielicki, B.

1990-01-01

6

Determination of cloud base height using the passive monostatic method  

NASA Astrophysics Data System (ADS)

Among passive methods for a cloud base height (CBH) detection, bistatic and monostatic methods are known. In the first case a triangulation method with two photodetectors is used. A drawback of this method is a need in obtaining images of the one overcast fragment by two spatially separated cameras in the course of shot time. In consequence, images have different view angles and the problem of identification of this fragment appears. The passive monostatic method for CBH detection does not have these demerits. For measurement by this method, linear sizes of object should be known. But for a case of CBH detection it is impossible, because cloudiness can change in the course of short time. The offered method does not demand knowledge about linear sizes of cloudiness fragments. The method uses dependence of scale change of object image at change of focal length of camera lens depending on distance up to object.

Zuev, S. V.; Krasnenko, N. P.

2008-05-01

7

A new approach to retrieve cloud base height of marine boundary layer clouds  

NASA Astrophysics Data System (ADS)

novel approach for estimating marine boundary layer cloud base height (CBH) is proposed based on calculated boundary layer lapse rates, collocated cloud top height (CTH), cloud top, and ocean surface temperatures from the A-Train satellite constellation. The method takes advantage of the assumption that decreases of temperature within and below water clouds may follow the different constant apparent lapse rates in the same region, respectively. The CBHs derived from the new method compare well with the coincident CBH product from the active sensors of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat. The correlation coefficient, the mean difference, and the standard deviation are 0.79 (0.54), 0.02 km (0.03 km), and ±0.35 km (±0.54 km), respectively, when CTH is derived from CALIPSO data (or Moderate Resolution Imaging Spectroradiometer retrieval). Besides the relatively small bias, the most important advantage of this method compared to previous CBH retrieval techniques is that it is independent of boundary layer cloud types, optical thickness, and illumination.

Li, J. M.; Yi, Y. H.; Stamnes, K.; Ding, X. D.; Wang, T. H.; Jin, H. C.; Wang, S. S.

2013-08-01

8

Intercomparisons of cloud-top and cloud-base heights from ground-based Lidar, CloudSat and CALIPSO measurements  

Microsoft Academic Search

This study presents results of the intercomparison of cloud-top height (CTH) and cloud-bottom height (CBH) obtained from a space-borne active sensor Cloud Profiling Radar (CPR), the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), the space-borne passive sensor Moderate Resolution Imaging Spectroradiometer (MODIS) and ground-based Lidar measurements. Three selected cases (one daytime and two night-time cases) involving various cloud conditions such as

Sang-Woo Kim; Eui-Seok Chung; Soon-Chang Yoon; Byung-Ju Sohn; Nobuo Sugimoto

2011-01-01

9

Latitudinal variations of cloud base height and lightning parameters in the tropics  

NASA Technical Reports Server (NTRS)

The observed reduction in cloud-to-ground lightning in the new-equational zone is examined from the perspective of the width of the main negative charge region. Thermodynamic observations of cloud base height also show a climatological minimum value in the near-equatorial region. The association of low cloud base with both narrow updrafts and narrow changing zones may impede the bridging of the large air gap to ground, and thereby suppress cloud-to-ground lightning activity. This width dependence may be more important than the approx. 10% variation in height of the freezing level in the encouraging flashes to ground.

Mushtak, V. C.; Williams, E. R.; Boccippio, D. J.

2006-01-01

10

Cloud-Base-Height Estimation from Paired Ground-Based Hemispherical Observations  

SciTech Connect

The Total Sky Imager (TSI) and Hemispheric Sky Imager (HSI) each have a hemispherical field-of-view (FOV) and many TSIs are now deployed. Currently, these instruments have been used routinely to provide a time series of the fractional sky cover only. In this study, we examine the possible retrieval of cloud base height (CBH) from TSI surface observations. This paper presents a validation analysis of a new retrieval using both a model-output inverse problem and independent, ground-based Micropulse Lidar data. The obtained results suggest that, at least for single layer cloud fields, moderately accurate (within ~0.35 km) CBH retrieval is possible.

Kassianov, Evgueni I.; Long, Charles N.; Christy, Jason E.

2005-08-01

11

Applications: Cloud Height at Night.  

ERIC Educational Resources Information Center

The method used at airports in determining the cloud height at night is presented. Several problems, the equation used, and a simple design of an alidade (an instrument that shows cloud heights directly) are also included. (MP)

Mathematics Teacher, 1980

1980-01-01

12

The Role of Cloud Base Height in the Convective Vigor and Flash Rate of Thunderstorms  

NASA Astrophysics Data System (ADS)

Earlier studies of atmospheric convection have established the following results: (1) Convective Available Potential Energy (CAPE) over tropical land areas is of the same order as over warm ocean regions, (2) updraft strengths in continental clouds are more than twice those in oceanic clouds, (3) cumulonimbus updraft widths are larger over land than over ocean, (4) thermal widths in the planetary boundary layer over land increase with the depth of the boundary layer. The present study is concerned with tests of the hypothesis that cumulonimbus updraft width scales with cloud base height, and the greater the width, the more efficient is the conversion of CAPE to updraft kinetic energy. The greater the kinetic energy, the greater is the lightning flash rate. Comparisons are made between cloud base height inferred from routine thermodynamic measurements throughout the tropics and thunderstorm flash rates (in proximity to the surface stations) observed by the Lightning Imaging Sensor on the NASA TRMM (Tropical Rainfall Measuring Mission) satellite. These comparisons indicate that, on average, thunderstorm flash rates increase exponentially with cloud base height, with an order of magnitude change in flash rate for a change in height from 500 m values typical for tropical oceans, to 2500 m values typical of extreme tropical continental conditions. These correlations, found to be statistically significant, support the foregoing hypothesis.

Williams, E. R.; Mushtak, V. C.; Boccippio, D. J.

2002-12-01

13

Relationship between cloud base height retrieved from lidar and downward longwave irradiance  

NASA Astrophysics Data System (ADS)

Downward longwave radiation is a key process to understand the climate change, energy budget, and water cycle at the earth's surface. Cloud is a dominant factor to determine the intensity of longwave radiation. It is widely known that cloud cover and cloud base height (CBH) have strong effects on the downward longwave radiation, however there are not so many studies regarding the quantitative evaluation of relationship between cloud properties and downward longwave radiation. The intent of the present study is to quantify the impact of cloud property on the downward longwave irradiance (DLI). We used the data obtained with CGR-4 pyrgeometer at Tateno, Japan for the period from January 2002 to December 2011. Cloud radiative contribution fraction (CRC) is evaluated with a ratio of the difference of DLI between observation under cloudy sky without precipitation and calculation assumed clear-sky condition to the observed DLI. The difference between calculation and observation is -4.60+/-3.00 W/m2, and the calculation method reproduced to observation. Cloud is classified into three types by CBH, low (CBH<2000 m), middle (2000?CBH<5000 m), and high (CBH?5000 m). In the results, CRC is almost proportional and inverse proportional to cloud cover (CC) and CBH in the average, respectively. However, CRC for low cloud shows proportion to CBH because existence of low altitude cloud is related to large precipitable water (PW).

Yamada, Kyohei; Hayasaka, Tadahiro; Sugimoto, Nobuo

2012-11-01

14

New Stereo Vision Digital Camera System for Simultaneous Measurement of Cloud Base Height and Atmospheric Visibility  

NASA Astrophysics Data System (ADS)

Clouds play an important role in many aspects of everyday life. They affect both the local weather as well as the global climate and are an important parameter on climate change studies. Cloud parameters are also important for weather prediction models which make use of actual measurements. It is thus important to have low-cost instrumentation that can be deployed in the field to measure those parameters. This kind of instruments should also be automated and robust since they may be deployed in remote places and be subject to adverse weather conditions. Although clouds are very important in environmental systems, they are also an essential component of airplane safety when visual flight rules (VFR) are enforced, such as in most small aerodromes where it is not economically viable to install instruments for assisted flying. Under VFR there are strict limits on the height of the cloud base, cloud cover and atmospheric visibility that ensure the safety of the pilots and planes. Although there are instruments, available in the market, to measure those parameters, their relatively high cost makes them unavailable in many local aerodromes. In this work we present a new prototype which has been recently developed and deployed in a local aerodrome as proof of concept. It is composed by two digital cameras that capture photographs of the sky and allow the measurement of the cloud height from the parallax effect. The new developments consist on having a new geometry which allows the simultaneous measurement of cloud base height, wind speed at cloud base height and atmospheric visibility, which was not previously possible with only two cameras. The new orientation of the cameras comes at the cost of a more complex geometry to measure the cloud base height. The atmospheric visibility is calculated from the Lambert-Beer law after the measurement of the contrast between a set of dark objects and the background sky. The prototype includes the latest hardware developments that allow its cost to remain low even with its increased functionality. Also, a new control software was also developed to ensure that the two cameras are triggered simultaneously. This is a major requirement that affects the final uncertainty of the measurements due to the constant movement of the clouds in the sky. Since accurate orientation of the cameras can be a very demanding task in field deployments, an automated calibration procedure has been developed, that removes the need for an accurate alignment. It consists on photographing the stars, which do not exhibit parallax due to the long distances involved, and deducing the inherent misalignments of the two cameras. The known misalignments are then used to correct the cloud photos. These developments will be described in the detail, along with an uncertainty analysis of the measurement setup. Measurements of cloud base height and atmospheric visibility will be presented and compared with measurements from other in-situ instruments. This work was supported by FCT project PTDC/CTE-ATM/115833/2009 and Program COMPETE FCOMP-01-0124-FEDER-014508

Janeiro, F. M.; Carretas, F.; Palma, N.; Ramos, P. M.; Wagner, F.

2013-12-01

15

Deriving Winds at Cloud-Base Height With an Infrared Camera  

Microsoft Academic Search

An uncooled commercial infrared camera is used to retrieve horizontal winds at cloud-base height. The camera is equipped with a microbolometer array of 320 times 240 pixels covering a field of view of 32deg times 24deg. It operates in the atmospheric window from 7.5 to 14 mum . In this wavelength range, the camera has day and night measurement capabilities,

Emmanuel Brocard; Marc Schneebeli; Christian Mätzler

2009-01-01

16

Evaluation of Satellite-Based Upper Troposphere Cloud Top Height Retrievals in Multilayer Cloud Conditions During TC4  

NASA Technical Reports Server (NTRS)

Upper troposphere cloud top heights (CTHs), restricted to cloud top pressures (CTPs) less than 500 hPa, inferred using four satellite retrieval methods applied to Twelfth Geostationary Operational Environmental Satellite (GOES-12) data are evaluated using measurements during the July August 2007 Tropical Composition, Cloud and Climate Coupling Experiment (TC4). The four methods are the single-layer CO2-absorption technique (SCO2AT), a modified CO2-absorption technique (MCO2AT) developed for improving both single-layered and multilayered cloud retrievals, a standard version of the Visible Infrared Solar-infrared Split-window Technique (old VISST), and a new version of VISST (new VISST) recently developed to improve cloud property retrievals. They are evaluated by comparing with ER-2 aircraft-based Cloud Physics Lidar (CPL) data taken during 9 days having extensive upper troposphere cirrus, anvil, and convective clouds. Compared to the 89% coverage by upper tropospheric clouds detected by the CPL, the SCO2AT, MCO2AT, old VISST, and new VISST retrieved CTPs less than 500 hPa in 76, 76, 69, and 74% of the matched pixels, respectively. Most of the differences are due to subvisible and optically thin cirrus clouds occurring near the tropopause that were detected only by the CPL. The mean upper tropospheric CTHs for the 9 days are 14.2 (+/- 2.1) km from the CPL and 10.7 (+/- 2.1), 12.1 (+/- 1.6), 9.7 (+/- 2.9), and 11.4 (+/- 2.8) km from the SCO2AT, MCO2AT, old VISST, and new VISST, respectively. Compared to the CPL, the MCO2AT CTHs had the smallest mean biases for semitransparent high clouds in both single-layered and multilayered situations whereas the new VISST CTHs had the smallest mean biases when upper clouds were opaque and optically thick. The biases for all techniques increased with increasing numbers of cloud layers. The transparency of the upper layer clouds tends to increase with the numbers of cloud layers.

Chang, Fu-Lung; Minnis, Patrick; Ayers, J. Kirk; McGill, Matthew J.; Palikonda, Rabindra; Spangenberg, Douglas A.; Smith, William L., Jr.; Yost, Christopher R.

2010-01-01

17

The coupling of cloud base height and surface fluxes: a transferability intercomparison  

NASA Astrophysics Data System (ADS)

This paper presents an evaluation of the simulated coupling between cloud base height (CBH) and surface fluxes over selected Coordinated Enhanced Observing Period (CEOP) reference stations by five regional climate models as part of a transferability intercomparison experiment. The model results are compared with station data obtained during the first phase of the CEOP measuring campaigns. The models gave a credible simulation of both diurnal and seasonal cycles of cloud base height and surface variables over the stations. However, the models exhibited some difficulty in reproducing the diurnal and seasonal temperatures over the tropical stations. The study used principal component analysis to show that three factors account for most of the variability in the observed and simulated data and to investigate the coupling between cloud base height and surface fluxes in the data. In the observations, CBH is well coupled with the surface fluxes over Cabauw, Bondville, Lamont, and Berms, but coupled only with temperature over Lindenberg and Tongyu. All models but GEMLAM simulate substantial coupling between CBH and surface fluxes at all stations; GEMLAM does not couple CBH with surface fluxes, but with surface temperature and specific humidity.

Gbobaniyi, Emiola O.; Abiodun, Babatunde J.; Tadross, Mark A.; Hewitson, Bruce C.; Gutowski, William J.

2011-11-01

18

Neural network sensor fusion: Creation of a virtual sensor for cloud-base height estimation  

NASA Astrophysics Data System (ADS)

Sensor fusion has become a significant area of signal processing research that draws on a variety of tools. Its goals are many, however in this thesis, the creation of a virtual sensor is paramount. In particular, neural networks are used to simulate the output of a LIDAR (LASER. RADAR) that measures cloud-base height. Eye-safe LIDAR is more accurate than the standard tool that would be used for such measurement; the ceilometer. The desire is to make cloud-base height information available at a network of ground-based meteorological stations without actually installing LIDAR sensors. To accomplish this, fifty-seven sensors ranging from multispectral satellite information to standard atmospheric measurements such as temperature and humidity, are fused in what can only be termed as a very complex, nonlinear environment. The result is an accurate prediction of cloud-base height. Thus, a virtual sensor is created. A total of four different learning algorithms were studied; two global and two local. In each case, the very best state-of-the-art learning algorithms have been selected. Local methods investigated are the regularized radial basis function network, and the support vector machine. Global methods include the standard backpropagation with momentum trained multilayer perceptron (used as a benchmark) and the multilayer perceptron trained via the Kalman filter algorithm. While accuracy is the primary concern, computational considerations potentially limit the application of several of the above techniques. Thus, in all cases care was taken to minimize computational cost. For example in the case of the support vector machine, a method of partitioning the problem in order to reduce memory requirements and make the optimization over a large data set feasible was employed and in the Kalman algorithm case, node-decoupling was used to dramatically reduce the number of operations required. Overall, the methods produced somewhat equivalent mean squared errors indicating that the descriptive capacity of the data had been reached. However, the support vector machine was the clear winner in terms of computational complexity. As well, through its ability to determine its own dimensionality it is able to relate information about the physics of the problem back to the user. This thesis, contributes to the literature on three fronts. First, it demonstrates the concept of creating of a virtual sensor via sensor fusion. Second, in the remote-sensing field where focus has typically been on pattern classification tasks, this thesis provides an in-depth look at the use of neural networks for tough regression problems. And lastly, it provides a useful tool for the meteorological community in creating the ability to add large-scale, cloud-field information to predictive models.

Pasika, Hugh Joseph Christopher

2000-10-01

19

Cloud base and top heights in the Hawaiian region determined with satellite and ground-based measurements  

NASA Astrophysics Data System (ADS)

We present a multi-year climatology of cloud-base-height (CBH), cloud-top-height (CTH), and trade wind inversion base height (TWIBH) for the Hawaiian region (18°N-22.5°N, 153.7°W-160.7°W). The new climatology is based on data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO), the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), ceilometer observations and radiosondes. The climatology reported here is well suited to evaluate climate model simulations and can serve as a reference state for studies of the impact of climate change on Hawaiian ecosystems. The averaged CBH from CALIPSO in the Hawaiian Region is 890 m. The mean CTH from CALIPSO is 2110 m, which is close to the mean TWIBH from COSMIC. For non-precipitating cases, the mean TWIBH at both Lihue and Hilo is close to 2000 m. For precipitating cases, the mean TWIBH is 2450 m and 2280 m at Hilo and Lihue, respectively. The potential cloud thickness (PCT) is defined as the difference between TWIBH and CBH and the mean PCT is several hundred meters thicker for precipitating than for the non-precipitating cases at both stations. We find that the PCT is more strongly correlated to the TWIBH than the CBH and that precipitation is unlikely to occur if the TWIBH is below 1500 m. The observed rainfall intensity is correlated to the PCT, i.e., thicker clouds are more likely to produce heavy rain.

Zhang, Chunxi; Wang, Yuqing; Lauer, Axel; Hamilton, Kevin; Xie, Feiqin

2012-08-01

20

Impact of Arctic sea-ice retreat on the recent change in cloud-base height during autumn  

NASA Astrophysics Data System (ADS)

Cloud-base observations over the ice-free Chukchi and Beaufort Seas in autumn were conducted using a shipboard ceilometer and radiosondes during the 1999-2010 cruises of the Japanese R/V Mirai. To understand the recent change in cloud base height over the Arctic Ocean, these cloud-base height data were compared with the observation data under ice-covered situation during SHEBA (the Surface Heat Budget of the Arctic Ocean project in 1998). Our ice-free results showed a 30 % decrease (increase) in the frequency of low clouds with a ceiling below (above) 500 m. Temperature profiles revealed that the boundary layer was well developed over the ice-free ocean in the 2000s, whereas a stable layer dominated during the ice-covered period in 1998. The change in surface boundary conditions likely resulted in the difference in cloud-base height, although it had little impact on air temperatures in the mid- and upper troposphere. Data from the 2010 R/V Mirai cruise were investigated in detail in terms of air-sea temperature difference. This suggests that stratus cloud over the sea ice has been replaced as stratocumulus clouds with low cloud fraction due to the decrease in static stability induced by the sea-ice retreat. The relationship between cloud-base height and air-sea temperature difference (SST-Ts) was analyzed in detail using special section data during 2010 cruise data. Stratus clouds near the sea surface were predominant under a warm advection situation, whereas stratocumulus clouds with a cloud-free layer were significant under a cold advection situation. The threshold temperature difference between sea surface and air temperatures for distinguishing the dominant cloud types was 3 K. Anomalous upward turbulent heat fluxes associated with the sea-ice retreat have likely contributed to warming of the lower troposphere. Frequency distribution of the cloud-base height (km) detected by a ceilometer/lidar (black bars) and radiosondes (gray bars), and profiles of potential temperature (K) for (a) ice-free cases (R/V Mirai during September) and (b) ice-covered case (SHEBA during September 1998). (c) Vertical profiles of air temperature from 1000 hPa to 150 hPa (solid lines: observations north of 75°N, and dashed lines: the ERA-Interim reanalysis over 75-82.5°N, 150-170°W). Green, blue, and red lines denote profiles derived from observations by NP stations (the 1980s), SHEBA (1998), and the R/V Mirai (the 2000s), respectively. (d) Temperature trend calculated by the ERA-Interim reanalysis over the area.

Sato, K.; Inoue, J.; Kodama, Y.; Overland, J. E.

2012-12-01

21

Estimating cloud top height and spatial displacement from scan-synchronous GOES images using simplified IR-based stereoscopic analysis  

Microsoft Academic Search

An efficient method for estimating cloud top heights and correcting cloud image spatial displacements was developed. The method applies stereoscopic analysis to a pair of scan-synchronous infrared cloud images received from two GOES satellites using a piecewise linear approximation of the relationship between height and infrared brightness temperature of top of the cloud element. The algorithm solves for cloud top

Shayesteh E. Mahani; Xiaogang Gao; Soroosh Sorooshian; Bisher Imam

2000-01-01

22

Impact of Arctic sea-ice retreat on the recent change in cloud-base height during autumn  

NASA Astrophysics Data System (ADS)

Cloud-base observations over the ice-free Chukchi and Beaufort Seas in autumn were conducted using a shipboard ceilometer and radiosondes during the 1999-2010 cruises of the Japanese R/V Mirai. In comparison with cloud-base heights in an ice-covered case (the Surface Heat Budget of the Arctic Ocean project in 1998), our ice-free results showed a 30% decrease (increase) in the frequency of low clouds with a ceiling below (above) 500 m. Temperature profiles revealed that the boundary layer was well developed over the ice-free ocean in the 2000s, whereas a stable layer dominated during the ice-covered period in 1998. The change in surface boundary conditions likely resulted in the difference in cloud-base height, although it had little impact on air temperatures in the mid- and upper troposphere. Data from the 2010 R/V Mirai cruise were investigated in detail in terms of air-sea temperature difference. Stratus clouds near the sea surface were predominant under a warm advection situation, whereas stratocumulus clouds with a cloud-free layer were significant under a cold advection situation. The threshold temperature difference between sea surface and air temperatures for distinguishing the dominant cloud types was 3 K. Anomalous upward turbulent heat fluxes associated with the sea-ice retreat have likely contributed to warming of the lower troposphere.

Sato, Kazutoshi; Inoue, Jun; Kodama, Yasu-Masa; Overland, James E.

2012-05-01

23

Cloud base height determination in rain, snow, and fog with a low-cost eye-safe lidar  

NASA Astrophysics Data System (ADS)

The main obstacles for a reliable cloud base height determination with a lidar system are hydrometeors and precipitation scattering the emitted laser light on its way into the atmosphere. In order to fulfill the requirements of airport and aviation safety, modern commercial ceilometers have to be designed in a way that especially takes care of this problem, and the fact that a great part of the light received by the lidar originates from multiple scattering. Results of measuring campaigns performed in Canada and Germany show that the new Hagenuk cloud height lidar LD-WH X 06 also gives reliable results in difficult weather situations. Additionally it offers features like easy servicability, high MTBF, extended maintensance intervals, and long lifetime of laser being of special interest for commercial applications. This presentation contains some examples of the measuring compaigns mentioned above along with a comparison of the cloud heights measured with two different ceilometers in Canada.

Muenkel, Christoph

1995-09-01

24

Development of an analysis tool for cloud base height and visibility  

NASA Astrophysics Data System (ADS)

The meteorological variables cloud base height (CBH) and horizontal atmospheric visibility (VIS) at surface level are of vital importance for safety and effectiveness in aviation. Around 20% of all civil aviation accidents in the USA from 2003 to 2007 were due to weather related causes, around 18% of which were owing to decreased visibility or ceiling (main CBH). The aim of this study is to develop a system generating quality-controlled gridded analyses of the two parameters based on the integration of various kinds of observational data. Upon completion, the tool is planned to provide guidance for nowcasting during take-off and landing as well as for flights operated under visual flight rules. Primary input data consists of manual as well as instrumental observation of CBH and VIS. In Austria, restructuring of part of the standard meteorological stations from human observation to automatic measurement of VIS and CBH is currently in progress. As ancillary data, satellite derived products can add 2-dimensional information, e.g. Cloud Type by NWC SAF (Nowcasting Satellite Application Facilities) MSG (Meteosat Second Generation). Other useful available data are meteorological surface measurements (in particular of temperature, humidity, wind and precipitation), radiosonde, radar and high resolution topography data. A one-year data set is used to study the spatial and weather-dependent representativeness of the CBH and VIS measurements. The VERA (Vienna Enhanced Resolution Analysis) system of the Institute of Meteorology and Geophysics of the University of Vienna provides the framework for the analysis development. Its integrated "Fingerprint" technique allows the insertion of empirical prior knowledge and ancillary information in the form of spatial patterns. Prior to the analysis, a quality control of input data is performed. For CBH and VIS, quality control can consist of internal consistency checks between different data sources. The possibility of two-dimensional consistency checks has to be explored. First results in the development of quality control features and fingerprints will be shown.

Umdasch, Sarah; Reinhold, Steinacker; Manfred, Dorninger; Markus, Kerschbaum; Wolfgang, Pöttschacher

2014-05-01

25

A feasibility study of cloud base height remote sensing by simulating ground-based thermal infrared brightness temperature measurements  

NASA Astrophysics Data System (ADS)

We attempt to study the feasibility of cloud base height (CBH) remote sensing by ground-based sky thermal infrared brightness temperature (Tb) observation and quantitative effects of the aerosol layer on it. Using the Modtran4.0 model simulation, the variations of Tb with zenith angle of observation for different types of aerosol and different visibilities under clear and cloudy sky conditions were systematically investigated. Based on the simulated results, the statistic equations for clear and cloudy sky Tb calculation were obtained respectively, and then a preliminary method of CBH estimation was developed. The results of simulation and preliminary experiments show that for low and middle clouds, the sky Tb observed on the ground is very sensitive to the variation of CBH, therefore it can be used to estimate CBH. The influence of aerosol (visibilities and aerosol types) above the ground on the sky Tb cannot be neglected, which must be corrected. Because the regularity of aerosol's influence on Tb with different zenith angles is fairly clear, it can be corrected well.

Zhang, W.-X.; Lü, D.-R.; Chang, Y.-L.

2007-03-01

26

Evaluation of SCIAMACHY Oxygen A band cloud heights using Cloudnet measurements  

NASA Astrophysics Data System (ADS)

Two SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) O2 A band cloud height products are evaluated using ground-based radar/lidar measurements between January 2003 and December 2011. The products are the ESA (European Space Agency) Level 2 (L2) version 5.02 cloud top height and the FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A band) version 6 cloud height. The radar/lidar profiles are obtained at the Cloudnet sites of Cabauw and Lindenberg, and are averaged for 1 h centered at the SCIAMACHY overpass time. In total we have 217 cases of single-layer clouds and 204 cases of multilayer clouds. We find that the ESA L2 cloud top height has a better agreement with the Cloudnet cloud top height than the Cloudnet cloud middle height. The ESA L2 cloud top height is on average 0.4 km higher than the Cloudnet cloud top height, with a standard deviation of 3.1 km. The FRESCO cloud height is closer to the Cloudnet cloud middle height than the Cloudnet cloud top height. The mean difference between the FRESCO cloud height and the Cloudnet cloud middle height is -0.1 km with a standard deviation of 1.9 km. The ESA L2 cloud top height is higher than the FRESCO cloud height. The differences between the SCIAMACHY cloud (top) height and the Cloudnet cloud top height are linked to cloud optical thickness. The SCIAMACHY cloud height products are further compared to the Cloudnet cloud top height and the Cloudnet cloud middle height in 1 km bins. For single-layer clouds, the difference between the ESA L2 cloud top height and the Cloudnet cloud top height is less than 1 km for each cloud bin at 3-7 km. The difference between the FRESCO cloud height and the Cloudnet cloud middle height is less than 1 km for each cloud bin at 0-6 km. The results are similar for multilayer clouds, but the percentage of cases having a bias within 1 km is smaller than for single-layer clouds. We may conclude that the FRESCO cloud height is accurate for low and middle level clouds, whereas the ESA L2 cloud top height is more accurate for middle level clouds. Both products are less accurate for high clouds.

Wang, P.; Stammes, P.

2014-05-01

27

Multi-year measurements of cloud base heights at South Pole by lidar  

Microsoft Academic Search

The Micropulse Lidar Network has operated a full-time lidar measurement program at South Pole Station since 2000. Observations from this instrument are an important multi-year record of clouds over the Antarctic plateau. Earlier South Pole observations relied mostly on passive measurements to characterize clouds; the lidar's active profiles present an opportunity to validate current understanding of Antarctic clouds, as well

Ashwin Mahesh; James R. Campbell; James D. Spinhirne

2005-01-01

28

Comparison between ATSR-2 stereo, MOS O2-A band and ground-based cloud top heights  

Microsoft Academic Search

A new method to retrieve cloud top heights stereoscopically using the dual?view facility of the Along Track Scanning Radiometer 2 (ATSR?2) instrument is assessed. This assessment is performed through a comparison of the cloud top heights obtained from ATSR?2 stereo and those derived from a 94?GHz radar, radiosonde profiles and independently from the Modular Optoelectronic Scanner (MOS) using the O2?A

C. Naud; K. L. Mitchell; E. E. Clothiaux; P. Albert; R. Preusker; J. Fischer; R. J. Hogan

2007-01-01

29

Measuring Cloud Heights: The Micropulse Lidar (MPL)  

NSDL National Science Digital Library

This middle/junior high school computer activity requires students to compare the lidar method with millimeter wave cloud radar to measure cloud heights using real data, and to identify cloud types using micropulse lidar. It is part of the Atmospheric Visualization Collection (AVC), which focuses on data from the Atmospheric Radiation Measurement (ARM) program's Southern Great Plains Cloud and Radiation Testbed site in Kansas and Oklahoma.

2003-05-09

30

Comparison of marine stratocumulus cloud top heights in the southeastern Pacific retrieved from satellites with coincident ship-based observations  

Microsoft Academic Search

In order to better understand the general problem of satellite cloud top height retrievals for low clouds, observations made by NOAA research vessels in the stratocumulus region in the southeastern Pacific during cruises in 2001 and 2003 to 2006 were matched with near-coincident retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging SpectroRadiometer (MISR) instruments on the Terra

Michael J. Garay; Simon P. de Szoeke; Catherine M. Moroney

2008-01-01

31

Computation of cloud base height from paired whole-sky imaging cameras.  

National Technical Information Service (NTIS)

A major goal for global change studies is to improve the accuracy of general circulation models (GCMs) capable of predicting the timing and magnitude of greenhouse gas-induced global warming. Research has shown that cloud radiative feedback is the single ...

M. C. Allmen W. P. Kegelmeyer

1994-01-01

32

Geometric Cloud Top Height Assignment by Geosynchronous Meteorological Satellite Images  

Microsoft Academic Search

In this research, the biases for Geometric Cloud Top Height (CTH) assignment are simulated for the current operational geostationary satellite constellation. The simulation shows that the geometric CTHs are best retrieved when the two satellites are separated by 60 degrees and presents CTHs properties for various satellite configurations. In addition, a case study based on GOES-10\\/12 images is shown to

Feng Lu; Jianmin Xu; W. Paul Menzel; Christopher S. Velden

2009-01-01

33

Comparison of MISR and MODIS cloud-top heights in the presence of cloud overlap  

Microsoft Academic Search

Coincident MISR and MODIS cloud-top heights retrieved above two vertically pointing radar sites (ARM-SGP and UK-CFARR) are compared for 54 scenes between March 2000 and October 2003. The difference between MODIS and MISR cloud-top heights is assessed in situations where multiple cloud layers are present in a vertical column (i.e., cloud overlap or multilayered cloud). MISR stereo cloud-top heights are

C. M. Naud; B. A. Baum; M. Pavolonis; A. Heidinger; R. Frey; H. Zhang

2007-01-01

34

Operational retrieval of cloud-top heights using MISR data  

Microsoft Academic Search

Due to its unique nine-angle configuration, the Multi-angle Imaging SpectroRadiometer (MISR) can retrieve cloud parameters such as cloud-motion vectors and cloud-top heights using a purely geometrical technique that involves locating the same cloud features at different viewing angles. The geometrical nature of this technique means that the retrievals are relatively insensitive to the absolute instrument calibration. Fast stereo-matching algorithms have

Catherine Moroney; Roger Davies; Jan-Peter Muller

2002-01-01

35

Enhanced IR imagery of cloud top temperatures, heights, cloud types and organizational patterns  

NSDL National Science Digital Library

Dorothea Ivanova, Embry-Riddle Aeronautical University Summary The object of this activity is to find enhanced IR imagery, to interpret cloud top temperatures and heights and to identify cloud types and ...

Ivanova, Dorothea

36

Stratocumulus cloud height variations determined from surface and satellite observations  

NASA Technical Reports Server (NTRS)

Determination of cloud-top heights from satellite-inferred cloud-top temperatures is a relatively straightforward procedure for a well-behaved troposphere. The assumption of a monotonically decreasing temperature with increasing altitude is commonly used to assign a height to a given cloud-top temperature. In the hybrid bispectral threshold method, or HBTM, Minnis et al. (1987) assume that the lapse rate for the troposphere is -6.5/Kkm and that the surface temperature which calibrated this lapse rate is the 24 hour mean of the observed or modeled clear-sky, equivalent blackbody temperature. The International Satellite Cloud Climatology Project (ISCCP) algorithm (Rossow et al., 1988) attempts a more realistic assignment of height by utilizing interpolations of analyzed temperature fields from the National Meteorological Center (NMC) to determine the temperature at a given level over the region of interest. Neither these nor other techniques have been tested to any useful extent. The First ISCCP Regional Experiment (FIRE) Intensive Field Observations (IFO) provide an excellent opportunity to assess satellite-derived cloud height results because of the availability of both direct and indirect cloud-top altitude data of known accuracy. The variations of cloud-top altitude during the Marine Stratocumulus IFO (MSIFO, June 29 to July 19, 1987) derived from surface, aircraft, and satellite data are examined.

Minnis, Patrick; Young, David F.; Davies, R.; Blaskovic, M.; Albrecht, Bruce A.

1990-01-01

37

Comparison of AIRS, MODIS, CloudSat and CALIPSO cloud top height retrievals  

Microsoft Academic Search

Knowledge of cloud properties like cloud top height (CTH) is essential to understand their impact on the earth's radiation budget and on climate change. High spectral resolution measurements from the Atmospheric Infrared Sounder (AIRS) are well suited to reveal valuable information about cloud altitude. The CTH retrievals derived from AIRS single field-of-view (FOV) radiance measurements are compared with the operational

Elisabeth Weisz; Jun Li; W. Paul Menzel; Andrew K. Heidinger; Brian H. Kahn; Chian-Yi Liu

2007-01-01

38

Estimation of cloud top height and effective cloud cover from infrared satellite soundings  

Microsoft Academic Search

The paper deals with a new method for simultaneous determination of cloud top height and effective cloud cover, using infrared radiance data of satellite-borne instruments. These cloud properties derived from the Selective Chopper Radiometer on the Nimbus 5 satellite are compared with nearly simultaneous observations by radiosondes and with satellite images. Encouraging results for Central-Europe during January, April, July, August

Gy. Molnár

1981-01-01

39

Automatic cloud top height determination using a cost-effective time-lapse camera system  

NASA Astrophysics Data System (ADS)

A new method for the determination of cloud top heights from the footage of a time-lapse camera is presented. Contact points between cloud tops and underlying terrain are automatically detected in the camera image based on differences in the brightness, texture and movement of cloudy and non-cloudy areas. The height of the detected cloud top positions is determined by comparison with a digital elevation model projected to the view of the camera. The technique has been validated using data about the cloud immersion of a second camera as well as via visual assessment. The validation shows a high detection quality, especially regarding the requirements for the validation of satellite cloud top retrieval algorithms.

Schulz, H. M.; Chang, S.-C.; Thies, B.; Bendix, J.

2014-03-01

40

Relationship between the summer mesopause and polar mesospheric cloud heights  

NASA Astrophysics Data System (ADS)

Satellite data analyses indicate that variations of daily mean polar mesospheric cloud (PMC) height and mesopause height correlate on a range of intraseasonal time scales both short and long (i.e., ˜4 days to 2 months). The average of a multiyear analysis from OSIRIS/Odin, SNOE, AIM, and SABER/TIMED data sets in the polar regions north (south) of 65°N (°S) shows that on a daily basis the mean PMC height (?max) is located 3.5 km ± 0.5 km below the mean mesopause height (?mes) in both hemispheres throughout the season and for all years examined. The data show that the relationship persists over multiple PMC seasons. This is a robust result that has also been verified with thermodynamic equilibrium and microphysical modeling. Model results from a large number of ensemble simulations show that ?max remains ˜3.5 km below ?mes as long as the vertical average of the ambient temperature minus the frost point temperature difference over the supersaturated region is about -10 K or less for all the individual simulations. ?max is located less than 3.5 km below ?mes for warmer supersaturated region temperatures. The distance between the cloud and the mesopause heights (Zmes - Zmax or ?Z) is controlled by the corresponding temperature structure in the supersaturated region. It is concluded that the variation of ?Z is mostly driven by the variation of the temperature structure instead of the H2O mixing ratio magnitude or vertical distribution.

Russell, James M.; Rong, Pingping; Bailey, Scott M.; Hervig, Mark E.; Petelina, Svetlana V.

2010-08-01

41

Cloud Height Maps for Hurricanes Frances and Ivan  

NASA Technical Reports Server (NTRS)

NASA's Multi-angle Imaging SpectroRadiometer (MISR) captured these images and cloud-top height retrievals of Hurricane Frances on September 4, 2004, when the eye sat just off the coast of eastern Florida, and Hurricane Ivan on September 5th, after this cyclone had devastated Grenada and was heading toward the central and western Caribbean. Hurricane Frances made landfall in the early hours of September 5, and was downgraded to Tropical Storm status as it swept inland through the Florida panhandle and continued northward. On the heels of Frances is Hurricane Ivan, which is on record as the strongest tropical cyclone to form at such a low latitude in the Atlantic, and was the most powerful hurricane to have hit the Caribbean in nearly a decade.

The ability of forecasters to predict the intensity and amount of rainfall associated with hurricanes still requires improvement, especially on the 24 to 48 hour timescale vital for disaster planning. To improve the operational models used to make hurricane forecasts, scientists need to better understand the multi-scale interactions at the cloud, mesoscale and synoptic scales that lead to hurricane intensification and dissipation, and the various physical processes that affect hurricane intensity and rainfall distributions. Because these uncertainties with regard to how to represent cloud processes still exist, it is vital that the model findings be evaluated against hurricane observations whenever possible. Two-dimensional maps of cloud height such as those shown here offer an unprecedented opportunity for comparing simulated cloud fields against actual hurricane observations.

The left-hand panel in each image pair is a natural color view from MISR's nadir camera. The right-hand panels are cloud-top height retrievals produced by automated computer recognition of the distinctive spatial features between images acquired at different view angles. These results indicate that at the time that these images were acquired, clouds within Frances and Ivan had attained altitudes of 15 kilometers and 16 kilometers above sea level, respectively. The height fields pictured here are uncorrected for the effects of cloud motion. Wind-corrected heights (which have higher accuracy but sparser spatial coverage) are within about 1 kilometer of the heights shown here.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82o north and 82o south latitude. These data products were generated from a portion of the imagery acquired during Terra orbits 25081 and 25094. The panels cover an area of 380 kilometers x 924 kilometers, and utilize data from within blocks 65 to 87 within World Reference System-2 paths 14 and 222, respectively.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California In

2004-01-01

42

Cloud Coverage and Height Distribution from the GLAS Polar Orbiting Lidar: Comparison to Passive Cloud Retrievals  

NASA Technical Reports Server (NTRS)

The Geoscience Laser Altimeter System (GLAS) began full on orbit operations in September 2003. A main application of the two-wavelength GLAS lidar is highly accurate detection and profiling of global cloud cover. Initial analysis indicates that cloud and aerosol layers are consistently detected on a global basis to cross-sections down to 10(exp -6) per meter. Images of the lidar data dramatically and accurately show the vertical structure of cloud and aerosol to the limit of signal attenuation. The GLAS lidar has made the most accurate measurement of global cloud coverage and height to date. In addition to the calibrated lidar signal, GLAS data products include multi level boundaries and optical depth of all transmissive layers. Processing includes a multi-variable separation of cloud and aerosol layers. An initial application of the data results is to compare monthly cloud means from several months of GLAS observations in 2003 to existing cloud climatologies from other satellite measurement. In some cases direct comparison to passive cloud retrievals is possible. A limitation of the lidar measurements is nadir only sampling. However monthly means exhibit reasonably good global statistics and coverage results, at other than polar regions, compare well with other measurements but show significant differences in height distribution. For polar regions where passive cloud retrievals are problematic and where orbit track density is greatest, the GLAS results are particularly an advance in cloud cover information. Direct comparison to MODIS retrievals show a better than 90% agreement in cloud detection for daytime, but less than 60% at night. Height retrievals are in much less agreement. GLAS is a part of the NASA EOS project and data products are thus openly available to the science community (see http://glo.gsfc.nasa.gov).

Spinhime, J. D.; Palm, S. P.; Hlavka, D. L.; Hart, W. D.; Mahesh, A.

2004-01-01

43

Cloud Height Estimation with a Single Digital Camera and Artificial Neural Networks  

NASA Astrophysics Data System (ADS)

Clouds influence the local weather, the global climate and are an important parameter in the weather prediction models. Clouds are also an essential component of airplane safety when visual flight rules (VFR) are enforced, such as in most small aerodromes where it is not economically viable to install instruments for assisted flying. Therefore it is important to develop low cost and robust systems that can be easily deployed in the field, enabling large scale acquisition of cloud parameters. Recently, the authors developed a low-cost system for the measurement of cloud base height using stereo-vision and digital photography. However, due to the stereo nature of the system, some challenges were presented. In particular, the relative camera orientation requires calibration and the two cameras need to be synchronized so that the photos from both cameras are acquired simultaneously. In this work we present a new system that estimates the cloud height between 1000 and 5000 meters. This prototype is composed by one digital camera controlled by a Raspberry Pi and is installed at Centro de Geofísica de Évora (CGE) in Évora, Portugal. The camera is periodically triggered to acquire images of the overhead sky and the photos are downloaded to the Raspberry Pi which forwards them to a central computer that processes the images and estimates the cloud height in real time. To estimate the cloud height using just one image requires a computer model that is able to learn from previous experiences and execute pattern recognition. The model proposed in this work is an Artificial Neural Network (ANN) that was previously trained with cloud features at different heights. The chosen Artificial Neural Network is a three-layer network, with six parameters in the input layer, 12 neurons in the hidden intermediate layer, and an output layer with only one output. The six input parameters are the average intensity values and the intensity standard deviation of each RGB channel. The output parameter in the output layer is the cloud height estimated by the ANN. The training procedure was performed, using the back-propagation method, in a set of 260 different clouds with heights in the range [1000, 5000] m. The training of the ANN has resulted in a correlation ratio of 0.74. This trained ANN can therefore be used to estimate the cloud height. The previously described system can also measure the wind speed and direction at cloud height by measuring the displacement, in pixels, of a cloud feature between consecutively acquired photos. Also, the geographical north direction can be estimated using this setup through sequential night images with high exposure times. A further advantage of this single camera system is that no camera calibration or synchronization is needed. This significantly reduces the cost and complexity of field deployment of cloud height measurement systems based on digital photography.

Carretas, Filipe; Janeiro, Fernando M.

2014-05-01

44

Deep Convective Cloud Top Heights and Their Thermodynamic Control During CRYSTAL-FACE  

NASA Technical Reports Server (NTRS)

Infrared (11 micron) radiances from GOES-8 and local radiosonde profiles, collected during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) in July 2002, are used to assess the vertical distribution of Florida-area deep convective cloud top height and test predictions as to its variation based on parcel theory. The highest infrared tops (Z(sub 11)) reached approximately to the cold point, though there is at least a 1-km uncertainty due to unknown cloud-environment temperature differences. Since lidar shows that visible 'tops' are 1 km or more above Z(sub 11), visible cloud tops frequently penetrated the lapse-rate tropopause (approx. 15 km). Further, since lofted ice content may be present up to approx. 1 km above the visible tops, lofting of moisture through the mean cold point (15.4 km) was probably common. Morning clouds, and those near Key West, rarely penetrated the tropopause. Non-entraining parcel theory (i.e., CAPE) does not successfully explain either of these results, but can explain some of the day-to-day variations in cloud top height over the peninsula. Further, moisture variations above the boundary layer account for most of the day-today variability not explained by CAPE, especially over the oceans. In all locations, a 20% increase in mean mixing ratio between 750 and 500 hPa was associated with about 1 km deeper maximum cloud penetration relative to the neutral level. These results suggest that parcel theory may be useful for predicting changes in cumulus cloud height over time, but that parcel entrainment must be taken into account even for the tallest clouds. Accordingly, relative humidity above the boundary layer may exert some control on the height of the tropical troposphere.

Sherwood, Steven C.; Minnis, Patrick; McGill, Matthew

2004-01-01

45

6.G Base and Height  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Mrs. Lito asked her students to label a base $b$ and its corresponding height $h$ in the triangle shown. Three students drew the figures below. Raul Ma...

46

Joint analysis of cloud top heights from CloudSat and CALIPSO: New insights into cloud top microphysics  

NASA Astrophysics Data System (ADS)

examined the differences in the cloud top heights (CTHs) detected by the CloudSat radar and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) lidar. Theoretical estimates have shown that CloudSat has higher sensitivity than CALIPSO does when large particles exist. In such case it might be possible that CloudSat-determined CTHs are larger than CALIPSO-determined CTHs. We compared the global distribution of CTHs detected by CloudSat and CALIPSO (version 3, V3) using our cloud mask schemes after carefully selecting data during September-November 2006. The global mean fraction of clouds where CloudSat-determined CTHs were larger than CALIPSO-determined CTHs turned out to be unexpectedly large. The fractions were 26% and 39% at low level and midlevel, and the corresponding CTH differences were 0.56 km and 0.86 km, respectively. On the western coasts of continents, these clouds occurred within temperature inversions. Accounting for the differences in sensitivity to particle size between CloudSat and CALIPSO, the existence of such clouds indicates that the cloud tops consist of large particles with small number concentration. The discovery of such clouds was revealed by our joint analysis of CloudSat and CALIPSO. When the standard vertical feature mask (VFM) V3 was used, these clouds were also found but the fractions were less pronounced. The differences were partly attributed to the overestimation of cloud fraction in the VFM V3, although the degree of misidentification in V3 was reduced compared with that of V2.

Hagihara, Yuichiro; Okamoto, Hajime; Luo, Zhengzhao Johnny

2014-04-01

47

A Simple Stochastic Model for Generating Broken Cloud Optical Depth and Top Height Fields  

NASA Technical Reports Server (NTRS)

A simple and fast algorithm for generating two correlated stochastic twodimensional (2D) cloud fields is described. The algorithm is illustrated with two broken cumulus cloud fields: cloud optical depth and cloud top height retrieved from Moderate Resolution Imaging Spectrometer (MODIS). Only two 2D fields are required as an input. The algorithm output is statistical realizations of these two fields with approximately the same correlation and joint distribution functions as the original ones. The major assumption of the algorithm is statistical isotropy of the fields. In contrast to fractals and the Fourier filtering methods frequently used for stochastic cloud modeling, the proposed method is based on spectral models of homogeneous random fields. For keeping the same probability density function as the (first) original field, the method of inverse distribution function is used. When the spatial distribution of the first field has been generated, a realization of the correlated second field is simulated using a conditional distribution matrix. This paper is served as a theoretical justification to the publicly available software that has been recently released by the authors and can be freely downloaded from http://i3rc.gsfc.nasa.gov/Public codes clouds.htm. Though 2D rather than full 3D, stochastic realizations of two correlated cloud fields that mimic statistics of given fields have proved to be very useful to study 3D radiative transfer features of broken cumulus clouds for better understanding of shortwave radiation and interpretation of the remote sensing retrievals.

Prigarin, Sergei M.; Marshak, Alexander

2007-01-01

48

The MISR Cloud Motion Vector Product: 10 years of height resolved, cloud-track winds  

NASA Astrophysics Data System (ADS)

By utilizing multiple camera views and fast image matching algorithms to identify common features and determine feature motion, the MISR instrument on NASA’s Terra satellite has now collected 10 years of height-resolved, cloud-track, vector winds using a single, globally consistent algorithm. MISR cloud-track winds are packaged within the new MISR Cloud Motion Vector product, reported on mesoscale domains of 70.4 km × 70.4 km and referenced to stereoscopically derived heights above the earth ellipsoid with a nominal precision of 230 m. Importantly, from the standpoint of climate research, the stereo height assignment and wind retrieval are largely insensitive to instrument calibration changes and independent of a priori assumptions because the product algorithms depend only on patterns of observed brightness variability. We will describe comparisons with other wind observations, including geostationary cloud drift winds, raob winds, and scatterometer surface winds that demonstrate the quality of the MISR winds. We will also show the coverage and resolution advantages that MISR provides relative to these other datasets. Additionally, we will analyze agreement and discrepancies between MISR winds and reanalysis winds.

Mueller, K.; Garay, M. J.; Jovanovic, V.; Moroney, C.; Wu, D. L.; Diner, D. J.

2010-12-01

49

A surface-based cloud observing system  

NASA Technical Reports Server (NTRS)

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.

Albrecht, B. A.; Ackerman, T. P.; Thomson, D. W.; Mace, G.; Miller, M. A.; Peters, R. M.

1991-01-01

50

Tornado occurrences related to overshooting cloud-top heights as determined from ATS pictures  

NASA Technical Reports Server (NTRS)

A sequence of ATS 3 pictures including the development history of large anvil clouds near Salina, Kansas was enlarged by NASA into 8X negatives which were used to obtain the best quality prints by mixing scan lines in 8 steps to minimize checker-board patterns. These images resulted in the best possible resolution, permitting use to compute the heights of overshooting tops above environmental anvil levels based on cloud shadow relationships along with the techniques of lunar topographic mapping. Of 39 heights computed, 6 were within 15 miles of reported positions of 3 tornadoes. It was found that the tornado proximity tops were mostly less than 5000 ft, with one exception of 7000 ft, suggesting that tornadoes are most likely to occur when overshooting height decreases. In order to simulate surface vortices induced by cloud-scale rotation and updraft fields, a laboratory model was constructed. The model experiment has shown that the rotation or updraft field induces a surface vortex but their combination does prevent the formation of the surface vortex. This research leads to a conclusion that the determination of the cloud-top topography and its time variation is of extreme importance in predicting severe local storms for a period of 0 to 6 hours.

Fujita, T. T.

1972-01-01

51

Temporal variation of the cloud top height over the tropical Pacific observed by geostationary satellites  

NASA Astrophysics Data System (ADS)

Stratiform clouds (nimbostratus and cirriform clouds) in the upper troposphere accompanied with cumulonimbus activity cover large part of the tropical region and largely affect the radiation and water vapor budgets there. Recently new satellites (CloudSat and CALIPSO) can give us the information of cloud height and cloud ice amount even over the open ocean. However, their coverage is limited just below the satellite paths; it is difficult to capture the whole shape and to trace the lifecycle of each cloud system by using just these datasets. We made, as a complementary product, a dataset of cloud top height and visible optical thickness with one-hour resolution over the wide region, by using infrared split-window data of the geostationary satellites (AGU fall meeting 2011) and released on the internet (http://database.rish.kyoto-u.ac.jp/arch/ctop/). We made lookup tables for estimating cloud top height only with geostationary infrared observations by comparing them with the direct cloud observation by CloudSat (Hamada and Nishi, 2010, JAMC). We picked out the same-time observations by MTSAT and CloudSat and regressed the cloud top height observation of CloudSat back onto 11?m brightness temperature (Tb) and the difference between the 11?m Tb and 12?m Tb. We will call our estimated cloud top height as "CTOP" below. The area of our coverage is 85E-155W (MTSAT2) and 80E-160W(MTSAT1R), and 20S-20N. The accuracy of the estimation with the IR split-window observation is the best in the upper tropospheric height range. We analyzed the formation and maintenance of the cloud systems whose top height is in the upper troposphere with our CTOP analysis, CloudSat 2B-GEOPROF, and GSMaP (Global Satellite Mapping of Precipitation) precipitation data. Most of the upper tropospheric stratiform clouds have their cloud top within 13-15 km range. The cloud top height decreases slowly when dissipating but still has high value to the end. However, we sometimes observe that a little lower cloud top height (6-10 km) is kept within one-two days. A typical example is observed on 5 January 2011 in a dissipating cloud system with 1000-km scale. This cluster located between 0-10N just west of the International Date Line and moved westward with keeping relatively lower cloud top (6-10 km) over one day. This top height is lower than the ubiquitous upper-tropospheric stratiform clouds but higher than the so-called 'congestus cloud' whose top height is around 0C. CloudSat data show the presence of convective rainfall. It suggests that this cloud system continuously kept making new anvil clouds in a little lower height than usual. We examined the seasonal variation of the distribution of cloud systems with a little lower cloud top height (6-11 km) during 2010-11. The number of such cloud systems is not constant with seasons but frequently increased in some specific seasons. Over the equatorial ocean region (east of 150E), they were frequently observed during the northern winter.

Nishi, N.; Hamada, A.

2012-12-01

52

Altimeter height measurement error introduced by the presence of variable cloud and rain attenuation  

NASA Technical Reports Server (NTRS)

It has recently been recognized that spatially inhomogeneous clouds and rain can substantially affect the height precision obtainable from a spaceborne radar altimeter system. Through computer simulation, it has been found that typical levels of cloud and rain intensities and associated spatial variabilities may degrade altimeter precision at 13.5 GHz and, in particular, cause severe degradation at 35 GHz. This degradation in precision is a result of radar signature distortion caused by variable attenuation over the beam limited altimeter footprint. Because attenuation effects increase with frequency, imprecision caused by them will significantly impact on the frequency selection of future altimeters. In this paper the degradation of altimeter precision introduced by idealized cloud and rain configurations as well as for a realistic rain configuration as measured with a ground based radar is examined.

Monaldo, F. M.; Goldhirsh, J.; Walsh, E. J.

1986-01-01

53

Arctic PBL Cloud Height and Motion Retrievals from MISR and MINX  

NASA Technical Reports Server (NTRS)

How Arctic clouds respond and feedback to sea ice loss is key to understanding of the rapid climate change seen in the polar region. As more open water becomes available in the Arctic Ocean, cold air outbreaks (aka. off-ice flow from polar lows) produce a vast sheet of roll clouds in the planetary boundary layer (PBl). The cold air temperature and wind velocity are the critical parameters to determine and understand the PBl structure formed under these roll clouds. It has been challenging for nadir visible/IR sensors to detect Arctic clouds due to lack of contrast between clouds and snowy/icy surfaces. In addition) PBl temperature inversion creates a further problem for IR sensors to relate cloud top temperature to cloud top height. Here we explore a new method with the Multiangle Imaging Spectro-Radiometer (MISR) instrument to measure cloud height and motion over the Arctic Ocean. Employing a stereoscopic-technique, MISR is able to measure cloud top height accurately and distinguish between clouds and snowy/icy surfaces with the measured height. We will use the MISR INteractive eXplorer (MINX) to quantify roll cloud dynamics during cold-air outbreak events and characterize PBl structures over water and over sea ice.

Wu, Dong L.

2012-01-01

54

A Comparison of Several Techniques to Assign Heights to Cloud Tracers.  

NASA Astrophysics Data System (ADS)

Satellite-derived cloud-motion vector (CMV) production has been troubled by inaccurate height assignment of cloud tracers, especially in thin semitransparent clouds. This paper presents the results of an intercomparison of current operational height assignment techniques. Currently, heights are assigned by one of three techniques when the appropriate spectral radiance measurements are available. The infrared window (IRW) technique compares measured brightness temperatures to forecast temperature profiles and thus infers opaque cloud levels. In semitransparent or small subpixel clouds, the carbon dioxide (CO2) technique uses the ratio of radiances from different layers of the atmosphere to infer the correct cloud height. In the water vapor (H2O) technique, radiances influenced by upper-tropospheric moisture and IRW radiances are measured for several pixels viewing different cloud amounts, and their linear relationship is used to extrapolate the correct cloud height. The results presented in this paper suggest that the H2O technique is a viable alternative to the CO2 technique for inferring the heights of semitransparent cloud elements. This is important since future National Environmental Satellite, Data, and Information Service (NESDIS) operations will have to rely on H20-derived cloud-height assignments in the wind field determinations with the next operational geostationary satellite. On a given day, the heights from the two approaches compare to within 60 110 hPa rms; drier atmospheric conditions tend to reduce the effectiveness of the H2O technique. By inference one can conclude that the present height algorithms used operationally at NESDIS (with the C02 technique) and at the European Satellite Operations Center (ESOC) (with their version of the H20 technique) are providing similar results. Sample wind fields produced with the ESOC and NESDIS algorithms using Meteosat-4 data show good agreement.

Nieman, Steven J.; Schmetz, Johannes; Menzel, W. Paul

1993-09-01

55

Global Moderate Resolution Imaging Spectroradiometer (MODIS) cloud detection and height evaluation using CALIOP  

Microsoft Academic Search

A global 2-month comparison is presented between the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and the Moderate Resolution Imaging Spectroradiometer (MODIS) for both cloud detection and cloud top height (CTH) retrievals. Both CALIOP and MODIS are part of the NASA A-Train constellation of satellites and provide continuous near-coincident measurements that result in over 28 million cloud detection comparisons and over

R. E. Holz; S. A. Ackerman; F. W. Nagle; R. Frey; S. Dutcher; R. E. Kuehn; M. A. Vaughan; B. Baum

2008-01-01

56

Improved Boundary Layer and Cloud Heights from the NASA Micro Pulse Lidar Network (MPLNET)  

NASA Astrophysics Data System (ADS)

The NASA Micro Pulse Lidar Network (MPLNET) Level 1.5b data product provides identification of aerosol and cloud layers. New algorithms have been developed for determining planetary boundary layer (PBL) heights and cloud heights from MPLNET data. An overview of the new methods will be discussed, along with their advantages and limitations. Seasonal and diurnal trends observed at the Goddard Space Flight Center site in Greenbelt, MD will also be evaluated. Results from the improved algorithms are compared to the current operational MPLNET cloud and PBL height products as well as the corresponding products from the GEOS-5 model.

Lewis, J.; Welton, E. J.; Belcher, L. R.; Mplnet Team

2011-12-01

57

Cloud top height comparisons from ASTER, MISR, and MODIS for trade wind cumuli  

Microsoft Academic Search

ASTER stereo and ASTER infrared (IR) retrieved cloud top heights (CTHs) at 90 m spatial resolution are compared to operational Multi-Angle Imaging SpectroRadiometer (MISR) stereo and MODerate Resolution Imaging Spectroradiometer (MODIS) thermal IR techniques at 1100 m and 5000 m spatial resolution, respectively. ASTER data availability limits this study to trade wind cumulus clouds only. ASTER IR, MISR stereo and MODIS IR cloud

Iliana Genkova; Gabriela Seiz; Paquita Zuidema; Guangyu Zhao; Larry Di Girolamo

2007-01-01

58

Base Survey of Cloud Cover by Two Spherical Mirrors.  

National Technical Information Service (NTIS)

Use of photos exposed through two spherical mirrors to obtain cloud base heights is explained. Space coordinates of points on the cloud cover are determined from measurements made on the photos. Measuring grids are made for plotting the cloud field. Mathe...

T. N. Bibikova

1973-01-01

59

Tropical cloud-top height distributions revealed by the Ice, Cloud, and Land Elevation Satellite (ICESat)\\/Geoscience Laser Altimeter System (GLAS)  

Microsoft Academic Search

We analyze cloud-top height data obtained at tropical latitudes between 29 September and 17 November, 2003, from the Geoscience Laser Altimeter System (GLAS), carried onboard the Ice, Cloud, and Land Elevation Satellite (ICESat). About 66% of the tropical observations show one or more cloud layers. Of those observations that do show a cloud, about half show two or more cloud

A. E. Dessler; S. P. Palm; J. D. Spinhirne

2006-01-01

60

Trends in ISCCP, MISR, and MODIS cloud-top-height and optical-depth histograms  

NASA Astrophysics Data System (ADS)

In this article, temporal changes in the Multiangle Imaging Spectro Radiometer (MISR) and Moderate Resolution Imaging Spectrometer (MODIS) joint histograms of cloud-top height (CTH) and optical depth (OD) over the period 2001 to 2011 are examined. The analysis shows no significant trend in total cloud cover averaged over all oceans between 60°N and 60°S from 2001 to 2011. There are, however, significant trends in the amount of some CTH-OD histogram components or cloud types. In particular, there was an increase in the amount of cloud with intermediate optical thickness (23 > OD > 3.6) and a decrease in the amount of the most optically thick cloud (OD > 23) over this period. The total cloud amount shows no trend because the increase in the amount of intermediate optically thick clouds is nearly balanced by the decrease in the amount of the most optically thick clouds. This balance is not due to a simple shift toward optically thinner clouds in all regions but has a complex spatial pattern both regionally and vertically. An examination of the geographic distribution of the change shows that the decrease in the amount of the most optically thick cloud occurred primarily in the extratropics. International Satellite Cloud Climatology Project (ISCCP) observations are briefly compared with those from MODIS and MISR. The comparison shows that ISCCP-retrieved total-cloud fraction is reasonably robust, but changes in the ISCCP component cloud fractions sometimes show large deviations from those of MISR and MODIS.

Marchand, Roger

2013-02-01

61

Cloud Based Design Optimization  

Microsoft Academic Search

Cloud based design optimization (CBDO) is an ap- proach to significantly improve robustness and optimality o f solu- tions sought in engineering design. One of the main featuresis the possibility to capture and model high-dimensional uncerta inty infor- mation, even in the case that the information available is in complete or unformalized. Continuing our past studies we present the graphical

Martin Fuchs

2009-01-01

62

Retrieval of cloud fraction and height anomalies and their trend from temporally and spatially averaged infrared spectra observed from space  

NASA Astrophysics Data System (ADS)

Understanding how clouds and atmospheric properties change with time under radiative forcing is necessary to understand feedback. Generally, global clouds and atmospheric Understanding how clouds and atmospheric properties change with time under radiative forcing is necessary to understand feedback. Generally, global clouds and atmospheric properties are retrieved from satellite-based instruments. Subsequently, retrieved values from an instrument's field-of-view are averaged and the time rate of change of cloud or atmospheric properties can be inferred from averaged properties. This is simple in concept but identifying artifacts of the retrieval is difficult in practice. An alternative way to derive a trend of cloud and atmospheric properties is tying their property change directly to the observed radiance change. This average-then-retrieve approach directly utilizes instrument stability but requires separating cloud and atmospheric property changes contributing to the highly spatially and temporally averaged observed radiance change. In this presentation, we demonstrate the average-then-retrieve approach by simulating the retrieval of cloud fraction and height anomalies from highly averaged longwave spectra. We use 28 years of reanalysis (Modern Era Retrospective-Analysis for Research MERRA) for the simulation and retrieve annual 10° zonal cloud fraction and height anomalies, as well as temperature and water vapor amount anomalies. The error in retrieved anomalies is estimated based on the method discussed in Kato et al. (2011). The uncertainty in the trend estimated from retrieved anomalies is also discussed. Reference Kato, S., B. A. Wielicki, F. G. Rose, X. Liu, P. C. Taylor, D. P. Kratz, M. G. Mlynczak, D. F. Young, N. Phojanamongkolkij, S. Sun-Mack, W. F. Miller, Y. Chen, 2011b, Detection of atmospheric changes in spatially and temporally averaged infrared spectra observed from space, J Climate, 24, 6392-6407, Doi: 10.1175/JCLI-D-10-05005.1.

Kato, S.; Rose, F. G.; Liu, X.; Wielicki, B. A.; Mlynczak, M. G.

2013-12-01

63

Estimation of cirrus and stratus cloud height using landsat data and 3D graphical representation  

NASA Astrophysics Data System (ADS)

Cirrus and stratus cloud heights are estimated using LANDSAT MSS(MultiSpectral Scanner) and TM(Thematic mapper) data. Cloud heights are calculated from the sun elevation angle and the horizontal distance between cloud and its shadow templates. The matching of these templates is accomplished by the 2D cross-correlation function. Before accomplishing the matching, histogram equalization, inversion of shadow template, and Fourier Fast Transformation are applied to both templates. Then 2D cross-correlation function is calculated in the frequency domain. Correlation coefficients are 3D graphically displayed to check visually how sharply the templates match. The effects of the skew angle and the nonnadir observation angle are taken into consideration to modify the direction from the cloud template to its corresponding shadow template. The results show that this method is accurate within several pixels.

Inomata, Y.; Takagi, K.; Shiiba, T.; Akitake, R.

64

A modified method for inferring upper troposphere cloud top height using the GOES 12 imager 10.7 and 13.3 ?m data  

Microsoft Academic Search

Passive satellite retrievals using conventional CO2 absorption techniques tend to systematically underestimate the upper transmissive cloud top heights (CTHs). These techniques are based on single-layer assumptions that the upper cloud occupies a geometrically thin layer above a cloud-free surface. This study presents a new modified CO2 absorption technique (MCO2AT) to improve the inference of transmissive CTHs in the upper troposphere

Fu-Lung Chang; Patrick Minnis; Bing Lin; Mandana M. Khaiyer; Rabindra Palikonda; Douglas A. Spangenberg

2010-01-01

65

Satellite and Surface Data Synergy for Developing a 3D Cloud Structure and Properties Characterization Over the ARM SGP. Stage 1: Cloud Amounts, Optical Depths, and Cloud Heights Reconciliation  

NASA Technical Reports Server (NTRS)

One of the primary Atmospheric Radiation Measurement (ARM) Program objectives is to obtain measurements applicable to the development of models for better understanding of radiative processes in the atmosphere. We address this goal by building a three-dimensional (3D) characterization of the cloud structure and properties over the ARM Southern Great Plains (SGP). We take the approach of juxtaposing the cloud properties as retrieved from independent satellite and ground-based retrievals, and looking at the statistics of the cloud field properties. Once these retrievals are well understood, they will be used to populate the 3D characterization database. As a first step we determine the relationship between surface fractional sky cover and satellite viewing angle dependent cloud fraction (CF). We elaborate on the agreement intercomparing optical depth (OD) datasets from satellite and ground using available retrieval algorithms with relation to the CF, cloud height, multi-layer cloud presence, and solar zenith angle (SZA). For the SGP Central Facility, where output from the active remote sensing cloud layer (ARSCL) valueadded product (VAP) is available, we study the uncertainty of satellite estimated cloud heights and evaluate the impact of this uncertainty for radiative studies.

Genkova, I.; Long, C. N.; Heck, P. W.; Minnis, P.

2003-01-01

66

Satellite-Derived Cloud-Top Heights and Cloud-Track Winds from MISR in the Subtropical Southeastern Pacific Compared with In-Situ and Scatterometer Measurements  

Microsoft Academic Search

Frequent observations made by NOAA research vessels in the stratocumulus region in the subtropical southeastern Pacific during cruises in 2001, and 2003 to 2006 provide high spatial and temporal resolution observations that can be used to validate satellite retrievals. Ship-based measurements of cloud-top height have been compared with near-coincident retrievals from the MISR and MODIS instruments on the Terra polar

M. J. Garay; S. P. de Szoeke; L. di Girolamo

2008-01-01

67

Latitudinal variation of Cloud Top Height throughout the seasons as seen from SEVIRI, AIRS and ATSR-2  

Microsoft Academic Search

The main objective of the presented study is to monitor temporal changes in the large scale distribution of Cloud Top Height\\/Pressure (CTH\\/CTP). as they are operationally generated by the EUMETSAT's Satellite Application Facility on Climate Monitoring (CM-SAF). CTH\\/CTP of CM-SAF is considered together with two datasets based on ATSR-2 (the Along Track Scanning Radiometer 2 aboard ERS-2) as well as

Anke Kniffka; Maarit Lockhoff; Rainer Hollmann

2010-01-01

68

Cloud Height Retrieval with Oxygen A and B Bands for the Deep Space Climate Observatory (DSCOVR) Mission  

NASA Technical Reports Server (NTRS)

Planned to fly in 2014, the Deep Space Climate Observatory (DSCOVR) would see the whole sunlit half of the Earth from the L 1 Lagrangian point and would provide simultaneous data on cloud and aerosol properties with its Earth Polychromatic Imaging Camera (EPIC). EPIC images the Earth on a 2Kx2K CCD array, which gives a horizontal resolution of about 10 km at nadir. A filter-wheel provides consecutive images in 10 spectral channels ranging from the UV to the near-IR, including the oxygen A and B bands. This paper presents a study of retrieving cloud height with EPIC's oxygen A and B bands. As the first step, we analyzed the effect of cloud optical and geometrical properties, sun-view geometry, and surface type on the cloud height determination. Second, we developed two cloud height retrieval algorithms that are based on the Mixed Lambertian-Equivalent Reflectivity (MLER) concept: one utilizes the absolute radiances at the Oxygen A and B bands and the other uses the radiance ratios between the absorption and reference channels of the two bands. Third, we applied the algorithms to the simulated EPIC data and to the data from SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY (SCIAMACHY) observations. Results show that oxygen A and B bands complement each other: A band is better suited for retrievals over ocean, while B band is better over vegetated land due to a much darker surface. Improvements to the MLER model, including corrections to surface contribution and photon path inside clouds, will also be discussed.

Yang, Yuekui; Marshak, Alexander; Mao, Jianping; Lyapustin, Alexei; Herman, Jay

2012-01-01

69

Latitudinal variation of Cloud Top Height throughout the seasons as seen from SEVIRI, AIRS and ATSR-2  

NASA Astrophysics Data System (ADS)

The main objective of the presented study is to monitor temporal changes in the large scale distribution of Cloud Top Height/Pressure (CTH/CTP). as they are operationally generated by the EUMETSAT's Satellite Application Facility on Climate Monitoring (CM-SAF). CTH/CTP of CM-SAF is considered together with two datasets based on ATSR-2 (the Along Track Scanning Radiometer 2 aboard ERS-2) as well as a combination of AIRS/AMSU-A (Atmospheric Infrared Sounder/ Advanced Microwave Sounding Unit) measurements. CM-SAF uses space-based observations from geostationary Meteosat Second Generation (MSG) satellites and polar orbiting NOAA and MetOp satellites to provide satellite-derived geophysical parameter data sets suitable for climate monitoring. CM-SAF's product suite includes cloud parameters, radiation fluxes, surface albedo, and atmospheric water vapour, temperature and humidity profiles on a regional and partially on a global scale. ATSR-2's cloud and aerosol products were produced within the project Global Retrieval of ATSR Cloud Parameters and Evaluation (GRAPE) employing an optimal estimation method for the retrieval. AIRS is installed together with AMSU-A on the Aqua mission, the cloud products as well as greenhouse gases and dust maps are produced at the Jet Propulsion Laboratory, California Institute of Technology. For the cloud retrieval the cloud-clearing approach is applied. The monthly mean products from a period between August 2006 and October 2010 from the three different instrument systems were analysed and compared. There are large differences in the derivation of the three data sets concerning the instrumentation and retrieval methods, not to forget that two of the instrument systems fly onboard of polar orbiting satellites while the other one is kept in a geostationary orbit. Nevertheless large scale distributions of the respective cloud top heights are quite comparable. As an example, the travelling of the ITCZ as depicted by the three different datasets is illustrated. For depicting interannual variations of cloud top height products, four months of daily mean fields are chosen, to represent the four seasons. Additionally the operational daily mean product is compared to the instantaneous CTH data in order to detect changes in variability on a larger spatial scale. For that purpose all the daily mean and instantaneous data are averaged over the individual months (January, April, July and October) and longitude, i.e. latitude dependent distributions of CTH data are considered and compared to the instantaneous data.

Kniffka, Anke; Lockhoff, Maarit; Hollmann, Rainer

2010-05-01

70

Multi-Sensor Analysis of Cloud-Top Height in Sc - Cu Transition Regions  

NASA Astrophysics Data System (ADS)

In the eastern basins of the subtropical oceans unbroken sheets of stratocumulus transition to fields of scattered cumulus as boundary-layer air masses advect equatorward in the trades. This shift in cloud regimes is the subject of intense modeling efforts, because it has profound effects on the local and the planetary albedo. To provide observational constraints for such modeling studies, we analyzed satellite measurements of boundary-layer cloud-top heights (CTHs) in the northeast and southeast Atlantic and Pacific. Our sensor suite comprised CALIPSO-CALIOP, MODIS, MISR, and Meteosat-9. The study covered the summer months June-August and September-November for the northern and southern hemisphere, respectively, spanning the period 2006-2009. We considered CALIOP lidar measurements the most accurate and, hence, used them as reference. The operational Collection 5 MODIS CTHs were based on fitting measured cloud-top temperatures (CTTs) to forecast temperature profiles and were known to have large biases in case of low-level inversions. Therefore, we also evaluated CTHs derived from CTT-SST differences and various lapse rate formulations, which is the method suggested for the upcoming Collection 6 dataset. The MISR stereo CTHs were computed from a purely geometric method, which, however, is rather sensitive to errors in along-track wind speed. Because our previous work indicated a MISR cross-swath speed bias, we created a modified CTH dataset by replacing MISR winds with Meteosat-9 winds to correct the raw MISR stereo heights. The various satellite retrievals were then compared over whole regions as well as along characteristic Sc-Cu transition trajectories computed with the HYSPLIT model. For context, results from LES transition simulations were also analyzed. Some highlights of our study are summarized below. The CALIOP, MISR, and lapse-rate-based MODIS CTHs all showed a systematic increase of 500-700 m in the southeast Atlantic and northeast Pacific as Sc transitioned to Cu. In the northeast Atlantic and southeast Pacific, however, these CTHs had no obvious trends and remained fairly constant. Operational MODIS CTHs indicated an erroneously decreasing trend along transition trajectories in all four regions due to large (500-1500 m) overestimations in the Sc regime (although they were fairly reasonable in the Cu regime). The best MODIS dataset was a hybrid one combining current operational retrievals and lapse-rate-based heights depending on the presence or lack of low-level inversions. Overall, MISR CTHs compared most favorably to CALIOP with typical correlations and biases of 0.7 and 150 m, respectively. In the southeast Atlantic, MISR CTH errors could be further reduced by 15-30% when using Meteosat-9 winds for height correction, thereby removing apparent cross-swath biases.

Ludewig, E.; Horvath, A.

2010-12-01

71

Height profile of particle concentration in an aeolian saltating cloud: A wind tunnel investigation by PIV MSD  

Microsoft Academic Search

Attempt is made to define the particle concentration in an aeolian saltating cloud and its variation with height using artificial spherical quartz sand in a wind tunnel. The height profiles of the relative particle concentration in aeolian saltating cloud at three wind velocities were detected by the state of the art PIV (Particle Image Velocimetry) MSD (Mie Scattering Diffusion) technique,

Zhibao Dong; Hongtao Wang; Xiaohang Zhang; Michael Ayrault

2003-01-01

72

Texture-based cloud classification  

NASA Technical Reports Server (NTRS)

The purpose of the 1988 ASEE Summer Program has been to broaden the application of texture-based cloud classification approaches to lower spatial resolution GOES imagery, and to design texture-based approaches for determining cloud cover over high albedo surfaces.

Welch, Ronald M.

1988-01-01

73

Improvements on the relationship between plume height and mass eruption rate: Implications for volcanic ash cloud forecasting  

NASA Astrophysics Data System (ADS)

Volcanic ash plumes and the dispersing clouds into the atmosphere are a hazard for local populations as well as for the aviation industry. Volcanic ash transport and dispersion (VATD) models, used to forecast the movement of these hazardous ash emissions, require eruption source parameters (ESP) such as plume height, eruption rate and duration. To estimate mass eruption rate, empirical relationships with observed plume height have been applied. Theoretical relationships defined by Morton et al. (1956) and Wilson et al. (1976) use default values for the environmental lapse rate (ELR), thermal efficiency, density of ash, specific heat capacity, initial temperature of the erupted material and final temperature of the material. Each volcano, based on its magma type, has a different density, specific heat capacity and initial eruptive temperature compared to these default parameters, and local atmospheric conditions can produce a very different ELR. Our research shows that a relationship between plume height and mass eruption rate can be defined for each eruptive event for each volcano. Additionally, using the one-dimensional modeling program, Plumeria, our analysis assesses the importance of factors such as vent diameter and eruption velocity on the relationship between the eruption rate and measured plume height. Coupling such a tool with a VATD model should improve pre-eruptive forecasts of ash emissions downwind and lead to improvements in ESP data that VATD models use for operational volcanic ash cloud forecasting.

Webley, P. W.; Dehn, J.; Mastin, L. G.; Steensen, T. S.

2011-12-01

74

Dependence of the drizzle growth process on the cloud top height and its relevance to the aerosol vertical profile  

NASA Astrophysics Data System (ADS)

Transitional processes among cloud droplets, drizzle and raindrops are still uncertain and more efforts are required for the better understanding. In this situation, difference in the drizzle growth process was examined according to the cloud top height using the CloudSat and MODIS synergetic datasets. From the CloudSat products such as 2B-GEOPROF, 2B-TAU, ECMWF-AUX, only one-layered water clouds whose top temperatures were warmer than 273K were extracted over China (a circular area having a diameter of 1800km of the center at 35°N and 120°E) and over ocean (a circular area having a diameter of 1500km of the center at 35°N and 150°E). Then a threshold of 3km of the cloud top height was adopted to divide the extracted clouds into upper and lower cases. First, the probability distribution functions (PDF) of the cloud droplet number density (Nc) and the effective particle radius (Re) were calculated for these four cases (land/ocean/upper/lower). Nc was obtained assuming the adiabatic liquid water content from MODIS-derived cloud optical depth and Re. Oceanic clouds had fewer Nc than land clouds, and almost the same for upper and lower cases. Land clouds had more Nc for the lower case than for the higher case. On the other hand, oceanic clouds had larger Re than land clouds, and almost the same for upper and lower cases. Land clouds had smaller Re for the lower case than for the higher case. These results quite agreed with our existing knowledge on the vertical profile of the aerosol number concentration over ocean (pristine) and land (polluted). Although the number of aerosol particles is fewer and almost the same regardless of the height over the ocean, it is more near the surface and it rapidly decreases according to the height over the land. Next, examining PDF of the radar reflectivity (Ze), we found that although PDFs of Ze were almost the same for oceanic clouds regardless of the cloud top height, PDF of land lower clouds were less frequent at around from -20(dBZ) to -5 (dBZ) than that of land upper clouds. The region from -20(dBZ) to -5 (dBZ) approximately corresponds to drizzle particles. The less frequency of Ze at the region is consistent with the smaller Re of lower clouds. Therefore, we conclude that this phenomenon can be understood as one of the presentations for the second kind of the aerosol indirect effect. PDF of radar reflectivity of upper and lower clouds over the ocean and China

Kawamoto, K.; Suzuki, K.

2013-12-01

75

An evaluation of operational GOES-derived single-layer cloud top heights with ARSCL data over the ARM Southern Great Plains Site  

Microsoft Academic Search

Cloud top heights retrieved from Geostationary Operational Environmental Satellite (GOES) data are evaluated using comparisons to 5 years of surface-based cloud radar and lidar data taken at the Atmospheric Radiation Measurement (ARM) program's site near Lamont, Oklahoma. Separate daytime and nighttime algorithms developed at NASA Langley Research Center (LaRC) applied to GOES imager data and an operational CO2-slicing technique applied

William L. Smith Jr; Patrick Minnis; Heather Finney; Rabindra Palikonda; Mandana M. Khaiyer

2008-01-01

76

Linear trends in cloud top height from passive observations in the oxygen A-band  

NASA Astrophysics Data System (ADS)

Measurements by the hyperspectral spectrometers GOME, SCIAMACHY and GOME-2 are used to determine the rate of linear change (and trends) in cloud top height (CTH) in the period between June 1996 and May 2012. The retrievals are obtained from Top-Of-Atmosphere (TOA) backscattered solar light in the oxygen A-band using the Semi-Analytical CloUd Retrieval Algorithm SACURA. The physical framework relies on the asymptotic equations of radiative transfer, valid for optically thick clouds. Using linear least-squares techniques, a global trend of -1.78 ± 2.14 m yr-1 in deseasonalized CTH has been found, in the latitude belt within ±60°, with diverging tendencies over land (+0.27 ± 3.2 m yr-1) and ocean (-2.51 ± 2.8 m yr-1). The El Niño-Southern Oscillation (ENSO), strongly coupled to CTH, forces clouds to lower altitudes. The global ENSO-corrected trend in CTH amounts to -0.49 ± 2.22 m yr-1. At a global scale, no explicit regional pattern of statistically significant trends (at 95% confidence level, estimated with bootstrap technique) have been found, which would be representative of typical natural synoptical features. One exception is North Africa, which exhibits the strongest upward trend in CTH sustained by an increasing trend in water vapour.

Lelli, L.; Kokhanovsky, A. A.; Rozanov, V. V.; Vountas, M.; Burrows, J. P.

2014-06-01

77

Cloud Agency: A Mobile Agent Based Cloud System  

Microsoft Academic Search

The cloud paradigm appeared on the computing scene in 2005 with the Amazon Elastic Compute Cloud (EC2). After this date, a large set of related technologies has been developed. In the academic world, and especially in the HPC area, cloud computing is in some way in competition with the GRID model, which offers a middleware based approach. One of the

Rocco Aversa; Beniamino Di Martino; Massimiliano Rak; Salvatore Venticinque

2010-01-01

78

Satellite retrieval of convective cloud base temperature based on the NPP/VIIRS Imager  

NASA Astrophysics Data System (ADS)

advent of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-Orbiting Partnership (NPP) satellite provided a quantum jump in the satellite capabilities of retrieving cloud properties, because it nearly tripled the resolution in the thermal channels (375 m). This allowed us to develop a methodology for retrieving convective cloud base temperature (Tb) and validate it over the Atmospheric System Research Southern Great Plains site for the satellite early afternoon overpass time. The standard error of the Tb retrieval was only 1.1°C. The knowledge of Tb allows the calculation of cloud base height and the depth of the boundary layer, as well as the boundary layer water vapor mixing ratio with an accuracy of about 10%. The feasibility of retrieving cloud base temperature and height is an essential component that is required for retrieving cloud condensation nuclei (CCN) from satellites by using convective clouds as natural CCN chambers.

Zhu, Yannian; Rosenfeld, Daniel; Yu, Xing; Liu, Guihua; Dai, Jin; Xu, Xiaohong

2014-02-01

79

Cloud-Based Data Storage  

ERIC Educational Resources Information Center

The vulnerability and inefficiency of backing up data on-site is prompting school districts to switch to more secure, less troublesome cloud-based options. District auditors are pushing for a better way to back up their data than the on-site, tape-based system that had been used for years. About three years ago, Hendrick School District in…

Waters, John K.

2011-01-01

80

Lidar-based remote sensing of atmospheric boundary layer height over land and ocean  

NASA Astrophysics Data System (ADS)

Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of the ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and the ABL vertical structure over ocean and land are analyzed. The new methods are then applied to satellite lidar measurements. The aerosol-derived global marine boundary layer heights are evaluated with marine ABL stratiform cloud top heights and results show a good agreement between them.

Luo, T.; Yuan, R.; Wang, Z.

2014-01-01

81

Novel Spectrograph/Radiometer for Cloud Top Height Measurement Using Three Complementary Techniques  

NASA Technical Reports Server (NTRS)

A proof-of-concept (POC) instrument system to measure cloud top height from space using three complementary techniques is presented. These techniques use measurements of: (1) thermal infrared (IR); (2) molecular oxygen 'A' band absorption; and (3) filling-in of Fraunhofer lines (the Ring effect), respectively. Combining three techniques is achieved with a single grating spectrograph with bandpass and order sorting filters by measuring I I jim radiation from the zeroth order of the grating for the IR, 750-780 nm radiation from the first order for the 'A' band absorption, and 390-400 mn radiation from the second order for the Ca K and H Fraunhofer line filling-in effect. The POC system and its measurement results with the POC system are described.

Park, Hongwoo; Soulen, Peter F.; Prasad, Coorg R.

1997-01-01

82

Lidar-based remote sensing of atmospheric boundary layer height over land and ocean  

NASA Astrophysics Data System (ADS)

Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and ABL vertical structure over ocean (TWP_C2 cite) and land (SGP_C1) are analyzed. The new methods are also applied to satellite lidar measurements. The derived global marine boundary layer structure database shows good agreement with marine ABL stratiform cloud top height.

Luo, T.; Yuan, R.; Wang, Z.

2013-09-01

83

Cloud Types  

NSDL National Science Digital Library

This table provides a quick reference to cloud types. Clouds are divided into groups mainly based on the height of the cloud's base above the Earth's surface. The table further divides the types according to group, atmospheric layer, and base height. Links to additional information are embedded in the text, and users can select beginner, intermediate, or advanced levels of difficulty. A Spanish translation is available.

84

Global Ice Cloud Properties Based on CALIPSO and CloudSat Measurements and Their Radiative Effect  

NASA Astrophysics Data System (ADS)

The radiative influence of atmospheric ice clouds varies widely from shortwave to longwave. This frequency-dependent response is convenient, and various techniques have been developed to better understand ice cloud properties. In recent years, the joint observations of the CloudSat Radar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar have frequently been used to examine clouds of varying optical depth (OD). The former excels in probing thick clouds, usually associated with cooling, while the latter performs better with thin clouds, which are generally associated with localized warming. This study aims at investigating global ice cloud properties based on DarDar (raDar/liDar) data that combines both lidar and radar observations, while at the same modeling ice cloud radiative effects. Using DarDar data, this study firstly examines global Ice Water Path (IWP), and shows a global mean IWP value of 113.55 g/m2 for all measurements and 196.34 g/m2 for cloudy situations. The global frequency of ice cloud occurrence reveals that ice clouds predominate in deep convectional regions and storm tracks. Conversely, the subtropics contain fewer ice clouds. Due to Intertropical Convergence Zone (ITCZ) seasonal shifting and storm seasonal changes, a global map of ice cloud occurrence likewise varies seasonally. Global ice cloud occurrence also depends on the day-night cycle. Occurrence at night is 4.8% higher than during the day. IWP, on the contrary, is 1.75 g/m2 lower at night. There is considerable variation among sampled clouds, in which the visible OD ranges from near zero to over 100. Within this range, thin cirrus with OD < 3.0 are most common (75.87%). To better ascertain ice cloud properties, we group ice clouds into five bins according to visible OD: 0 < OD < 0.03, 0.03 < OD < 0.3, 0.3 < OD < 3.0, 3.0 < OD < 20 and OD > 20. The ice clouds with lowest OD are common at midlatitudes, while those with largest OD occur mostly in tropical convective zones and storm track regions. Vertical distributions of ice clouds show that the most frequent height for occurrence in the tropics is near 15 km for cirrus and near 10 km for thick ice clouds. At mid or high latitudes, the vertical maximum for thin cirrus is much lower (near 1.5 km); for thick clouds, it is around 5 km. 3-D images of ice cloud distribution also show that tropical ice clouds prefer a temperatures range between 195 - 230 K with Ice Water Content (IWC) ranging from 0.001 to 0.01 g/m3. At midlatitudes, ice cloud occurrence reaches its maximum when temperatures are 225 - 255 K and IWC is around 0.01 g/m3.

Hong, Y.; Liu, G.

2013-12-01

85

Satellite-Observed Location of Stratocumulus Cloud-Top Heights in the Presence of Strong Inversions  

Microsoft Academic Search

Infrared channels on the Moderate Resolution Imaging Spectroradiometer (MODIS) are used to infer cloud-top pressure (CTP), temperature, and effective cloud amount or emissivity. For low clouds, those with tops at pressures greater than 700 hPa, the infrared window 11-mum channel brightness temperature is used to determine the CTP and the corresponding cloud-top temperature by comparison with the temperature profile obtained

Harshvardhan; Guangyu Zhao; Larry Di Girolamo; Robert N. Green

2009-01-01

86

Factors Limiting Convective Cloud-Top Height at the ARM Nauru Island Climate Research Facility  

Microsoft Academic Search

Cumulus congestus clouds, with moderate shortwave albedos and cloud-top temperatures near freezing, occur fairly often in the Tropics. These clouds may play an important role in the evolution of the Madden- Julian oscillation and the regulation of relative humidity in the midtroposphere. Despite this importance they are not necessarily simulated very well in global climate models. Surface remote sensing observations

Michael P. Jensen; Anthony D. Del Genio

2006-01-01

87

Validation of Satellite-Based Objective Overshooting Cloud-Top Detection Methods Using CloudSat Cloud Profiling Radar Observations  

NASA Technical Reports Server (NTRS)

Two satellite infrared-based overshooting convective cloud-top (OT) detection methods have recently been described in the literature: 1) the 11-mm infrared window channel texture (IRW texture) method, which uses IRW channel brightness temperature (BT) spatial gradients and thresholds, and 2) the water vapor minus IRW BT difference (WV-IRW BTD). While both methods show good performance in published case study examples, it is important to quantitatively validate these methods relative to overshooting top events across the globe. Unfortunately, no overshooting top database currently exists that could be used in such study. This study examines National Aeronautics and Space Administration CloudSat Cloud Profiling Radar data to develop an OT detection validation database that is used to evaluate the IRW-texture and WV-IRW BTD OT detection methods. CloudSat data were manually examined over a 1.5-yr period to identify cases in which the cloud top penetrates above the tropopause height defined by a numerical weather prediction model and the surrounding cirrus anvil cloud top, producing 111 confirmed overshooting top events. When applied to Moderate Resolution Imaging Spectroradiometer (MODIS)-based Geostationary Operational Environmental Satellite-R Series (GOES-R) Advanced Baseline Imager proxy data, the IRW-texture (WV-IRW BTD) method offered a 76% (96%) probability of OT detection (POD) and 16% (81%) false-alarm ratio. Case study examples show that WV-IRW BTD.0 K identifies much of the deep convective cloud top, while the IRW-texture method focuses only on regions with a spatial scale near that of commonly observed OTs. The POD decreases by 20% when IRW-texture is applied to current geostationary imager data, highlighting the importance of imager spatial resolution for observing and detecting OT regions.

Bedka, Kristopher M.; Dworak, Richard; Brunner, Jason; Feltz, Wayne

2012-01-01

88

Ship based cloud and radiation measurements on the Atlantic Ocean  

NASA Astrophysics Data System (ADS)

Clouds remain one of the biggest obstacles in our understanding of the coupled ocean-atmosphere climate system. Because of the strong inhomogeneity of cloud pattern on those scales that are relevant for the radiative transfer processes it is clear that subgrid-scale processes must be accounted for in radiative transfer parameterizations. Combined observations of cloud physical and radiative properties are a key to adjust or to validate such parameterizations. In spring and in fall 2007 the cruises ANT-XXIII-10 and ANT-XXIV-1 of the German research vessel Polarstern from South Africa to Germany and back have been utilized to perform continuous measurements of the radiation budget at the sea surface and the corresponding cloud properties under tropical, subtropical and mid-latitude climate conditions. For the first time, a multichannel microwave radiometer has been operated under open ocean conditions to obtain profiles of humidity, temperature, as well as liquid water path and water vapor path with 1 Hz temporal resolution. Cloud cover, cloud type and cloud bottom height have been obtained from continuous sky imaging and ceilometer measurements. Satellite based surface radiation budget estimates from Meteosat-7 SEVIRI measurements provided by the Climate Monitoring - Satellite Application Facilities CM-SAF have been compared to ship based measurements. Differences between the two will be discussed in terms of climatological and meteorological conditions. The high resolution ship based observations of cloud and radiation properties have been applied to improve exisiting surface radiation parameterizations with special considerations of rapid fluctuations due to the dynamics of clouds. Both campaigns in 2007 are test phases for the German national project OCEANET where temporarilly high resolved measurements of the chemical and biological composition of the upper ocean are combined with energy- and CO2-flux measurements at the ocean surface to improve our understanding of ocean-atmosphere interactions. To this end intensive measurements during six Atlantic transects of RV Polarstern between 2008 and 2010 will be performed.

Macke, A.; Kalisch, J.; Hollmann, R.; Sinitsyn, A.; Wassmann, A.

2007-12-01

89

Satellite-Based Insights into Precipitation Formation Processes in Continental and Maritime Convective Clouds  

Microsoft Academic Search

Multispectral analyses of satellite images are used to calculate the evolution of the effective radius of convective cloud particles with temperature, and to infer from that information about precipitation forming processes in theclouds. Different microphysical processes are identified at different heights. From cloud base to top, the microphysical classification includes zones of diffusional droplet growth, coalescence droplet growth, rainout, mixed-phase

Daniel Rosenfeld; Itamar M. Lensky

1998-01-01

90

Identity-Based Authentication for Cloud Computing  

NASA Astrophysics Data System (ADS)

Cloud computing is a recently developed new technology for complex systems with massive-scale services sharing among numerous users. Therefore, authentication of both users and services is a significant issue for the trust and security of the cloud computing. SSL Authentication Protocol (SAP), once applied in cloud computing, will become so complicated that users will undergo a heavily loaded point both in computation and communication. This paper, based on the identity-based hierarchical model for cloud computing (IBHMCC) and its corresponding encryption and signature schemes, presented a new identity-based authentication protocol for cloud computing and services. Through simulation testing, it is shown that the authentication protocol is more lightweight and efficient than SAP, specially the more lightweight user side. Such merit of our model with great scalability is very suited to the massive-scale cloud.

Li, Hongwei; Dai, Yuanshun; Tian, Ling; Yang, Haomiao

91

An assessment of factors limiting tropical congestus cloud-top heights  

Microsoft Academic Search

I investigate the capping mechanisms behind mid-level cumulus congestus clouds. Two theories are analyzed using two months (January-February 2007) of collocated data between the Atmospheric InfraRed Sounder (AIRS) onboard Aqua and the Cloud Profiling Radar (CPR) onboard CloudSat, as well as data from the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (a, ERA) Interim Reanalysis. The first theory is

Sean Patrick Casey

2009-01-01

92

Interactive Physically-Based Cloud Simulation  

Microsoft Academic Search

Articial clouds play an important role in the computer generation of natural outdoor scenes. Realistic modeling and rendering of such scenes is important for applications in games, military training simulations, ight simulations, and even in the creation of digital artistic media. We pro- pose a model for simulating cloud formation based on an efcient computational uid solver. We combine the

Derek Overby; Zeki Melek; John Keyser

2002-01-01

93

The effects of cloud inhomogeneities upon radiative fluxes, and the supply of a cloud truth validation dataset  

NASA Technical Reports Server (NTRS)

A series of cloud and sea ice retrieval algorithms are being developed in support of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Science Team objectives. These retrievals include the following: cloud fractional area, cloud optical thickness, cloud phase (water or ice), cloud particle effective radius, cloud top heights, cloud base height, cloud top temperature, cloud emissivity, cloud 3-D structure, cloud field scales of organization, sea ice fractional area, sea ice temperature, sea ice albedo, and sea surface temperature. Due to the problems of accurately retrieving cloud properties over bright surfaces, an advanced cloud classification method was developed which is based upon spectral and textural features and artificial intelligence classifiers.

Welch, Ronald M.

1993-01-01

94

Access Control of Cloud Service Based on UCON  

NASA Astrophysics Data System (ADS)

Cloud computing is an emerging computing paradigm, and cloud service is also becoming increasingly relevant. Most research communities have recently embarked in the area, and research challenges in every aspect. This paper mainly discusses cloud service security. Cloud service is based on Web Services, and it will face all kinds of security problems including what Web Services face. The development of cloud service closely relates to its security, so the research of cloud service security is a very important theme. This paper introduces cloud computing and cloud service firstly, and then gives cloud services access control model based on UCON and negotiation technologies, and also designs the negotiation module.

Danwei, Chen; Xiuli, Huang; Xunyi, Ren

95

Cirrus clouds and condensation trail on 18 Oct. 1989 over the North sea (ICE '89). Determination of height and optical depth using ALEX, AVHRR and HIRS  

NASA Astrophysics Data System (ADS)

Data from International Cloud Experiment (ICE) on the height and optical depth of cirrus clouds obtained either by the Aircraftborne Aerosol Experiment (ALEX), or by satellite observations, Advanced Very High Resolution Radiometer (AVHRR) and High resolution Infrared Radiation Sounder (HIRS), are compared. It is shown that a 30 percent agreement is to be expected with regard to error estimation. The comparison between satellite data and aircraft observations of derived cloud parameters, shows that satellite data can give quantitative information on the physical properties of clouds.

Kaestner, Martina; Kriebel, Karl-Theodor; Meerkoetter, Ralf; Renger, Wolfgang; Ruppersberg, Gerhard; Wendling, Peter

1991-09-01

96

Local boundary layer, vertical motions measured with 1290 MHz profiler and Ceilometer cloud heights over a high altitude location in the central Himalaya  

NASA Astrophysics Data System (ADS)

Manora peak is a high altitude station (about 2 km, amsl) in the central Himalays, well above planetary boundary layer, hence the observations of clouds and study of the local boundary over the station is essential to understand the dynamics caused by mountains and meteorology of the region. Vaisala Radar Wind Profiler (RWP) to measure the winds and vertical motions in the lowest 4 km of the troposphere, and to find the cloud heights a Vaisala Ceilometer (VCEIL) were installed and operated at the ARM mobile facility site (AMF1) ARIES, Nainital (29.50N, 79.50E, ~2 km amsl), under the Indo-US collaborative field programme termed as Regional Aerosols Warming Experiment-Ganges Valley Aerosol Experiment (RAWEX-GVAX). Observations with RWP commenced since November 2011, whereas Ceilometer had been operational since June 2011 and collected data during monsoon and the campaign ended in March 2012. RWP is an active remote sensing device that operates unattended and provides continuous, real-time observations with excellent spatial and temporal (60 m) resolution. RWP observations do not show significant variations in the local boundary layer within the season e.g. winter months and spring, but 200m about 500m variation from winter to spring. Over the entire period of observation, anabatic winds are found usually in the forenoon and sinking motions in the evening hours mostly within 1 ms-1. VCEIL is a self-contained, ground-based, active remote-sensing device designed to measure cloud-base height to a maximum of 7.6 km and potential backscatter signals by aerosols. In case of the Ceilometer, cloud height varies from day to day, but the observed values during monsoon months of 2011, range between 400 m to 3000 m, above ground level. In addition, the observations made with micro pulse Lidar, Doppler Lidar and the co-located facilities for meteorological parameters, will be utilized to understand the lower atmospheric dynamics over the mountains. Details will be discussed during the presentation.

Singh, N.; Naja, M. K.; Dumka, U. C.; Phanikumar, D.; Pant, P.; Sagar, R.; Satheesh, S.; Krishnamoorthy, K.; Kotamarthi, V. R.

2012-12-01

97

Clouds  

NSDL National Science Digital Library

In this scenario-based, problem-based learning (PBL) activity, students investigate cloud formation, cloud classification, and the role of clouds in heating and cooling the Earth; how to interpret TRMM (Tropical Rainfall Measuring Mission) images and data; and the role clouds play in the Earthâs radiant budget and climate. Students assume the role of weather interns in a state climatology office and assist a frustrated student in a homework assignment. Learning is supported by a cloud in a bottle and an ice-albedo demonstration, a three-day cloud monitoring outdoor activity, and student journal assignments. The hands-on activities require two 2-liter soda bottles, an infrared heat lamp, and two thermometers. The resource includes a teacher's guide, questions and answer key, assessment rubric, glossary, and an appendix with information supporting PBL in the classroom.

98

Comparison of macroscopic cloud data from ground-based measurements using VIS\\/NIR and IR instruments at Lindenberg, Germany  

Microsoft Academic Search

A comparison between different types of ground-based sensors has been carried out to derive macroscopic cloud data such as cloud cover and cloud-base heights. The instruments compared in the campaign at the Meteorological Observatory Lindenberg in the period May to September 2006 include an infrared (IR) sky scanner called Nubiscope, a Daylight VIS\\/NIR Whole Sky Imager (WSI), a ceilometer LD-40

Uwe Feister; Hans Möller; Theo Sattler; Janet Shields; Ulrich Görsdorf; Jürgen Güldner

2010-01-01

99

An improved algorithm for polar cloud-base detection by ceilometer over the ice sheets  

NASA Astrophysics Data System (ADS)

Optically thin ice and mixed-phase clouds play an important role in polar regions due to their effect on cloud radiative impact and precipitation. Cloud-base heights can be detected by ceilometers, low-power backscatter lidars that run continuously and therefore have the potential to provide basic cloud statistics including cloud frequency, base height and vertical structure. The standard cloud-base detection algorithms of ceilometers are designed to detect optically thick liquid-containing clouds, while the detection of thin ice clouds requires an alternative approach. This paper presents the polar threshold (PT) algorithm that was developed to be sensitive to optically thin hydrometeor layers (minimum optical depth ? ≥ 0.01). The PT algorithm detects the first hydrometeor layer in a vertical attenuated backscatter profile exceeding a predefined threshold in combination with noise reduction and averaging procedures. The optimal backscatter threshold of 3 × 10-4 km-1 sr-1 for cloud-base detection near the surface was derived based on a sensitivity analysis using data from Princess Elisabeth, Antarctica and Summit, Greenland. At higher altitudes where the average noise level is higher than the backscatter threshold, the PT algorithm becomes signal-to-noise ratio driven. The algorithm defines cloudy conditions as any atmospheric profile containing a hydrometeor layer at least 90 m thick. A comparison with relative humidity measurements from radiosondes at Summit illustrates the algorithm's ability to significantly discriminate between clear-sky and cloudy conditions. Analysis of the cloud statistics derived from the PT algorithm indicates a year-round monthly mean cloud cover fraction of 72% (±10%) at Summit without a seasonal cycle. The occurrence of optically thick layers, indicating the presence of supercooled liquid water droplets, shows a seasonal cycle at Summit with a monthly mean summer peak of 40 % (±4%). The monthly mean cloud occurrence frequency in summer at Princess Elisabeth is 46% (±5%), which reduces to 12% (±2.5%) for supercooled liquid cloud layers. Our analyses furthermore illustrate the importance of optically thin hydrometeor layers located near the surface for both sites, with 87% of all detections below 500 m for Summit and 80% below 2 km for Princess Elisabeth. These results have implications for using satellite-based remotely sensed cloud observations, like CloudSat that may be insensitive for hydrometeors near the surface. The decrease of sensitivity with height, which is an inherent limitation of the ceilometer, does not have a significant impact on our results. This study highlights the potential of the PT algorithm to extract information in polar regions from various hydrometeor layers using measurements by the robust and relatively low-cost ceilometer instrument.

Van Tricht, K.; Gorodetskaya, I. V.; Lhermitte, S.; Turner, D. D.; Schween, J. H.; Van Lipzig, N. P. M.

2014-05-01

100

DEVELOPMENT OF A PROCEDURE FOR VERTICAL STRUCTURE ANALYSIS AND 3D-SINGLE TREE EXTRACTION WITHIN FORESTS BASED ON LIDAR POINT CLOUD  

Microsoft Academic Search

A procedure for both vertical canopy structure analysis and 3D single tree extraction based on Lidar raw point cloud is presented in this paper. The whole study area is segmented into small study cells by a raster net. For each cell, a normalized point cloud whose point heights represent the absolute heights of the ground objects is generated from the

Yunsheng Wang; Holger Weinacker; Barbara Koch

2007-01-01

101

Lidar retrievals of cloud droplet number concentration at the cumulus base: A feasibility study  

NASA Astrophysics Data System (ADS)

The properties of atmospheric aerosol under a cumulus base were studied using three-wavelength lidar. A growth of hygroscopic aerosol particles in a convective updraft and the activation of cloud condensation nuclei (CCN) were observed. A simple and robust model of droplet formation in a rising parcel was used as a closing assumption to the original approach of cloud droplet number concentration (CDNC) retrieval. The potential to retrieve the vertical profile of the effective radius of droplets near the cloud base and the height of activation and condensation of nuclei is demonstrated.

Stacewicz, T.; Posyniak, M.; Sitarek, S.; Malinowski, S. P.

2014-06-01

102

Comparison of Cloud Boundaries Measured with 8.6 mm Radar and 10.6 Micrometer Lidar.  

National Technical Information Service (NTIS)

One of the most basic cloud properties is location; the height of cloud base and the height of cloud top. The glossary of meteorology defines cloud base (top) as follows: 'For a given cloud or cloud layer, that lowest (highest) level in the atmosphere at ...

T. Uttal J. M. Intrieri

1993-01-01

103

Macrophysical and optical properties of midlatitude high-altitude clouds from 4 ground-based lidars and collocated CALIOP observations  

NASA Astrophysics Data System (ADS)

Cirrus clouds not only play a major role in the energy budget of the Earth-Atmosphere system, but are also important in the hydrological cycle [Stephens et al., 1990; Webster, 1994]. According to satellite passive remote sensing, high-altitude clouds cover as much as 40% of the earth's surface on average (Liou 1986; Stubenrauch et al., 2006) and can reach 70% of cloud cover over the Tropics (Wang et al., 1996; Nazaryan et al., 2008). Hence, given their very large cloud cover, they have a major role in the climate system (Lynch et al. 2001). Cirrus clouds can be classified into three distinct families according to their optical thickness, namely subvisible clouds (OD<0.03), semi-transparent clouds (0.03clouds (0.3clouds represent 50% or more of cirrus cloud population. The radiative effects of cirrus clouds are found to be significant by many studies both at the top of the atmosphere and surface. The contribution of the subvisible and semi-transparent classes is strongly affected by levels of other scatterers in the atmosphere (gases, aerosols). This makes them quite an important topic of study at the global scale. In the present work, we applied the cloud structure analysis algorithm STRAT to long time series of lidar backscatter profiles from multiple locations around the world. Our goal was to establish a Mid-Latitude climatology of cirrus clouds macrophysical properties based on active remote sensing: ground-based lidars at four mid-latitude observatories and the spaceborne instrument CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization). Lidar sampling, macrophysical (cloud base height, cloud top height, cloud thickness) and optical (cloud optical thickness) properties statistics are then evaluated and compared between the four observatories ground-based lidar measurements and quasi-simultaneously CALIOP overpasses. We note an overall good consistency in the macrophysical properties statistics derived from ground- based Lidar and CALIOP. For high altitude clouds, using consistent transmission-based retrieval methods, discrepancies are found in COT retrievals between ground Lidars and CALIOP. Ground-based Lidar retrievals contain less thick cirrus clouds than CALIOP. Overall, the results show that cirrus clouds with COD<0.1 (not included in historical cloud climatologies) represent 30-50% of the non-opaque cirrus class (COD<3, Pressure<440mb from ISCCP). Finally, we analyze the statistic consistencies between each dataset and investigate the possible bias due to lidar sampling and instrument/algorithm differences between ground-based lidar and CALIOP.

Dupont, J. C.; Haeffelin, M.; Morille, Y.; Noel, V.; Keckhut, P.; Comstock, J.; Winker, D.; Chervet, P.; Roblin, A.

2009-04-01

104

Community-based cloud for emergency management  

Microsoft Academic Search

Natural and man-made emergencies pose an ever-present threat to the society. In response to the growing number of recent disasters, such as the Indonesian volcanic eruption, Gulf of Mexico oil spill, Haitian earthquake, Pakistani floods, and in particular, the Red River crest that causes flood almost every year here in Fargo, North Dakota, we propose a community- based scalable cloud

Juan Li; Qingrui Li; Samee Ullah Khan; Nasir Ghani

2011-01-01

105

Biological ice nuclei at tropospheric cloud heights: potential conditioning of precipitation  

NASA Astrophysics Data System (ADS)

Different substances present in the atmosphere enhance the aggregation of water molecules into ice structures, but particularly effective seem to be aerosols of biological origin, active at temperatures up to -2°C. Yet, the relevance of biological ice nucleation for cloud processes, such as initiating precipitation, remains ambiguous. We try to understand the meteorological conditions and the environmental factors controlling the abundance of biological ice nuclei (IN) in precipitation. One full year of observations has been carried out at the High Altitude Research station of Jungfraujoch, in the Swiss Alps, 3580 m a.s.l. Fresh snow was collected each month and analysed immediately on site for the concentration of IN active at temperatures warmer than -12°C. For this purpose we had developed an innovative system automatically recording freezing events of samples in closed tubes. Additional information was gained through the recording of meteorological parameters associated with the precipitation events, and the determination of stable isotopes (2H and 18O) and of bacterial concentrations (direct epifluorescence microscope counting, live/dead staining) in precipitation. Our analysis of the data suggests that the abundance of ice nuclei in snowfall is characterized not only by seasonality, but also by the geographical origin of precipitating air masses. Further, it seems that the more water an air mass has lost through previous precipitation, the smaller is the biological IN abundance in the remaining precipitation. Moreover, the loss of biological IN with precipitation seems to be much faster than that of other suspended particles in the same air mass, pointing towards a role of biological IN in conditioning the development of precipitation at its early stages.

Stopelli, Emiliano; Conen, Franz; Alewell, Christine; Morris, Cindy

2014-05-01

106

Spatial relationship representation based on cloud model  

NASA Astrophysics Data System (ADS)

By introducing the object cloud into topological space, the spatial relationships between fuzzy objects transform to cloud relationships in cloud space. According to cloud theory, all the spatial objects can be represented by three types object cloud: point-cloud, line-cloud and area-cloud. So the 9-intersection model of spatial topological relations proposed by Egenhofer can be extended by using the new definition of object cloud. The relationship between object clouds is flexible relationship. Different from the crisp relationship model, 9IM, the flexible relationship model by object cloud can be simplified to 4-intersection cloud model(4ICM), including to equal, contain, intersect and disjoint. The cloud operation and virtue cloud can be introduced to representing the fuzzy and uncertain topological relations. The method makes spatial data model enable to model the spatial phenomena with fuzziness and uncertainties, and enriches the cloud theory.

Wang, Zuocheng; Xue, Lixia

2009-10-01

107

Variations in Forest Canopy Height structure across the Amazon Basin, Brazil based on GLAS LiDAR  

NASA Astrophysics Data System (ADS)

LiDAR remote sensing has proven to be a valuable source of information for remote characterization of vegetation structure. The data coverage provided by GLAS, over 14 million returns throughout the Brazilian Amazon basin provides a unique opportunity to further understanding of canopy structure. Previous research at Tapajós National Forest, in the state of Pará, Brazil, has shown an increasing trend in canopy height based on distance from water (Hunter, et al. 2007). This trend may be due to a combination of factors such as soil type, forest history and disturbance pattern. This work tests this relationship throughout the Brazilian Amazon, and compares results with regional flooding regimes. Using a type cover map based upon PRODES 2006, with clouded regions filled in where possible using PRODES 2005, forest and water coverages were separated from other cover types. Over a million GLAS waveforms are available within forest cover types within 3 kilometers of water. Distributions of canopy height estimates (Lefsky, ICESat Vegetation Product, heights ver 0.3) were used to calculate variation of canopy height with distance from water. The Brazilian Amazon was divided into regions of 2 x 2 degrees. The change in 10th percentile height was positive for 84 of 91 regions tested, with a mean increase of approximately 3m. The strongest relationships were found along the main branch of the Amazon River.

Hunter, M.; Keller, M.; Braswell, R.; Lefsky, M.

2008-12-01

108

Arctic Stratus Cloud Properties and Radiative Forcing Derived from Ground-Based Data Collected at Barrow, Alaska.  

NASA Astrophysics Data System (ADS)

A record of single-layer and overcast low-level Arctic stratus cloud properties has been generated using data collected from May to September 2000 at the Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) (71.3°N, 156.6°W) site near Barrow, Alaska. The record includes liquid-phase and liquid dominant mixed-phase Arctic stratus macrophysical, microphysical, and radiative properties, as well as surface radiation budget and cloud radiative forcing. The macrophysical properties consist of cloud fractions, cloud-base/top heights and temperatures, and cloud thickness derived from a ground-based radar and lidar pair, and rawinsonde sounding. The microphysical properties include cloud liquid water path and content, and cloud-droplet effective radius and number concentration obtained from microwave radiometer brightness temperature measurements, and the new cloud parameterization. The radiative properties contain cloud optical depth, effective solar transmission, and surface/cloud/top-of-atmosphere albedos derived from the new cloud parameterization and standard Epply precision spectral pyranometers. The shortwave, longwave, and net cloud radiative forcings at the surface are inferred from measurements by standard Epply precision spectral pyranometers and pyrgeometers. There are approximately 300 h and more than 3600 samples (5-min resolution) of single-layer and overcast low-level stratus during the study period. The 10-day averaged total and low-level cloud (Ztop < 3 km) fractions are 0.87 and 0.55, and low-level cloud-base and -top heights are around 0.4 and 0.8 km. The cloud-droplet effective radii and number concentrations in the spring are similar to midlatitude continental stratus cloud microphysical properties, and in the summer they are similar to midlatitude marine stratus clouds. The total cloud fractions in this study show good agreement with the satellite and surface results compiled from data collected during the First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) Arctic Cloud Experiment (ACE) and the Surface Heat Budget of the Arctic Ocean (SHEBA) (77°N, 165°W) field experiments in 1998. The cloud microphysics derived from this study are similar, in general, to those collected in past field programs, although these comparisons are based on data collected at different locations and years. At the ARM NSA site, the summer cooling period is much longer (2-3 months vs 1-2 weeks), and the summer cooling magnitude is much larger (100 W m2 vs 5 W m2) than at the SHEBA ship under the conditions of all skies at the SHEBA and overcast low-level stratus clouds at the NSA site.

Dong, Xiquan; Mace, Gerald G.

2003-02-01

109

Cloud-Based Mobile Computing Applications Platform for First Responders.  

National Technical Information Service (NTIS)

A cloud-based Mobile Computing Applications Platform (MCAP) for enhanced situational awareness and mobile command and control for first responders is introduced. MCAP is a cloud-enabled platform for defining, developing, and deploying apps on smartphones,...

C. Chung C. Misner D. Egan N. Caruso R. Wallace

2013-01-01

110

NASA Cloud-Based Climate Data Services  

NASA Astrophysics Data System (ADS)

Cloud-based scientific data services are becoming an important part of NASA's mission. Our technological response is built around the concept of specialized virtual climate data servers, repetitive cloud provisioning, image-based deployment and distribution, and virtualization-as-a-service (VaaS). A virtual climate data server (vCDS) is an Open Archive Information System (OAIS) compliant, iRODS-based data server designed to support a particular type of scientific data collection. iRODS is data grid middleware that provides policy-based control over collection-building, managing, querying, accessing, and preserving large scientific data sets. We have deployed vCDS Version 1.0 in the Amazon EC2 cloud using S3 object storage and are using the system to deliver a subset of NASA's Intergovernmental Panel on Climate Change (IPCC) data products to the latest CentOS federated version of Earth System Grid Federation (ESGF), which is also running in the Amazon cloud. vCDS-managed objects are exposed to ESGF through FUSE (Filesystem in User Space), which presents a POSIX-compliant filesystem abstraction to applications such as the ESGF server that require such an interface. A vCDS manages data as a distinguished collection for a person, project, lab, or other logical unit. A vCDS can manage a collection across multiple storage resources using rules and microservices to enforce collection policies. And a vCDS can federate with other vCDSs to manage multiple collections over multiple resources, thereby creating what can be thought of as an ecosystem of managed collections. With the vCDS approach, we are trying to enable the full information lifecycle management of scientific data collections and make tractable the task of providing diverse climate data services. In this presentation, we describe our approach, experiences, lessons learned, and plans for the future.; (A) vCDS/ESG system stack. (B) Conceptual architecture for NASA cloud-based data services.

McInerney, M. A.; Schnase, J. L.; Duffy, D. Q.; Tamkin, G. S.; Strong, S.; Ripley, W. D., III; Thompson, J. H.; Gill, R.; Jasen, J. E.; Samowich, B.; Pobre, Z.; Salmon, E. M.; Rumney, G.; Schardt, T. D.

2012-12-01

111

PoU based sharp features extraction from point cloud  

Microsoft Academic Search

Sharp features of 3D point clouds play an important role in many geometric computations and modeling application. In this paper, a novel modified Partition of Unity (PoU) Based Sharp feature extraction algorithm is proposed, which is directly operated on discrete point clouds. For every point in target point cloud, spherical neighborhood with radius ? is acquired with the help of

Cao Juming; W. Slam; Liang Jin; Liang Xinhe; Zhang Dehai; Liu Jianwei; Yao Xinhui

2010-01-01

112

Research on electronic data security strategy based on cloud computing  

Microsoft Academic Search

Cloud computing is a new network computing paradigm based on IP architecture, it is everywhere, pick up any tech magazine or visit almost any IT website or blog and you'll be sure to see talk about cloud computing. Cloud computing applications without borders, mobility and other characteristics has led to their own safety and security issues in the security field.

Guoman Lin

2012-01-01

113

Pervasive Forensic Analysis Based on Mobile Cloud Computing  

Microsoft Academic Search

Cloud computing has become one of mobile's hottest topics. Moving computing processing and data storage away from mobile devices and into large data centers, mobile applications enable the users to improve productivity, to share data and to collaborate with others. Considering the benefits of mobile cloud computing, the forensic service based on mobile cloud computing could be good solution to

Jooyoung Lee; Dowon Hong

2011-01-01

114

Research of mobile learning system based on cloud computing  

Microsoft Academic Search

Mobile learning is one of the most important e-Learning models, with the development of technology, cloud computing provides a new idea for mobile learning. After analyzing mobile learning and the various advantages it got from the cloud computing, the paper introduces a cloud-computing-based mobile learning system model, in order to promote the development of mobile learning.

Shaoyong Chen; Min Lin; Huanming Zhang

2011-01-01

115

Collaboration-Based Cloud Computing Security Management Framework  

Microsoft Academic Search

Although the cloud computing model is considered to be a very promising internet-based computing platform, it results in a loss of security control over the cloud-hosted assets. This is due to the outsourcing of enterprise IT assets hosted on third-party cloud computing platforms. Moreover, the lack of security constraints in the Service Level Agreements between the cloud providers and consumers

Mohemed Almorsy; John Grundy; Amani S. Ibrahim

2011-01-01

116

CLOUDS.  

National Technical Information Service (NTIS)

This report is an in-depth Users Manual for the ANSI FORTRAN computer program CLOUDS. CLOUDS is designed in two major blocks: cloud field generation and cloud-free line-of-sight (CFLOS) calculation. The cloud field generation block models observed cloud f...

M. K. Seager

1979-01-01

117

Initial assessment of space-based lidar CALIOP aerosol and cloud layer structures through inter-comparison with a ground-based back-scattering lidar and CloudSat  

NASA Astrophysics Data System (ADS)

This study presents results of the intercomparison of aerosol/cloud top and bottom heights obtained from a space-borne active sensor Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard CALIPSO, and the Cloud Profiling Radar (CPR) onboard CloudSat, and the space-borne passive sensor Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua, and ground-based 2-wavelenght polarization lidar system (532 and 1064 nm) at Seoul National University (SNU), Seoul, South Korea. This result confirms that the CALIPSO science team algorithms for the discrimination of cloud and aerosol as well as for the detection of layer top and base altitude provide reliable information both under cloud-free conditions and in cases of multiple aerosol layers underlying semi-transparent cirrus clouds. Simultaneous space-borne CALIOP, CPR and ground-based SNU lidar (SNU-L) measurements complement each other and can be combined to provide full information on the vertical distribution of aerosols and clouds, especially for thick opaque clouds. The aerosol extinction profiles from both lidars show good agreement for aerosols within the planetary boundary layer under cloud-free conditions and for the night-time CALIOP flight.

Kim, S.-W.; Yoon, S.-C.; Chung, E.-S.; Sohn, B.-J.; Berthier, S.; Raut, J.-C.; Chazette, P.; Dulac, F.

2009-03-01

118

Temporal and spatial variations of global deep cloud systems based on CloudSat and CALIPSO satellite observations  

NASA Astrophysics Data System (ADS)

The spatial and temporal global distribution of deep clouds was analyzed using a four-year dataset (2007-10) based on observations from CloudSat and CALIPSO. Results showed that in the Northern Hemisphere, the number of deep cloud systems (DCS) reached a maximum in summer and a minimum in winter. Seasonal variations in the number of DCS varied zonally in the Southern Hemisphere. DCS occurred most frequently over central Africa, the northern parts of South America and Australia, and Tibet. The mean cloud-top height of deep cloud cores (TDCC) decreased toward high latitudes in all seasons. DCS with the highest TDCC and deepest cores occurred over east and south Asian monsoon regions, west-central Africa and northern South America. The width of DCS (WDCS) increased toward high latitudes in all seasons. In general, DCS were more developed in the horizontal than in the vertical direction over high latitudes and vice versa over lower latitudes. Findings from this study show that different mechanisms are behind the development of DCS at different latitudes. Most DCS at low latitudes are deep convective clouds which are highly developed in the vertical direction but cover a relatively small area in the horizontal direction; these DCS have the highest TDCC and smallest WDCS. The DCS at midlatitudes are more likely to be caused by cyclones, so they have less vertical development than DCS at low latitudes. DCS at high latitudes are mainly generated by large frontal systems, so they have the largest WDCS and the smallest TDCC.

Peng, Jie; Zhang, Hua; Li, Zhanqing

2014-05-01

119

Policy Based Resource Allocation in Cloud Systems  

Microsoft Academic Search

Cloud Systems provide computing resources in a flexible manner. There are several key requirements that need to be addressed regarding the resource allocation in Clouds and the most important of them is providing on demand elasticity. This paper focuses on adding new features to the Cloud resource allocation mechanism that enhance on demand elasticity. Most of the resource managers that

Elena Apostol; Catalin Leordeanu; Valentin Cristea

2011-01-01

120

A Lidar Point Cloud Based Procedure for Vertical Canopy Structure Analysis And 3D Single Tree Modelling in Forest  

PubMed Central

A procedure for both vertical canopy structure analysis and 3D single tree modelling based on Lidar point cloud is presented in this paper. The whole area of research is segmented into small study cells by a raster net. For each cell, a normalized point cloud whose point heights represent the absolute heights of the ground objects is generated from the original Lidar raw point cloud. The main tree canopy layers and the height ranges of the layers are detected according to a statistical analysis of the height distribution probability of the normalized raw points. For the 3D modelling of individual trees, individual trees are detected and delineated not only from the top canopy layer but also from the sub canopy layer. The normalized points are resampled into a local voxel space. A series of horizontal 2D projection images at the different height levels are then generated respect to the voxel space. Tree crown regions are detected from the projection images. Individual trees are then extracted by means of a pre-order forest traversal process through all the tree crown regions at the different height levels. Finally, 3D tree crown models of the extracted individual trees are reconstructed. With further analyses on the 3D models of individual tree crowns, important parameters such as crown height range, crown volume and crown contours at the different height levels can be derived.

Wang, Yunsheng; Weinacker, Holger; Koch, Barbara

2008-01-01

121

Graph Cut Based Point-Cloud Segmentation for Polygonal Reconstruction  

Microsoft Academic Search

The reconstruction of 3D objects from a point-cloud is based on sufficient separation of the points representing objects of\\u000a interest from the points of other, unwanted objects. This operation called segmentation is discussed in this paper. We present\\u000a an interactive unstructured point-cloud segmentation based on graph cut method where the cost function is derived from euclidean\\u000a distance of point-cloud points.

David Sedlacek; Jiri Zara

2009-01-01

122

Comparison of the CALIPSO satellite and ground-based observations of cirrus clouds at the ARM TWP sites  

NASA Astrophysics Data System (ADS)

Statistics of ice cloud macrophysical and optical properties from the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP) instrument on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite are compared with those from ground-based lidar observations over a 31 month period. Ground-based lidar observations are taken from the micropulse lidars (MPL) at the three Department of Energy Atmospheric Radiation Measurement (ARM) tropical western pacific (TWP) sites: Manus, Nauru and Darwin. CALIPSO observations show a larger cloud fraction at high altitudes while the ground-based MPLs show a larger cloud fraction at low altitudes. The difference in mean ice cloud top and base heights at the Manus and Nauru sites are all within 0.51 km, although differences are statistically significant. Mean ice cloud geometrical thickness agree to within 0.05 km at the Manus and Nauru sites. Larger differences exist at Darwin due to excessive degradation of the MPL output power during our sampling period. Both sets of observations show thicker clouds during the nighttime which may be real but could also be partially an artifact of the decreased signal-to-noise ratio during the daytime. The number of ice cloud layers per profile are also shown to be consistent after accounting for the difference in spatial resolution. For cloud optical depths, four different retrieval methods are compared, two for each set of observations. All products show that the majority of ice cloud optical depths (˜60%) fall below an optical depth of 0.2. For most comparisons all four retrievals agree to within the uncertainty intervals. We find that both CALIPSO retrievals agree best to ground-based optical depths when the lidar ratio in the latter is retrieved instead of set to a fixed value. Also thoroughly compared is the cloud properties for the subset of ice clouds which reside in the tropical tropopause layer (TTL).

Thorsen, Tyler J.; Fu, Qiang; Comstock, Jennifer

2011-11-01

123

Determination of the normal height of the Everest based on EGM 2008  

NASA Astrophysics Data System (ADS)

The orthometric height H is the height above the geoid, which is the equi-geopotential surface nearest to the mean sea level. The normal height H*, however, is the height above the quasi-geoid, which fast coincides with the geoid in the ocean but deviates from the geoid a little in the land areas. In China, the height datum system is based on the quasi-geoid, i.e., in most cases we use the normal height. GPS technique provides the coordinates of an arbitrary point P on ground with the accuracy better than 1 cm, in the geocentric Earth-fixed system. Hence, with the same accuracy, GPS technique provides the geodetic coordinates of the point P . Then, if the quasi-geoid is determined, the normal height can be subsequently determined. In the present paper, we focus on the determination of the normal height of the Everest based on the international gravity field model, EGM 2008. The geodetic coordinates of the Everest could be obtained by different sources. We use the coordinates provided by Chinese Surveying Bureau. In the frame of Molodensky theory, based on EGM 2008 (with degree 2190), we determine the normal height of the Everest by two approaches: point-wise approach and area-average approach. By point-wise and area-average approaches, our results show that the normal heights of the Everest are HEGM2008* = 8847.32 m and HEGM2008* = 8847.37 m, respectively. Concerning the normal height determination of the Everest, we find that the difference between our result and the result provided recently by Chinese Surveying Bureau is less than 0.1 m. Using EGM 96 however, we find that the difference is around 1 m. This study is supported by National 863 Project of China (Grant No.: 2006AA12Z211) and National Natural Science Foundation of China (Grant No.: 40637034; 40574004).

Shen, W. B.; Li, Jin; Han, J.

2009-04-01

124

Clouds  

NSDL National Science Digital Library

Clouds comprise a wonderful focus for classroom study. They're ubiquitous, ever-changing, scientifically interesting and, most importantly for teachers, they're cheap. The material presented here includes sections on cloud formation, cloud types, cloud pictures, other cloud-related phenomena, and a glossary.

Wozniak, Carl

125

Feasibility of a linear model of the ionospheric scale height based on LEO GNSS occultation data  

NASA Astrophysics Data System (ADS)

GPS radio occultations allow the sounding of the Earth's atmosphere, in particular the ionosphere. The physical observables estimated with this technique allow to test theoretical models of the ionosphere, as, for example, the Chapman and the Vary-Chap models. The former is characterized by a constant scale height, whereas the latter considers a more general function of the scale height and the height. We propose to investigate the feasibility of a novel and simple model where the scale height varies linearly with the height. The scale height data provided by the radio occultations from a receiver on board a low Earth orbit (LEO) satellite, obtained by iterating with a local Chapman model at every point of the vertical profile provided by the GNSS satellite occultation, are fitted with the height, by means of a linear least squares fit (LLS), in order to test this hypothesis. Preliminary results, based on FORMOSAT-3/COSMIC GPS occultation data, show that the scale height presents a more clear linear trend above the F2 layer peak height (hmF2) which can be in agreement with a temperature dependence, following ionospheric models like the IRI. Moreover, according to this preliminary analysis, the parameters of the linear fit do not depend significantly on the local time, whereas they do on latitude.

Olivares, German; Hernandez-Pajares, Manuel; Aragon, Angela; Sanz, Juan

2013-04-01

126

CloudMap: a cloud-based pipeline for analysis of mutant genome sequences.  

PubMed

Whole genome sequencing (WGS) allows researchers to pinpoint genetic differences between individuals and significantly shortcuts the costly and time-consuming part of forward genetic analysis in model organism systems. Currently, the most effort-intensive part of WGS is the bioinformatic analysis of the relatively short reads generated by second generation sequencing platforms. We describe here a novel, easily accessible and cloud-based pipeline, called CloudMap, which greatly simplifies the analysis of mutant genome sequences. Available on the Galaxy web platform, CloudMap requires no software installation when run on the cloud, but it can also be run locally or via Amazon's Elastic Compute Cloud (EC2) service. CloudMap uses a series of predefined workflows to pinpoint sequence variations in animal genomes, such as those of premutagenized and mutagenized Caenorhabditis elegans strains. In combination with a variant-based mapping procedure, CloudMap allows users to sharply define genetic map intervals graphically and to retrieve very short lists of candidate variants with a few simple clicks. Automated workflows and extensive video user guides are available to detail the individual analysis steps performed (http://usegalaxy.org/cloudmap). We demonstrate the utility of CloudMap for WGS analysis of C. elegans and Arabidopsis genomes and describe how other organisms (e.g., Zebrafish and Drosophila) can easily be accommodated by this software platform. To accommodate rapid analysis of many mutants from large-scale genetic screens, CloudMap contains an in silico complementation testing tool that allows users to rapidly identify instances where multiple alleles of the same gene are present in the mutant collection. Lastly, we describe the application of a novel mapping/WGS method ("Variant Discovery Mapping") that does not rely on a defined polymorphic mapping strain, and we integrate the application of this method into CloudMap. CloudMap tools and documentation are continually updated at http://usegalaxy.org/cloudmap. PMID:23051646

Minevich, Gregory; Park, Danny S; Blankenberg, Daniel; Poole, Richard J; Hobert, Oliver

2012-12-01

127

STUDY OF GRIDDED MIXING HEIGHTS AD CLOUD FIELDS DERIVED FROM THE MESOSCALE METEOROLOGICAL MODEL WITH FOUR DIMENSIONAL DATA ASSIMILATION  

EPA Science Inventory

Meteorological data including wind, temperature and moisture variables, as well as boundary layer parameters including surface fluxes, depth of the mixed layer and cloud and precipitation information are integral components of air quality simulations models (AQSMS). QSMs require ...

128

Cloud based firewall system and service  

US Patent & Trademark Office Database

A cloud-based firewall system and service is provided to protect customer sites from attacks, leakage of confidential information, and other security threats. In various embodiments, such a firewall system and service can be implemented in conjunction with a content delivery network (CDN) having a plurality of distributed content servers. The CDN servers receive requests for content identified by the customer for delivery via the CDN. The CDN servers include firewalls that examine those requests and take action against security threats, so as to prevent them from reaching the customer site. The CDN provider implements the firewall system as a managed firewall service, with the operation of the firewalls for given customer content being defined by that customer, independently of other customers. In some embodiments, a customer may define different firewall configurations for different categories of that customer's content identified for delivery via the CDN.

2013-06-04

129

Comparison of macroscopic cloud data from ground-based measurements using VIS/NIR and IR instruments at Lindenberg, Germany  

NASA Astrophysics Data System (ADS)

A comparison between different types of ground-based sensors has been carried out to derive macroscopic cloud data such as cloud cover and cloud-base heights. The instruments compared in the campaign at the Meteorological Observatory Lindenberg in the period May to September 2006 include an infrared (IR) sky scanner called Nubiscope, a Daylight VIS/NIR Whole Sky Imager (WSI), a ceilometer LD-40 measuring in the near infrared region (NIR) and a Ka band cloud radar measuring in the micro wave band (extremely high frequency or EHF) region. In addition, our data analysis included regular hourly cloud observations by weather observers, and vertical profiles of temperature, humidity and winds taken from six-hourly radio soundings at the site. The comparison has been focused on performance and features of the Nubiscope as a prototype instrument for automatic cloud observations. Cloud cover (CC) derived from the Nubiscope cloud algorithm compares quite well with CC derived from both WSI and from observations. CC differences are within ± 2 Okta in 67% of cases between Nubiscope and observations, and in 90% of cases between Nubiscope and WSI. The cloud detection capability as derived from the zenith signals of Nubiscope and WSI shows coincidence in about 90% of cases. For cloud-base heights (CBHs) from Nubiscope data and ceilometer as well as from radar reflectivity, the comparison showed a general good correspondence in the lower and middle troposphere up to heights of about 6 km with some systematic difference due to the different detection methods. For the upper troposphere above 6 km the differences become widespread and more random. Cloud detection capabilities of the instruments are also illustrated by a case study of moving clouds with patterns similar to contrails that were erroneously classified as such by the weather observer mainly due to lack of height information that the ceilometer did not provide. By combined information from WSI, radio sonde humidity and radar, they were shown not to be contrails, but most likely low-level water clouds either of natural origin or built from aircraft at their ascent or descent flight close to the airport.

Feister, Uwe; Möller, Hans; Sattler, Theo; Shields, Janet; Görsdorf, Ulrich; Güldner, Jürgen

2010-05-01

130

Cloudy sounding and cloud-top height retrieval from AIRS alone single field-of-view radiance measurements  

Microsoft Academic Search

High-spectral resolution measurements from the Atmospheric Infrared Sounder (AIRS) onboard the EOS (Earth Observing System) Aqua satellite provide unique information about atmospheric state, surface and cloud properties. This paper presents an AIRS alone single field-of-view (SFOV) retrieval algorithm to simultaneously retrieve temperature, humidity and ozone profiles under all weather conditions, as well as cloud-top pressure (CTP) under cloudy skies. For

Elisabeth Weisz; Jun Li; Jinlong Li; Daniel K. Zhou; Hung-Lung Huang; Mitchell D. Goldberg; Ping Yang

2007-01-01

131

Efficient modeling of height datum based on GIS  

NASA Astrophysics Data System (ADS)

Since the proposal of Digital Earth, its research and applications are continuing to be deepened, and now Smart City is more indepth implementation of the Digital Earth. The unification of global or regional vertical datums has always been one of the main geodesy studies to achieve Smart City, as Smart City must first realize the seamless integration of multi-source geo-dataset. This paper introduces spatio-temporal data management and interactive visualization into the entire process of vertical datum modelling. We demonstrate that the efficiency of modelling is greatly improved. In this paper GIS database is used to manage all dataset such as tidal station data, gravity field model data, GPS leveling data, and vertical datum data for evaluation and analysis. We use geographic information visualization technique to graphically display the results, together with the interactive browsing, to convert tedious digital information to easy-to-understand images. Consequently, researchers can quickly and comprehensively grasp the macro and micro information. Finally, an efficient and interactive prototype operating platforms for vertical datum modeling is constructed based on GIS.

Qiao, Q.

2014-04-01

132

S'COOL Lesson: Estimating Altitude of Water Cloud Base  

NSDL National Science Digital Library

Students begin by determining dew point using an aluminum can, stirring rod, ice and thermometer. Air temperature is also measured and recorded. Students then use those two data in conjunction with the Lifting Condensation Level approximation, to estimate the base altitude of visible (low level) clouds. The Students' Cloud Observations On-Line (S'COOL) project engages students in making and reporting ground truth observations of clouds then comparing those observations with data from the CERES satellite instrument.

133

Context Model Based on Ontology in Mobile Cloud Computing  

Microsoft Academic Search

\\u000a Mobile Cloud Computing has become as a new IT paradigm because of the growth of mobile device like smartphone and appearance\\u000a of Cloud Computing environment. This mobile cloud environment provides various services and IT resources according to users‘\\u000a requests, so an effective management of service and IT resources is required. Hence, this paper designs a context model based\\u000a on ontology

Changbok Jang; Euiin Choi

134

Cloud Base Signature in Transmission Spectra of Exoplanet Atmospheres  

NASA Astrophysics Data System (ADS)

We present an analytical model for the transmission spectrum of a transiting exoplanet, showing that a cloud base can produce an observable inflection point in the spectrum. The wavelength and magnitude of the inflection can be used to break the degeneracy between the atmospheric pressure and the abundance of the main cloud material, however, the abundance still depends on cloud particle size. An observed inflection also provides a specific point on the atmospheric P-T profile, giving us a "thermometer" to directly validate or rule out postulated cloud species. We apply the model to the transit spectrum of HD 189733b.

Vahidinia, Sanaz; Cuzzi, Jeffrey N.; Marley, Mark; Fortney, Jonathan

2014-07-01

135

Height compensation using ground inclination estimation in inertial sensor-based pedestrian navigation.  

PubMed

In an inertial sensor-based pedestrian navigation system, the position is estimated by double integrating external acceleration. A new algorithm is proposed to reduce z axis position (height) error. When a foot is on the ground, a foot angle is estimated using accelerometer output. Using a foot angle, the inclination angle of a road is estimated. Using this road inclination angle, height difference of one walking step is estimated and this estimation is used to reduce height error. Through walking experiments on roads with different inclination angles, the usefulness of the proposed algorithm is verified. PMID:22164061

Park, Sang Kyeong; Suh, Young Soo

2011-01-01

136

Distributed Search Engine for an IaaS Based Cloud  

Microsoft Academic Search

Cloud based online storage enables the storage of massive data. In these systems, a full text search engine is very important for finding documents. In this paper, we propose a distributed search engine suitable for searching a cloud. In our previous work, we developed a distributed search engine, the cooperative search engine (CSE). We now extend the CSE to search

Yuuta Ichikawa; Minoru Uehara

2011-01-01

137

The Content Delivery Network System Based on Cloud Storage  

Microsoft Academic Search

Numerous Cloud storage service have recently emerged to provide Internet-enabled content storage and delivery capabilities. The CDN system based on Cloud storage, adopting distributed storage technology and the cache technology, can provide content creators with cheap CDN service and content consumers (mobile WAP users) with less response time and wider bandwidth WAP service. For the mobile WAP service users, the

Yuedui Wang; Xiangming Wen; Yong Sun; Zhenmin Zhao; Tianpu Yang

2011-01-01

138

Summer cloud and precipitation properties at Utsteinen, Dronning Maud Land, Antarctica, measured by ground-based remote sensing instruments  

NASA Astrophysics Data System (ADS)

A unique comprehensive observatory on meteorological-cloud-precipitation interactions has been built at the new Belgian Princess Elisabeth station, situated on the Utsteinen ridge, at the foot of Sør Rondane mountains in East Antarctica (http://ees.kuleuven.be/hydrant). The instruments already installed include an automatic weather station (AWS) and three ground-based cloud and precipitation remote sensing instruments (ceilometer, infra-red pyrometer and 24GHz vertically pointing radar). The cloud and precipitation instruments have been operating during three summer periods (2009-2010, 2010-2011 and 2011-2012), while the AWS has been operating almost continuously since February 2009 through present time. The measurements are combined in order to obtain basic statistics of clouds properties (height and cloud base temperature), their radiative forcing, as well as frequency and vertical extension of snowfall events, together with the meteorological situation at Utsteinen. Measurements during the first two summer campaigns showed that cloud base temperatures ranged between -200C for low-level clouds (1-1.5 km agl) and -350C - -400C for midlevel clouds (2-4 km agl). The 1-3 km height range was found to have the highest cloud frequency. Synoptic events with and without snowfall have been related to the water vapor transport and local cloud properties. One of the analyzed storms with snowfall in February 2010 showed a two-day evolution with low-level and mid-level clouds observed during the first day, forming multiple layers with short periods of light precipitation, and lowering cloud bases during the second day followed by snowfall and blowing snow. Increase in the cloud base temperature associated both with warm air advection and cloud base lowering (to 1-1.5 km agl) before the snowfall resulted in significant increase in downwelling longwave flux (up to 20 W m-2) recorded by the AWS pyrgeometer. While ceilometer measurements are limited during the storm due to the signal attenuation by the falling and/or blowing snow, the radar measurements indicated that the depth of precipitating layer ranged from 1 km to at least 3 km agl (the limit of the radar vertical resolution). Analysis will be completed with the new data from the recent Antarctic summer season 2011-2012. With this new observatory, we aim at improving our understanding of the Antarctic hydrologic cycle and accumulation

Gorodetskaya, I. V.; van Lipzig, N. P. M.; Kneifel, S.; Maahn, M.; Crewell, S.; Van den Broeke, M.

2012-04-01

139

Clouds  

NSDL National Science Digital Library

First, the Project Atmosphere Canada offers a module to educate primary and secondary students about cloud formation and characteristics (1). The website outlines key points and offers a more in-depth discussion of water vapor, cloud formation, convection, air motion, severe weather, and more. The second website, by Scholastic, supplies many pdf documents of activities and lesson plans for all types of weather phenomena including clouds (2). Students can learn about condensation, discover what makes up a cloud, and find a key identifying the cloud types. Next, USA Today offers an online tutorial of the differing characteristics of clouds (3). Users can learn about Mammatus clouds, contrails, cloud seeding, and other cloud-related topics. At the fourth website, visitors can view meteorologist Dan Satterfield's amazing cloud photographs (4). Educators may find useful materials to supplement their lectures. Next, NASA's Climate and Radiation Branch furnishes "information on the fantastic variety of cloud forms and structures, and their implications for climate" (5). While the website is still being constructed, users can find useful information about the Bounded Cascades Fractal Cloud model, animations, and definitions of inhomogeneous cloud terminology. The sixth website, created by the National Center for Atmospheric Research and the University Corporation for Atmospheric Research, addresses how clouds impact our lives, how they cause chaos, and how they form (6). The enlightening descriptions are packed with colorful images and short quizzes. Next, The Australian Government's Bureau of Meteorology describes the useful of clouds as an indicator of weather conditions (7). After learning how moist air can form clouds, individuals can view images of the ten most common cloud types. Lastly, Enchanted Learning offers a table of the cloud types with their abbreviation, appearance, composition, and altitude along with explanations of cloud formation and the atmosphere (8). Educators can find simple activities dealing with cloud types and the water cycle.

140

Estimating plot-level tree heights with lidar: local filtering with a canopy-height based variable window size  

Microsoft Academic Search

In recent years, the use of airborne lidar technology to measure forest biophysical characteristics has been rapidly increasing. This paper discusses processing algorithms for deriving the terrain model and estimating tree heights by using a multiple return, high–density, small-footprint lidar data set. The lidar data were acquired over deciduous, coniferous, and mixed stands of varying age classes and settings typical

Sorin C. Popescu; Randolph H. Wynne; Ross F. Nelson

2002-01-01

141

Extensive ground-based Lidar and Radiometer Measurements of Aerosol and Cloud for the Comparison and Validation of CALIPSO retrievals  

NASA Astrophysics Data System (ADS)

We present the results of collocated measurements from CCNY ground-based multiwavelength Raman-Mie lidar and a CIMEL Sun/sky radiometer with CALIPSO overpasses near New York City (40.821N,73.949W). The data set consists of 19 days of observations conducted under the clear, hazy, and cloudy skies. In particular, statistical comparisons are made between the CALIPSO Level-2 5-km layer products and the ground-based lidar observations. We find in general excellent correlations exist between both cloud base and cloud top even for multiple deck cases that are not to close. In the clear skies, the CALIPSO aerosol layer tops are consistent with ground-lidar derived PBL heights although the accuracy degrades if capped by cloud layers. In addition, we perform a detailed comparison for smoke and polluted dust entrainments including aerosol classification, derivation of extinction profiles and lidar ratios. Aerosol extinction profiles are shown to be in good agreement when processed directly using the Fernald algorithm. Problems are seen when CALIPSO misidentifies plumes as clouds and processes the extinction data incorrectly. Finally, we derive planetary boundary layer (PBL) heights directly from the CALIPSO level-1B profiles and show reasonable statistical agreement to the Level-2 layer height product. Comparisons to PBL heights in urban areas are also performed.

Wu, Y.; Herman, B.; Gross, B.; Moshary, F.; Ahmed, S.

2008-12-01

142

Cloud detection and classification based on MAX-DOAS observations  

NASA Astrophysics Data System (ADS)

Multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations of aerosols and trace gases can be strongly influenced by clouds. Thus, it is important to identify clouds and characterise their properties. In this study we investigate the effects of clouds on several quantities which can be derived from MAX-DOAS observations, like radiance, the colour index (radiance ratio at two selected wavelengths), the absorption of the oxygen dimer O4 and the fraction of inelastically scattered light (Ring effect). To identify clouds, these quantities can be either compared to their corresponding clear-sky reference values, or their dependencies on time or viewing direction can be analysed. From the investigation of the temporal variability the influence of clouds can be identified even for individual measurements. Based on our investigations we developed a cloud classification scheme, which can be applied in a flexible way to MAX-DOAS or zenith DOAS observations: in its simplest version, zenith observations of the colour index are used to identify the presence of clouds (or high aerosol load). In more sophisticated versions, other quantities and viewing directions are also considered, which allows subclassifications like, e.g., thin or thick clouds, or fog. We applied our cloud classification scheme to MAX-DOAS observations during the Cabauw intercomparison campaign of Nitrogen Dioxide measuring instruments (CINDI) campaign in the Netherlands in summer 2009 and found very good agreement with sky images taken from the ground and backscatter profiles from a lidar.

Wagner, T.; Apituley, A.; Beirle, S.; Dörner, S.; Friess, U.; Remmers, J.; Shaiganfar, R.

2014-05-01

143

Cloud detection and classification based on MAX-DOAS observations  

NASA Astrophysics Data System (ADS)

Multi-AXis-Differential Optical Absorption Spectroscopy (MAX-DOAS) observations of aerosols and trace gases can be strongly influenced by clouds. Thus it is important to identify clouds and characterise their properties. In this study we investigate the effects of clouds on several quantities which can be derived from MAX-DOAS observations, like the radiance, the colour index (radiance ratio at two selected wavelengths), the absorption of the oxygen dimer O4 and the fraction of inelastically scattered light (Ring effect). To identify clouds, these quantities can be either compared to their corresponding clear sky reference values, or their dependencies on time or viewing direction can be analysed. From the investigation of the temporal variability the influence of clouds can be identified even for individual measurements. Based on our investigations we developed a cloud classification scheme, which can be applied in a flexible way to MAX-DOAS or zenith DOAS observations: in its simplest version, zenith observations of the colour index are used to identify the presence of clouds (or high aerosol load). In more sophisticated versions, also other quantities and viewing directions are considered, which allows sub-classifications like e.g. thin or thick clouds, or fog. We applied our cloud classification scheme to MAX-DOAS observations during the CINDI campaign in the Netherlands in Summer 2009 and found very good agreement with sky images taken from ground.

Wagner, T.; Beirle, S.; Dörner, S.; Friess, U.; Remmers, J.; Shaiganfar, R.

2013-12-01

144

Describing the NPOESS Preparatory Project Visible/Infrared Imaging Radiometer Suite (VIIRS) Cloud Environmental Data Records  

NASA Astrophysics Data System (ADS)

The Visible/Infrared Imaging Radiometer Suite (VIIRS) is one of the instruments that make up the suite of sensors on the NPOESS Preparatory Project (NPP) scheduled to launch in 2010. VIIRS will produce seven Environmental Data Records (EDRs) describing cloud properties. The VIIRS Cloud EDRs include the Cloud Optical Thickness (COT), Cloud Effective Particle Size Parameter (CEPS), Cloud Top Pressure (CTP), Cloud Top Height (CTH), Cloud Top Temperature (CTT), Cloud Cover/Layers (CCL), and Cloud Base Height (CBH). This paper will describe the VIIRS algorithms used to generate these EDRs and provide a current estimate of performance based on pre-Launch test data.

Hoffman, C.; Guenther, B.; Kilcoyne, H.; Mineart, G.; St. Germain, K.; Reed, B.

2008-12-01

145

Parameterizations of Cloud-Radiation Interactions Based on Detailed Cloud Microphysics  

NASA Astrophysics Data System (ADS)

Cloud-radiation effects still account for much of the variation among leading global climate models in sensitivity to greenhouse gases. A single-column model (SCM) allows results of different cloud-radiation parameterizations to be compared directly with measurements. The relevant fields include cloud altitude, cloud amount, liquid and ice content, particle size spectra, and radiative fluxes at the surface and the top of the atmosphere. Comparisons with data from the Atmospheric Radiation Measurement (ARM) Program show conclusively that prognostic cloud algorithms with detailed microphysics are far more realistic than simpler approaches. Long-term comparisons of SCM quantities strongly modulated by clouds, such as monthly mean downwelling surface shortwave radiation, clearly demonstrate the superiority of parameterizations based on comprehensive treatments of cloud microphysics and radiative interactions. The single-column model was run at the ARM Southern Great Plains, Tropical Western Pacific, and North Slope of Alaska sites using forcing data derived from operational numerical weather prediction models. Our results indicate that atmospheric radiative fluxes are sensitive to the scheme used to specify the ice particle effective radius by up to 30 W m-2 on a daily time scale and up to 5 W m-2 on a seasonal time scale. Differing treatments of ice particle fallout have a significant effect on the amount and location of high cirrus clouds. An unexpected finding was that the variance of the modeled ice particle effective radius at a given level is considerably smaller than that suggested by ARM cloud radar measurements. Our results indicate that this theoretical underestimate of the ice particle effective radius variance can have effects on modeled radiative fluxes comparable in magnitude to those cited above for sensitivity to the mean values of ice particle effective radius.

Iacobellis, S. F.; Somerville, R. C.; McFarquhar, G. M.; Mitchell, D.

2002-12-01

146

pCloud: A Cloud-based Power Market Simulation Environment  

SciTech Connect

This research conducted by the Newton Energy Group, LLC (NEG) is dedicated to the development of pCloud: a Cloud-based Power Market Simulation Environment. pCloud is offering power industry stakeholders the capability to model electricity markets and is organized around the Software as a Service (SaaS) concept -- a software application delivery model in which software is centrally hosted and provided to many users via the internet. During the Phase I of this project NEG developed a prototype design for pCloud as a SaaS-based commercial service offering, system architecture supporting that design, ensured feasibility of key architecture's elements, formed technological partnerships and negotiated commercial agreements with partners, conducted market research and other related activities and secured funding for continue development of pCloud between the end of Phase I and beginning of Phase II, if awarded. Based on the results of Phase I activities, NEG has established that the development of a cloud-based power market simulation environment within the Windows Azure platform is technologically feasible, can be accomplished within the budget and timeframe available through the Phase II SBIR award with additional external funding. NEG believes that pCloud has the potential to become a game-changing technology for the modeling and analysis of electricity markets. This potential is due to the following critical advantages of pCloud over its competition: - Standardized access to advanced and proven power market simulators offered by third parties. - Automated parallelization of simulations and dynamic provisioning of computing resources on the cloud. This combination of automation and scalability dramatically reduces turn-around time while offering the capability to increase the number of analyzed scenarios by a factor of 10, 100 or even 1000. - Access to ready-to-use data and to cloud-based resources leading to a reduction in software, hardware, and IT costs. - Competitive pricing structure, which will make high-volume usage of simulation services affordable. - Availability and affordability of high quality power simulators, which presently only large corporate clients can afford, will level the playing field in developing regional energy policies, determining prudent cost recovery mechanisms and assuring just and reasonable rates to consumers. - Users that presently do not have the resources to internally maintain modeling capabilities will now be able to run simulations. This will invite more players into the industry, ultimately leading to more transparent and liquid power markets.

Rudkevich, Aleksandr; Goldis, Evgeniy

2012-12-02

147

S'COOL Cloud Types Tutorial  

NSDL National Science Digital Library

This tutorial provides detailed information about how clouds receive their names and the importance of root words. It was designed to help students make accurate observations for the Students' Cloud Observations On-Line (S'COOL) project. Students will also learn to associate different clouds into height groupings. Information is provided about the cloud types and on how to distinguish similar clouds based on their level (i.e. cumulus, altocumulus and cirrocumulus).

2005-01-01

148

Clouds  

NSDL National Science Digital Library

Students learn about the varieties of clouds, what they look like and how they can affect our lives. Introduction: Have you ever wondered what kind of cloud makes rain, or which one makes fog? Have you ever wondered if there are clouds that mean the weather if going to be good or not? Today, we're going to learn about three different clouds that may ...

Doxey, Ms.

2010-03-26

149

The Cumulus Cloud Applet (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

This applet determines the height of the base of any cumulus cloud that might form due to convection, when the temperature and dew point sliders are adjusted. The applet displays clouds between 1000 and 10,000 feet.

Ackerman, Steve; Whittaker, Tom

150

Lidar based vegetation height models to quantify carbon stocks in Galveston saltmarshes  

NASA Astrophysics Data System (ADS)

Concern over global climate change has stimulated much interest in identifying existing and potential carbon sinks. Wetland ecosystems are highly recognized for their high productivity and thus as major terrestrial carbon (C) sinks. The rapid decline in the extent and health of these wetland ecosystems has created a need for non-destructive methods for the study of their C dynamics. However, these biomass estimates are mostly based on vegetation structural properties, particularly based on vegetation height models. Hence, for better quantification of vegetation biomass and C estimates, the accuracy of vegetation height models derived using lidar data is of paramount importance. Yet, unlike in woody vegetation dominated ecosystems, the use of lidar in saltmarshes is limited due to several reasons: 1) relatively dense vegetation cover limits laser penetration affecting the accuracy of terrain and thus vegetation height estimates; and 2) relatively shorter vegetation demands high point density data with high vertical accuracy to capture relatively smaller differences between terrain and vegetation canopy surfaces. Thus, the use of lidar data to characterize saltmarsh vegetation community demands appropriate methodologies. Our overall objective in this study was to develop a methodology for deriving salt marsh vegetation height models using airborne lidar data. More specific objectives involved: (1) understanding the interaction between discrete-return airborne lidar data and marsh vegetation; (2) finding appropriate grid sizes for deriving terrain and vegetation height models; and (3) analyze lidar-derived surface accuracies by comparing estimates to field measurements. In this study, we used 1m point spacing airborne lidar data from Federal Emergency Management Agency (FEMA) program to derive vegetation height models (VHM) for Spartina alterniflora saltmarshes in Galveston, Texas. We first derived digital terrain models (DEMs) and verified their vertical accuracy using field elevation data obtained using survey grade GPS. These DEMs served as input for deriving VHMs at different grid sizes (i.e. 1m, 3m, 5m and 10m). These VHMs were evaluated against field-collected vegetation height measurements collected using different approaches. Field measurements of vegetation heights include visual estimates for different grid sizes and also individual plant and culm heights. With this work, we seek to develop a remote sensing (RS) based approach to predict vegetation biomass (and thus C) in these salt marsh ecosystems using lidar data available for much of the coastal United States. Our study brings a contribution to the methods of estimating biomass and thus C estimates based on light detection and ranging (lidar) data as a nondestructive method.

Kulawardhana, R. W.; Popescu, S. C.; Feagin, R. A.

2012-12-01

151

Uav-Based Photogrammetric Point Clouds - Tree STEM Mapping in Open Stands in Comparison to Terrestrial Laser Scanner Point Clouds  

NASA Astrophysics Data System (ADS)

In both ecology and forestry, there is a high demand for structural information of forest stands. Forest structures, due to their heterogeneity and density, are often difficult to assess. Hence, a variety of technologies are being applied to account for this "difficult to come by" information. Common techniques are aerial images or ground- and airborne-Lidar. In the present study we evaluate the potential use of unmanned aerial vehicles (UAVs) as a platform for tree stem detection in open stands. A flight campaign over a test site near Freiburg, Germany covering a target area of 120 × 75 [m2] was conducted. The dominant tree species of the site is oak (quercus robur) with almost no understory growth. Over 1000 images with a tilt angle of 45° were shot. The flight pattern applied consisted of two antipodal staggered flight routes at a height of 55 [m] above the ground. We used a Panasonic G3 consumer camera equipped with a 14-42 [mm] standard lens and a 16.6 megapixel sensor. The data collection took place in leaf-off state in April 2013. The area was prepared with artificial ground control points for transformation of the structure-from-motion (SFM) point cloud into real world coordinates. After processing, the results were compared with a terrestrial laser scanner (TLS) point cloud of the same area. In the 0.9 [ha] test area, 102 individual trees above 7 [cm] diameter at breast height were located on in the TLS-cloud. We chose the software CMVS/PMVS-2 since its algorithms are developed with focus on dense reconstruction. The processing chain for the UAV-acquired images consists of six steps: a. cleaning the data: removing of blurry, under- or over exposed and off-site images; b. applying the SIFT operator [Lowe, 2004]; c. image matching; d. bundle adjustment; e. clustering; and f. dense reconstruction. In total, 73 stems were considered as reconstructed and located within one meter of the reference trees. In general stems were far less accurate and complete as in the TLS-point cloud. Only few stems were considered to be fully reconstructed. From the comparison of reconstruction achievement with respect to height above ground, we can state that reconstruction accuracy decreased in the crown layer of the stand. In addition we were cutting 50 [cm] slices in z-direction and applied a robust cylinder fit to the stem slices. Radii of the TLS-cloud and the SFM-cloud surprisingly correlated well with a Pearson's correlation coefficient of r = 0.696. This first study showed promising results for UAV-based forest structure modelling. Yet, there is a demand for additional research with regard to vegetation stages, flight pattern, processing setup and the utilisation of spectral information.

Fritz, A.; Kattenborn, T.; Koch, B.

2013-08-01

152

Validation of aerosol and cloud layer structures from the space-borne lidar CALIOP using Seoul National University ground-based lidar  

NASA Astrophysics Data System (ADS)

We present first observationally based validations of the space-borne lidar CALIOP onboard CALIPSO satellite using coincidental observations from a ground-based SNU lidar for 3 different types of atmospheric scenes. Both lidar measurements were taken in nearly same airmass in space and time. Total attenuated backscatters at 532 nm from the two instruments show similar aerosol and cloud layer structures (the top and bottom heights) both under cloud-free conditions and in case of multi-aerosol layers underlying semi-transparent cirrus clouds. This result confirms that the CALIPSO science team algorithms of the discrimination of cloud and aerosol as well as of their layer top and base altitudes are sound. Under thick clouds conditions, only information on the cloud top (bottom) height is reliable from CALIOP (ground-based lidar) observations due to strong signal attenuations. However, simultaneous space-borne CALIOP and ground-based SNU lidar measurements complement each other and provide full information on the vertical distribution of aerosols and clouds. Discrepancies between space-borne and ground-based lidar signals are partly explained by the strong spatial and vertical inhomogeneous distributions of clouds at few kilometer horizontal scales.

Kim, S.-W.; Berthier, S.; Chazette, P.; Raut, J.-C.; Dulac, F.; Yoon, S.-C.

2007-08-01

153

Cloud cover classification through simultaneous ground-based measurements of solar and infrared radiation  

NASA Astrophysics Data System (ADS)

Simultaneous measurements of downwelling short-wave solar irradiance and incoming total radiation flux were performed at the Reeves Nevè glacier station (1200 m MSL) in Antarctica on 41 days from late November 1994 to early January 1995, employing the upward sensors of an albedometer and a pyrradiometer. The downwelling short-wave radiation measurements were analysed following the Duchon and O'Malley [J. Appl. Meteorol. 38 (1999) 132] procedure for classifying clouds, using the 50-min running mean values of standard deviation and the ratio of scaled observed to scaled clear-sky irradiance. Comparing these measurements with the Duchon and O'Malley rectangular boundaries and the local human observations of clouds collected on 17 days of the campaign, we found that the Duchon and O'Malley classification method obtained a success rate of 93% for cirrus and only 25% for cumulus. New decision criteria were established for some polar cloud classes providing success rates of 94% for cirrus, 67% for cirrostratus and altostratus, and 33% for cumulus and altocumulus. The ratios of the downwelling short-wave irradiance measured for cloudy-sky conditions to that calculated for clear-sky conditions were analysed in terms of the Kasten and Czeplak [Sol. Energy 24 (1980) 177] formula together with simultaneous human observations of cloudiness, to determine the empirical relationship curves providing reliable estimates of cloudiness for each of the three above-mentioned cloud classes. Using these cloudiness estimates, the downwelling long-wave radiation measurements (obtained as differences between the downward fluxes of total and short-wave radiation) were examined to evaluate the downwelling long-wave radiation flux normalised to totally overcast sky conditions. Calculations of the long-wave radiation flux were performed with the MODTRAN 3.7 code [Kneizys, F.X., Abreu, L.W., Anderson, G.P., Chetwynd, J.H., Shettle, E.P., Berk, A., Bernstein, L.S., Robertson, D.C., Acharya, P., Rothman, L.S., Selby, J.E.A., Gallery, W.O., Clough, S.A., 1996. In: Abreu, L.W., Anderson, G.P. (Eds.), The MODTRAN 2/3 Report and LOWTRAN 7 MODEL. Contract F19628-91-C.0132, Phillips Laboratory, Geophysics Directorate, PL/GPOS, Hanscom AFB, MA, 261 pp.] for both clear-sky and cloudy-sky conditions, considering various cloud types characterised by different cloud base altitudes and vertical thicknesses. From these evaluations, best-fit curves of the downwelling long-wave radiation flux were defined as a function of the cloud base height for the three polar cloud classes. Using these relationship curves, average estimates of the cloud base height were obtained from the three corresponding sub-sets of long-wave radiation measurements. The relative frequency histograms of the cloud base height defined by examining these three sub-sets were found to present median values of 4.7, 1.7 and 3.6 km for cirrus, cirrostratus/altostratus and cumulus/altocumulus, respectively, while median values of 6.5, 1.8 and 2.9 km were correspondingly determined by analysing only the measurements taken together with simultaneous cloud observations.

Orsini, Antonio; Tomasi, Claudio; Calzolari, Francescopiero; Nardino, Marianna; Cacciari, Alessandra; Georgiadis, Teodoro

2002-04-01

154

The DSO Feature Based Point Cloud Simplification  

Microsoft Academic Search

This study proposes an effective low-error point cloud simplification method to retain the physical features of the models. The value of Discrete Shape Operator (DSO) is adopted to extract the features points of the models, and those are postponed to simplify. The value of DSO is defined as the discrete sum over the directional curvature and torsion. The proposed method

Pai-Feng Lee; Chia-Ping Huang

2011-01-01

155

Cloud Computing Based E-Learning System  

ERIC Educational Resources Information Center

Cloud computing technologies although in their early stages, have managed to change the way applications are going to be developed and accessed. These technologies are aimed at running applications as services over the internet on a flexible infrastructure. Microsoft office applications, such as word processing, excel spreadsheet, access database…

Al-Zoube, Mohammed; El-Seoud, Samir Abou; Wyne, Mudasser F.

2010-01-01

156

Underestimation of deep convective cloud tops by thermal imagery  

Microsoft Academic Search

The most common method of ascertaining cloud heights from space is from thermal brightness temperatures. Deep convective clouds of high water content are expected to radiate as black bodies. Here, thermal cloud top estimates from GOES-8 are compared with direct estimates of where the top should be sensed, based on colocated Goddard Cloud Physics Lidar (CPL) observations collected during the

Steven C. Sherwood; Jung-Hyo Chae; Patrick Minnis; Matthew McGill

2004-01-01

157

Vision-Based Approach Angle and Height Estimation for UAV Landing  

Microsoft Academic Search

In order to estimate the approach angle and relative height of Unmanned Aircraft Vehicle (UAV) which lands autonomously, a combinational approach of monocular vision and stereo vision is presented. From monocular sequences, vanishing line is extracted by Hough transform and RANSAC algorithm, and then approach angle of UAV is calculated through vanishing line geometry. From stereo sequences, feature-based matching is

Xiang Pan; De-qiang Ma; Li-ling Jin; Zhe-sheng Jiang

2008-01-01

158

Gas cloud infrared image enhancement based on anisotropic diffusion  

NASA Astrophysics Data System (ADS)

Leakage of dangerous gases will not only pollute the environment, but also seriously threat public safety. Thermal infrared imaging has been proved to be an efficient method to qualitatively detect the gas leakage. But some problems are remained, especially when monitoring the leakage in a passive way. For example, the signal is weak and the edge of gas cloud in the infrared image is not obvious enough. However, we notice some important characteristics of the gas plume and therefore propose a gas cloud infrared image enhancement method based on anisotropic diffusion. As the gas plume presents a large gas cloud in the image and the gray value is even inside the cloud, strong forward diffusion will be used to reduce the noise and to expand the range of the gas cloud. Frames subtraction and K-means cluttering pop out the gas cloud area. Forward-and-Backward diffusion is to protect background details. Additionally, the best iteration times and the time step parameters are researched. Results show that the gas cloud can be marked correctly and enhanced by black or false color, and so potentially increase the possibility of gas leakage detection.

Li, Jiakun; Wang, Lingxue; Zhang, Changxing; Long, Yunting; Zhang, Bei

2011-05-01

159

Cloud-based printing for mobile devices  

NASA Astrophysics Data System (ADS)

Consumers are increasingly using their smart phones to view web pages. However, there is no native operating system support for printing these web pages. We propose to overcome two barriers to printing from mobile devices - the inability to connect and transmit to a printer and the typically poor format of printed web pages. Our system includes a client component that causes the web browser to upload the page (as a URL reference for public pages or the DOM content for private pages) to a cloud service that extracts the content and formats it for printing. We transfer the printready content to the HP CloudPrint service and leverage its ability to locate printers and transmit print jobs. We have built a working system the uses iPhones and Windows Mobile devices clients, but the system can be extended to include other clients.

Bhatti, Nina; O'Brien-Strain, Eamonn; Liu, Jerry

2010-02-01

160

Land appraisal based on cloud model and sales comparison approach  

NASA Astrophysics Data System (ADS)

Focusing on the two key aspects of the traditional sales comparison approach, case selection and case quantification of the factors, this article tries to introduce the cloud model and Case-Based Reasoning into sales comparison approach, and brings about the land appraisal approach based on the cloud model and the sales comparison approach. This approach is based on the cloud model, completely considers the fuzziness and the randomness in objects and human knowledge, describes case features with the cloud model, uses cloud uncertainty reasoning, realizes the conversion between the qualitative description and the quantification value of transaction case features ; Also based on case-based reasoning, it analyzes the correlation among different cases, searches for the required comparable one; After the modification of the different land prices of different cases, it completely considers the case features and the weight of the cases, sets up land appraisal model, and finds the price of the case. At last, it gives an example analysis whose result proves the validity and feasibility of the method.

Hu, Shiyuan; Li, Deren; Liu, Yaolin; Li, Deyi; Yu, Haifeng

2007-08-01

161

A Cloud-Based Simulation Architecture for Pandemic Influenza Simulation  

PubMed Central

High-fidelity simulations of pandemic outbreaks are resource consuming. Cluster-based solutions have been suggested for executing such complex computations. We present a cloud-based simulation architecture that utilizes computing resources both locally available and dynamically rented online. The approach uses the Condor framework for job distribution and management of the Amazon Elastic Computing Cloud (EC2) as well as local resources. The architecture has a web-based user interface that allows users to monitor and control simulation execution. In a benchmark test, the best cost-adjusted performance was recorded for the EC2 H-CPU Medium instance, while a field trial showed that the job configuration had significant influence on the execution time and that the network capacity of the master node could become a bottleneck. We conclude that it is possible to develop a scalable simulation environment that uses cloud-based solutions, while providing an easy-to-use graphical user interface.

Eriksson, Henrik; Raciti, Massimiliano; Basile, Maurizio; Cunsolo, Alessandro; Froberg, Anders; Leifler, Ola; Ekberg, Joakim; Timpka, Toomas

2011-01-01

162

Global surface-based cloud observation for ISCCP  

NASA Technical Reports Server (NTRS)

Visual observations of cloud cover are hindered at night due to inadequate illumination of the clouds. This usually leads to an underestimation of the average cloud cover at night, especially for the amounts of middle and high clouds, in climatologies on surface observations. The diurnal cycles of cloud amounts, if based on all the surface observations, are therefore in error, but they can be obtained more accurately if the nighttime observations are screened to select those made under sufficient moonlight. Ten years of nighttime weather observations from the northern hemisphere in December were classified according to the illuminance of moonlight or twilight on the cloud tops, and a threshold level of illuminance was determined, above which the clouds are apparently detected adequately. This threshold corresponds to light from a full moon at an elevation angle of 6 degrees or from a partial moon at higher elevation, or twilight from the sun less than 9 degrees below the horizon. It permits the use of about 38% of the observations made with the sun below the horizon. The computed diurnal cycles of total cloud cover are altered considerably when this moonlight criterion is imposed. Maximum cloud cover over much of the ocean is now found to be at night or in the morning, whereas computations obtained without benefit of the moonlight criterion, as in our published atlases, showed the time of maximum to be noon or early afternoon in many regions. Cloud cover is greater at night than during the day over the open oceans far from the continents, particularly in summer. However, near noon maxima are still evident in the coastal regions, so that the global annual average oceanic cloud cover is still slightly greater during the day than at night, by 0.3%. Over land, where daytime maxima are still obtained but with reduced amplitude, average cloud cover is 3.3% greater during the daytime. The diurnal cycles of total cloud cover we obtain are compared with those of ISCCP for a few regions; they are generally in better agreement if the moonlight criterion is imposed on the surface observations. Using the moonlight criterion, we have analyzed ten years (1982-1991) of surface weather observations over land and ocean, worldwide, for total cloud cover and for the frequency of occurrence of clear sky, fog and precipitation The global average cloud cover (average of day and night) is about 2% higher if we impose the moonlight criterion than if we use all observations. The difference is greater in winter than in summer, because of the fewer hours of darkness in the summer. The amplitude of the annual cycle of total cloud cover over the Arctic Ocean and at the South Pole is diminished by a few percent when the moonlight criterion is imposed. The average cloud cover for 1982-1991 is found to be 55% for northern hemisphere land, 53% for southern hemisphere land, 66% for northern hemisphere ocean, and 70% for southern hemisphere ocean, giving a global average of 64%. The global average for daytime is 64.6% for nighttime 63.3%.

1994-01-01

163

Vertical cloud structures of the boreal summer intraseasonal variability based on CloudSat observations and ERA-interim reanalysis  

NASA Astrophysics Data System (ADS)

The boreal summer intraseasonal variability (BSISV), which is characterized by pronounced meridional propagation from the equatorial zone to the Indian Continent, exerts significant modulation of the active/break phases of the south Asian monsoon. This form of variability provides a primary source of subseasonal predictive skill of the Asian summer monsoon. Unfortunately, current general circulation models display large deficiencies in representing this variability. The new cloud observations made available by the CloudSat mission provide an unprecedented opportunity to advance our characterization of the BSISV. In this study, the vertical structures of cloud water content and cloud types associated with the BSISV over the Indian Ocean and subcontinent are analyzed based on CloudSat observations from 2006 to 2008. These cloud structures are also compared to their counterparts as derived from ERA-interim reanalysis. A marked vertical tilting structure in cloud water is illustrated during the northward propagation of the BSISV based on both datasets. Increased cloud liquid water content (LWC) tends to appear to the north of the rainfall maximum, while ice water content (IWC) in the upper troposphere slightly lags the convection. This northward shift of increased LWC, which is in accord with local enhanced moisture as previously documented, may play an important role in the northward propagation of the BSISV. The transition in cloud structures associated with BSISV convection is further demonstrated based on CloudSat, with shallow cumuli at the leading edge, followed by the deep convective clouds, and then upper anvil clouds. Some differences in cloud water structures between CloudSat and ERA-interim are also noted, particularly in the amplitudes of IWC and LWC fields.

Jiang, Xianan; Waliser, Duane E.; Li, Jui-Lin; Woods, Christopher

2011-06-01

164

A vegetation height classification approach based on texture analysis of a single VHR image  

NASA Astrophysics Data System (ADS)

Vegetation height is a crucial feature in various applications related to ecological mapping, enhancing the discrimination among different land cover or habitat categories and facilitating a series of environmental tasks, ranging from biodiversity monitoring and assessment to landscape characterization, disaster management and conservation planning. Primary sources of information on vegetation height include in situ measurements and data from active satellite or airborne sensors, which, however, may often be non-affordable or unavailable for certain regions. Alternative approaches on extracting height information from very high resolution (VHR) satellite imagery based on texture analysis, have recently been presented, with promising results. Following the notion that multispectral image bands may often be highly correlated, data transformation and dimensionality reduction techniques are expected to reduce redundant information, and thus, the computational cost of the approaches, without significantly compromising their accuracy. In this paper, dimensionality reduction is performed on a VHR image and textural characteristics are calculated on its reconstructed approximations, to show that their discriminatory capabilities are maintained up to a large degree. Texture analysis is also performed on the projected data to investigate whether the different height categories can be distinguished in a similar way.

Petrou, Z. I.; Manakos, I.; Stathaki, T.; Tarantino, C.; Adamo, M.; Blonda, P.

2014-03-01

165

Comparing the cloud vertical structure derived from several methods based on measured atmospheric profiles and active surface measurements  

NASA Astrophysics Data System (ADS)

The cloud vertical distribution and especially the cloud base height, which is linked to cloud type, is an important characteristic in order to describe the impact of clouds on climate. In this work several methods to estimate the cloud vertical structure (CVS) based on atmospheric sounding profiles are compared, considering number and position of cloud layers, with a ground based system which is taken as a reference: the Active Remote Sensing of Clouds (ARSCL). All methods establish some conditions on the relative humidity, and differ on the use of other variables, the thresholds applied, or the vertical resolution of the profile. In this study these methods are applied to 193 radiosonde profiles acquired at the ARM Southern Great Plains site during all seasons of year 2009 and endorsed by GOES images, to confirm that the cloudiness conditions are homogeneous enough across their trajectory. The perfect agreement (i.e. when the whole CVS is correctly estimated) for the methods ranges between 26-64%; the methods show additional approximate agreement (i.e. when at least one cloud layer is correctly assessed) from 15-41%. Further tests and improvements are applied on one of these methods. In addition, we attempt to make this method suitable for low resolution vertical profiles, like those from the outputs of reanalysis methods or from the WMO's Global Telecommunication System. The perfect agreement, even when using low resolution profiles, can be improved up to 67% (plus 25% of approximate agreement) if the thresholds for a moist layer to become a cloud layer are modified to minimize false negatives with the current data set, thus improving overall agreement.

Costa-Surós, M.; Calbó, J.; González, J. A.; Long, C. N.

2014-04-01

166

Ground-based measurements of tropospheric and stratospheric BrO at Arrival Heights, Antarctica  

Microsoft Academic Search

Ground-based measurements of BrO slant column densities (SCDs) were performed using zenith sky DOAS (Differential Optical Absorption Spectroscopy) during autumn (February to May) and spring (August to October) of 1995 at Arrival Heights (77.8°S, 166.7°E). In both August and September, single episode of sudden large BrO column enhancement (of magnitude 3.5 and 3.2×1014molec.cm-2 respectively) were observed. The episode in August

K. Kreher; P. V. Johnston; S. W. Wood; B. Nardi; U. Platt

1997-01-01

167

Point Cloud Segmentation Based on Radial Reflection  

NASA Astrophysics Data System (ADS)

This paper introduces a novel 3D segmentation algorithm, which works directly on point clouds to address the problem of partitioning a 3D object into useful sub-parts. In the last few decades, many different algorithms have been proposed in this growing field, but most of them are only working on complete meshes. However, in robotics, computer graphics, or other fields it is not always possible to work directly on a mesh. Experimental evaluations of a number of complex objects demonstrate the robustness and the efficiency of the proposed algorithm and the results prove that it compares well with a number of state-of-the-art 3D object segmentation algorithms.

Richtsfeld, Mario; Vincze, Markus

168

Ground-based remote sensing of methane height profiles with a tunable diode laser heterodyne spectrometer  

SciTech Connect

Height distributions of methane in the troposphere and stratosphere were derived from high resolution absorption spectra observed with a ground-based tunable diode laser heterodyne spectrometer. The center wavenumber of the measured methane absorption line is 1223.1561/cm. In the retrieval of methane height profiles, a volume mixing ratio of methane was assumed to have a constant value in the troposphere and to decrease with a constant rate in the stratosphere. The tropospheric mixing ratio and the decreasing rate in stratosphere were derived to be 1.7 +/- 0.1 ppmv and -0.06 ppmv/km, respectively, for measurements at Tsukuba (36.0 deg N, 140.1 deg E) on December 17 and 20, 1991.

Koide, M.; Taguchi, M.; Fukunsishi, H.; Okano, S. [Tohoku Univ., Sendai (Japan)] [Tohoku Univ., Sendai (Japan)

1995-02-01

169

INS/EKF-based stride length, height and direction intent detection for walking assistance robots.  

PubMed

We propose an algorithm used to obtain the information on stride length, height difference, and direction based on user's intent during walking. For exoskeleton robots used to assist paraplegic patients' walking, this information is used to generate gait patterns by themselves in on-line. To obtain this information, we attach an inertial measurement unit(IMU) on crutches and apply an extended kalman filter-based error correction method to reduce the phenomena of drift due to bias of the IMU. The proposed method is verifed in real walking scenarios including walking, climbing up-stairs, and changing direction of walking with normal. PMID:22275567

Brescianini, Dario; Jung, Jun-Young; Jang, In-Hun; Park, Hyun Sub; Riener, Robert

2011-01-01

170

Determination of mixing layer heights by ceilometer and influences upon air quality at Mexico City airport  

Microsoft Academic Search

Monitoring of mixing layer height (MLH) was performed during different measurement campaigns in urban and suburban area (Hannover, Munich, Budapest, Zürich, Augsburg) by the Vaisala ceilometer LD40. It is an eye-safe commercial lidar and designed originally to detect cloud base heights and vertical visibility for aviation safety purposes. Software for routine retrieval of mixing layer height from ceilometer data was

Klaus Schäfer; Edgar Flores-Jardines; Stefan Emeis; Michel Grutter; Ralf Kurtenbach; Peter Wiesen; Christoph Münkel

2009-01-01

171

A secure medical data exchange protocol based on cloud environment.  

PubMed

In recent years, health care technologies already became matured such as electronic medical records that can be easily stored. However, how to get medical resources more convenient is currently concern issue. In spite of many literatures discussed about medical systems, but these literatures should face many security challenges. The most important issue is patients' privacy. Therefore, we propose a secure medical data exchange protocol based on cloud environment. In our scheme, we use mobile device's characteristics, allowing peoples use medical resources on the cloud environment to seek medical advice conveniently. PMID:25037716

Chen, Chin-Ling; Yang, Tsai-Tung; Shih, Tzay-Farn

2014-09-01

172

A Blog Personality Recommender System Based on Cloud Computing Infrastructure  

Microsoft Academic Search

Blog is an important carrier of the current network information, and it has quick update, high quality and personalized characteristic. However, as the number of blogs increase sharply, it becomes more difficult to find high quality and personalized blog. In order to resolve this problem, this paper presents a new blog recommender system based on cloud computing infrastructure. This system

Jie Jiang; Weiwei Pang; Yule Deng; Kate He; Zhuyan Gu

2012-01-01

173

A cloud-based approach to medical NLP.  

PubMed

Natural Language Processing (NLP) enables access to deep content embedded in medical texts. To date, NLP has not fulfilled its promise of enabling robust clinical encoding, clinical use, quality improvement, and research. We submit that this is in part due to poor accessibility, scalability, and flexibility of NLP systems. We describe here an approach and system which leverages cloud-based approaches such as virtual machines and Representational State Transfer (REST) to extract, process, synthesize, mine, compare/contrast, explore, and manage medical text data in a flexibly secure and scalable architecture. Available architectures in which our Smntx (pronounced as semantics) system can be deployed include: virtual machines in a HIPAA-protected hospital environment, brought up to run analysis over bulk data and destroyed in a local cloud; a commercial cloud for a large complex multi-institutional trial; and within other architectures such as caGrid, i2b2, or NHIN. PMID:22195072

Chard, Kyle; Russell, Michael; Lussier, Yves A; Mendonça, Eneida A; Silverstein, Jonathan C

2011-01-01

174

Constrained density functional theory based configuration interaction improves the prediction of reaction barrier heights  

NASA Astrophysics Data System (ADS)

In this work, a constrained density functional theory based configuration interaction approach (CDFT-CI) is applied to calculating transition state energies of chemical reactions that involve bond forming and breaking at the same time. At a given point along the reaction path, the configuration space is spanned by two diabaticlike configurations: reactant and product. Each configuration is constructed self-consistently with spin and charge constraints to maximally retain the identities of the reactants or the products. Finally, the total energy is obtained by diagonalizing an effective Hamiltonian constructed in the basis spanned by these two configurations. By design, this prescription does not affect the energies of the reactant or product species but will affect the energy at intermediate points along the reaction coordinate, most notably by modifying the reaction barrier height. When tested with a large set of reactions that include hydrogen transfer, heavy atom transfer, and nucleophilic substitution, CDFT-CI is found to improve the prediction of barrier heights by a factor of 2-3 for some commonly used local, semilocal, and hybrid functionals. Thus, just as CDFT can be used to cure energy errors in charge localized states, CDFT-CI can recover the correct energy for charge delocalized states by approximating the true wave function as a linear combination of localized configurations (e.g., reactant and product). The well-defined procedure and the promising results of CDFT-CI suggest that it could broaden the applicability of traditional DFT methods for reaction barrier heights.

Wu, Qin; Kaduk, Benjamin; van Voorhis, Troy

2009-01-01

175

Nuclear spectroscopy pulse height analysis based on digital signal processing techniques  

SciTech Connect

A digital approach to pulse height analysis is presented. It consists of entire pulse digitization, using a flash analog-to-digital converter (ADC), being its height estimated by a floating point digital signal processor (DSP) as one parameter of a model best fitting to the pulse samples. The differential nonlinearity (DNL) is reduced by simultaneously adding to the pulse, prior to its digitization, two analog signals provided by a digital-to-analog converter (DAC). One of them is a small amplitude dither signal used to eliminate a bias introduced by the fitting algorithm. The other, with large amplitude, corrects the ADC nonlinearities by a method similar to the well known Gatti`s sliding scale. The simulations carried out showed that, using a 12-bit flash ADC, a 14-bit DAC and a dedicated floating point DSP performing a polynomial fitting to the samples around the pulse peak, it is actually possible to process about 10,000 events per second, with a constant height pulse dispersion of only 4 on 8,192 channels and a very good differential linearity. A prototype system based on the Texas Instruments floating point DSP TMS320C31 and built following the presented methodology has already been tested and performed as expected.

Simoes, J.B.; Simoes, P.C.P.S.; Correia, C.M.B.A. [Univ. of Coimbra (Portugal). Physics Dept.] [Univ. of Coimbra (Portugal). Physics Dept.

1995-08-01

176

A cloud-based medical image repository  

NASA Astrophysics Data System (ADS)

Many widely used digital medical image collections have been established but these are generally used as raw data sources without related image analysis toolsets. Providing associated functionality to allow specific types of operations to be performed on these images has proved beneficial in some cases (e.g. brain image registration and atlases). However, toolset development to provide generic image analysis functions on medical images has tended to be ad hoc, with Open Source options proliferating (e.g. ITK). Our Automated Medical Image Collection Annotation (AMICA) system is both an image repository, to which the research community can contribute image datasets, and a search/retrieval system that uses automated image annotation. AMICA was designed for the Windows Azure platform to leverage the flexibility and scalability of the cloud. It is intended that AMICA will expand beyond its initial pilot implementation (for brain CT, MR images) to accommodate a wide range of modalities and anatomical regions. This initiative aims to contribute to advances in clinical research by permitting a broader use and reuse of medical image data than is currently attainable. For example, cohort studies for cases with particular physiological or phenotypical profiles will be able to source and include enough cases to provide high statistical power, allowing more individualised risk factors to be assessed and thus allowing screening and staging processes to be optimised. Also, education, training and credentialing of clinicians in image interpretation, will be more effective because it will be possible to select instances of images with specific visual aspects, or correspond to types of cases where reading performance improvement is desirable.

Maeder, Anthony J.; Planitz, Birgit M.; El Rifai, Diaa

2012-02-01

177

Cloud Protocols  

NSDL National Science Digital Library

The purpose of this activity is to observe the type and cover of clouds including contrails. Students observe which of ten types of clouds and how many of three types of contrails are visible and how much of the sky is covered by clouds (other than contrails) and how much is covered by contrails. Intended outcomes are that students learn how to make estimates from observations and how to categorize specific clouds following general descriptions for the categories. They will learn the meteorological concepts of cloud heights, types, and cloud cover and learn the ten basic cloud types. Supporting background materials for both student and teacher are included.

The GLOBE Program, UCAR (University Corporation for Atmospheric Research)

2003-08-01

178

A Cloud-based Multimodality Case File for Mobile Devices.  

PubMed

Recent improvements in Web and mobile technology, along with the widespread use of handheld devices in radiology education, provide unique opportunities for creating scalable, universally accessible, portable image-rich radiology case files. A cloud database and a Web-based application for radiologic images were developed to create a mobile case file with reasonable usability, download performance, and image quality for teaching purposes. A total of 75 radiology cases related to breast, thoracic, gastrointestinal, musculoskeletal, and neuroimaging subspecialties were included in the database. Breast imaging cases are the focus of this article, as they best demonstrate handheld display capabilities across a wide variety of modalities. This case subset also illustrates methods for adapting radiologic content to cloud platforms and mobile devices. Readers will gain practical knowledge about storage and retrieval of cloud-based imaging data, an awareness of techniques used to adapt scrollable and high-resolution imaging content for the Web, and an appreciation for optimizing images for handheld devices. The evaluation of this software demonstrates the feasibility of adapting images from most imaging modalities to mobile devices, even in cases of full-field digital mammograms, where high resolution is required to represent subtle pathologic features. The cloud platform allows cases to be added and modified in real time by using only a standard Web browser with no application-specific software. Challenges remain in developing efficient ways to generate, modify, and upload radiologic and supplementary teaching content to this cloud-based platform. Online supplemental material is available for this article. ©RSNA, 2014. PMID:24819664

Balkman, Jason D; Loehfelm, Thomas W

2014-01-01

179

The impacts of an observationally-based cloud fraction and condensate overlap parameterization on a GCM's Cloud Radiative Effect  

NASA Astrophysics Data System (ADS)

It has been shown that the details of how cloud fraction overlap is treated in GCMs has substantial impact on shortwave and longwave fluxes. Because cloud condensate is also horizontally heterogeneous at GCM grid scales, another aspect of cloud overlap should in principle also be assessed, namely the vertical overlap of hydrometeor distributions. This type of overlap is usually examined in terms of rank correlations, i.e., linear correlations between hydrometeor amount ranks of the overlapping parts of cloud layers at specific separation distances. The cloud fraction overlap parameter and the rank correlation of hydrometeor amounts can be both expressed as inverse exponential functions of separation distance characterized by their respective decorrelation lengths (e-folding distances). Larger decorrelation lengths mean that hydrometeor fractions and probability distribution functions have high levels of vertical alignment. An analysis of CloudSat and CALIPSO data reveals that the two aspects of cloud overlap are related and their respective decorrelation lengths have a distinct dependence on latitude that can be parameterized and included in a GCM. In our presentation we will contrast the Cloud Radiative Effect (CRE) of the GEOS-5 atmospheric GCM (AGCM) when the observationally-based parameterization of decorrelation lengths is used to represent overlap versus the simpler cases of maximum-random overlap and globally constant decorrelation lengths. The effects of specific overlap representations will be examined for both diagnostic and interactive radiation runs in GEOS-5 and comparisons will be made with observed CREs from CERES and CloudSat (2B-FLXHR product). Since the radiative effects of overlap depend on the cloud property distributions of the AGCM, the availability of two different cloud schemes in GEOS-5 will give us the opportunity to assess a wide range of potential cloud overlap consequences on the model's climate.

Oreopoulos, L.; Lee, D.; Norris, P. M.; Yuan, T.

2011-12-01

180

The Impacts of an Observationally-Based Cloud Fraction and Condensate Overlap Parameterization on a GCM's Cloud Radiative Effect  

NASA Technical Reports Server (NTRS)

It has been shown that the details of how cloud fraction overlap is treated in GCMs has substantial impact on shortwave and longwave fluxes. Because cloud condensate is also horizontally heterogeneous at GCM grid scales, another aspect of cloud overlap should in principle also be assessed, namely the vertical overlap of hydrometeor distributions. This type of overlap is usually examined in terms of rank correlations, i.e., linear correlations between hydrometeor amount ranks of the overlapping parts of cloud layers at specific separation distances. The cloud fraction overlap parameter and the rank correlation of hydrometeor amounts can be both expressed as inverse exponential functions of separation distance characterized by their respective decorrelation lengths (e-folding distances). Larger decorrelation lengths mean that hydrometeor fractions and probability distribution functions have high levels of vertical alignment. An analysis of CloudSat and CALIPSO data reveals that the two aspects of cloud overlap are related and their respective decorrelation lengths have a distinct dependence on latitude that can be parameterized and included in a GCM. In our presentation we will contrast the Cloud Radiative Effect (CRE) of the GEOS-5 atmospheric GCM (AGCM) when the observationally-based parameterization of decorrelation lengths is used to represent overlap versus the simpler cases of maximum-random overlap and globally constant decorrelation lengths. The effects of specific overlap representations will be examined for both diagnostic and interactive radiation runs in GEOS-5 and comparisons will be made with observed CREs from CERES and CloudSat (2B-FLXHR product). Since the radiative effects of overlap depend on the cloud property distributions of the AGCM, the availability of two different cloud schemes in GEOS-5 will give us the opportunity to assess a wide range of potential cloud overlap consequences on the model's climate.

Oreopoulos, Lazaros; Lee, Dongmin; Norris, Peter; Yuan, Tianle

2011-01-01

181

Intelligent person identification system using stereo camera-based height and stride estimation  

NASA Astrophysics Data System (ADS)

In this paper, a stereo camera-based intelligent person identification system is suggested. In the proposed method, face area of the moving target person is extracted from the left image of the input steros image pair by using a threshold value of YCbCr color model and by carrying out correlation between the face area segmented from this threshold value of YCbCr color model and the right input image, the location coordinates of the target face can be acquired, and then these values are used to control the pan/tilt system through the modified PID-based recursive controller. Also, by using the geometric parameters between the target face and the stereo camera system, the vertical distance between the target and stereo camera system can be calculated through a triangulation method. Using this calculated vertical distance and the angles of the pan and tilt, the target's real position data in the world space can be acquired and from them its height and stride values can be finally extracted. Some experiments with video images for 16 moving persons show that a person could be identified with these extracted height and stride parameters.

Ko, Jung-Hwan; Jang, Jae-Hun; Kim, Eun-Soo

2005-05-01

182

Comparisons of Aerosol-Cloud Observations Between a Ground-based Raman-Mie Lidar and CALIPSO  

NASA Astrophysics Data System (ADS)

Global vertical profiles of aerosol and cloud are currently being observed by satellite CALIPSO. Based on the inherent properties of elastic-scattering lidar, the lidar ratio (extinction-to-backscatter ratio) becomes very important to quantitatively retrieve the distribution of aerosol/cloud extinction or backscatter coefficient. In this presentation, we examine the feasibility of using MODIS-retrieved aerosol optical depth over ocean to constrain the aerosol lidar ratio in the CALIPSO retrieval of aerosol extinction profile with Fernald algorithm, and then compare these lidar-ratios to those derived from both column measurements by the CIMEL Sunphotometer and a combination of the ground-based lidar and radiometer. We explore the variability of lidar ratios for the different types of aerosol over the US east coast. In addition, we present our validation measurements for aerosol vertical profiles. So far, 13 near simultaneous observations by our ground-based multi-wavelength Raman-Mie lidar which operated in New York City (40.821N, 73.949W), have been obtained together with other supporting measurements. In particular, comparisons of aerosol extinction profiles are performed between the ground- based lidar and CALIPSO observations and the vertical distribution of smoke plumes, aloft aerosol layer, urban aerosol and PBL height are presented and compared. Retrievals of optically thin clouds heights and optical depth in the low- and high-altitude from CALIPSO and MODIS/Aqua, respectively, are examined with respect to ground- based lidar measurements and several biases in the measurements are presented.

Wu, Y.; Chaw, S.; Gross, B.; Charles, L.; Vladutescu, V.; Cao, N.; Moshary, F.; Ahmed, S.

2007-12-01

183

Distributions and radiative forcings of various cloud types based on active and passive satellite datasets - Part 1: Geographical distributions and overlap of cloud types  

NASA Astrophysics Data System (ADS)

Based on four year' 2B-CLDCLASS-Lidar (Radar-Lidar) cloud classification product from CloudSat, we analyze the geographical distributions of different cloud types and their co-occurrence frequency across different seasons, moreover, utilize the vertical distributions of cloud type to further evaluate the cloud overlap assumptions. The statistical results show that more high clouds, altocumulus, stratocumulus or stratus and cumulus are identified in the Radar-Lidar cloud classification product compared to previous results from Radar-only cloud classification (2B-CLDCLASS product from CloudSat). In particularly, high clouds and cumulus cloud fractions increased by factors 2.5 and 4-7, respectively. The new results are in more reasonable agreement with other datasets (typically the International Satellite Cloud Climatology Project (ISCCP) and surface observer reports). Among the cloud types, altostratus and altocumulus are more popular over the arid/semi-arid land areas of the Northern and Southern Hemispheres, respectively. These features weren't observed by using the ISCCP D1 dataset. For co-occurrence of cloud types, high cloud, altostratus, altocumulus and cumulus are much more likely to co-exist with other cloud types. However, stratus/stratocumulus, nimbostratus and convective clouds are much more likely to exhibit individual features. After considering the co-occurrence of cloud types, the cloud fraction based on the random overlap assumption is underestimated over the vast ocean except in the west-central Pacific Ocean warm pool. Obvious overestimations are mainly occurring over land areas in the tropics and subtropics. The investigation therefore indicates that incorporate co-occurrence information of cloud types based on Radar-Lidar cloud classification into the overlap assumption schemes used in the current GCMs possible be able to provide an better predictions for vertically projected total cloud fraction.

Li, J.; Huang, J.; Stamnes, K.; Wang, T.; Yi, Y.; Ding, X.; Lv, Q.; Jin, H.

2014-04-01

184

Smart learning services based on smart cloud computing.  

PubMed

Context-aware technologies can make e-learning services smarter and more efficient since context-aware services are based on the user's behavior. To add those technologies into existing e-learning services, a service architecture model is needed to transform the existing e-learning environment, which is situation-aware, into the environment that understands context as well. The context-awareness in e-learning may include the awareness of user profile and terminal context. In this paper, we propose a new notion of service that provides context-awareness to smart learning content in a cloud computing environment. We suggest the elastic four smarts (E4S)--smart pull, smart prospect, smart content, and smart push--concept to the cloud services so smart learning services are possible. The E4S focuses on meeting the users' needs by collecting and analyzing users' behavior, prospecting future services, building corresponding contents, and delivering the contents through cloud computing environment. Users' behavior can be collected through mobile devices such as smart phones that have built-in sensors. As results, the proposed smart e-learning model in cloud computing environment provides personalized and customized learning services to its users. PMID:22164048

Kim, Svetlana; Song, Su-Mi; Yoon, Yong-Ik

2011-01-01

185

A Unified View of Cloud-to-Ground, Cloud-to-Cloud and Cloud-to-Ionosphere Discharges, Based on Joint Effects of Electric Reconnection and Critical Velocity  

Microsoft Academic Search

This paper attempts to explain recently observed multiple coupling among cloud-to-ground, cloud-to-cloud, and cloud-to-ionosphere discharges on the basis of joint effects of electric reconnection and critical velocity. These observations indicate that the cloud shape and charge distribution is thought to be inclined and extended rather horizontally with a sequence of electrically cusped charge distribution or horizontal double layers in contrast

Hiroshi Kikuchi

2001-01-01

186

Correlating Ground-Based Lightning Measurements with Ash Cloud Satellite Data from the 2010 Eruption of Eyjafjallajökull Volcano, Iceland  

NASA Astrophysics Data System (ADS)

Airborne volcanic ash is a major aviation hazard. For example, the 2010 eruption of Eyjafjallajökull volcano in Iceland resulted in the largest air-traffic shutdown since World War II. More than 100,000 flights were grounded, stranding passengers in Europe and across the globe, and producing a multi-billion dollar economic impact. Because of the high impact on aviation, sophisticated tools are needed to provide real-time alerts, tracking, and forecasting of volcanic clouds. In an attempt address the 5-minute volcanic cloud warning criteria established by the international aviation community, an automated volcanic cloud alert system for the Geostationary Operational Environmental Satellite - R Series (GOES-R) built upon the automated ash cloud alert system for the Advanced Very High Resolution Radiometer (AVHRR) is in development. The new system will be capable of identifying ash and SO2 clouds with greater accuracy. One component of GOES-R will be a lightning mapper. To study the temporal, spatial, and physical relationships between ash clouds and lightning, and the utility of lightning detection in a real-time alert system, we analyze data collected by the Lightning Mapping Array, a ground-based lightning detection network, in conjunction with satellite data gathered by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instrument aboard Meteosat-9 during in the 2010 eruption of Eyjafjallajökull volcano. We correlate lightning characteristics, intensity, and distribution with plume location, height, mass loading, and effective particle radius. Lightning mapping in volcanic ash clouds potentially will allow for better characterization of the ash cloud and aid in forecasting the distribution of ash and its effects on aviation.

McMahon, N. D.; Thomas, R. J.; Pavolonis, M. J.; Sieglaff, J.; Aster, R. C.

2012-12-01

187

VOF-Based Height Function Method for 3D Calculation of Contact Line Phenomena  

NASA Astrophysics Data System (ADS)

A rigorous methodology is presented for applying a contact angle as a contact line boundary condition within a 3D VOF-based flow algorithm. Based on the recently-developed height function methodology, an approach for modeling contact lines is presented that yields accurate interface normals and curvatures from volume fractions and allows the rigorous representation of surface tension forces at contact lines, values that converge with spatial refinement. Although VOF methods have been used before to model phenomena that includes contact lines, the implementation details have rarely been presented. Here a detailed implementation is presented, that includes algorithms for identifying so-called ``contact line'' and ``adjacent'' cells, as well as for calculating normals and curvatures in these cells. The efficacy of this approach is demonstrated via examples of both static and dynamic contact line phenomena. The model is shown to accurately predict steady state configurations defined by the imposed contact angles, from initial conditions far from equilibrium.

Afkhami, Shahriar

2008-11-01

188

High-speed nuclear quality pulse height analyzer for synchrotron-based applications  

SciTech Connect

A high throughput Pulse Height Analyzer system for synchrotron-based applications requiring high resolution, high processing speed and low dead time has been developed. The system is comprised of a 120ns 12-bit nuclear quality Analog to Digital converter with a self-adaptive fast peak detector-stretcher and a custom-made fast histogramming memory module that records and processes the digitized data. The histogramming module is packaged in a VME or VXI compatible interface. Data is transferred through a fast optical link from the memory interface to a computer. A dedicated data acquisition program matches the hardware characteristics of the histogramming memory module. The data acquisition system allows for two data collection modes: ''standard'' data acquisition mode where the data is accumulated and read in synchronization with an external trigger and ''live'' data acquisition mode where the system operates as a standard Pulse Height Analyzer. The acquisition, standard or live, can be performed on several channels simultaneously. A two-channel prototype has been demonstrated at the Stanford Synchrotron Radiation Laboratory accelerator in conjunction with an X-ray Fluorescence Absorption Spectroscopy experiment. A detailed description of the entire system is given and experimental data is shown.

Beche, Jean-Francois; Bucher, Jerome J.; Fabris, Lorenzo; Riot, Vincent J.

2001-04-01

189

An Optimal Workflow Based Scheduling and Resource Allocation in Cloud  

Microsoft Academic Search

\\u000a The objective of Optimal Workflow based Scheduling (OWS) algorithm is to find a solution that meets the user-preferred Quality\\u000a of Service (QoS) parameters. The work presented focuses on scheduling cloud workflows. First, the Resource discovery algorithm,\\u000a indexes all the resources and this helps in locating the free resources. Second, the scheduling algorithm that takes user\\u000a specified QoS parameters (execution time,

P. Varalakshmi; Aravindh Ramaswamy; Aswath Balasubramanian; Palaniappan Vijaykumar

190

Cloud Based Metalearning System for Predictive Modeling of Biomedical Data  

PubMed Central

Rapid growth and storage of biomedical data enabled many opportunities for predictive modeling and improvement of healthcare processes. On the other side analysis of such large amounts of data is a difficult and computationally intensive task for most existing data mining algorithms. This problem is addressed by proposing a cloud based system that integrates metalearning framework for ranking and selection of best predictive algorithms for data at hand and open source big data technologies for analysis of biomedical data.

Vukicevic, Milan

2014-01-01

191

Cloud cover estimation: Use of GOES imagery in development of cloud cover data base for insolation assessment  

NASA Technical Reports Server (NTRS)

The potential of using digital satellite data to establish a cloud cover data base for the United States, one that would provide detailed information on the temporal and spatial variability of cloud development are studied. Key elements include: (1) interfacing GOES data from the University of Wisconsin Meteorological Data Facility with the Jet Propulsion Laboratory's VICAR image processing system and IBIS geographic information system; (2) creation of a registered multitemporal GOES data base; (3) development of a simple normalization model to compensate for sun angle; (4) creation of a variable size georeference grid that provides detailed cloud information in selected areas and summarized information in other areas; and (5) development of a cloud/shadow model which details the percentage of each grid cell that is cloud and shadow covered, and the percentage of cloud or shadow opacity. In addition, comparison of model calculations of insolation with measured values at selected test sites was accomplished, as well as development of preliminary requirements for a large scale data base of cloud cover statistics.

Huning, J. R.; Logan, T. L.; Smith, J. H.

1982-01-01

192

Validation of aerosol and cloud layer structures from the space-borne lidar CALIOP using a ground-based lidar in Seoul, Korea  

NASA Astrophysics Data System (ADS)

We present initial validation results of the space-borne lidar CALIOP onboard CALIPSO satellite using coincidental observations from a ground-based lidar in Seoul National University (SNU), Seoul, Korea (37.46° N, 126.95° E). We analyze six selected cases between September 2006 and February 2007, including 3 daytime and 3 night-time observations and covering different types of clear and cloudy atmospheric conditions. Apparent scattering ratios calculated from the two lidar measurements of total attenuated backscatter at 532 nm show similar aerosol and cloud layer structures both under cloud-free conditions and in cases of multiple aerosol layers underlying semi-transparent cirrus clouds. Agreement on top and base heights of cloud and aerosol layers is generally within 0.10 km, particularly during night-time. This result confirms that the CALIPSO science team algorithms for the discrimination of cloud and aerosol as well as for the detection of layer top and base altitude provide reliable information in such atmospheric conditions. This accuracy of the planetary boundary layer top height under cirrus cloud appears, however, limited during daytime. Under thick cloud conditions, however, information on the cloud top (bottom) height only is reliable from CALIOP (ground-based lidar) due to strong signal attenuations. However, simultaneous space-borne CALIOP and ground-based SNU lidar (SNU-L) measurements complement each other and can be combined to provide full information on the vertical distribution of aerosols and clouds. An aerosol backscatter-to-extinction ratio (BER) estimated from lidar and sunphotometer synergy at the SNU site during the CALIOP overpass is assessed to be 0.023±0.004 sr-1 (i.e. a lidar ratio of 43.2±6.2 sr) from CALIOP and 0.027±0.006 sr-1 (37.4±7.2 sr) from SNU-L. For aerosols within the planetary boundary layer under cloud-free conditions, the aerosol extinction profiles from both lidars are in agreement within about 0.02 km-1. Under semi-transparent cirrus clouds, such profiles also show good agreement for the night-time CALIOP flight, but large discrepancies are found for the daytime flights due to a small signal-to-noise ratio of the CALIOP data.

Kim, S.-W.; Berthier, S.; Raut, J.-C.; Chazette, P.; Dulac, F.; Yoon, S.-C.

2008-07-01

193

Dimensionality Based Scale Selection in 3d LIDAR Point Clouds  

NASA Astrophysics Data System (ADS)

This papers presents a multi-scale method that computes robust geometric features on lidar point clouds in order to retrieve the optimal neighborhood size for each point. Three dimensionality features are calculated on spherical neighborhoods at various radius sizes. Based on combinations of the eigenvalues of the local structure tensor, they describe the shape of the neighborhood, indicating whether the local geometry is more linear (1D), planar (2D) or volumetric (3D). Two radius-selection criteria have been tested and compared for ?nding automatically the optimal neighborhood radius for each point. Besides, such procedure allows a dimensionality labelling, giving signi?cant hints for classi?cation and segmentation purposes. The method is successfully applied to 3D point clouds from airborne, terrestrial, and mobile mapping systems since no a priori knowledge on the distribution of the 3D points is required. Extracted dimensionality features and labellings are then favorably compared to those computed from constant size neighborhoods.

Demantké, J.; Mallet, C.; David, N.; Vallet, B.

2011-09-01

194

Observations of the Interaction and/or Transport of Aerosols with Cloud or Fog during DRAGON Campaigns from AERONET Ground-Based Remote Sensing  

NASA Astrophysics Data System (ADS)

Ground-based remote sensing observations from Aerosol Robotic Network (AERONET) sun-sky radiometers have recently shown several instances where cloud-aerosol interaction had resulted in modification of aerosol properties and/or in difficulty identifying some major pollution transport events due to aerosols being imbedded in cloud systems. AERONET has established Distributed Regional Aerosol Gridded Observation Networks (DRAGON) during field campaigns that are short-term (~2-3 months) relatively dense spatial networks of ~15 to 45 sun and sky scanning photometers. Recent major DRAGON field campaigns in Japan and South Korea (Spring 2012) and California (Winter 2013) have yielded observations of aerosol transport associated with clouds and/or aerosol properties modification as a result of fog interaction. Analysis of data from the Korean and Japan DRAGON campaigns shows that major fine-mode aerosol transport events are sometimes associated with extensive cloud cover and that cloud-screening of observations often filter out significant pollution aerosol transport events. The Spectral De-convolution Algorithm (SDA) algorithm was utilized to isolate and analyze the fine-mode aerosol optical depth signal for these cases of persistent and extensive cloud cover. Additionally, extensive fog that was coincident with aerosol layer height on some days in both Korea and California resulted in large increases in fine mode aerosol radius, with a mode of cloud-processed or residual aerosol of radius ~0.4-0.5 micron sometimes observed. Cloud processed aerosol may occur much more frequently than AERONET data suggest due to inherent difficulty in observing aerosol properties near clouds from remote sensing observations. These biases of aerosols associated with clouds would likely be even greater for satellite remote sensing retrievals of aerosol properties near clouds due to 3-D effects and sub-pixel cloud contamination issues.

Eck, Thomas; Holben, Brent; Schafer, Joel; Giles, David; Kim, Jhoon; Kim, Young; Sano, Itaru; Reid, Jeffrey; Pickering, Kenneth; Crawford, James; Sinyuk, Alexander; Trevino, Nathan

2014-05-01

195

Realization of open cloud computing federation based on mobile agent  

Microsoft Academic Search

Although cloud computing is generally recognized as a technology which will has a significant impact on IT in the future. However, Cloud computing is still in its infancy, currently, there is not a standard available for it, portability and interoperability is also impossible between different Cloud Computing Service Providers, therefore, handicaps the widely deploy and quick development of cloud computing,

Zehua Zhang; Xuejie Zhang

2009-01-01

196

Remote Sensing of Aerosol and Cloud Properties from Ground Based and Satellite Remote Sensors to Explore Aerosol-Cloud Interaction  

NASA Astrophysics Data System (ADS)

The measurements of both aerosol and cloud properties are critical for climate studies since these mechanisms have the largest uncertainty in energy balance calculations. In addition, aerosols and clouds do not act independently but can significantly couple to each other. It is clear that being able to quantify these interactions is crucial to climate models. While there are many possible aerosol-cloud interactions, we limit our investigation to the Twomey indirect effect which relates how aerosols can modify the physical properties of clouds thereby changing the radiative properties. Verifying and quantifying such mechanisms on a global scale requires accurate measurements of both aerosols and clouds from satellites. Unfortunately, assessing this mechanism has been very difficult from satellites since both aerosols and cloud properties would have to be simultaneously measured. Therefore, only statistical approaches have been tried but it is easy to see that such approaches will tend to obscure the interpretation of local interaction mechanisms. In this thesis, we investigate the potential of both satellites and ground based approaches to measure Aerosol Cloud Interaction parameters. After assessing the limitations of satellite based approaches, we focus on the use of ground based remote sensing using a combination of Lidar, Microwave radiometry, Doppler Lidar and sky radiometry. This instrumentation suite offers a more direct approach that can probe the properties of both aerosols and clouds simultaneously allowing us to investigate real time aerosol-cloud processes which occur on time scale < 1 minute. To this end, we first provide a thorough description of the multi-sensor approach and how it can be implemented including a sensitivity analysis taking into account both atmospheric and surface variability as well as uncertainty in both the Liquid Water Path (LWP) and diffuse transmittance measurements. In addition, we use the Southern Great Plain (SGP) data to test our cloud parameter inversion algorithm against other algorithms. In addition, we illustrate the need to account for aloft aerosols in observations of aerosol cloud interactions. Finally, we describe how the CCNY site may ultimately be used for further improve ground observations of aerosol cloud interactions.

He, Yuzhe

197

First common volume ground-based and space measurements of the mesospheric front in noctilucent clouds  

NASA Astrophysics Data System (ADS)

report on the first common volume ground-based and space measurements of the mesospheric front in noctilucent clouds (NLCs). The detailed ground-based observations were performed with automated digital cameras located at the Athabasca University Geophysical Observatory (Canada) on the night of 29-30 June 2012, while simultaneous space measurements were conducted onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite using the Sounding of the Atmosphere using Broadband Emission Radiometry instrument. The large temperature difference of 20-25 K between two different air masses at about 85 km altitude was responsible for the front jump separating the area filled with NLCs from the area with no NLCs. The front jump (soliton) had a pronounced elevation of 12 km up to the altitude of 96 km relative to the undisturbed NLC layer located between 84.5 and 86.3 km. Considering present and previous ground-based measurements of the NLC height, we conclude that altitude of 96-97 km is the upper limit of possible heights of NLCs.

Dalin, P.; Connors, M.; Schofield, I.; Dubietis, A.; Pertsev, N.; Perminov, V.; Zalcik, M.; Zadorozhny, A.; McEwan, T.; McEachran, I.; Grønne, J.; Hansen, O.; Andersen, H.; Frandsen, S.; Melnikov, D.; Romejko, V.; Grigoryeva, I.

2013-12-01

198

An Implementation of Embedded Geographic Information System Based on Cloud Computing  

Microsoft Academic Search

An implementation of embedded geographic information system is proposed based on cloud computing mode. With cloud computing, the newest geographic information can be gotten in the terminal, meanwhile, good mobility and real-time performance can be obtained. MapX is used in cloud server to accomplish the integrated developing of GIS server. The geographic information is located there, so that it is

Yiqin Lu; Kanghua Yu; Yuan Liu

2011-01-01

199

CloudSat Preps for Launch at Vandenberg Air Force Base, CA  

NASA Technical Reports Server (NTRS)

The CloudSat spacecraft sits encapsulated within its Boeing Delta launch vehicle dual payload attach fitting at Vandenberg Air Force Base, Calif. CloudSat will share its ride to orbit late next month with NASA's CALIPSO spacecraft. The two spacecraft are designed to reveal the secrets of clouds and aerosols.

2005-01-01

200

Efficient Nash equilibrium based cloud resource allocation by using a continuous double auction  

Microsoft Academic Search

To allocate cloud resources efficiently and obtain the maximum economic benefit are the major goals of the cloud resource providers and users. The objective of this paper is to present a novel cloud resource allocation algorithm named NECDA to overcome some of the shortcomings of the current mechanisms. A cloud resource allocation model of m*n type based on M\\/M\\/1 queuing

Dawei Sun; Guiran Chang; Chuan Wang; Yu Xiong; Xingwei Wang

2010-01-01

201

An analysis of the scale heights in the lower topside ionosphere based on the Arecibo incoherent scatter radar measurements  

NASA Astrophysics Data System (ADS)

We statistically analyze the ionospheric scale heights in the lower topside ionosphere based on the electron density (Ne) and temperature profiles observed from the incoherent scatter radar (ISR) at Arecibo (293.2°E, 18.3°N), Puerto Rico. In this study, a database containing the Arecibo ISR observations from 1966 to 2002 has been used in order to investigate the diurnal and seasonal variations and solar activity dependences of the vertical scale height (VSH), which is deduced from the electron concentration profiles defined as the value of -dh/d(ln(Ne)), and the effective scale height (Hm), which is defined as the scale height in the Chapman-? function to approximate the Ne profiles. As a measure of the slope of the height profiles of the topside electron density, the derived VSH and Hm show marked diurnal and seasonal variations and solar activity dependences. Their features are discussed in terms of thermal structures in the lower topside ionosphere. We also investigate the quantitative relationships between Hm, VSH, and plasma scale height (Hp) over Arecibo. The similarities and differences in these scale heights are discussed. Results suggest that both the contributions from topside temperature structure and diffusion processes can also greatly control VSH and Hm through changing the profile shape.

Liu, Libo; Le, Huijun; Wan, Weixing; Sulzer, Mike P.; Lei, Jiuhou; Zhang, Man-Lian

2007-06-01

202

Ground-based measurements of tropospheric and stratospheric BrO at Arrival Heights, Antarctica  

NASA Astrophysics Data System (ADS)

Ground-based measurements of BrO slant column densities (SCDs) were performed using zenith sky DOAS (Differential Optical Absorption Spectroscopy) during autumn (February to May) and spring (August to October) of 1995 at Arrival Heights (77.8°S, 166.7°E). In both August and September, single episodes of sudden large BrO column enhancement (of magnitude 3.5 and 3.2 × 1014 molec. cm-2 respectively) were observed. The episode in August did not coincide with changes of other stratospheric parameters (OClO, NO2 and temperature). Furthermore, the diurnal variation in the SCD during these events was indicative of a tropospheric rather than a stratospheric absorber. The tropospheric BrO mixing ratios deduced from the data are similar to those observed by ground-based measurements in the Arctic boundary layer (˜30 ppt). Simultaneous balloon soundings, one during each of the two events, showed statistically significant (2 ?) tropospheric ozone depletion between 0.5 and 2 km in August and 1.5 and 2.8 km in September. Our results strongly suggest that halogen catalysed boundary layer ozone depletion not only occurs in the Arctic but also in Antarctica. This has the implication that Arctic Haze and anthropogenic influence is unlikely as a cause for this phenomenon.

Kreher, K.; Johnston, P. V.; Wood, S. W.; Nardi, B.; Platt, U.

203

Toward understanding of differences in current cloud retrievals of ARM ground-based measurements  

SciTech Connect

Accurate observations of cloud microphysical properties are needed for evaluating and improving the representation of cloud processes in climate models and better estimate of the Earth radiative budget. However, large differences are found in current cloud products retrieved from ground-based remote sensing measurements using various retrieval algorithms. Understanding the differences is an important step to address uncertainties in the cloud retrievals. In this study, an in-depth analysis of nine existing ground-based cloud retrievals using ARM remote sensing measurements is carried out. We place emphasis on boundary layer overcast clouds and high level ice clouds, which are the focus of many current retrieval development efforts due to their radiative importance and relatively simple structure. Large systematic discrepancies in cloud microphysical properties are found in these two types of clouds among the nine cloud retrieval products, particularly for the cloud liquid and ice particle effective radius. Note that the differences among some retrieval products are even larger than the prescribed uncertainties reported by the retrieval algorithm developers. It is shown that most of these large differences have their roots in the retrieval theoretical bases, assumptions, as well as input and constraint parameters. This study suggests the need to further validate current retrieval theories and assumptions and even the development of new retrieval algorithms with more observations under different cloud regimes.

Zhao C.; Dunn M.; Xie, S.; Klein, S. A.; Protat, A.; Shupe, M. D.; McFarlane, S. A.; Comstock, J. M.; Delanoë, J.; Deng, M.; Hogan, R. J.; Huang, D.; Jensen, M. P.; Mace, G. G.; McCoy, R.; O’Connor, E. J.; Turner, D. D.; Wang, Z.

2012-05-30

204

Temporal adaptive neural network-based satellite cloud imagery classification  

NASA Astrophysics Data System (ADS)

Highly efficient automatic cloud classification from satellite imagery is very important for a number of meteorological studies including weather forecasting. This dissertation presents the study of temporal adaptive neural network based cloud classification. Several advanced image processing techniques namely Singular Value Decomposition (SVD) and Wavelet Packets (WP) were first examined to extract the salient features of the satellite imagery. Their performances were compared with the widely used Gray-Level Co-occurrence Matrix approach. A feature selection scheme was also developed to reduce the redundancy in the feature sets. Two different kinds of neural network classifiers namely Kohonen self-organization map (SOM) and probabilistic neural networks (PNN) were analyzed. The SOM can explore the natural structure of the input feature space without any a priori class knowledge. The PNN, on the other hand, is a supervised network and is configured based on Bayes rule. In this study, the original PNN was improved by using Gaussian mixture models. Two different training algorithms for PNN were developed based on the Maximum Likelihood and Minimum Classification Error criteria. In order to utilize the rich spatial contextual information in satellite images, a post-processing scheme was also developed to improve the classification accuracy of PNN. The temporal issue arises when sequences of satellite images need to be processed. Due to the sun angle and ground temperature changes, the same cloud may look different at different time of the day. Consequently, a fixed neural network may not be able to deal with the temporal variations in the satellite image sequences. This problem was addressed in this project by proposing a novel updating solution for the PNN classifier. Two temporal updating schemes for the PNN classifier were developed in this study. They are Maximum Likelihood- based estimation approach and the temporal transform- based scheme. The proposed cloud classification schemes are examined on the GOES-8 satellite image data set. Overall, relatively high classification accuracy has been achieved. Moreover, when processing the satellite image sequence, the temporal updated PNN achieved much better results than that of the fixed classifier. The simulation results clearly demonstrate the promise of the proposed schemes.

Tian, Bin

1998-10-01

205

CloudWF: A Computational Workflow System for Clouds Based on Hadoop  

Microsoft Academic Search

This paper describes CloudWF, a scalable and lightweight computational workflow system for clouds on top of Hadoop. CloudWF\\u000a can run workflow jobs composed of multiple Hadoop MapReduce or legacy programs. Its novelty lies in several aspects: a simple\\u000a workflow description language that encodes workflow blocks and block-to-block dependencies separately as standalone executable\\u000a components; a new workflow storage method that uses

Chen Zhang; Hans De Sterck

2009-01-01

206

Determination of corner positions for calculation of step height of atomic force microscope images based on ISO 5436-1.  

PubMed

Step height is defined as the vertical spacing between two plane-parallel planes comprising an elevation or an indentation and the substrate. In atomic force microscopy (AFM), there are many algorithms for determining feature dimensions such as step height and width. One common problem of many algorithms is the difficulty for users to accurately determine the corner positions needed to properly implement the said algorithms. A new algorithm based on ISO 5436-1 is proposed that determines the necessary corner positions along with two examples illustrating the implementation of this algorithm. We propose calling this new method the determinant method. Since the corner positions are automatically decided, feature dimensions such as step height of an AFM image are easily determined. Comparative experiments carried out to compare the step height measurement using this algorithm and the SPIP software from Image Metrology show encouraging results. PMID:23534886

Adebayo, Adedayo S; Xuezeng, Zhao; Weijie, Wang

2013-06-01

207

Temporal and spatial variability of extreme significant wave heights in southern Europe based on satellite and reanalysis data bases  

NASA Astrophysics Data System (ADS)

Wave reanalysis data bases and satellite measurements provide information about both temporal and spatial variability of wave climate. However, the accuracy or inhomogeneities of these data sets require taking special caution to assess reliable climate variability of extreme values. We use a time-dependent extreme value model for monthly maxima of significant wave height to describe variations at different time scales in the southern Europe. The model is applied to hindcast data and satellite data covering different periods (1958-2001 for the reanalysis, and 1992-2007 for the instrumental data bases). Satellite data require a special statistical treatment due to its spatial and temporal inhomogeneities. As the number of satellite observations per month (N) is increasing through time, we have modified the extreme value model for block maxima considering that N can change in order to avoid artificial shifts in the maxima time series. Monthly maxima show a clear non-stationary behavior within a year, suggesting that the seasonality can be represented by using intrannual harmonic functions (Menendez et al., 2008). Seasonality explains great part of the variability of data, removing noises in larger time scale analysis. Once the seasonality is taken into account, the interannual variability is modelled including different covariates such as the North Atlantic Oscillation (NAO), the East Atlantic (EA) or Scandinavian (SCA) indices. The model allows to quantify the influence of these indices (i.e. every unit of the EA index explains 30 cm of the extreme wave height in the Gulf of Biscay). Results show maps of influence of the climate indices on extreme wave heights in the South of Europe (Northeast Atlantic Ocean and Mediterranean Sea).

Menendez, M.; Izaguirre, C.; Mendez, F. J.; Losada, I. J.; Luceño, A.

2009-04-01

208

Quantitative trait locus analysis for ear height in maize based on a recombinant inbred line population.  

PubMed

Maize (Zea mays L.) is among the crops with the greatest worldwide economic importance. Ear height is a very important trait that is considered necessary in maize and is related to morphology, lodging, and yield. To realize its genetic basis, an F9 recombinant inbred line population and a genetic map consisting of 101 simple sequence repeat markers were used to detect the quantitative trait locus (QTL) for ear height, and the result showed that one QTL on chromosome 1 was identified with a mapping interval of 5 cM to its linked marker Umc1358. The QTL from elite inbred line Mo17 could explain 9.55% of the phenotypic variance, and because of the additive effect, it could result in an ear height increase of 4.86 cm. This result was beneficial for understanding the genetic basis of ear height in maize. PMID:24535872

Li, Z Q; Zhang, H M; Wu, X P; Sun, Y; Liu, X H

2014-01-01

209

Preliminary Results of Measurements by Automated Probes Vega 1 and 2 or Particle Concentration in Clouds of Venus at Heights 47-63 Km.  

National Technical Information Service (NTIS)

Results of the preliminary processing of the Vega 1 and 2 descender data on the cloud layer structure of the Venusian atmosphere are discussed. A photoelectric counter for aerosol particles is described together with its optical and pneumatic circuits and...

Y. V. Zhulanov L. M. Mukhin D. F. Nenarokov

1986-01-01

210

Estimating crown base height for Scots pine by means of the 3D geometry of airborne laser scanning data  

Microsoft Academic Search

Crown base height (CBH) is an important factor in relation to several characteristics of the tree stock. This paper introduces approaches for estimating tree-level CBH from airborne laser scanning (ALS) data that employ features of computational geometry. For that purpose, the concepts of Delaunay triangulations and alpha shapes were applied and compared with approaches based on analysing return frequencies and

Jari Vauhkonen

2008-01-01

211

Importance of aggregation and small ice crystals in cirrus clouds, based on observations and an ice particle growth model  

NASA Technical Reports Server (NTRS)

The 1 November 1986 FIRE I case study was used to test an ice particle growth model which predicts bimodal size spectra in cirrus clouds. The model was developed from an analytically based model which predicts the height evolution of monomodal ice particle size spectra from the measured ice water content (IWC). Size spectra from the monomodal model are represented by a gamma distribution, N(D) = N(sub o)D(exp nu)exp(-lambda D), where D = ice particle maximum dimension. The slope parameter, lambda, and the parameter N(sub o) are predicted from the IWC through the growth processes of vapor diffusion and aggregation. The model formulation is analytical, computationally efficient, and well suited for incorporation into larger models. The monomodal model has been validated against two other cirrus cloud case studies. From the monomodal size spectra, the size distributions which determine concentrations of ice particles less than about 150 mu m are predicted.

Mitchell, David L.; Chai, Steven K.; Dong, Yayi; Arnott, W. Patrick; Hallett, John

1993-01-01

212

Cloud Thickness from Offbeam Returns - Thor Lidar  

NASA Technical Reports Server (NTRS)

Physical thickness of a cloud layer, and sometimes multiple cloud layers, can be estimated from the time delay of off-beam returns from a pulsed laser source illuminating one side of the cloud layer. In particular, the time delay of light returning from the outer diffuse halo of light surrounding the beam entry point, relative to the time delay at beam center, determines the cloud physical thickness. The delay combined with the pulse stretch gives the optical thickness. The halo method works best for thick cloud layers, typically optical thickness exceeding 2, and thus compliments conventional lidar which cannot penetrate thick clouds. Cloud layer top and base have been measured independently over the ARM/SGP site using conventional laser ranging (lidar) and the top minus base thickness are compared with a cloud top halo estimate obtained from the NASA/Goddard THOR System (THOR = THickness from Offbeam Returns). THOR flies on the NASA P3, and measures the halo timings from several km above cloud top, at the same time providing conventional lidar cloud top height. The ARM/SGP micropulse lidar provides cloud base height for validation.

Cahalan, R.; Kolasinski, J.; McGill, M.; Lau, William K. M. (Technical Monitor)

2002-01-01

213

An Expert Fitness Diagnosis System Based on Elastic Cloud Computing  

PubMed Central

This paper presents an expert diagnosis system based on cloud computing. It classifies a user's fitness level based on supervised machine learning techniques. This system is able to learn and make customized diagnoses according to the user's physiological data, such as age, gender, and body mass index (BMI). In addition, an elastic algorithm based on Poisson distribution is presented to allocate computation resources dynamically. It predicts the required resources in the future according to the exponential moving average of past observations. The experimental results show that Naïve Bayes is the best classifier with the highest accuracy (90.8%) and that the elastic algorithm is able to capture tightly the trend of requests generated from the Internet and thus assign corresponding computation resources to ensure the quality of service.

Tseng, Kevin C.; Wu, Chia-Chuan

2014-01-01

214

Min-Cut Based Segmentation of Airborne LIDAR Point Clouds  

NASA Astrophysics Data System (ADS)

Introducing an organization to the unstructured point cloud before extracting information from airborne lidar data is common in many applications. Aggregating the points with similar features into segments in 3-D which comply with the nature of actual objects is affected by the neighborhood, scale, features and noise among other aspects. In this study, we present a min-cut based method for segmenting the point cloud. We first assess the neighborhood of each point in 3-D by investigating the local geometric and statistical properties of the candidates. Neighborhood selection is essential since point features are calculated within their local neighborhood. Following neighborhood determination, we calculate point features and determine the clusters in the feature space. We adapt a graph representation from image processing which is especially used in pixel labeling problems and establish it for the unstructured 3-D point clouds. The edges of the graph that are connecting the points with each other and nodes representing feature clusters hold the smoothness costs in the spatial domain and data costs in the feature domain. Smoothness costs ensure spatial coherence, while data costs control the consistency with the representative feature clusters. This graph representation formalizes the segmentation task as an energy minimization problem. It allows the implementation of an approximate solution by min-cuts for a global minimum of this NP hard minimization problem in low order polynomial time. We test our method with airborne lidar point cloud acquired with maximum planned post spacing of 1.4 m and a vertical accuracy 10.5 cm as RMSE. We present the effects of neighborhood and feature determination in the segmentation results and assess the accuracy and efficiency of the implemented min-cut algorithm as well as its sensitivity to the parameters of the smoothness and data cost functions. We find that smoothness cost that only considers simple distance parameter does not strongly conform to the natural structure of the points. Including shape information within the energy function by assigning costs based on the local properties may help to achieve a better representation for segmentation.

Ural, S.; Shan, J.

2012-07-01

215

Comparison of Cloud Properties from CALIPSO-CloudSat and Geostationary Satellite Data  

NASA Technical Reports Server (NTRS)

Cloud properties are being derived in near-real time from geostationary satellite imager data for a variety of weather and climate applications and research. Assessment of the uncertainties in each of the derived cloud parameters is essential for confident use of the products. Determination of cloud amount, cloud top height, and cloud layering is especially important for using these real -time products for applications such as aircraft icing condition diagnosis and numerical weather prediction model assimilation. Furthermore, the distribution of clouds as a function of altitude has become a central component of efforts to evaluate climate model cloud simulations. Validation of those parameters has been difficult except over limited areas where ground-based active sensors, such as cloud radars or lidars, have been available on a regular basis. Retrievals of cloud properties are sensitive to the surface background, time of day, and the clouds themselves. Thus, it is essential to assess the geostationary satellite retrievals over a variety of locations. The availability of cloud radar data from CloudSat and lidar data from CALIPSO make it possible to perform those assessments over each geostationary domain at 0130 and 1330 LT. In this paper, CloudSat and CALIPSO data are matched with contemporaneous Geostationary Operational Environmental Satellite (GOES), Multi-functional Transport Satellite (MTSAT), and Meteosat-8 data. Unlike comparisons with cloud products derived from A-Train imagers, this study considers comparisons of nadir active sensor data with off-nadir retrievals. These matched data are used to determine the uncertainties in cloud-top heights and cloud amounts derived from the geostationary satellite data using the Clouds and the Earth s Radiant Energy System (CERES) cloud retrieval algorithms. The CERES multi-layer cloud detection method is also evaluated to determine its accuracy and limitations in the off-nadir mode. The results will be useful for constraining the use of the passive retrieval data in models and for improving the accuracy of the retrievals.

Nguyen, L.; Minnis, P.; Chang, F.; Winker, D.; Sun-Mack, S.; Spangenberg, D.; Austin, R.

2007-01-01

216

MAP-MRF cloud detection based on PHD filtering  

Microsoft Academic Search

Temporal correlation has been recently taken into consideration to improve the performances of cloud detection algorithms. We exploit this concept within the Maximum A Posteriori Markov Random Field MAP-MRF framework by adding a penalization term which is determined according to the hystory of cloud masses. Multi Target Tracking of clouds is accomplished by methods of FInite Set Statistics (FISS) and

Paolo Addesso; Roberto Conte; Maurizio Longo; Rocco Restaino; Gemine Vivone

2011-01-01

217

MAP-MRF Cloud Detection Based on PHD Filtering  

Microsoft Academic Search

Temporal correlation has been recently taken into consideration to improve the performances of cloud detection algorithms. We exploit this concept within the Maximum A Posteriori Markov Random Field (MAP-MRF) framework by adding a penalty term which is determined according to the history of cloud masses. Multi Target Tracking of clouds is accomplished by methods of FInite Set STatistics (FISST) and

Paolo Addesso; Roberto Conte; Maurizio Longo; Rocco Restaino; Gemine Vivone

2012-01-01

218

Cloud optical thickness retrievals from ground-based pyranometer measurements  

NASA Astrophysics Data System (ADS)

A method is developed to retrieve total cloud optical thickness (COT) from global solar radiation (GSR) detected by ground-based pyranometer, and approaches to input aerosol/molecular/gas parameters for COT retrievals are presented. On the basis of numerical simulations and comparative tests, main error factors of COT retrievals are analyzed, which include radiation data error, cloud inhomogeneity, uncertainties of aerosol optical parameters, and surface albedo. The retrieved COT error, caused by a -5% or 5% systematic error of the GSR measurement, is within ±0.6 and ±5.0 for COT ranges of 0-5.0 and 5-100, respectively. The AOT, the aerosol single scatter albedo (SSA), and the surface albedo are three significant parameters affecting COT retrieval accuracy. The mean SSA in the pyranometer spectral response range and the broadband surface albedo are suitably used in the retrievals. If uncertainties of AOT, SSA, and surface albedo are within ±0.1, ±0.05, and ±0.05, respectively, the retrieval accuracy is accepted for most applications. Furthermore, COTs (?Pyr) from pyranometer data at two meteorological observatories are compared with COTs (?ISCCP) from ISCCP and COTs (?MODIS) from MODIS. The relative standard deviations between monthly mean ?Pyr and ?MODIS, or ?Pyr and ?ISCCP, are all less than 45.4% for both sites. The agreement among the yearly mean ?Pyr,?MODIS, and ?ISCCP is satisfactory. The absolute (relative) deviations between the yearly mean ?Pyr and ?MODIS are within ±1.55 (8%) for both sites, and the deviations between the ?Pyr and ?ISCCP are within ±1.94 (25%). The yearly mean ?Pyr also agrees considerably well with ?ISCCP in the broken cloud case.

Qiu, Jinhuan

2006-11-01

219

A High Resolution Hydrometer Phase Classifier Based on Analysis of Cloud Radar Doppler Spectra.  

SciTech Connect

The lifecycle and radiative properties of clouds are highly sensitive to the phase of their hydrometeors (i.e., liquid or ice). Knowledge of cloud phase is essential for specifying the optical properties of clouds, or else, large errors can be introduced in the calculation of the cloud radiative fluxes. Current parameterizations of cloud water partition in liquid and ice based on temperature are characterized by large uncertainty (Curry et al., 1996; Hobbs and Rangno, 1998; Intriery et al., 2002). This is particularly important in high geographical latitudes and temperature ranges where both liquid droplets and ice crystal phases can exist (mixed-phase cloud). The mixture of phases has a large effect on cloud radiative properties, and the parameterization of mixed-phase clouds has a large impact on climate simulations (e.g., Gregory and Morris, 1996). Furthermore, the presence of both ice and liquid affects the macroscopic properties of clouds, including their propensity to precipitate. Despite their importance, mixed-phase clouds are severely understudied compared to the arguably simpler single-phase clouds. In-situ measurements in mixed-phase clouds are hindered due to aircraft icing, difficulties distinguishing hydrometeor phase, and discrepancies in methods for deriving physical quantities (Wendisch et al. 1996, Lawson et al. 2001). Satellite-based retrievals of cloud phase in high latitudes are often hindered by the highly reflecting ice-covered ground and persistent temperature inversions. From the ground, the retrieval of mixed-phase cloud properties has been the subject of extensive research over the past 20 years using polarization lidars (e.g., Sassen et al. 1990), dual radar wavelengths (e.g., Gosset and Sauvageot 1992; Sekelsky and McIntosh, 1996), and recently radar Doppler spectra (Shupe et al. 2004). Millimeter-wavelength radars have substantially improved our ability to observe non-precipitating clouds (Kollias et al., 2007) due to their excellent sensitivity that enables the detection of thin cloud layers and their ability to penetrate several non-precipitating cloud layers. However, in mixed-phase clouds conditions, the observed Doppler moments are dominated by the highly reflecting ice crystals and thus can not be used to identify the cloud phase. This limits our ability to identify the spatial distribution of cloud phase and our ability to identify the conditions under which mixed-phase clouds form.

Luke,E.; Kollias, P.

2007-08-06

220

The Open Cloud Testbed: Supporting Open Source Cloud Computing Systems Based on Large Scale High Performance, Dynamic Network Services  

NASA Astrophysics Data System (ADS)

Recently, a number of cloud platforms and services have been developed for data intensive computing, including Hadoop, Sector, CloudStore (formerly KFS), HBase, and Thrift. In order to benchmark the performance of these systems, to investigate their interoperability, and to experiment with new services based on flexible compute node and network provisioning capabilities, we have designed and implemented a large scale testbed called the Open Cloud Testbed (OCT). Currently OCT has 120 nodes in 4 data centers: Baltimore, Chicago (two locations), and San Diego. In contrast to other cloud testbeds, which are in small geographic areas and which are based on commodity Internet services, the OCT is a wide area testbed and the 4 data centers are connected with a high performance 10Gb/s network, based on a foundation of dedicated lightpaths. This testbed can address the requirements of extremely large data streams that challenge other types of distributed infrastructure. We have also developed several utilities to support the development of cloud computing systems and services, including novel node and network provisioning services, a monitoring system, and an RPC system. In this paper, we describe the OCT concepts, architecture, infrastructure, a few benchmarks that were developed for this platform, interoperability studies, and results.

Grossman, Robert; Gu, Yunhong; Sabala, Michal; Bennet, Colin; Seidman, Jonathan; Mambratti, Joe

221

Building Height  

NSDL National Science Digital Library

Working in pairs, students create a clinometer and use isosceles right triangles to find the height of a building. The class will compare measurements, discuss their results, and select the best measure of central tendency to report the most accurate height. All handouts and excellent class discussion questions are provided.

Hendrickson, Katie

2000-01-01

222

Height Museum  

NSDL National Science Digital Library

In this activity, children use strips of paper cut to their height to make comparisons. They are asked to make predictions such as "Is the oldest student the tallest?" and then check their predictions. A suggested variation is to predict changes in height over time by repeating the exercise in three months.

2010-01-01

223

Video-based real-time measurement for human body height  

NASA Astrophysics Data System (ADS)

Height measurement for a moving human body is a hard task for human body estimation. We propose a novel algorithm for real-time human height measurement without knowing any camera parameter, just having a vertical reference height. As contrasted with the previous research methods in the context of camera calibration, the studied algorithm reduces the complexity of user operations and the economy cost. First, three or more pairs of top-points and bottom-points are extracted by detecting the moving human body to solve the vertical vanishing point and the horizontal vanishing line. Then, the height of the moving human body on ground plane or stepped plane is obtained using the solved vanishing point, the vanishing line, and a given reference height. Considering the importance of the vanishing point and the vanishing line and the sensitivity of both to noise, an optimal approach is adopted. Finally, we show the optimal number and position of the human body in a camera field. Both computer simulation and real testing data validate the robustness and the effectiveness of the proposed algorithm.

Li, Weisheng; Wang, Weixing; Gao, Hongbo; Zhang, Licheng

2012-08-01

224

Investigating Clouds  

NSDL National Science Digital Library

This field activity has two parts: Elementary school students are asked to draw and verbally describe clouds and are given web access to cloud pictures. High school students are taken outdoors to describe cloud height, shape, and cover; and wind speed before answering questions. The activity is part of the Atmospheric Visualization Collection (AVC), which focuses on data from the Atmospheric Radiation Measurement (ARM) program.

2003-05-09

225

A method for cloud detection and opacity classification based on ground based sky imagery  

NASA Astrophysics Data System (ADS)

Digital images of the sky obtained using a total sky imager (TSI) are classified pixel by pixel into clear sky, optically thin and optically thick clouds. A new classification algorithm was developed that compares the pixel red-blue ratio (RBR) to the RBR of a clear sky library (CSL) generated from images captured on clear days. The difference, rather than the ratio, between pixel RBR and CSL RBR resulted in more accurate cloud classification. High correlation between TSI image RBR and aerosol optical depth (AOD) measured by an AERONET photometer was observed and motivated the addition of a haze correction factor (HCF) to the classification model to account for variations in AOD. Thresholds for clear and thick clouds were chosen based on a training image set and validated with set of manually annotated images. Misclassifications of clear and thick clouds into the opposite category were less than 1%. Thin clouds were classified with an accuracy of 60%. Accurate cloud detection and opacity classification techniques will improve the accuracy of short-term solar power forecasting.

Ghonima, M. S.; Urquhart, B.; Chow, C. W.; Shields, J. E.; Cazorla, A.; Kleissl, J.

2012-11-01

226

A method for cloud detection and opacity classification based on ground based sky imagery  

NASA Astrophysics Data System (ADS)

Digital images of the sky obtained using a total sky imager (TSI) are classified pixel by pixel into clear sky, optically thin and optically thick clouds. A new classification algorithm was developed that compares the pixel red-blue ratio (RBR) to the RBR of a clear sky library (CSL) generated from images captured on clear days. The difference, rather than the ratio, between pixel RBR and CSL RBR resulted in more accurate cloud classification. High correlation between TSI image RBR and aerosol optical depth (AOD) measured by an AERONET photometer was observed and motivated the addition of a haze correction factor (HCF) to the classification model to account for variations in AOD. Thresholds for clear and thick clouds were chosen based on a training image set and validated with set of manually annotated images. Misclassifications of clear and thick clouds into the opposite category were less than 1%. Thin clouds were classified with an accuracy of 60%. Accurate cloud detection and opacity classification techniques will improve the accuracy of short-term solar power forecasting.

Ghonima, M. S.; Urquhart, B.; Chow, C. W.; Shields, J. E.; Cazorla, A.; Kleissl, J.

2012-07-01

227

Study on China's National Height Datum based on Analyzing The Dagang Tidal Data  

NASA Astrophysics Data System (ADS)

China's current National Height Datum, 1985 National Height Datum, was defined by the mean sea level at Dagang tidal gauge, which was obtained by averaging 10 mean sea levels of a 19 year period analyzing 1952~1979 tidal data. In order to investigate the stability of the 1985 National Height Datum, we have studied the changes in the mean sea level by analyzing the 1980~2011 Dagang tidal data. First the frequencies and amplitudes of main tides are determined by the Fouirer transform. Then the actual amplitudes and variations are obtained by the harmonic analysis. Next the changes of the mean sea level at Dagang tidal gauge during the period of 1952~2011 are studied by the harmonic analysis and the shifting averaging of 18.61 year period. And finally by averaging 18.61 year period during the period of 1952~1979, the mean sea level is achieved.

WU, Fumei; WEI, Ziqing; LI, Yingchun

2014-05-01

228

Estimating radiation effective doses from whole body computed tomography scans based on U.S. soldier patient height and weight  

PubMed Central

Background The purpose of this study is to explore how a patient's height and weight can be used to predict the effective dose to a reference phantom with similar height and weight from a chest abdomen pelvis computed tomography scan when machine-based parameters are unknown. Since machine-based scanning parameters can be misplaced or lost, a predictive model will enable the medical professional to quantify a patient's cumulative radiation dose. Methods One hundred mathematical phantoms of varying heights and weights were defined within an x-ray Monte Carlo based software code in order to calculate organ absorbed doses and effective doses from a chest abdomen pelvis scan. Regression analysis was used to develop an effective dose predictive model. The regression model was experimentally verified using anthropomorphic phantoms and validated against a real patient population. Results Estimates of the effective doses as calculated by the predictive model were within 10% of the estimates of the effective doses using experimentally measured absorbed doses within the anthropomorphic phantoms. Comparisons of the patient population effective doses show that the predictive model is within 33% of current methods of estimating effective dose using machine-based parameters. Conclusions A patient's height and weight can be used to estimate the effective dose from a chest abdomen pelvis computed tomography scan. The presented predictive model can be used interchangeably with current effective dose estimating techniques that rely on computed tomography machine-based techniques.

2011-01-01

229

Impact of a cloud thermodynamic phase parameterization based on CALIPSO observations on climate simulation  

NASA Astrophysics Data System (ADS)

This study examines the impact of a new cloud thermodynamic phase parameterization on climate simulation. The new parameterization is based on CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations and replaces the default parameterization in the Community Atmosphere Model version 4. It is shown that the application of the new cloud phase parameterization results in a small increase in global-mean liquid water path (LWP) and a small decrease in global-mean ice water path (IWP). Large regional increases in LWP mainly occur in tropical regions such as the western Pacific warm pool and northeastern Indian Ocean and middle latitudes, while large decreases in IWP occur in the midlatitude storm track regions. The increase in zonal-mean cloud water content occurs at temperatures between -15°C and -30°C and cloud fraction increases occur at higher altitudes near the -30°C isotherm. Two other sensitivity experiments that favor more ice-phase clouds also increase cloud fractions at the same altitudes, but decrease cloud water content at slightly lower altitudes. It is found that relative humidity increases at the same altitudes where the cloud fraction increases, caused by radiative cooling that is induced by cloud fraction increases but not changes in cloud water content. This result points to a deficiency in cloud fraction parameterizations that rely solely on ambient humidity without taking cloud water/ice content into account. Zonal-mean cloud albedo forcing is sensitive to LWP in mixed-phase clouds and the comparison with observations suggests that the CALIPSO and default parameterizations perform well in the extratropical regions.

Cheng, Anning; Xu, Kuan-Man; Hu, Yongxiang; Kato, Seiji

2012-05-01

230

CloudAnalyst: A CloudSim-Based Visual Modeller for Analysing Cloud Computing Environments and Applications  

Microsoft Academic Search

Abstract—Advances in Cloud computing opens up many new possibilities for Internet applications developers. Previously, a main,concern of Internet applications developers was deployment and hosting of applications, because it required acquisition of a server with a fixed capacity able to handle the expected application peak demand and the installation and maintenance of the whole software infrastructure of the platform supporting the

Bhathiya Wickremasinghe; Rodrigo N. Calheiros; Rajkumar Buyya

2010-01-01

231

CloudWF: A Computational Workflow System for Clouds Based on Hadoop  

NASA Astrophysics Data System (ADS)

This paper describes CloudWF, a scalable and lightweight computational workflow system for clouds on top of Hadoop. CloudWF can run workflow jobs composed of multiple Hadoop MapReduce or legacy programs. Its novelty lies in several aspects: a simple workflow description language that encodes workflow blocks and block-to-block dependencies separately as standalone executable components; a new workflow storage method that uses Hadoop HBase sparse tables to store workflow information internally and reconstruct workflow block dependencies implicitly for efficient workflow execution; transparent file staging with Hadoop DFS; and decentralized workflow execution management relying on the MapReduce framework for task scheduling and fault tolerance. This paper describes the design and implementation of CloudWF.

Zhang, Chen; de Sterck, Hans

232

Research on texture feature of RS image based on cloud model  

NASA Astrophysics Data System (ADS)

This paper presents a new method applied to texture feature representation in RS image based on cloud model. Aiming at the fuzziness and randomness of RS image, we introduce the cloud theory into RS image processing in a creative way. The digital characteristics of clouds well integrate the fuzziness and randomness of linguistic terms in a unified way and map the quantitative and qualitative concepts. We adopt texture multi-dimensions cloud to accomplish vagueness and randomness handling of texture feature in RS image. The method has two steps: 1) Correlativity analyzing of texture statistical parameters in Grey Level Co-occurrence Matrix (GLCM) and parameters fuzzification. GLCM can be used to representing the texture feature in many aspects perfectly. According to the expressive force of texture statistical parameters and by Correlativity analyzing of texture statistical parameters, we can abstract a few texture statistical parameters that can best represent the texture feature. By the fuzziness algorithm, the texture statistical parameters can be mapped to fuzzy cloud space. 2) Texture multi-dimensions cloud model constructing. Based on the abstracted texture statistical parameters and fuzziness cloud space, texture multi-dimensions cloud model can be constructed in micro-windows of image. According to the membership of texture statistical parameters, we can achieve the samples of cloud-drop. By backward cloud generator, the digital characteristics of texture multi-dimensions cloud model can be achieved and the Mathematical Expected Hyper Surface(MEHS) of multi-dimensions cloud of micro-windows can be constructed. At last, the weighted sum of the 3 digital characteristics of micro-window cloud model was proposed and used in texture representing in RS image. The method we develop is demonstrated by applying it to texture representing in many RS images, various performance studies testify that the method is both efficient and effective. It enriches the cloud theory, and proposes a new idea for image texture representing and analyzing, especially RS image.

Wang, Zuocheng; Xue, Lixia

2008-10-01

233

Analysis of the Security and Privacy Requirements of Cloud-Based Electronic Health Records Systems  

PubMed Central

Background The Cloud Computing paradigm offers eHealth systems the opportunity to enhance the features and functionality that they offer. However, moving patients’ medical information to the Cloud implies several risks in terms of the security and privacy of sensitive health records. In this paper, the risks of hosting Electronic Health Records (EHRs) on the servers of third-party Cloud service providers are reviewed. To protect the confidentiality of patient information and facilitate the process, some suggestions for health care providers are made. Moreover, security issues that Cloud service providers should address in their platforms are considered. Objective To show that, before moving patient health records to the Cloud, security and privacy concerns must be considered by both health care providers and Cloud service providers. Security requirements of a generic Cloud service provider are analyzed. Methods To study the latest in Cloud-based computing solutions, bibliographic material was obtained mainly from Medline sources. Furthermore, direct contact was made with several Cloud service providers. Results Some of the security issues that should be considered by both Cloud service providers and their health care customers are role-based access, network security mechanisms, data encryption, digital signatures, and access monitoring. Furthermore, to guarantee the safety of the information and comply with privacy policies, the Cloud service provider must be compliant with various certifications and third-party requirements, such as SAS70 Type II, PCI DSS Level 1, ISO 27001, and the US Federal Information Security Management Act (FISMA). Conclusions Storing sensitive information such as EHRs in the Cloud means that precautions must be taken to ensure the safety and confidentiality of the data. A relationship built on trust with the Cloud service provider is essential to ensure a transparent process. Cloud service providers must make certain that all security mechanisms are in place to avoid unauthorized access and data breaches. Patients must be kept informed about how their data are being managed.

Fernandez, Gonzalo; Lopez-Coronado, Miguel

2013-01-01

234

Cloud based intelligent system for delivering health care as a service.  

PubMed

The promising potential of cloud computing and its convergence with technologies such as mobile computing, wireless networks, sensor technologies allows for creation and delivery of newer type of cloud services. In this paper, we advocate the use of cloud computing for the creation and management of cloud based health care services. As a representative case study, we design a Cloud Based Intelligent Health Care Service (CBIHCS) that performs real time monitoring of user health data for diagnosis of chronic illness such as diabetes. Advance body sensor components are utilized to gather user specific health data and store in cloud based storage repositories for subsequent analysis and classification. In addition, infrastructure level mechanisms are proposed to provide dynamic resource elasticity for CBIHCS. Experimental results demonstrate that classification accuracy of 92.59% is achieved with our prototype system and the predicted patterns of CPU usage offer better opportunities for adaptive resource elasticity. PMID:24139021

Kaur, Pankaj Deep; Chana, Inderveer

2014-01-01

235

Remote Sensing of Cloud Properties using Ground-based Measurements of Zenith Radiance  

NASA Technical Reports Server (NTRS)

An extensive verification of cloud property retrievals has been conducted for two algorithms using zenith radiances measured by the Atmospheric Radiation Measurement (ARM) Program ground-based passive two-channel (673 and 870 nm) Narrow Field-Of-View Radiometer. The underlying principle of these algorithms is that clouds have nearly identical optical properties at these wavelengths, but corresponding spectral surface reflectances (for vegetated surfaces) differ significantly. The first algorithm, the RED vs. NIR, works for a fully three-dimensional cloud situation. It retrieves not only cloud optical depth, but also an effective radiative cloud fraction. Importantly, due to one-second time resolution of radiance measurements, we are able, for the first time, to capture detailed changes in cloud structure at the natural time scale of cloud evolution. The cloud optical depths tau retrieved by this algorithm are comparable to those inferred from both downward fluxes in overcast situations and microwave brightness temperatures for broken clouds. Moreover, it can retrieve tau for thin patchy clouds, where flux and microwave observations fail to detect them. The second algorithm, referred to as COUPLED, couples zenith radiances with simultaneous fluxes to infer 2. In general, the COUPLED and RED vs. NIR algorithms retrieve consistent values of tau. However, the COUPLED algorithm is more sensitive to the accuracies of measured radiance, flux, and surface reflectance than the RED vs. NIR algorithm. This is especially true for thick overcast clouds where it may substantially overestimate z.

Chiu, J. Christine; Marshak, Alexander; Knyazikhin, Yuri; Wiscombe, Warren J.; Barker, Howard W.; Barnard, James C.; Luo, Yi

2006-01-01

236

3-D Command state-based modifiable walking of a humanoid robot on uneven terrain with different inclinations and heights  

Microsoft Academic Search

This paper proposes 3-D command state (3-D CS)-based modifiable walking pattern generator (MWPG) on the uneven terrain with the different inclinations and heights for humanoid robots. In the previous researches on walking pattern generation on the uneven terrain, the humanoid robot was unable to modify a walking pattern on the uneven terrain without any additional footstep for adjusting the center

Young-Dae Hong; Jong-Hwan Kim

2011-01-01

237

Height at the withers estimation in the horses based on the internal dimension of cranial cavity.  

PubMed

The investigations were carried out on 17 modern half-breed horse skulls and their metacarpal and metatarsal bones. The basal length (BL), total length (TL), internal cranial cavity dimension and maximal length of metacarpus and metatarsus and maximal lateral length of metacarpus and metatarsus were measured according to Kiesewalter and von den Driesch. During height at the withers estimation, the Kiesewaler and Vitt methods were used. The Wyrost and Kucharczyk mathematical formula was modified for height at the withers calculation (Hestmd = 1.016 × D) in horses. All height at the withers estimation methods were statistically analysed and compared. The analysis of variance ANOVA proved the lack of significant difference between the investigated values. The results achieved using Wyrost and Kucharczyk modified method are strongly comparable to Kiesewalter methods results computed using the metacarpal and metatarsal bones measurements. The height at the withers calculated on the basis of TL slightly differs from 2 above-mentioned methods. The BL Vitt's method was the least exact. PMID:24902091

Chrószcz, A; Janeczek, M; Pasicka, E; Kle?kowska-Nawrot, J

2014-05-01

238

Combined satellite and radar retrievals of drop concentration and CCN at convective cloud base  

NASA Astrophysics Data System (ADS)

number of activated cloud condensation nuclei (CCN) into cloud drops at the base of convective clouds (Na) is retrieved based on the high-resolution (375 m) satellite retrievals of vertical profiles of convective cloud drop effective radius (re). The maximum cloud base supersaturation (S) is calculated when Na is combined with radar-measured updraft and yields CCN(S), which was validated well against ground-based CCN measurements during the conditions of well-mixed boundary layer over the U.S. Department of Energy's Atmospheric System Research Southern Great Plains site. Satellite retrieving Na is a new capability, which is one essential component of simultaneous measurements of cloud microstructure and CCN from space by using clouds as natural CCN chambers. This has to be complemented by a methodology for satellite estimates of cloud base updraft, which is yet to be developed and demonstrated. In the mean time, the retrieved Na can be used for the assimilation of the combined CCN and updraft effects on clouds in models.

Rosenfeld, Daniel; Fischman, Baruch; Zheng, Youtong; Goren, Tom; Giguzin, David

2014-05-01

239

A Cloud Computing Based Patient Centric Medical Information System  

NASA Astrophysics Data System (ADS)

This chapter discusses an emerging concept of a cloud computing based Patient Centric Medical Information System framework that will allow various authorized users to securely access patient records from various Care Delivery Organizations (CDOs) such as hospitals, urgent care centers, doctors, laboratories, imaging centers among others, from any location. Such a system must seamlessly integrate all patient records including images such as CT-SCANS and MRI'S which can easily be accessed from any location and reviewed by any authorized user. In such a scenario the storage and transmission of medical records will have be conducted in a totally secure and safe environment with a very high standard of data integrity, protecting patient privacy and complying with all Health Insurance Portability and Accountability Act (HIPAA) regulations.

Agarwal, Ankur; Henehan, Nathan; Somashekarappa, Vivek; Pandya, A. S.; Kalva, Hari; Furht, Borko

240

An improved approach for flow-based cloud point extraction.  

PubMed

Novel strategies are proposed to circumvent the main drawbacks of flow-based cloud point extraction (CPE). The surfactant-rich phase (SRP) was directly retained into the optical path of the spectrophotometric cell, thus avoiding its dilution previously to the measurement and yielding higher sensitivity. Solenoid micro-pumps were exploited to improve mixing by the pulsed flow and also to modulate the flow-rate for retention and removal of the SRP, thus avoiding the elution step, often carried out with organic solvents. The heat released and the increase of the salt concentration provided by an on-line neutralization reaction were exploited to induce the cloud point without an external heating device. These innovations were demonstrated by the spectrophotometric determination of iron, yielding a linear response from 10 to 200?gL(-1) with a coefficient of variation of 2.3% (n=7). Detection limit and sampling rate were estimated at 5?gL(-1) (95% confidence level) and 26 samples per hour, respectively. The enrichment factor was 8.9 and the procedure consumed only 6?g of TAN and 390?g of Triton X-114 per determination. At the 95% confidence level, the results obtained for freshwater samples agreed with the reference procedure and those obtained for digests of bovine muscle, rice flour, brown bread and tort lobster agreed with the certified reference values. The proposed procedure thus shows advantages in relation to previously proposed approaches for flow-based CPE, being a fast and environmental friendly alternative for on-line separation and pre-concentration. PMID:24745739

Frizzarin, Rejane M; Rocha, Fábio R P

2014-04-11

241

An Integrated Method to Generate a Cloud-Free Image Automatically Based on Landsat5 Data  

Microsoft Academic Search

How to remove cloud and shadow completely through several (more than 2) images is considered in this paper. Based on landsat5 data, when enter several images, it can automatically find one image with the least cloud and shadow as the base image. Then mosaic with other images which are taken in different time for the same area, an image without

Ying-zhao Ma; Wei-li Jiao; Gui-zhou Wang; Teng-fei Long; Wei Wang

2010-01-01

242

Retrieval of atmospheric attenuation using combined ground-based and airborne 95-GHz cloud radar measurements  

NASA Technical Reports Server (NTRS)

This paper discusses cloud radar calibration and intercomparison of airborne and ground-based radar measurements and presents a unique algorithm for attenuation retrieval. This algorithm is based on dual 95-GHz radar measurements of the same cloud and precipitation volumes collected from opposing viewing angles.

Li, L.; Sekelsky, S.; Reising, S.; Swift, C.; Durden, S.; Sadowy, G.; Dinardo, S.; Li, F.; Huffman, A.; Stephens, G.; Babb, D.; Rosenberger, H.

2001-01-01

243

A cloud cover model based on satellite data  

NASA Technical Reports Server (NTRS)

A model for worldwide cloud cover using a satellite data set containing infrared radiation measurements is proposed. The satellite data set containing day IR, night IR and incoming and absorbed solar radiation measurements on a 2.5 degree latitude-longitude grid covering a 45 month period was converted to estimates of cloud cover. The global area was then classified into homogeneous cloud cover regions for each of the four seasons. It is noted that the developed maps can be of use to the practicing climatologist who can obtain a considerable amount of cloud cover information without recourse to large volumes of data.

Somerville, P. N.; Bean, S. J.

1980-01-01

244

Predictions of age-age correlations of total height based on serial correlations between height increments in Maritime pine (Pinus pinaster Ait.).  

PubMed

Successive annual height increments (AHIs) are considered to be elements of a time series. Empirical data in Maritime pine (Pinus pinaster Ait.) show that genetic correlations between successive AHIs (serial correlation) decrease when the lag between corresponding growing seasons increases. When separated by more than 13 years AHIs are no longer genetically correlated. It is shown that age-age correlations between total heights depend on three components: the serial correlation structure between AHIs, the genetic coefficient of variation of AHIs, and the phenotypic growth curve of AHIs. Age-age correlations are computed in various combinations of the three components. Serial correlation structure and the genetic coefficient of variation had the more pronounced effect on age-age correlations. The genetic correlation between height at age 10 and height at age 50 varies between 0.764 and -0.136 according to the different combinations. Results obtained by simulations are comparable to those issued from previous empirical methods. mplications on early selection procedures and on optimal selection age are discussed. PMID:24197298

Kremer, A

1992-11-01

245

Arctic cloudiness - Comparison of ISCCP-C2 and Nimbus-7 satellite-derived cloud products with a surface-based cloud climatology  

NASA Technical Reports Server (NTRS)

One surface-based and two satellite arctic cloud climatologies are compared in terms of the annual cycle and spatial patterns of total monthly cloud amounts. Additionally, amounts and spatial patterns of low, middle, and high cloud type are compared. The surface-based dataset is for the years 1951-81, while the satellite-based data are for 1979-85 and 1983-86. The satellite cloud amounts are generally 5-35 percent less than the surface observations over the entire Arctic. However, regional differences may be as high as 45 percent. During July the surface-based cloud amounts for the central Arctic are about 40 percent greater than the satellite-based, but only 10 percent greater in the Norwegian Sea area. Surprisingly, (ISCCP) cloud climatology and surface observations agree better during winter than during summer. Possible reasons for these differences are discussed.

Schweiger, Axel J.; Key, Jeffrey R.

1992-01-01

246

Cloud-based large-scale air traffic flow optimization  

NASA Astrophysics Data System (ADS)

The ever-increasing traffic demand makes the efficient use of airspace an imperative mission, and this paper presents an effort in response to this call. Firstly, a new aggregate model, called Link Transmission Model (LTM), is proposed, which models the nationwide traffic as a network of flight routes identified by origin-destination pairs. The traversal time of a flight route is assumed to be the mode of distribution of historical flight records, and the mode is estimated by using Kernel Density Estimation. As this simplification abstracts away physical trajectory details, the complexity of modeling is drastically decreased, resulting in efficient traffic forecasting. The predicative capability of LTM is validated against recorded traffic data. Secondly, a nationwide traffic flow optimization problem with airport and en route capacity constraints is formulated based on LTM. The optimization problem aims at alleviating traffic congestions with minimal global delays. This problem is intractable due to millions of variables. A dual decomposition method is applied to decompose the large-scale problem such that the subproblems are solvable. However, the whole problem is still computational expensive to solve since each subproblem is an smaller integer programming problem that pursues integer solutions. Solving an integer programing problem is known to be far more time-consuming than solving its linear relaxation. In addition, sequential execution on a standalone computer leads to linear runtime increase when the problem size increases. To address the computational efficiency problem, a parallel computing framework is designed which accommodates concurrent executions via multithreading programming. The multithreaded version is compared with its monolithic version to show decreased runtime. Finally, an open-source cloud computing framework, Hadoop MapReduce, is employed for better scalability and reliability. This framework is an "off-the-shelf" parallel computing model that can be used for both offline historical traffic data analysis and online traffic flow optimization. It provides an efficient and robust platform for easy deployment and implementation. A small cloud consisting of five workstations was configured and used to demonstrate the advantages of cloud computing in dealing with large-scale parallelizable traffic problems.

Cao, Yi

247

A New Height Datum for Iran Based on the Combination of the Gravimetric and Geometric Geoid Models  

Microsoft Academic Search

A new geoid model for Iran (IRG04) is computed based on the method of least squares modification of Stokes formula based on\\u000a the most recent gravity anomaly database, SRTM high resolution Digital Elevation Model (DEM) and GRACE GGM02 Global Geopotential\\u000a Model. In order to define a new height datum for Iran, we attempt to combine this high resolution gravimetric geoid

R. Kiamehr

248

Wide-angle airborne laser range data analysis for relative height determination of ground-based benchmarks  

Microsoft Academic Search

.  ?A wide-angle airborne laser ranging system has been developed for the determination of relative heights of ground-based benchmarks\\u000a in regional-scale networks (typically 100 laser reflectors spread over 100 km2). A first prototype demonstrated a 1–2 mm accuracy in radial distance measurement in a ground-based experiment in 1995. The\\u000a first aircraft experiment was conducted in 1998, over a small area (1

O. Bock; C. Thom

2002-01-01

249

A global model of the ionospheric F2 peak height based on EOF analysis  

Microsoft Academic Search

The ionospheric F2 peak height hmF2 is an important parameter that is much needed in ionospheric research and practical applications. In this paper, an attempt is made to develop a global model of hmF2. The hmF2 data, used to construct the global model, are converted from the monthly median hourly values of the ionospheric propagation factor M(3000)F2 observed by ionosondes\\/digisondes

M.-L. Zhang; C. Liu; W. Wan; L. Liu; B. Ning

2009-01-01

250

Reference values for height and weight in Prader-Willi syndrome based on 315 patients  

Microsoft Academic Search

The spontaneous growth of 315 patients (109 girls and 208 boys) with Prader-Willi syndrome (PWS) was analysed in a mixed\\u000a longitudinal and cross-sectional manner. 33 patients were seen in the department between 1970 and 1994; height and weight\\u000a of 76 patients from Germany were evaluated by means of a questionnaire with detailed measuring instructions, and 206 definite\\u000a cases were added

H. A. Wollmann; U. Schultz; M. L. Grauer; M. B. Ranke

1998-01-01

251

Interactive 3D modeling based on point-clouds with reflectance image  

Microsoft Academic Search

Mid-range and long-range laser scanners can capture dense point-clouds of indoor and outdoor environment. However, such point-clouds are measured only from a few sides and large portions of the data are missing. In this paper, we propose a method for generating 3D models from incomplete point-clouds by applying image-based modeling techniques, since recent laser scanners can output the reflectance value

Nozomi Kanata; Satoshi Fujii; Hiroshi Masuda

2009-01-01

252

A method for object reconstruction based on point-cloud data via 3D scanning  

Microsoft Academic Search

With the development of computer technology, the reconstruction technologies using point-cloud data from 3D scanner have been widely used. But as the original point-cloud is huge, redundant and may have many noise and holes, the following reconstructing process becomes slow and the reconstructed model may not be accurate. In this paper, a method for reconstructing object based on point-cloud data

Fengxia Li; Rong Tang; Chen Liu; Haikun Yu

2010-01-01

253

A Point-Cloud-Based Multiview Stereo Algorithm for Free-Viewpoint Video  

Microsoft Academic Search

This paper presents a robust multiview stereo (MVS) algorithm for free-viewpoint video. Our MVS scheme is totally point-cloud-based and consists of three stages: point cloud extraction, merging, and meshing. To guarantee reconstruction accuracy, point clouds are first extracted according to a stereo matching metric which is robust to noise, occlusion, and lack of texture. Visual hull information, frontier points, and

Yebin Liu; Qionghai Dai; Wenli Xu

2010-01-01

254

The study on data security in Cloud Computing based on Virtualization  

Microsoft Academic Search

Cloud computing is defined as a pool of virtualized computer resources. Based on this Virtualization the Cloud Computing paradigm allows workloads to be deployed and scaled-out quickly through the rapid provisioning of VMs or physical machines. A Cloud Computing platform supports redundant, self-recovering, highly scalable programming models that allow workloads to recover from many inevitable hardware\\/software failures. A virtual appliance

Fu Wen; Li Xiang

2011-01-01

255

How Accurate is Web-Based Self-Reported Height, Weight, and Body Mass Index in Young Adults?  

PubMed Central

Background Web-based approaches are an effective and convenient medium to deliver eHealth interventions. However, few studies have attempted to evaluate the accuracy of online self-reported weight, and only one has assessed the accuracy of online self-reported height and body mass index (BMI). Objective This study aimed to validate online self-reported height, weight, and calculated BMI against objectively measured data in young Australian adults. Methods Participants aged 18-35 years were recruited via advertisements on social media sites and reported their current height and weight as part of an online survey. They then subsequently had the same measures objectively assessed by a trained researcher. Results Self-reported height was significantly overestimated by a mean of 1.36 cm (SD 1.93; P<.001), while self-reported weight was significantly underestimated by –0.55 kg (SD 2.03; P<.001). Calculated BMI was also underestimated by –0.56 kg/m2 (SD 0.08; P<.001). The discrepancy in reporting resulted in the misclassification of the BMI category of three participants. Measured and self-reported data were strongly positively correlated (height: r=.98, weight: r=.99, BMI: r=.99; P<.001). When accuracy was evaluated by BMI category and gender, weight remained significantly underreported by females (P=.002) and overweight/obese participants (P=.02). Conclusions There was moderate to high agreement between self-reported and measured anthropometric data. Findings suggest that online self-reported height and weight can be a valid method of collecting anthropometric data.

2014-01-01

256

Unification of Intercontinental Height Systems based on the Fixed Geodetic Boundary Value Problem - A Case Study in Spherical Approximation  

NASA Astrophysics Data System (ADS)

In general, national height reference systems are related to individual vertical datums defined by specific tide gauges. The discrepancy of these vertical datums causes height system biases that range in an order of 1-2 m at a global scale. Continental height systems can be connected by spirit leveling and gravity measurements along the leveling lines as performed for the definition of the European Vertical Reference Frame. In order to unify intercontinental height systems, an indirect connection is needed. For this purpose, global geopotential models derived from recent satellite missions like GOCE provide an important contribution. However, to achieve a highly-precise solution, a combination with local terrestrial gravity data is indispensable. Such combinations result in the solution of a Geodetic Boundary Value Problem (GBVP). In contrast to previous studies, mostly related to the traditional (scalar) free GBVP, the present paper discusses the use of the fixed GBVP for height system unification, where gravity disturbances instead of gravity anomalies are applied as boundary values. The basic idea of our approach is a conversion of measured gravity anomalies to gravity disturbances, where unknown datum parameters occur that can be associated with height system biases. In this way, the fixed GBVP can be extended by datum parameters for each datum zone. By evaluating the GBVP at GNSS/leveling benchmarks, the unknown datum parameters can be estimated in a least squares adjustment. Beside the developed theory, we present numerical results of a case study based on the spherical fixed GBVP and boundary values simulated by the use of the global geopotential model EGM2008. In a further step, the impact of approximations like linearization as well as topographic and ellipsoidal effects is taken into account by suitable reduction and correction terms.

Grombein, T.; Seitz, K.; Heck, B.

2013-12-01

257

FAME-C: cloud property retrieval using synergistic AATSR and MERIS observations  

NASA Astrophysics Data System (ADS)

A newly developed daytime cloud property retrieval algorithm FAME-C (Freie Universität Berlin AATSR MERIS Cloud) is presented. Synergistic observations from AATSR and MERIS, both mounted on the polar orbiting satellite ENVISAT, are used for cloud screening. For cloudy pixels two main steps are carried out in a sequential form. First, a micro-physical cloud property retrieval is performed using an AATSR near-infrared and visible channel. Cloud phase, cloud optical thickness, and effective radius are retrieved, and subsequently cloud water path is computed. Second, two independent cloud top height products are retrieved. For cloud top temperature AATSR brightness temperatures are used, while for cloud top pressure the MERIS oxygen-A absorption channel is used. Results from the micro-physical retrieval serve as input for the two cloud top height retrievals. Introduced are the AATSR and MERIS forward models and auxiliary data needed in FAME-C. Also, the optimal estimation method with uncertainty estimates, which also provides for uncertainty estimated of the retrieved property on a pixel-basis, is presented. Within the frame of the ESA Climate Change Initiative project first global cloud property retrievals have been conducted for the years 2007-2009. For this time period verification efforts are presented comparing FAME-C cloud micro-physical properties to MODIS-TERRA derived cloud micro-physical properties for four selected regions on the globe. The results show reasonable accuracies between the cloud micro-physical retrievals. Biases are generally smallest for marine stratocumulus clouds; -0.28, 0.41?m and -0.18 g m-2 for cloud optical thickness, effective radius and cloud water path, respectively. This is also true for the root mean square error. Also, both cloud top height products are compared to cloud top heights derived from ground-based cloud radars located at several ARM sites. FAME-C mostly shows an underestimation of cloud top heights when compared to radar observations, which is partly attributed to the difficulty of accurate cloud property retrievals for optically thin clouds and multi-layer clouds. The bias is smallest, -0.9 km, for AATSR derived cloud top heights for single-layer clouds.

Carbajal Henken, C. K.; Lindstrot, R.; Preusker, R.; Fischer, J.

2014-05-01

258

A cloud climatology of the Southern Great Plains ARM CART  

SciTech Connect

Cloud amount statistics from three different sources were processed and compared. Surface observations from a National Centers for Environmental Prediction dataset were used. The data (Edited Cloud Report; ECR) consist of synoptic weather reports that have been edited to facilitate cloud analysis. Two stations near the Southern Great Plains (SGP) Cloud and Radiation Test Bed (CART) in north-central Oklahoma (Oklahoma City, Oklahoma and Wichita, Kansas) were selected. The ECR data span a 10-yr period from December 1981 to November 1991. The International Satellite Cloud Climatology Project (ISCCP) provided cloud amounts over the SGP CART for an 8-yr period (1983--91). Cloud amounts were also obtained from Micro Pulse Lidar (MPL) and Belfort Ceilometer (BLC) cloud-base height measurements made at the SGP CART over a 1-yr period. The annual and diurnal cycles of cloud amount as a function of cloud height and type were analyzed. The three datasets closely agree for total cloud amount. Good agreement was found in the ECR and MPL-BLC monthly low cloud amounts. With the exception of summer and midday in other seasons, the ISCCP low cloud amount estimates are generally 5%--10% less than the others. The ECR high cloud amount estimates are typically 10%--15% greater than those obtained from either the ISCCP or MPL-BLC datasets. The observed diurnal variations of altocumulus support the authors' model results of radiatively induced circulations.

Lazarus, S.M.; Krueger, S.K.; Mace, G.G.

2000-05-15

259

Analysis of cloud-based solutions on EHRs systems in different scenarios.  

PubMed

Nowadays with the growing of the wireless connections people can access all the resources hosted in the Cloud almost everywhere. In this context, organisms can take advantage of this fact, in terms of e-Health, deploying Cloud-based solutions on e-Health services. In this paper two Cloud-based solutions for different scenarios of Electronic Health Records (EHRs) management system are proposed. We have researched articles published between the years 2005 and 2011 about the implementation of e-Health services based on the Cloud in Medline. In order to analyze the best scenario for the deployment of Cloud Computing two solutions for a large Hospital and a network of Primary Care Health centers have been studied. Economic estimation of the cost of the implementation for both scenarios has been done via the Amazon calculator tool. As a result of this analysis two solutions are suggested depending on the scenario: To deploy a Cloud solution for a large Hospital a typical Cloud solution in which are hired just the needed services has been assumed. On the other hand to work with several Primary Care Centers it's suggested the implementation of a network, which interconnects these centers with just one Cloud environment. Finally it's considered the fact of deploying a hybrid solution: in which EHRs with images will be hosted in the Hospital or Primary Care Centers and the rest of them will be migrated to the Cloud. PMID:22492177

Fernández-Cardeñosa, Gonzalo; de la Torre-Díez, Isabel; López-Coronado, Miguel; Rodrigues, Joel J P C

2012-12-01

260

A statistical based resource allocation scheme in cloud  

Microsoft Academic Search

Recently, cloud computing has emerged as a new computing paradigm on the Internet. With the development of cloud computing, enterprise data centers shift towards a utility computing model where many critical business applications share a common pool of infrastructure resources offering capacity on demand. The virtual machine with the features of strong isolation and flexible is usually assigned as the

Zhenzhong Zhang; Haiyan Wang; Limin Xiao; Li Ruan

2011-01-01

261

Analysis on Cloud-Based Security Vulnerability Assessment  

Microsoft Academic Search

Cloud computing delivery model can significantly reduce enterprise IT costs and complexities. This technology can handle the rapidly gowning environment and provide more flexible resources sharing and hence it has become as anew information technology infrastructure recently. In contrast to traditional enterprise IT solution, cloud computing moves the application software and databases to the servers in large data centers which

Huan-Chung Li; Po-Huei Liang; Jiann-Min Yang; Shiang-Jiun Chen

2010-01-01

262

Voronoi-Based Curvature and Feature Estimation from Point Clouds  

Microsoft Academic Search

We present an efficient and robust method for extracting curvature information, sharp features, and normal directions of a piecewise smooth surface from its point cloud sampling in a unified framework. Our method is integral in nature and uses convolved covariance matrices of Voronoi cells of the point cloud which makes it provably robust in the presence of noise. We show

Quentin Merigot; Maks Ovsjanikov; Leonidas J. Guibas

2011-01-01

263

Failure Rules Based Node Resource Provision Policy for Cloud Computing  

Microsoft Academic Search

As a novel computing paradigm, e.g., cloud computing, become popular, researchers proposed various resource sharing techniques and resource provision techniques. However, very limited literatures pay attentions to the reliability of dynamically provided resources. In this paper, we propose a failure rules aware node resource provision policy for heterogeneous services consolidated in cloud computing infrastructure. We evaluate our proposed policy with

Guanhua Tian; Dan Meng

2010-01-01

264

Study and Application on Cloud Covered Rate for Agroclimatical Distribution Using In Guangxi Based on Modis Data  

NASA Astrophysics Data System (ADS)

Based on analyzing of the physical characteristics of cloud and importance of cloud in agricultural production and national economy, cloud is a very important climatic resources such as temperature, precipitation and solar radiation. Cloud plays a very important role in agricultural climate division .This paper analyzes methods of cloud detection based on MODIS data in China and Abroad . The results suggest that Quanjun He method is suitable to detect cloud in Guangxi. State chart of cloud cover in Guangxi is imaged by using Quanjun He method .We find out the approach of calculating cloud covered rate by using the frequency spectrum analysis. At last, the Guangxi is obtained. Taking Rongxian County Guangxi as an example, this article analyze the preliminary application of cloud covered rate in distribution of Rong Shaddock pomelo . Analysis results indicate that cloud covered rate is closely related to quality of Rong Shaddock pomelo.

Yang, Xin; Zhong, Shiquan; Sun, Han; Tan, Zongkun; Li, Zheng; Ding, Meihua

265

Effects of Plant Density on Frequency Distributions of Plant Height in Chenopodium album Stands: Analysis Based on Continuous Monitoring of Height-growth of Individual Plants  

Microsoft Academic Search

Height-growth of individual plants of Chenopodium album in even-aged monospecific stands with initial densities of 400, 800, and 3600 plants m-2 was followed from emergence to fruit maturation to elucidate the factors responsible for size hierarchy formation. Many individuals stopped growing rather abruptly at relatively early stages in the vegetative phase and some of them eventually died. The other plants

Hisae Nagashima; Ichiro Terashima; Sakae Katoh

1995-01-01

266

The variability of tropical ice cloud properties as a function of the large-scale context from ground-based radar-lidar observations over Darwin, Australia  

NASA Astrophysics Data System (ADS)

The high complexity of cloud parameterizations now held in models puts more pressure on observational studies to provide useful means to evaluate them. One approach to the problem put forth in the modelling community is to evaluate under what atmospheric conditions the parameterizations fail to simulate the cloud properties and under what conditions they do a good job. It is the ambition of this paper to characterize the variability of the statistical properties of tropical ice clouds in different tropical "regimes" recently identified in the literature to aid the development of better process-oriented parameterizations in models. For this purpose, the statistical properties of non-precipitating tropical ice clouds over Darwin, Australia are characterized using ground-based radar-lidar observations from the Atmospheric Radiation Measurement (ARM) Program. The ice cloud properties analysed are the frequency of ice cloud occurrence, the morphological properties (cloud top height and thickness), and the microphysical and radiative properties (ice water content, visible extinction, effective radius, and total concentration). The variability of these tropical ice cloud properties is then studied as a function of the large-scale cloud regimes derived from the International Satellite Cloud Climatology Project (ISCCP), the amplitude and phase of the Madden-Julian Oscillation (MJO), and the large-scale atmospheric regime as derived from a long-term record of radiosonde observations over Darwin. The vertical variability of ice cloud occurrence and microphysical properties is largest in all regimes (1.5 order of magnitude for ice water content and extinction, a factor 3 in effective radius, and three orders of magnitude in concentration, typically). 98 % of ice clouds in our dataset are characterized by either a small cloud fraction (smaller than 0.3) or a very large cloud fraction (larger than 0.9). In the ice part of the troposphere three distinct layers characterized by different statistically-dominant microphysical processes are identified. The variability of the ice cloud properties as a function of the large-scale atmospheric regime, cloud regime, and MJO phase is large, producing mean differences of up to a factor 8 in the frequency of ice cloud occurrence between large-scale atmospheric regimes and mean differences of a factor 2 typically in all microphysical properties. Finally, the diurnal cycle of the frequency of occurrence of ice clouds is also very different between regimes and MJO phases, with diurnal amplitudes of the vertically-integrated frequency of ice cloud occurrence ranging from as low as 0.2 (weak diurnal amplitude) to values in excess of 2.0 (very large diurnal amplitude). Modellers should now use these results to check if their model cloud parameterizations are capable of translating a given atmospheric forcing into the correct statistical ice cloud properties.

Protat, A.; Delanoë, J.; May, P. T.; Haynes, J.; Jakob, C.; O'Connor, E.; Pope, M.; Wheeler, M. C.

2011-08-01

267

Intercomparison of satellite- and ground-based cloud fraction over Switzerland (2000-2012)  

NASA Astrophysics Data System (ADS)

Satellite data provide the opportunity for systematic and continuous observation of cloud cover over large spatial scales. In this paper, we describe the generation of two new high spatial resolution (0.05°) daytime cloud fraction data sets over Switzerland. The data sets are based on the Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask products. The data sets cover the period from March 1, 2000 to February 29, 2012 (Terra/MODIS) and July 1, 2002 to February 29, 2012 (Aqua/MODIS) and represent mid-morning and early-afternoon cloud cover over Switzerland. Time series clearly reflected seasonal variations in cloud fraction over Switzerland. A comparison with cloud fraction observations at four Synop stations (Chur, Locarno/Monti, Payerne, Zurich/Kloten) revealed an agreement of monthly mean mid-morning cloud fraction (MMCF) within ± 1 octa (i.e., 12.5%). Relative to Synop observations, MMCF was positively biased by 0.3-5.0%, except at Payerne (- 2.5%). Linear correlation coefficients ranged from 0.878 to 0.972. Results were similar for monthly mean early-afternoon cloud fraction (MACF). Cloud fraction was found to be higher in the early-afternoon when compared to mid-morning, except at Payerne and Zurich/Kloten in fall, which is explained by typical daytime cloud cover patterns in Switzerland. Analysis of daily mid-morning cloud fraction showed that largest discrepancies were observed in partly cloudy conditions, which is mainly explained by differences in observation times and observation geometry. Our results demonstrate that the newly processed cloud fraction data sets from the MODIS sensor can play an important role in complementing traditional Synop observations in support of systematic cloud cover monitoring within the National Climate Observing System (GCOS Switzerland).

Fontana, Fabio; Lugrin, David; Seiz, Gabriela; Meier, Marion; Foppa, Nando

2013-07-01

268

Cloud parameters using Ground Based Remote Sensing Systems and Satellites over urban coastal area  

NASA Astrophysics Data System (ADS)

Determining cloud radiative and microphysical properties are very important as a means to assess their effect on earths energy balance. While MODIS and GOES have been used for estimating cloud properties, assessing cloud properties directly has been difficult due the lack of consistent ground based sensor measurements except in such established places such as the ARM site in Oklahoma. However, it is known that significant aerosol seeding from urban and/or maritime sources can modify cloud properties such as effective radius and cloud optical depth and therefore evaluation of satellite retrievals in such a unique area offers novel opportunities to assess the potential of satellite retrievals to distinguish these mechanisms In our study, we used a multi-filter rotating shadow band radiometer (MFRSR) and micro wave radiometer (MWR) to retrieve the cloud optical depth and cloud droplets effective radius . In particular, we make a statistical study during summer 2013 where water phase clouds dominate and assess the accuracy of both MODIS and GOES satellite cloud products including LWP, COD and Reff. Most importantly, we assess performance against satellite observing geometries. Much like previous studies at the ARM site, we observe significant biases in the effective radius when the solar zenith angle is too large. In addition, we show that biases are also sensitive to the LWP limiting such measurement s in assessing potential aerosol-cloud signatures Finally, we discuss preliminary aerosol-cloud interactions from our ground system where local lidar is used to assess aerosols below clouds and explore the Aerosol Cloud Index.

Han, Z. T.; Gross, B.; Moshary, F.; Wu, Y.; Ahmed, S. A.

2013-12-01

269

ISCCP Cloud Properties Associated with Standard Cloud Types Identified in Individual Surface Observations  

NASA Technical Reports Server (NTRS)

Individual surface weather observations from land stations and ships are compared with individual cloud retrievals of the International Satellite Cloud Climatology Project (ISCCP), Stage C1, for an 8-year period (1983-1991) to relate cloud optical thicknesses and cloud-top pressures obtained from satellite data to the standard cloud types reported in visual observations from the surface. Each surface report is matched to the corresponding ISCCP-C1 report for the time of observation for the 280x280-km grid-box containing that observation. Classes of the surface reports are identified in which a particular cloud type was reported present, either alone or in combination with other clouds. For each class, cloud amounts from both surface and C1 data, base heights from surface data, and the frequency-distributions of cloud-top pressure (p(sub c) and optical thickness (tau) from C1 data are averaged over 15-degree latitude zones, for land and ocean separately, for 3-month seasons. The frequency distribution of p(sub c) and tau is plotted for each of the surface-defined cloud types occurring both alone and with other clouds. The average cloud-top pressures within a grid-box do not always correspond well with values expected for a reported cloud type, particularly for the higher clouds Ci, Ac, and Cb. In many cases this is because the satellites also detect clouds within the grid-box that are outside the field of view of the surface observer. The highest average cloud tops are found for the most extensive cloud type, Ns, averaging 7 km globally and reaching 9 km in the ITCZ. Ns also has the greatest average retrieved optical thickness, tau approximately equal 20. Cumulonimbus clouds may actually attain far greater heights and depths, but do not fill the grid-box. The tau-p(sub c) distributions show features that distinguish the high, middle, and low clouds reported by the surface observers. However, the distribution patterns for the individual low cloud types (Cu, Sc, St) occurring alone overlap to such an extent that it is not possible to distinguish these cloud types from each other on the basis of tau-p(sub c) values alone. Other cloud types whose tau-p(sub c) distributions are indistinguishable are Cb, Ns, and thick As. However, the tau-p(sub c) distribution patterns for the different low cloud types are nevertheless distinguishable when all occurrences of a low cloud type are included, indicating that the different low types differ in their probabilities of co-occurrence with middle and high clouds.

Hahn, Carole J.; Rossow, William B.; Warren, Stephen G.

1999-01-01

270

Charge measurements in stratiform cloud from a balloon based sensor  

NASA Astrophysics Data System (ADS)

The electrification of stratiform clouds has is little investigated in comparison with thunderstorms and fair weather atmospheric electricity. Theory indicates that, at the upper and lower horizontal boundaries of layer clouds, charging will arise from vertical flow of cosmogenic ions in the global atmospheric electric circuit. Charge is transferred to droplets and particles, affecting cloud microphysical processes such as collision and droplet activation. Due to the lack of in-situ measurements, the magnitude and distribution of charge in stratiform clouds is not well known. A sensitive, inexpensive, balloon borne charge sensor has been developed to make in-situ measurements of edge charging in stratiform cloud using a standard meteorological radiosonde system. The charge sensor has now been flown through over 20 stratiform clouds and frequently detected charge up to 200 pC m-3 near cloud edges. These results are compared with measurements from the same sensor used to investigate charge in particle layers, such as volcanic ash from the Eyjafjallajökull eruption, and Saharan dust in the Cape Verde Isles.

Nicoll, K. A.; Harrison, R. G.

2011-06-01

271

Automatic road extraction from lidar data based on height fitting difference  

NASA Astrophysics Data System (ADS)

In this paper, a new method for automatic detection of roads from Light Detection and Ranging (LIDAR) data is presented. A morphological filter and an elevation difference threshold are first combined to classify the original data. In the following step, a height fitting difference algorithm is introduced and performed to calculate height fitting difference with a multi-direction template for each pixel. The algorithm acquires two pieces of information about roads: the least squares fitting difference and the corresponding orientation. Then, the Otsu's method is applied to obtain a road map with the fitting difference feature. After performing the Euclidean distance transform on the segmented road map, road centerlines are searched in the distance map. Next, the centerlines are connected and optimized so that long and smooth road centerlines are obtained. Finally, road boundaries are found by setting a proper width value for each road centerline. The proposed method has been tested on various complicated urban images. Experimental results demonstrate that our new method works efficiently and correctly.

Zhou, Shaoguang; He, Shuangjian; Li, Hao

2011-06-01

272

A resource allocation method based on the limited English combinatorial auction under cloud computing environment  

Microsoft Academic Search

On account of the resource characteristics under cloud computing environment and the flexibility and availability of applying economic mechanism to resource allocation, a resource allocation model based on the limited English combinatorial auction under cloud computing environment is advanced. An improved periodical auction model is constructed, and then ribbon capacity is adopted to describe the special storage capacity for special

Xing-wei Wang; Xue-yi Wang; Min Huang

2012-01-01

273

Autonomous adaptive agents for market-based resource allocation of cloud computing  

Microsoft Academic Search

The application of market mechanisms for the resource allocation of cloud computing services is a demanding task, which requires bridging economic and associated software agent technical challenges. Dynamic changes in the availability of resources over time makes the treatment more complicated. Here we employ an allocation mechanism and pricing mechanism as a market-based model to allocate resources in a cloud

Yee-Ming Chen; Hsin-Mei Yeh

2010-01-01

274

The research of Cloud Computing based on service plane over optical networks  

Microsoft Academic Search

The implementation of Cloud Computing over optical networks faces many challenges and opportunities. A cloud computing architecture over optical networks is proposed based on the service plane. And the validity of the architecture we proposed was experimentally demonstrated in our Adaptive Multi-Service Optical Network testbed.

Zhen Li; Dahai Han; Jie Zhang; Xiuzhong Chen; Wanyi Gu; Yuefeng Ji

2009-01-01

275

End-to-End Policy-Based Encryption and Management of Data in the Cloud  

Microsoft Academic Search

This paper introduces and discusses a data management solution to provide accountability within the cloud as well as addressing privacy issues. The central idea is as follows: Customers allow cloud (service) providers to have access to specific data based on agreed policies and by forcing interactions with interchangeable independent third parties called Trust Authorities. The access to data can be

Siani Pearson; Marco Casassa Mont; Liqun Chen; Archie Reed

2011-01-01

276

From Desktop to Cloud: A Primer on Internet-Based Computing for Librarians  

Microsoft Academic Search

In the past several years, cloud-based computing has become a major trend for all levels of computer users. This article examines the reasons surrounding this trend. It focuses in particular on how cloud computing is being used by librarians, scientists, and end users. Data storage and sharing, applications, and product development are examples of the growing number of functions finding

Karen Sorensen; Nancy R. Glassman

2011-01-01

277

Scattering height estimation using scintillating Wide Area Augmentation System\\/Satellite Based Augmentation System and GPS satellite signals  

Microsoft Academic Search

An experiment to measure equatorial amplitude scintillations on the geostationary Wide Area Augmentation System (WAAS) Satellite Based Augmentation System (SBAS) signal was conducted in Cachoeira Paulista (22.70°S, 45.01°W geographic coordinates; ?17.74°N, 21.74°E geomagnetic coordinates), Brazil from December 2003 through February 2004. The purpose of this paper is to estimate the scattering height of the irregularities using the WAAS signal scintillations

A. P. Cerruti; B. M. Ledvina; P. M. Kintner

2006-01-01

278

An analysis of the scale heights in the lower topside ionosphere based on the Arecibo incoherent scatter radar measurements  

Microsoft Academic Search

We statistically analyze the ionospheric scale heights in the lower topside ionosphere based on the electron density (Ne) and temperature profiles observed from the incoherent scatter radar (ISR) at Arecibo (293.2°E, 18.3°N), Puerto Rico. In this study, a database containing the Arecibo ISR observations from 1966 to 2002 has been used in order to investigate the diurnal and seasonal variations

Libo Liu; Huijun Le; Weixing Wan; Mike P. Sulzer; Jiuhou Lei; Man-Lian Zhang

2007-01-01

279

An analysis of the scale heights in the lower topside ionosphere based on the Arecibo incoherent scatter radar measurements  

Microsoft Academic Search

We statistically analyze the ionospheric scale heights in the lower topside ionosphere based on the electron density (N e) and temperature profiles observed from the incoherent scatter radar (ISR) at Arecibo (293.2°E, 18.3°N), Puerto Rico. In this study, a database containing the Arecibo ISR observations from 1966 to 2002 has been used in order to investigate the diurnal and seasonal

Libo Liu; Huijun Le; Weixing Wan; Jiuhou Lei; Man-Lian Zhang

2007-01-01

280

Vertical cloud water structures of the boreal summer intraseasonal variability based on CloudSat observations and ERA-Interim reanalysis  

NASA Astrophysics Data System (ADS)

The boreal summer intraseasonal variability (BSISV), which is characterized by pronounced meridional propagation from equatorial zone to the Indian Continent, exerts significant modulation of the active/break phase of the south Asian monsoon. This form of variability provides a primary source for subseasonal predictive skills of the Asian summer monsoon. Unfortunately, the current general circulation models display large deficiencies in representing this variability. The new cloud observations made available by the CloudSat mission provide unprecedented opportunity to advance our understanding of the BSISV. In this study, the vertical structures of cloud water content and cloud types associated with the BSISV over the Indian Ocean and subcontinent are analyzed based on the CloudSat observations from 2006 to 2009. These cloud water structures are also compared to their counterparts as derived from the recently released ERA-Interim reanalysis. Results based on both datasets suggest that during the northward propagation of the BSISV, while the cloud ice water content (IWC) in upper troposphere are largely in phase with (or slightly lags) the convection, a marked vertical tilting structure is evident in cloud liquid water content (LWC). Increased LWC tends to appear to the north of rainfall maximum, i.e., leads the convection, particularly in the lower troposphere. This northward shift of increased LWC, which is in accord with local enhanced moisture as previously documented, could be fundamental responsible for the northward propagation of the BSISV. Nevertheless, some differences in the cloud water structures between the CloudSat and ERA-Interim are also noted, particularly in the amplitudes of IWC and LWC fields. Further analysis based on CloudSat data indicates that IWC variability of the BSISV is largely associated with deep convective clouds. While LWC is mainly linked to non-precipitating alto-cumulus at mid-level and drizzling stratocumulus cloud at low-level. These aforementioned results would provide valuable information for climate modeling efforts in describing subseasonal variability of tropical convection.

Jiang, X.; Waliser, D. E.; Li, J. F.; Woods, C. P.

2009-12-01

281

Sensitivity of raindrop formation in ascending cloud parcels to cloud condensation nuclei and thermodynamic conditions  

NASA Astrophysics Data System (ADS)

This paper uses a 2000-bin spectral microphysics cloud parcel model to investigate the effects of aerosol particles on droplet spectrum evolution and warm rain formation in ascending cloud parcels under maritime, intermediate, and continental unstable thermodynamic conditions. Cloud parcels of different cloud depth are simulated for each thermodynamic condition. Concentration and size distribution of cloud condensation nuclei (CCN) were varied within a wide range for each cloud depth. Cloud parcels were divided into three groups with respect to the relationship between cloud depth Hc and the distance of the collision triggering level Hcol above cloud base. The sensitivity of precipitation to CCN variations is quite different for the different groups. Parcels of the first group (Hc < Hcol) do not precipitate. Precipitation from cloud parcels belonging to the second group, in which collisions start at a small distance below the maximum cloud-top height (Hc Hcol), turns out to be highly sensitive to the variation of CCN concentration and size distribution. For these parcels an increase in the concentration of large CCN can result in an increase in precipitation amount by several factors. Many cloud parcels arising under continental and intermediate conditions, as well as not very deep maritime clouds, can be assigned to this group. The precipitation amount from cloud parcels belonging to the third group (Hc Hcol), represented by deep tropical clouds, turns out to be insensitive to CCN distribution and droplet concentration within a wide range of their variations. Comparable effects of small and large CCN on precipitation formation are analysed for each group of cloud parcels.

These results are closely related to the problem of rain enhancement via hygroscopic seeding. It is shown that there is a certain range of cloud depths within which cloud seeding can potentially lead to a significant (several times) increase in rain within ascending parcels. Rain formed in cloud parcels with depths beyond this range is only slightly sensitive to the CCN concentration.

Segal, Y.; Khain, A.; Pinsky, M.; Sterkin, A.

2004-01-01

282

New Cloud-Based hp-Finite Element Method.  

National Technical Information Service (NTIS)

A hybrid computational method for solving boundary-value problems is introduced which combines features of the meshless hp-cloud methods with features of conventional finite elements. The method admits straightforward nonuniform hp-type approximations, ea...

J. T. Oden C. A. Duarte O. C. Zienkiewicz

1996-01-01

283

MVC-based Content Management on the Cloud.  

National Technical Information Service (NTIS)

Cloud computing describes a new distributed computing paradigm for IT data and services that involves over-the-Internet provision of dynamically scalable and often virtualized resources. While cost reduction and flexibility in storage, services, and maint...

D. Drusinsky

2011-01-01

284

Complicated Simulation Visualization Based on Grid and Cloud Computing  

Microsoft Academic Search

\\u000a Many complicated applications use grid and cloud computing for their visualization. After completion of each partial simulation\\u000a step, the results are stored in reserved output area of the storage element and accessible for further processing.  In this\\u000a paper we present a visualization tool to visualize astrophysical simulations and natural disasters simulations using grid\\u000a and cloud computing.

Eva Pajorova; Ladislav Hluchý

2010-01-01

285

Cloud-property retrieval using merged HIRS and AVHRR data  

NASA Technical Reports Server (NTRS)

A technique is developed that uses a multispectral, multiresolution method to improve the overall retrieval of mid- to high-level cloud properties by combining HIRS sounding channel data with higher spatial resolution AVHRR radiometric data collocated with the HIRS footprint. Cirrus cloud radiative and physical properties are determined using satellite data, surface-based measurements provided by rawinsondes and lidar, and aircraft-based lidar data collected during the First International Satellite Cloud Climatology Program Regional Experiment in Wisconsin during the months of October and November 1986. HIRS cloud-height retrievals are compared to ground-based lidar and aircraft lidar when possible. Retrieved cloud heights are found to have close agreement with lidar for thin cloud, but are higher than lidar for optically thick cloud. The results of the reflectance-emittance relationships derived are compared to theoretical scattering model results for both water-droplet spheres and randomly oriented hexagonal ice crystals. It is found that the assumption of 10-micron water droplets is inadequate to describe the reflectance-emittance relationship for the ice clouds seen here. Use of this assumption would lead to lower cloud heights using the ISCCP approach. The theoretical results show that use of hexagonal ice crystal phase functions could lead to much improved results for cloud retrieval algorithms using a bispectral approach.

Baum, Bryan A.; Wielicki, Bruce A.; Minnis, Patrick; Parker, Lindsay

1992-01-01

286

Cloud parallel processing of tandem mass spectrometry based proteomics data.  

PubMed

Data analysis in mass spectrometry based proteomics struggles to keep pace with the advances in instrumentation and the increasing rate of data acquisition. Analyzing this data involves multiple steps requiring diverse software, using different algorithms and data formats. Speed and performance of the mass spectral search engines are continuously improving, although not necessarily as needed to face the challenges of acquired big data. Improving and parallelizing the search algorithms is one possibility; data decomposition presents another, simpler strategy for introducing parallelism. We describe a general method for parallelizing identification of tandem mass spectra using data decomposition that keeps the search engine intact and wraps the parallelization around it. We introduce two algorithms for decomposing mzXML files and recomposing resulting pepXML files. This makes the approach applicable to different search engines, including those relying on sequence databases and those searching spectral libraries. We use cloud computing to deliver the computational power and scientific workflow engines to interface and automate the different processing steps. We show how to leverage these technologies to achieve faster data analysis in proteomics and present three scientific workflows for parallel database as well as spectral library search using our data decomposition programs, X!Tandem and SpectraST. PMID:22916831

Mohammed, Yassene; Mostovenko, Ekaterina; Henneman, Alex A; Marissen, Rob J; Deelder, André M; Palmblad, Magnus

2012-10-01

287

Spatial distribution of cloud overlap parameter: assessment based on satellite data  

NASA Astrophysics Data System (ADS)

Assumptions on cloud overlap implemented in a climate model may affect markedly modeled radiative fluxes. To increase the ability of climate models to simulate the real climate, it is preferable to know the value of the cloud overlap parameter ? which is a measure of the relative weight of maximum (? = 1) and random (? = 0) overlap. This parameter may be used to diagnose relative contribution of convective and stratiform cloudiness to total cloud fraction. Here we present an estimate of geographical distribution of ? derived from up-to-date satellite observations. To assess values of total cloud fraction, we used cloud masks CERES and MODIS, which both are based on multispectral passive observations from Aqua satellite (CERES SSF product and MODIS collection 5.1). Active CALIOP lidar observations were used to evaluate cloud fraction at different levels (CALIPSO-GOCCP dataset). Cloud overlap parameter ? was calculated by merging passive and active satellite datasets. Only monthly means for 2006-2010 were used in these calculations. The most prominent annual cycle of ? is noted in the monsoon regions where ? is close to 1 in winter and almost 0 in summer. For CERES total cloud fraction, ? is equal to 0.36 in July (0.38 in January) for the entire Earth, it is 0.39 (0.44) in Northern Hemisphere and 0.33 (0.33) in Southern Hemisphere. Values of ? are lower when MODIS total cloud fraction is used: global annual mean ? is 0.37 for CERES and 0.25 for MODIS. We found that ? is linearly dependent on total cloud fraction in most regions, except in the southern tropics. The maximum cloud overlap (? is close to 1) is associated with small values of cloud fraction and occurs in subtropical highs over the ocean and in subtropical and polar deserts over land. On the other hand, the random cloud overlap (? is close to 0) occurs in regions with large values of cloud fraction (e.g. ITCZ and midlatitudinal storm tracks). Moreover, we found that vast regions of the Southern Ocean (around 60S) are characterized by negative values of ?, mostly in summer. Presumably, an assumption of the minimum overlap of cloud layers should be used in these regions due to strong baroclinic instability and horizontal shift of cloud layers. The work has been supported by the grant of the RF President MK-3259.2012.5 and by the Russian Foundation of Basic Research under grant 12-05-00972.

Chernokulsky, Alexander; Eliseev, Alexey

2013-04-01

288

Calibration and Unfolding of the Pulse Height Spectra of Liquid Scintillator-Based Neutron Detectors Using Photon Sources  

NASA Astrophysics Data System (ADS)

An accurate energy calibration of a 5? × 2? BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with 22Na, 137Cs and 54Mn photon sources and simulated using the GRESP code, which was developed at the Physikalisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in tokamak experiments.

Xie, Xufei; Yuan, Xi; Zhang, Xing; Fan, Tieshuan; Chen, Jinxiang; Li, Xiangqing

2012-06-01

289

CloudSat-CALIPSO characterizations of cloud during the active and the break periods of Indian summer monsoon  

NASA Astrophysics Data System (ADS)

Here we report cloud macrophysical (cloud top height (CTH), cloud base height (CBH), cloud geometrical depth), microphysical (liquid and ice water contents, water paths, effective radii and number concentration) and radiative (heating rate) properties over the North Central India (18-28°N, 65-88°E) region (core monsoon zone) during the active and the break periods (2006-2010) of the Indian summer monsoon (ISM). Synergetic data from the CloudSat radar and the CALIPSO lidar are used. Analysis shows that the CTH and CBH have bimodal distributions during both the phases of monsoon. We have classified clouds into four type's viz., high-, mid-, low- and vertically extended deep clouds. The low-level clouds and optically thick cirrus are more dominant of the total observations and they occur more frequently during the active period compared to that of the break period. In contrast, the high-level clouds and optically thin cirrus are more frequent during the break phase of monsoon. The integrated depolarization ratio of high-level cloud exhibits bimodal distribution. It is observed that there is a significant variation in macrophysical, microphysical, optical and radiative properties of all the four types of clouds during the active and the break periods. As little observational evidence exists in the vertical structure of clouds during the active and the break periods of the ISM, the current results would be useful in understanding the characteristics of monsoon clouds, which have implications in the Earth's radiation budget and global climate models.

Das, Subrata Kumar; Uma, K. N.; Konwar, M.; Ernest Raj, P.; Deshpande, S. M.; Kalapureddy, M. C. R.

2013-05-01

290

Effect of Clouds on Apertures of Space-based Air Fluorescence Detectors  

NASA Technical Reports Server (NTRS)

Space-based ultra-high-energy cosmic ray detectors observe fluorescence light from extensive air showers produced by these particles in the troposphere. Clouds can scatter and absorb this light and produce systematic errors in energy determination and spectrum normalization. We study the possibility of using IR remote sensing data from MODIS and GOES satellites to delimit clear areas of the atmosphere. The efficiency for detecting ultra-high-energy cosmic rays whose showers do not intersect clouds is determined for real, night-time cloud scenes. We use the MODIS SST cloud mask product to define clear pixels for cloud scenes along the equator and use the OWL Monte Carlo to generate showers in the cloud scenes. We find the efficiency for cloud-free showers with closest approach of three pixels to a cloudy pixel is 6.5% exclusive of other factors. We conclude that defining a totally cloud-free aperture reduces the sensitivity of space-based fluorescence detectors to unacceptably small levels.

Sokolsky, P.; Krizmanic, J.

2003-01-01

291

A shape-based segmentation method for mobile laser scanning point clouds  

NASA Astrophysics Data System (ADS)

Segmentation of mobile laser point clouds of urban scenes into objects is an important step for post-processing (e.g., interpretation) of point clouds. Point clouds of urban scenes contain numerous objects with significant size variability, complex and incomplete structures, and holes or variable point densities, raising great challenges for the segmentation of mobile laser point clouds. This paper addresses these challenges by proposing a shape-based segmentation method. The proposed method first calculates the optimal neighborhood size of each point to derive the geometric features associated with it, and then classifies the point clouds according to geometric features using support vector machines (SVMs). Second, a set of rules are defined to segment the classified point clouds, and a similarity criterion for segments is proposed to overcome over-segmentation. Finally, the segmentation output is merged based on topological connectivity into a meaningful geometrical abstraction. The proposed method has been tested on point clouds of two urban scenes obtained by different mobile laser scanners. The results show that the proposed method segments large-scale mobile laser point clouds with good accuracy and computationally effective time cost, and that it segments pole-like objects particularly well.

Yang, Bisheng; Dong, Zhen

2013-07-01

292

The variability of tropical ice cloud properties as a function of the large-scale context from ground-based radar-lidar observations over Darwin, Australia  

NASA Astrophysics Data System (ADS)

The statistical properties of non-precipitating tropical ice clouds over Darwin, Australia are characterized using ground-based radar-lidar observations from the Atmospheric Radiation Measurement (ARM) Program. The ice cloud properties analysed are the frequency of ice cloud occurrence, the morphological properties (cloud top height and thickness, cloud fraction as derived considering a typical large-scale model grid box), and the microphysical and radiative properties (ice water content, visible extinction, effective radius, terminal fall speed, and total concentration). The variability of these tropical ice cloud properties is then studied as a function of the large-scale cloud regimes derived from the International Satellite Cloud Climatology Project (ISCCP), the amplitude and phase of the Madden-Julian Oscillation (MJO), and the large-scale atmospheric regime as derived from a long-term record of radiosonde observations over Darwin. The rationale for characterizing this variability is to provide an observational basis to which model outputs can be compared for the different regimes or large-scale characteristics and from which new parameterizations accounting for the large-scale context can be derived. The mean vertical variability of ice cloud occurrence and microphysical properties is large (1.5 order of magnitude for ice water content and extinction, a factor 3 in effective radius, and three orders of magnitude in concentration, typically). 98% of ice clouds in our dataset are characterized by either a small cloud fraction (smaller than 0.3) or a very large cloud fraction (larger than 0.9). Our results also indicate that, at least in the northern Australian region, the upper part of the troposphere can be split into three distinct layers characterized by different statistically-dominant microphysical processes. The variability of the ice cloud properties as a function of the large-scale atmospheric regime, cloud regime, and MJO phase is found to be large, producing mean differences of up to a factor of 8 in the frequency of ice cloud occurrence between large-scale atmospheric regimes, a factor of 3 to 4 for the ISCCP regimes and the MJO phases, and mean differences of a factor of 2 typically in all microphysical properties analysed in the present paper between large-scale atmospheric regimes or MJO phases. Large differences in occurrence (up to 60-80%) are also found in the main patterns of the cloud fraction distribution of ice clouds (fractions smaller than 0.3 and larger than 0.9). Finally, the diurnal cycle of the frequency of occurrence of ice clouds is also very different between regimes and MJO phases, with diurnal amplitudes of the vertically-integrated frequency of ice cloud occurrence ranging from as low as 0.2 (almost no detectable diurnal cycle) to values in excess of 2.0 (very large diurnal amplitude).

Protat, A.; Delanoë, J.; May, P. T.; Haynes, J.; Jakob, C.; O'Connor, E.; Pope, M.; Wheeler, M. C.

2010-08-01

293

A characterization of cloud base aerosol and associated microphysics in southeast Queensland  

NASA Astrophysics Data System (ADS)

In response to a severe drought experienced over the past few years, the Queensland government subsequently sponsored a Cloud Seeding Research Program (CSRP) in southeast Queensland. The Queensland CSRP is a cloud seeding feasibility study conducted in the Brisbane, Australia region of southeast Queensland for the past two austral summers. In the CSRP, two Doppler radars (one with dual-polarization capabilities) and an aircraft with microphysical instrumentation and seeding capabilities were employed. The overall goal of the Queensland CSRP is to assess the impact of hygroscopic seeding on convective clouds in the region. Assessing the variety of aerosol regimes, as well as the frequency of occurrence for each regime in the CSRP domain, and studying the effectiveness of warm rain processes under each aerosol regime is crucial to assess the effectiveness of hygroscopic seeding, as well as to gain a better understanding of the nature of precipitation processes across the varying aerosol conditions in the region. The aircraft observations collected included fine through coarse mode aerosol measurements (utilizing DMA, PCASP, and FSSP instrumentation) and aerosol filter sampling to assess the composition and deliquescence of the measured aerosol. Cloud microphysical measurements included a cloud condensation nuclei (CCN) counter, and cloud droplet spectrometers and imaging probes. On each flight in the field program, the aircraft took standard measurements of cloud base aerosol and CCN, as well as the initial drop size distribution (DSD) in the cloud above cloud base. These basic measurements allowed us to build a climatology of cloud base aerosol conditions and relate them to the initial DSDs in the clouds. Our observations indicate that the domain of the southeast Queensland CSRP experienced great variations in sub-cloud aerosol conditions, even over the course of a few days, from more continental to more maritime in nature. We have run HYSPLIT back trajectories for each of our cloud base measurements and classified them into four regimes by similar trajectory path (whether it was over land or ocean and north or south of Brisbane). From this we have studied the characteristics of the cloud base aerosol and CCN in each regime. The aerosol measurements in the more maritime regimes are cleaner, less variable, and tend to have more robust coarse mode aerosol sizes than those from continental sources. Furthermore, our preliminary measurements of initial DSDs in each regime suggests that the continental regimes exhibit more narrow droplet spectra, while the maritime regimes exhibit broader, but more variable, droplet spectra. Nonetheless, the total droplet concentrations are similar among all regimes, ranging from 100-800/cc. This paper will present the cloud base aerosol and CCN climatology from the Queensland CSRP field program and the cloud base aerosol measurements will be related to the initial cloud droplet spectra under each observed regime to characterize the influence of the cloud base aerosol on the cloud microphysics.

Tessendorf, S. A.; Arnold, C.; Bruintjes, R. T.; Axisa, D.; Peter, J.; Wilson, L.; Siems, S.; Manton, M.; May, P. T.; Stone, R.

2009-12-01

294

Cloud layer thicknesses from a combination of surface and upper-air observations  

NASA Technical Reports Server (NTRS)

Cloud layer thicknesses are derived from base and top altitudes by combining 14 years (1975-1988) of surface and upper-air observations at 63 sites in the Northern Hemisphere. Rawinsonde observations are employed to determine the locations of cloud-layer top and base by testing for dewpoint temperature depressions below some threshold value. Surface observations serve as quality checks on the rawinsonde-determined cloud properties and provide cloud amount and cloud-type information. The dataset provides layer-cloud amount, cloud type, high, middle, or low height classes, cloud-top heights, base heights and layer thicknesses, covering a range of latitudes from 0 deg to 80 deg N. All data comes from land sites: 34 are located in continental interiors, 14 are near coasts, and 15 are on islands. The uncertainties in the derived cloud properties are discussed. For clouds classified by low-, mid-, and high-top altitudes, there are strong latitudinal and seasonal variations in the layer thickness only for high clouds. High-cloud layer thickness increases with latitude and exhibits different seasonal variations in different latitude zones: in summer, high-cloud layer thickness is a maximum in the Tropics but a minimum at high latitudes. For clouds classified into three types by base altitude or into six standard morphological types, latitudinal and seasonal variations in layer thickness are very small. The thickness of the clear surface layer decreases with latitude and reaches a summer minimum in the Tropics and summer maximum at higher latitudes over land, but does not vary much over the ocean. Tropical clouds occur in three base-altitude groups and the layer thickness of each group increases linearly with top altitude. Extratropical clouds exhibit two groups, one with layer thickness proportional to their cloud-top altitude and one with small (less than or equal to 1000 m) layer thickness independent of cloud-top altitude.

Poore, Kirk D.; Wang, Junhong; Rossow, William B.

1995-01-01

295

Preliminary results of measurements by automated probes Vega 1 and 2 or particle concentration in clouds of Venus at heights 47-63 KM  

NASA Technical Reports Server (NTRS)

Results of the preliminary processing of the Vega 1 and 2 descender data on the cloud layer structure of the Venusian atmosphere are discussed. A photoelectric counter for aerosol particles is described together with its optical and pneumatic circuits and operation algorithm. Vertical profiles of concentrations of particles with a diameter of 0.4 microns agree quantitatively with the Pioneer-Venus and Venera 9 and 10 data. Concentrations of these particles are: in the B layer, up to 190/cu cm; in the C layer, up to 10/cu cm; and in the D layer, up to 130/cu cm. Layers have sharp boundaries with a significant vertical heterogeneity of the aerosol concentration field inside them.

Zhulanov, Y. V.; Mukhin, L. M.; Nenarokov, D. F.

1986-01-01

296

Vertical Structure of Ice Cloud Layers From CloudSat and CALIPSO Measurements and Comparison to NICAM Simulations  

NASA Technical Reports Server (NTRS)

The shape of the vertical profile of ice cloud layers is examined using 4 months of CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) global measurements taken on January, April, July, and October 2007. Ice clouds are selected using temperature profiles when the cloud base is located above the 253K temperature level. The obtained ice water content (IWC), effective radius, or extinction coefficient profiles are normalized by their layer mean values and are expressed in the normalized vertical coordinate, which is defined as 0 and 1 at the cloud base and top heights, respectively. Both CloudSat and CALIPSO observations show that the maximum in the IWC and extinction profiles shifts toward the cloud bottom, as the cloud depth increases. In addition, clouds with a base reaching the surface in a high-latitude region show that the maximum peak of the IWC and extinction profiles occurs near the surface, which is presumably due to snow precipitation. CloudSat measurements show that the seasonal difference in normalized cloud vertical profiles is not significant, whereas the normalized cloud vertical profile significantly varies depending on the cloud type and the presence of precipitation. It is further examined if the 7 day Nonhydrostatic Icosahedral Atmospheric Model (NICAM) simulation results from 25 December 2006 to 1 January 2007 generate similar cloud profile shapes. NICAM IWC profiles also show maximum peaks near the cloud bottom for thick cloud layers and maximum peaks at the cloud bottom for low-level clouds near the surface. It is inferred that oversized snow particles in the NICAM cloud scheme produce a more vertically inhomogeneous IWC profile than observations due to quick sedimentation.

Ham, Seung-Hee; Sohn, Byung-Ju; Kato, Seiji; Satoh, Masaki

2013-01-01

297

An Efficient Cloud Computing-Based Architecture for Freight System Application in China Railway  

NASA Astrophysics Data System (ADS)

Cloud computing is a new network computing paradigm of distributed application environment. It utilizes the computing resource and storage resource to dynamically provide on-demand service for users. The distribution and parallel characters of cloud computing can leverage the railway freight system. We implement a cloud computing-based architecture for freight system application, which explores the Tashi and Hadoop for virtual resource management and MapReduce-based search technology. We propose the semantic model and setup configuration parameter by experiment, and develop the prototype system for freight search and tracking.

Zhang, Baopeng; Zhang, Ning; Li, Honghui; Liu, Feng; Miao, Kai

298

Cloud Properties Derived from Surface-Based Near-Infrared Spectral Transmission  

NASA Technical Reports Server (NTRS)

Surface based near-infrared cloud spectral transmission measurements from a recent precipitation/cloud physics field study are used to determine cloud physical properties and relate them to other remote sensing and in situ measurements. Asymptotic formulae provide an effective means of closely approximating the qualitative and quantitative behavior of transmission computed by more laborious detailed methods. Relationships derived from asymptotic formulae are applied to measured transmission spectra to test objectively the internal consistency of data sets acquired during the field program and they confirmed the quality of the measurements. These relationships appear to be very useful in themselves, not merely as a quality control measure, but also a potentially valuable remote-sensing technique in its own right. Additional benefits from this analysis have been the separation of condensed water (cloud) transmission and water vapor transmission and the development of a method to derive cloud liquid water content.

Pilewskie, Peter; Twomey, S.; Gore, Warren J. Y. (Technical Monitor)

1996-01-01

299

Limitations of microphysical property retrievals in marine water clouds based on satellite-based passive remote sensing  

NASA Astrophysics Data System (ADS)

In satellite-based passive remote sensing, the cloud droplet effective radius (re), which has a strong influence on cloud radiative effects, is derived together with cloud optical thickness (?) from reflectance measurements at two wavelengths, so called bi-spectral method. Since the bias to the re of marine water clouds can lead to a global radiative forcing error, it is critical to identify the sources and magnitudes of errors in the retrieval. Due to the use of loop-up tables, a bi-spectral method has limitations in optical and microphysical properties retrieval. It might be problematic for optically very thin clouds, and also erroneous for the clouds having very large radius droplets or large thickness due to the upper limits of retrieval method. This study investigates the occurrence rate and sources of the failed effective radius retrievals on Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua satellite together with Cloud Profiling Radar (CPR) observation on CloudSat satellite. First, a typical failed retrieval case will be shown to identify the characteristics. And, we investigate potential reasons of failed retrieval by demonstrating the dependency on the relevant parameters, such as optical thickness, horizontal homogeneity and reflectances. The difference between collections of MODIS data set will also be investigated. The CPR measurement collocated with MODIS can help to identify the source of failed retrieval, especially for the large particle. Preliminary result shows that the significant fractions (about 15%) of water clouds are failed in the MODIS re retrievals.

Cho, H.; Zhang, Z.; Platnick, S.; Lebsock, M. D.

2012-12-01

300

Diagnosing causes of cloud parameterization deficiencies using ARM measurements over SGP site  

SciTech Connect

Decade-long continuous surface-based measurements at Great Southern Plains (SGP) collected by the US Department of Energy’s Atmospheric Radiation Measurement (ARM) Climate Research Facility are first used to evaluate the three major reanalyses (i.e., ERA-Interim, NCEP/NCAR Reanalysis I and NCEP/DOE Reanalysis II) to identify model biases in simulating surface shortwave cloud forcing and total cloud fraction. The results show large systematic lower biases in the modeled surface shortwave cloud forcing and cloud fraction from all the three reanalysis datasets. Then we focus on diagnosing the causes of these model biases using the Active Remote Sensing of Clouds (ARSCL) products (e.g., vertical distribution of cloud fraction, cloud-base and cloud-top heights, and cloud optical depth) and meteorological measurements (temperature, humidity and stability). Efforts are made to couple cloud properties with boundary processes in the diagnosis.

Wu, W.; Liu, Y.; Betts, A. K.

2010-03-15

301

Raman Lidar Retrievals of Mixed Layer Heights  

NASA Astrophysics Data System (ADS)

Accurate determination of the atmospheric mixing layer (ML) height is important for modeling the transport of aerosols and aerosol precursors and forecasting air quality. Aerosol and water vapor profiles measured by the DOE ARM SGP and the new TWP (Darwin) ground based Raman lidars provide direct measurements of the vertical structure of ML. We have developed automated algorithms to identify sharp gradients in aerosols and water vapor at the top of the ML and have used these algorithms to derive ML heights for extended periods over the last few years. During the afternoon, these ML heights generally compare favorably with ML heights derived from potential temperature profiles derived from coincident radiosondes. However, retrieving ML heights via lidar measurements of water vapor and aerosol gradients is problematic in the presence of elevated aerosol and water vapor layers which are often observed, especially at night. Consequently, we take advantage of recent modifications to these lidars that permit continuous temperature profiling, and compute ML heights using potential temperature profiles derived from Raman lidar and Atmospheric Emitted Radiance Interferometer (AERI) measurements. The resulting ML heights agree well with ML heights derived from radiosondes and provide a more realistic representation of the diurnal ML behavior. We use the Raman lidar aerosol and water vapor profiles and ML heights to derive the fractions of total column precipitable water vapor and aerosol optical thickness within and above the ML and show how the ML heights and these fractions vary with time of day and season. The SGP Raman lidar measurements show that the fraction of the aerosol optical thickness and precipitable water vapor above the ML increases from 30-60% during the day to 60-80% at night. The Darwin Raman lidar measurements reveal a shallow, moist cloud-topped ML with little diurnal variability during the austral summer and deeper ML with more diurnal variability during the austral winter. The Darwin Raman lidar measurements of the diurnal and seasonal variabilities of ML heights and the aerosol and water vapor distributions relative to these ML heights will also be presented.

Ferrare, R. A.; Clayton, M.; Turner, D. D.; Newsom, R. K.; Goldsmith, J.

2012-12-01

302

Securing the mobile enterprise with network-based security and cloud computing  

Microsoft Academic Search

This paper proposes a new security architecture for the mobile enterprise which uses network-based security and cloud computing to both simplify and enhance the security of enterprises, and reinstate the currently disappearing security perimeter.

Gustavo de los Reyes; Sanjay Macwan; Deepak Chawla; Cristina Serban

2012-01-01

303

Using sky radiances measured by ground based AERONET Sun-Radiometers for cirrus cloud detection  

NASA Astrophysics Data System (ADS)

Screening of cirrus clouds using observations of optical depth (OD) only has proven to be a difficult task due mostly to some clouds having temporally and spatially stable OD. On the other hand, the sky radiances measurements which in AERONET protocol are taken throughout the day may contain additional cloud information. In this work the potential of using sky radiances for cirrus cloud detection is investigated. The detection is based on differences in the angular shape of sky radiances due to cirrus clouds and aerosol (see Figure). The range of scattering angles from 3 to 6 degrees was selected due to two primary reasons: high sensitivity to cirrus clouds presence, and close proximity to the Sun. The angular shape of sky radiances was parametrized by its curvature, which is a parameter defined as a combination of the first and second derivatives as a function of scattering angle. We demonstrate that a slope of the logarithm of curvature versus logarithm of scattering angle in this selected range of scattering angles is sensitive to cirrus cloud presence. We also demonstrate that restricting the values of the slope below some threshold value can be used for cirrus cloud screening. The threshold value of the slope was estimated using collocated measurements of AERONET data and MPLNET lidars.

Sinyuk, A.; Holben, B. N.; Eck, T. F.; Slutsker, I.; Lewis, J. R.

2013-12-01

304

Buildings and Terrain of Urban Area Point Cloud Segmentation based on PCL  

NASA Astrophysics Data System (ADS)

One current problem with laser radar point data classification is building and urban terrain segmentation, this paper proposes a point cloud segmentation method base on PCL libraries. PCL is a large cross-platform open source C++ programming library, which implements a large number of point cloud related efficient data structures and generic algorithms involving point cloud retrieval, filtering, segmentation, registration, feature extraction and curved surface reconstruction, visualization, etc. Due to laser radar point cloud characteristics with large amount of data, unsymmetrical distribution, this paper proposes using the data structure of kd-tree to organize data; then using Voxel Grid filter for point cloud resampling, namely to reduce the amount of point cloud data, and at the same time keep the point cloud shape characteristic; use PCL Segmentation Module, we use a Euclidean Cluster Extraction class with Europe clustering for buildings and ground three-dimensional point cloud segmentation. The experimental results show that this method avoids the multiple copy system existing data needs, saves the program storage space through the call of PCL library method and class, shortens the program compiled time and improves the running speed of the program.

Liu, Ying; Zhong, Ruofei

2014-03-01

305

Age-Based Reference Ranges for Annual Height Velocity in US Children.  

PubMed

Objective: Clinicians caring for children rely on measures of linear growth as a biomarker of development and overall health. Current reference ranges for height velocity (HV) for US children are unable to provide HV percentiles or Z-scores for early maturing and late maturing children at ages other than age at peak velocity. We present empirically acquired, age-specific reference ranges for HV from a contemporary sample of US youth. Study Design: Subjects were enrolled in the Bone Mineral Density in Childhood Study, a large, multicenter, multiethnic, contemporary cohort of children (aged 5-19 y at enrollment) from the United States followed for up to 7 years. More than 4000 annual (12 ± 1 mo) HV measurements from approximately 1500 children were available. Pubertal status was determined by breast stage or testicular volume assessed by experienced health providers. Age-specific reference ranges were determined using the LMS method. Results: Reference ranges (third to 97th percentiles) were generated for the entire cohort and for subgroups whose pubertal timing was defined as "earlier," "average," or "later." African American girls experienced earlier pubertal onset and had greater HV at younger ages and lower HV at older ages, compared to non-African American girls; differences did not persist after adjustment for pubertal timing. These differences were not observed for males. Conclusions: These reference ranges for annual HV can be used to assess growth relative to peers of the same age and sex, with consideration of pubertal timing. Z-scores and exact percentiles for HV can also be determined for population studies. PMID:24601728

Kelly, Andrea; Winer, Karen K; Kalkwarf, Heidi; Oberfield, Sharon E; Lappe, Joan; Gilsanz, Vicente; Zemel, Babette S

2014-06-01

306

A Comparison of Satellite-Based Multilayered Cloud Detection Methods  

NASA Technical Reports Server (NTRS)

Both techniques show skill in detecting multilayered clouds, but they disagree more than 50% of the time. BTD method tends to detect more ML clouds than CO2 method and has slightly higher detection accuracy. CO2 method might be better for minimizing false positives, but further study is needed. Neither method as been optimized for GOES data. BTD technique developed on AVHRR, better BTD signals & resolution. CO2 developed on MODIS, better resolution & 4 CO2 channels. Many additional comparisons with ARSCL data will be used to optimize both techniques. A combined technique will be examined using MODIS & Meteosat-8 data. After optimization, the techniques will be implemented in the ARM operational satellite cloud processing.

Minnis, Patrick; Chang, Fu-Lung; Khaiyer, Mandana M.; Ayers, Jeffrey K.; Palikonda, Rabindra; Nordeen, Michele L.; Spangenberg, Douglas A.

2007-01-01

307

Variability of Cloud Vertical Structure during ASTEX Observed from a Combination of Rawinsonde, Radar, Ceilometer, and Satellite  

Microsoft Academic Search

The macroscale cloud vertical structure (CVS), including cloud-base and -top heights and layer thickness, and characteristics of multilayered clouds, is studied at Porto Santo Island during the Atlantic Stratocumulus Transition Experiment (ASTEX) by using rawinsonde, radar, ceilometer, and satellite data. The comparisons of CVS parameters obtained from four different approaches show that 1) by using the method developed by Wang

Junhong Wang; William B. Rossow; Taneil Uttal; Margaret Rozendaal

1999-01-01

308

A new NASA/MSFC mission analysis global cloud cover data base  

NASA Technical Reports Server (NTRS)

A global cloud cover data set, derived from the USAF 3D NEPH Analysis, was developed for use in climate studies and for Earth viewing applications. This data set contains a single parameter - total sky cover - separated in time by 3 or 6 hr intervals and in space by approximately 50 n.mi. Cloud cover amount is recorded for each grid point (of a square grid) by a single alphanumeric character representing each 5 percent increment of sky cover. The data are arranged in both quarterly and monthly formats. The data base currently provides daily, 3-hr observed total sky cover for the Northern Hemisphere from 1972 through 1977 less 1976. For the Southern Hemisphere, there are data at 6-hr intervals for 1976 through 1978 and at 3-hr intervals for 1979 and 1980. More years of data are being added. To validate the data base, the percent frequency of or = 0.3 and or = 0.8 cloud cover was compared with ground observed cloud amounts at several locations with generally good agreement. Mean or other desired cloud amounts can be calculated for any time period and any size area from a single grid point to a hemisphere. The data base is especially useful in evaluating the consequence of cloud cover on Earth viewing space missions. The temporal and spatial frequency of the data allow simulations that closely approximate any projected viewing mission. No adjustments are required to account for cloud continuity.

Brown, S. C.; Jeffries, W. R., III

1985-01-01

309

Sensitivity of a physically-based cloud package in the NCAR/CCM2  

SciTech Connect

Based on our earlier investigation on the performance of the National Center for Atmospheric Research Community Climate Model Version 2 (CCM2), we have incorporated into this model a physically-based cloud package. This package allows for the prognostic computation of cloud liquid water which is advected using the semi-Lagrangrian transport scheme of CCM2 the formation of anvil clouds from deep convective systems, and the coupling of physically based cloud optical properties to the CCM2`s shortwave and longwave radiation treatment. In this paper, the effect of the cloud package is assessed by comparing the January results of the simulation to model output from a control run over the same period using the original version of CCM2. The model results are also compared to data from the global reanalysis for the same period conducted by the National Center for Experimental Prediction (NCEP) and NCAR. In this paper, we place particular emphasis on the cloud package`s effect on the climate patterns in the Pacific North American Region. The sensitivity of the model performance to the threshold relative humidity for cloud formation in the scheme is also assessed.

Kao, Chih-Yue Jim [Los Alamos National Lab., NM (United States); Smith, W.S. [Scripps Institution of Oceanography, La Jolla, CA (United States)

1997-02-01

310

Reputation-Based QoS Provisioning in Cloud Computing via Dirichlet Multinomial Model  

Microsoft Academic Search

In Cloud computing, users with different service requirements often need to negotiate with service provider via Service Level Agreement (SLA). The unique pay-as-you-go billing way in Cloud computing challenges resource provisioning for service providers. In this paper, based on the Dirichlet multinomial model, we present an efficient reputation-based QoS provisioning scheme, which can minimize the cost of computing resources, while

Yanping Xiao; Chuang Lin; Yixin Jiang; Xiaowen Chu; Xuemin Shen

2010-01-01

311

The Cloud Detection and Ultraviolet Monitoring Experiment (CLUE)  

NASA Technical Reports Server (NTRS)

In this paper we describe a new balloon instrument - CLUE - which is designed to monitor ultraviolet (uv) nightglow levels and determine cloud cover and cloud heights with a CO2 slicing technique. The CO2 slicing technique is based on the MODIS instrument on NASA's Aqua and Terra spacecraft. CLUE will provide higher spatial resolution (0.5 km) and correlations between the uv and the cloud cover.

Barbier, Louis M.; Loh, Eugene C.; Krizmanic, John F.; Sokolsky, Pierre; Streitmatter, Robert E.

2004-01-01

312

Integration of cloud-based storage in BES III computing environment  

NASA Astrophysics Data System (ADS)

We present an on-going work that aims to evaluate the suitability of cloud-based storage as a supplement to the Lustre file system for storing experimental data for the BES III physics experiment and as a backend for storing files belonging to individual members of the collaboration. In particular, we discuss our findings regarding the support of cloud-based storage in the software stack of the experiment. We report on our development work that improves the support of CERN' s ROOT data analysis framework and allows efficient remote access to data through several cloud storage protocols. We also present our efforts providing the experiment with efficient command line tools for navigating and interacting with cloud storage-based data repositories both from interactive sessions and grid jobs.

Wang, L.; Hernandez, F.; Deng, Z.

2014-06-01

313

Prediction Based Design of Fire Detection for Buildings with Ceiling Heights between 9m and 18m  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to provide the experimental and theoretical background necessary to extend guidelines to ceiling heights between 9 m and 18 m. Based on the results of experiments conducted in 15 m and 22 m high hangars, detector activation thresholds and detector spacing are analyzed for both smoke and heat detectors. Only ceiling mounted detection devices are analyzed in this paper. In addition to the detector threshold study, the predictive capabilities of computer fire model simulations were compared with experimental results. This comparison, which is based on 12 fire tests, resulted in the development of a new ceiling jet algorithm to model phenomena which had not been included in previous algorithms. The improved algorithm provides a better representation of the development of the ceiling jet temperature to a growing hot layer and a better estimation of plume centerline temperature. Guidelines are examined, based on the experimental results, for fire detector spacing, placement, and sensitivity. Recommendations concerning the use of computer fire models at these heights are made as a function of fire size and hot layer development. The role of draft curtains is discussed and their impact on detector activation is demonstrated.

Davis, W. D.; Notarianni, K. A.

1998-01-01

314

A point cloud data reduction method based on curvature  

Microsoft Academic Search

As a non-contact-type device could sample part surface data with high speed and accuracy, it becomes the most popular instrument for capturing the surface data of a part. However, it creates a large amount of point data which must be reduced to decrease computational time and to lower the storage requirement. Aiming at the limitations of point cloud data reduction

Xiaolei Du; Yong Zhuo

2009-01-01

315

A new online trading platform based on cloud computing  

Microsoft Academic Search

Along with the development of grid computing and cloud computing, finite computing resources supplied by standalone server usually become the bottleneck in the process of system implementation of online trading platform. Moreover, It is difficult to reuse algorithm module and the system also becomes more complicated to achieve. Traditional online trading framework can not preferably solve the problem listed above.

Zhou Yixin

2010-01-01

316

Move It or Lose It: Cloud-Based Data Storage  

ERIC Educational Resources Information Center

There was a time when school districts showed little interest in storing or backing up their data to remote servers. Nothing seemed less secure than handing off data to someone else. But in the last few years the buzz around cloud storage has grown louder, and the idea that data backup could be provided as a service has begun to gain traction in…

Waters, John K.

2010-01-01

317

Evaluation of Cirrus Cloud Properties Derived from MODIS Data Using Cloud Properties Derived from Ground-Based Observations Collected at the ARM SGP Site.  

NASA Astrophysics Data System (ADS)

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board the NASA Terra satellite has been collecting global data since March 2000 and the one on the Aqua satellite since June 2002. In this paper, cirrus cloud properties derived from ground-based remote sensing data are compared with similar cloud properties derived from MODIS data on Terra. To improve the space-time correlation between the satellite and ground-based observations, data from a wind profiler are used to define the cloud advective streamline along which the comparisons are made. In this paper, approximately two dozen cases of cirrus are examined and a statistical approach to the comparison that relaxes the requirement that clouds occur over the ground-based instruments during the overpass instant is explored. The statistical comparison includes 168 cloudy MODIS overpasses of the Southern Great Plains (SGP) region and approximately 300 h of ground-based cirrus observations. The physical and radiative properties of cloud layers are derived from MODIS data separately by the MODIS Atmospheres Team and the Clouds and the Earth's Radiant Energy System (CERES) Science Team using multiwavelength reflected solar and emitted thermal radiation measurements. Using two ground-based cloud property retrieval algorithms and the two MODIS algorithms, a positive correlation in the effective particle size, the optical thickness, the ice water path, and the cloud-top pressure between the various methods is shown, although sometimes there are significant biases. Classifying the clouds by optical thickness, it is demonstrated that the regionally averaged cloud properties derived from MODIS are similar to those diagnosed from the ground. Because of a conservative approach toward identifying thin cirrus pixels over this region, the area-averaged cloud properties derived from the MODIS Atmospheres MOD06 product tend to be biased slightly toward the optically thicker pixels. This bias tendency has implications for model validation and parameterization development applied to thin cirrus retrieved over SGP-like land surfaces. A persistent bias is also found in the derived cloud tops of thin cirrus with both satellite algorithms reporting cloud top several hundred meters less than that reported by the cloud radar. Overall, however, it is concluded that the MODIS retrieval algorithms characterize with reasonable accuracy the properties of thin cirrus over this region.

Mace, Gerald G.; Zhang, Yuying; Platnick, Steven; King, Michael D.; Minnis, Patrick; Yang, Ping

2005-02-01

318

Polar Stratospheric Clouds from ground-based lidar and CALIPSO observations and Chemistry Climate Models evaluation  

NASA Astrophysics Data System (ADS)

We evaluate the Antarctic PSC observational databases of CALIPSO and the ground-based lidars of NDACC (Network for Detection of Atmospheric Composition Changes) located in McMurdo and Dumont D'Urville stations and provide a process-oriented evaluation of PSC in a subset of CCMVAL-2 chemistry-climate models. Lidar observatories have a decadal coverage, albeit with discontinuities, spanning from 1992 to today hence offering a unique database. A clear issue is the representativeness of ground-based long-term data series of the Antarctic stratosphere conditions that may limit their value in climatological studies and model evaluation. The comparison with the CALIPSO observations with a global coverage is, hence, a key issue. In turn, models can have a biased representation of the stratospheric conditions and of the PSC microphysics leading to large discrepancies in PSC occurrence and composition. CALIPSO observations indicate a large longitudinal variability in PSC formation in the polar atmosphere and ground-based observations are hence representative of different cloud conditions. Point-to-point comparison is difficult due to sparseness of the database (or PSC appearance at the edge of the vortex) and to intrinsic differences in spatial distribution between models and observations. So the use of simple diagnostics that are independent from instrumental coverage is fundamental. Comparison between ground-based and satellite borne-lidar is overall satisfactory and differences may be attributed to differences in coverage. As expected, McMurdo site is dominated by a NAT-type regime that is a clear feature of the eastern part of polar vortex while Dumont D'Urville is largely influenced by the transition at the edge the polar vortex resulting, on average, in a much reduced PSC coverage with a partition between NAT and STS cloud types. Data from the 5 CCMs having provided PSC surface areas on daily basis have been evaluated using the same diagnostic type that may be derived CALIPSO (i.e. frequency of PSC occurrence function of lon-lat, height and temperature) showing large differences that may be explained by the interplay of model temperatures that may show a large bias (negative for 3 models over 5) and the microphysical scheme itself. Two models in fact show an excess of NAT formation relative to ice clouds while two others have an unrealistic dominance of ice. Most of them show a somewhat too efficient PSC production with temperature decrease below NAT formation temperature. Evaluation CCMs with ground-based instruments databases should be done with great care due to the large spatial differences inside the polar vortex that are not fully reproduced by the models. In turn, longer series as provided by NDACC should be used to evaluate interannual variability and trends that is difficult to identify in the shorter CALIPSO database.

Fierli, Federico; Di Liberto, Luca; Cairo, Francesco; Cagnazzo, Chiara; Snels, Marcel; Keckhut, Philippe; Jumelet, Julien; Pitts, Michael C.

2014-05-01

319

COMBAT: mobile-Cloud-based cOmpute/coMmunications infrastructure for BATtlefield applications  

NASA Astrophysics Data System (ADS)

The amount of data processed annually over the Internet has crossed the zetabyte boundary, yet this Big Data cannot be efficiently processed or stored using today's mobile devices. Parallel to this explosive growth in data, a substantial increase in mobile compute-capability and the advances in cloud computing have brought the state-of-the- art in mobile-cloud computing to an inflection point, where the right architecture may allow mobile devices to run applications utilizing Big Data and intensive computing. In this paper, we propose the MObile Cloud-based Hybrid Architecture (MOCHA), which formulates a solution to permit mobile-cloud computing applications such as object recognition in the battlefield by introducing a mid-stage compute- and storage-layer, called the cloudlet. MOCHA is built on the key observation that many mobile-cloud applications have the following characteristics: 1) they are compute-intensive, requiring the compute-power of a supercomputer, and 2) they use Big Data, requiring a communications link to cloud-based database sources in near-real-time. In this paper, we describe the operation of MOCHA in battlefield applications, by formulating the aforementioned mobile and cloudlet to be housed within a soldier's vest and inside a military vehicle, respectively, and enabling access to the cloud through high latency satellite links. We provide simulations using the traditional mobile-cloud approach as well as utilizing MOCHA with a mid-stage cloudlet to quantify the utility of this architecture. We show that the MOCHA platform for mobile-cloud computing promises a future for critical battlefield applications that access Big Data, which is currently not possible using existing technology.

Soyata, Tolga; Muraleedharan, Rajani; Langdon, Jonathan; Funai, Colin; Ames, Scott; Kwon, Minseok; Heinzelman, Wendi

2012-05-01

320

Cloud detection and classification with the use of whole-sky ground-based images  

NASA Astrophysics Data System (ADS)

A simple whole sky imaging system, based on a commercial digital camera with a fish-eye lens and a hemispheric dome, is used for the automatic estimation of total cloud coverage and classification. For the first time, a multi color criterion is applied on sky images, in order to improve the accuracy in detection of broken and overcast clouds under large solar zenith angles. The performance of the cloud detection algorithm is successfully compared with ground based weather observations. A simple method is presented for the detection of raindrops standing on the perimeter of hemispheric dome. Based on previous works on cloud classification, an improved k-Nearest-Neighbor algorithm is presented, based not only on statistical color and textural features, but taking also into account the solar zenith angle, the cloud coverage, the visible fraction of solar disk and the existence of raindrops in sky images. The successful detection percentage of the classifier ranges between 78 and 95% for seven cloud types.

Kazantzidis, A.; Tzoumanikas, P.; Bais, A. F.; Fotopoulos, S.; Economou, G.

2012-09-01

321

Forest height estimation from mountain forest areas using general model-based decomposition for polarimetric interferometric synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

The estimation of forest parameters over mountain forest areas using polarimetric interferometric synthetic aperture radar (PolInSAR) images is one of the greatest interests in remote sensing applications. For mountain forest areas, scattering mechanisms are strongly affected by the ground topography variations. Most of the previous studies in modeling microwave backscattering signatures of forest area have been carried out over relatively flat areas. Therefore, a new algorithm for the forest height estimation from mountain forest areas using the general model-based decomposition (GMBD) for PolInSAR image is proposed. This algorithm enables the retrieval of not only the forest parameters, but also the magnitude associated with each mechanism. In addition, general double- and single-bounce scattering models are proposed to fit for the cross-polarization and off-diagonal term by separating their independent orientation angle, which remains unachieved in the previous model-based decompositions. The efficiency of the proposed approach is demonstrated with simulated data from PolSARProSim software and ALOS-PALSAR spaceborne PolInSAR datasets over the Kalimantan areas, Indonesia. Experimental results indicate that forest height could be effectively estimated by GMBD.

Minh, Nghia Pham; Zou, Bin; Cai, Hongjun; Wang, Chengyi

2014-01-01

322

Development and clinical study of mobile 12-lead electrocardiography based on cloud computing for cardiac emergency.  

PubMed

To improve emergency services for accurate diagnosis of cardiac emergency, we developed a low-cost new mobile electrocardiography system "Cloud Cardiology®" based upon cloud computing for prehospital diagnosis. This comprises a compact 12-lead ECG unit equipped with Bluetooth and Android Smartphone with an application for transmission. Cloud server enables us to share ECG simultaneously inside and outside the hospital. We evaluated the clinical effectiveness by conducting a clinical trial with historical comparison to evaluate this system in a rapid response car in the real emergency service settings. We found that this system has an ability to shorten the onset to balloon time of patients with acute myocardial infarction, resulting in better clinical outcome. Here we propose that cloud-computing based simultaneous data sharing could be powerful solution for emergency service for cardiology, along with its significant clinical outcome. PMID:23920851

Fujita, Hideo; Uchimura, Yuji; Waki, Kayo; Omae, Koji; Takeuchi, Ichiro; Ohe, Kazuhiko

2013-01-01

323

Categorization of lung morphology based on FRC and height: computer simulations of aerosol deposition  

Microsoft Academic Search

The aim of this work was to compare human subject experimental measurements of particle deposition within the lungs using the aerosol bolus technique with the results of analytical modeling as a basis for assessing the influence of lung morphology on inhaled particle deposition patterns. A methodology for scaling the lung morphology, based on a classic symmetric dichotomous model, as a

M. Pichelin; G. Caillibotte; I. Katz; T. Martonen

2011-01-01

324

New MISR Cloud Data  

... are provided for 70% of clouds observed by MISR with vector RMS difference from atmospheric motion vectors from other sources ranging from ... m/s. Cloud top heights are provided for 80% of clouds with RMS differences of less than 1 km (the same as for the existing Level 2 Stereo ...

2013-08-06

325

Global distribution of total cloud cover and cloud type amounts over the ocean  

SciTech Connect

This is the fourth of a series of atlases to result from a study of the global cloud distribution from ground-based observations. The first two atlases (NCAR/TN-201+STR and NCAR/TN-241+STR) described the frequency of occurrence of each cloud type and the co-occurrence of different types, but included no information about cloud amounts. The third atlas (NCAR/TN-273+STR) described, for the land areas of the earth, the average total cloud cover and the amounts of each cloud type, and their geographical, diurnal, seasonal, and interannual variations, as well as the average base heights of the low clouds. The present atlas does the same for the ocean areas of the earth.

Warren, S.G.; Hahn, C.J.; London, J.; Chervin, R.M.; Jenne, R.L. (Washington Univ., Seattle, WA (USA). Dept. of Atmospheric Sciences; Colorado Univ., Boulder, CO (USA). Cooperative Inst. for Research in Environmental Sciences; Colorado Univ., Boulder, CO (USA). Dept. of Astrophysical, Planetary, and Atmospheric Sciences; National Center for Atmospheric Research, Boulder, CO (USA))

1988-12-01

326

Climatic impact of tropical lowland deforestation on nearby montane cloud forests.  

PubMed

Tropical montane cloud forests (TMCFs) depend on predictable, frequent, and prolonged immersion in cloud. Clearing upwind lowland forest alters surface energy budgets in ways that influence dry season cloud fields and thus the TMCF environment. Landsat and Geostationary Operational Environmental Satellite imagery show that deforested areas of Costa Rica's Caribbean lowlands remain relatively cloud-free when forested regions have well-developed dry season cumulus cloud fields. Further, regional atmospheric simulations show that cloud base heights are higher over pasture than over tropical forest areas under reasonable dry season conditions. These results suggest that land use in tropical lowlands has serious impacts on ecosystems in adjacent mountains. PMID:11641496

Lawton, R O; Nair, U S; Pielke Sr, R A; Welch, R M

2001-10-19

327

A commandable pulse height analysis system based on custom VLSI ASICs for the Cassini space mission  

Microsoft Academic Search

The authors have implemented a new commandable threshold PHA-accumulation unit for the MIMI\\/LEMMS particle detection instrument of the Cassini mission to Saturn. The implementation is based on two full custom VLS ASICs specifically designed, fabricated, and space qualified for this project. The present system overcomes common fine tuning pre-flight and in-flight calibration difficulties associated with conventional fixed threshold systems of

N. Paschalidis; N. Chrissostomidis; N. Stamatopoulos; P. Houlis; E. Sarris; S. Jaskulek; M. Mitchell; B. Tossman; S. Krimigis

1997-01-01

328

Gamma rays from cloud penetration at the base of AGN jets  

NASA Astrophysics Data System (ADS)

Context. Dense and cold clouds seem to populate the broad line region surrounding the central black hole in AGNs. These clouds may interact with the AGN jet base which could have observational consequences. Aims: We study the gamma-ray emission produced by these jet-cloud interactions, and explore the conditions under which this radiation would be detectable. Methods: We investigate the hydrodynamical properties of jet-cloud interactions and the resulting shocks, and develop a model to compute the spectral energy distribution of the emission generated by the particles accelerated in these shocks. We discuss our model in the context of radio-loud AGNs, with applications to two representative cases, the low-luminous Centaurus A and the powerful 3C 273. Results: Some fraction of the jet power may be channelled into gamma-ray energy, which is likely to be dominated by synchrotron self-Compton radiation, and have typical variability timescales similar to the cloud lifetime within the jet, which is longer than several hours. Many clouds can interact with the jet simultaneously leading to fluxes significantly higher than in one interaction, but then variability will be smoothed out. Conclusions: Jet-cloud interactions may produce detectable gamma-rays in non-blazar AGNs that are transient in nearby low-luminous sources such as Cen A, and steady in the case of powerful objects of FR II type.

Araudo, A. T.; Bosch-Ramon, V.; Romero, G. E.

2010-11-01

329

RAS-M: Resource Allocation Strategy Based on Market Mechanism in Cloud Computing  

Microsoft Academic Search

Resource management is one of the main issues in cloud computing. in order to improve resource utilization of large data centers while delivering services with higher QoS to cloud clients, a resource allocation strategy based on market (RAS-M) is proposed. Firstly, the architecture and the market model of RAS-M are constructed, in which a QoS-refection utility function is designed according

Xindong You; Xianghua Xu; Jian Wan; Dongjin Yu

2009-01-01

330

3D Reconstruction from Multi-view Point Cloud Based on Particle System  

Microsoft Academic Search

Reconstructing accurate 3D object shapes from multi-view sampling points is one of the most challenging tasks to the scientists and engineers in reverse engineering. Aiming to this question, a merging and reconstructing algorithm based on particle system is presented for 3D topology reconstruction from multi-view point cloud in this paper. First one initial meshes of each point cloud in one

Hu Wenqiang; Qu Yi

2009-01-01

331

ACCENT: Cognitive cryptography plugged compression for SSL\\/TLS-based cloud computing services  

Microsoft Academic Search

Emerging cloud services, including mobile offices, Web-based storage services, and content delivery services, run diverse workloads under various device platforms, networks, and cloud service providers. They have been realized on top of SSL\\/TLS, which is the de facto protocol for end-to-end secure communication over the Internet. In an attempt to achieve a cognitive SSL\\/TLS with heterogeneous environments (device, network, and

Ki-Woong Park; Kyu Ho Park

2011-01-01

332

Using ground-based stereo cameras to derive cloud-level wind fields.  

PubMed

Upper-level wind fields are obtained by tracking the motion of cloud features as seen in calibrated ground-based stereo cameras. By tracking many cloud features, it is possible to obtain horizontal wind speed and direction over a cone area throughout the troposphere. Preliminary measurements were made at the Mauna Loa Observatory, and resulting wind measurements are compared with winds from the Hilo, Hawaii radiosondes. PMID:19684790

Porter, John N; Cao, Guang Xia

2009-08-15

333

Remote Sensing of Cloud Optical Properties from Ground-Based Measurements of Transmittance: A Feasibility Study  

Microsoft Academic Search

The authors present a retrieval technique for the inference of cloud optical depth from data obtained by a ground-based multichannel radiometer for use in climate-related studies. The basic steps of the analysis procedure are considered, including accurate calculations of the atmosphere and cloud properties. An approach is described that uses observed and model-simulated transmittances rather than irradiances and that does

E. Leontieva; K. Stamnes

1996-01-01

334

Cloud-computing-based framework for multi-camera topology inference in smart city sensing system  

Microsoft Academic Search

This paper proposes a cloud-computing-based algorithmic framework which is scalable and adaptive to online smart city video sensing system. One of the most cost-expensive works in such a system is to infer the topology structure of video camera network, thus spatio-temporal relationship inference for large-scale camera network is simulated on a cloud-computing platform to validate the proposed framework. The simulation

Ye Wen; Xiaokang Yang; Yi Xu

2010-01-01

335

Classification of cloud types based on data of multiple satellite sensors  

NASA Astrophysics Data System (ADS)

Taking advantage of multispectral radiometers of VTIR of MOS-1 consisting of water vapor absorption and split-window channels, an attempt is made to develop an algorithm to classify cloud types of synopic meteorological significance. Verification of the algorithm based on the data of 4 channels of VTIR ( 1 visible, 1 water vapor absorption, 2 split window channels) onboard MOS-1 indicate that the algorithm works well for identifying well developed cumulonimbus, multilayered thick clouds and stratus/dense deep fog.

Tokuno, Masami; Tsuchiya, Kiyoshi

1994-03-01

336

Cloud Detection Method Based on Feature Extraction in Remote Sensing Images  

NASA Astrophysics Data System (ADS)

In remote sensing images, the existence of the clouds has a great impact on the image quality and subsequent image processing, as the images covered with clouds contain little useful information. Therefore, the detection and recognition of clouds is one of the major problems in the application of remote sensing images. Present there are two categories of method to cloud detection. One is setting spectrum thresholds based on the characteristics of the clouds to distinguish them. However, the instability and uncertainty of the practical clouds makes this kind of method complexity and weak adaptability. The other method adopts the features in the images to identify the clouds. Since there will be significant overlaps in some features of the clouds and grounds, the detection result is highly dependent on the effectiveness of the features. This paper presented a cloud detection method based on feature extraction for remote sensing images. At first, find out effective features through training pattern, the features are selected from gray, frequency and texture domains. The different features in the three domains of the training samples are calculated. Through the result of statistical analysis of all the features, the useful features are picked up to form a feature set. In concrete, the set includes three feature vectors, respectively, the gray feature vector constituted of average gray, variance, first-order difference, entropy and histogram, the frequency feature vector constituted of DCT high frequency coefficient and wavelet high frequency coefficient, and the texture feature vector constituted of the hybrid entropy and difference of the gray-gradient co-occurrence matrix and the image fractal dimension. Secondly, a thumbnail will be obtained by down sampling the original image and its features of gray, frequency and texture are computed. Last but not least, the cloud region will be judged by the comparison between the actual feature values and the thresholds determined by the sample training process. Experimental results show that the clouds and ground objects can be separated efficiently, and our method can implement rapid clouds detection and cloudiness calculation.

Changhui, Y.; Yuan, Y.; Minjing, M.; Menglu, Z.

2013-05-01

337

Analysis of interstellar cloud structure based on IRAS images  

NASA Technical Reports Server (NTRS)

The goal of this project was to develop new tools for the analysis of the structure of densely sampled maps of interstellar star-forming regions. A particular emphasis was on the recognition and characterization of nested hierarchical structure and fractal irregularity, and their relation to the level of star formation activity. The panoramic IRAS images provided data with the required range in spatial scale, greater than a factor of 100, and in column density, greater than a factor of 50. In order to construct densely sampled column density maps of star-forming clouds, column density images of four nearby cloud complexes were constructed from IRAS data. The regions have various degrees of star formation activity, and most of them have probably not been affected much by the disruptive effects of young massive stars. The largest region, the Scorpius-Ophiuchus cloud complex, covers about 1000 square degrees (it was subdivided into a few smaller regions for analysis). Much of the work during the early part of the project focused on an 80 square degree region in the core of the Taurus complex, a well-studied region of low-mass star formation.

Scalo, John M.

1992-01-01

338

An intercomparison of radar-based liquid cloud microphysics retrievals and implication for model evaluation studies  

NASA Astrophysics Data System (ADS)

To assess if current radar-based liquid cloud microphysical retrievals of the Atmospheric Radiation Measurement (ARM) program can provide useful constraints for modeling studies, this paper presents intercomparison results of three cloud products at the Southern Great Plains (SGP) site: the ARM MICROBASE, University of Utah (UU), and University of North Dakota (UND) products over the nine-year period from 1998 to 2006. The probability density and spatial autocorrelation functions of the three cloud Liquid Water Content (LWC) retrievals appear to be consistent with each other, while large differences are found in the droplet effective radius retrievals. The differences in the vertical distribution of both cloud LWC and droplet effective radius retrievals are found to be alarmingly large, with the relative difference between nine-year mean cloud LWC retrievals ranging from 20% at low altitudes to 100% at high altitudes. Nevertheless, the spread in LWC retrievals is much smaller than that in cloud simulations by climate and cloud resolving models. The MICROBASE effective radius ranges from 2.0 at high altitudes to 6.0 ?m at low altitudes and the UU and UND droplet effective radius is 6 ?m larger. Further analysis through a suite of retrieval experiments shows that the difference between MICROBASE and UU LWC retrievals stems primarily from the partition total Liquid Water path (LWP) into supercooled and warm liquid, and from the input cloud boundaries and LWP. The large differences between MICROBASE and UU droplet effective radius retrievals are mainly due to rain/drizzle contamination and the assumptions of cloud droplet concentration used in the retrieval algorithms. The large discrepancy between different products suggests caution in model evaluation with these observational products, and calls for improved retrievals in general.

Huang, D.; Zhao, C.; Dunn, M.; Dong, X.; Mace, G. G.; Jensen, M. P.; Xie, S.; Liu, Y.

2011-12-01

339

Improvement in cloud predictions using satellite data assimilation for real-time forecasting  

NASA Astrophysics Data System (ADS)

The accuracy of quantitative forecasting of low-level operational cloud products such as the cloud top height, cloud top pressure and cloud thickness is rather low. Reliable forecasting of the low-level clouds (cloud top altitudes below 2-3 km) such as fog, stratus or stratocumulus is essential for aviation safety purposes. With the advent of an increased number of spectral channels and high-resolution imagers on the Geostationary Operational Environmental Satellite, cloud products can be diagnostically extracted and, furthermore, these cloud products can be used to modify the initial conditions for numerical weather prediction. Although operational methods are relatively successful in determining the cloud top altitudes for deep clouds and high clouds (usually above 5 km), there is no unique way of inferring the cloud top heights for low-level clouds due to their optical properties and low-level inversions. An algorithm has been developed in this study to classify the low-level cloud types using the brightness temperatures extracted from the GOES satellite visible and infrared channels. Cloud top temperatures above 8° C characterize low-level clouds. The brightness temperature differences between the window channel (11 ìm) and the shortwave infrared channel (4 ìm) are used to segregate the optically thin and thick clouds, and the relative humidity obtained from the surface stations is used to distinguish the fog or clouds formed by fog lifting. The infrared satellite imagery on 29 June 2006 is considered for this study with domain coverage of 400 x 400 km2 . The ground-truth observations were obtained from the surface weather station located at the Naval Air Station, Fallon (NASF), Nevada. Upon classification of low-level clouds in the satellite imagery, (a) the first step is to compute the cloud base temperature in the low-level cloudy pixels using the surface temperature and cloud base height obtained from the ceilometer measurements (at NASF) following a dry adiabatic lapse rate; (b) the second step is to compute the cloud top height using cloud base temperature, and the satellite- derived cloud top temperature following the wet adiabatic lapse rate in the cloud layer; (c) the third step is to obtain a representative lapse rate for the computing domain; (d) the fourth step is to compute the cloud top heights for the individual satellite pixels in the entire domain. The information on cloud top height and cloud top temperature obtained from the cloudy pixels is then dynamically assimilated into the model analysis using Cressman's objective analysis. Using the improved model analyses, a deterministic forecast will be carried out with an option of four-dimensional data assimilation of model winds and thermodynamic variables for a pre- forecast period of one complete diurnal cycle. Verification will be carried out using the hourly surface observations and cloud base measurements, and also using the satellite cloud imagery against the simulated cloud imagery and associated cloud products. The data assimilation of the derived cloud products is being tested in modeling systems such as the Mesoscale Model 5 (MM5) and the Weather Research Forecasting Model (WRF). The data assimilation of cloud products and verification is intended for the pre-processing module in a real-time forecasting system using various objective analysis procedures such as the Cressman-type, multi-quadric and 3DVAR. This study is to develop an efficient forecasting system to support naval aircraft and rotorcraft operations at the Fallon Naval Air Station, Fallon, Nevada.

Vellore, R.; Koracin, D.; Wetzel, M.

2006-12-01

340

Integrating Mesh and Meshfree Methods for Physics-Based Fracture and Debris Cloud Simulation  

Microsoft Academic Search

We present a hybrid framework for physics-based simulation of fracture and debris clouds. Previous methods mainly consider bulk fractures. However, in many situations, small fractured pieces and debris are visually impor- tant. Our framework takes a hybrid approach that integrates both tetrahedron-based finite element and particle- based meshfree methods. The simulation starts with a tetrahedral mesh. When the damage of

Nan Zhang; Xiangmin Zhou; Desong Sha; Xiaoru Yuan; Kumar Tamma; Baoquan Chen

2006-01-01

341

Comparison of CloudSat cloud liquid water paths in arctic summer using ground-based microwave radiometer  

Microsoft Academic Search

Arctic clouds strongly influence the regional radiation balance, temperature, melting of sea ice, and freezing of sea water.\\u000a Despite their importance, there is a lack of systematic and reliable observations of Arctic clouds. The CloudSat satellite\\u000a launched in 2006 with a 94 GHz Cloud Profiling Radar (CPR) may contribute to close this gap. Here we compare one of the key

Shuang Liu; Georg Heygster; Suping Zhang

2010-01-01

342

Implications of cloud obscuration on ground-based laser systems for strategic defense. Technical report  

SciTech Connect

The evolution and the current status of the Strategic Defense System Phase II Ground-Based Laser (GBL) System Concept is reviewed in this report. In particular, the impact of clouds on system configuration and site selection is discussed. By using current models of correlated probabilities of cloud-free line of sight and cloud-free arc (CFLOS4D and CFARC) for several ground stations with cloud realizations provided by the Boehm Saw Tooth generator, we have determined the number of ground sites required to achieve various levels of desired system weather availability. We briefly describe potential improvements in the models and discuss the necessity for using the Whole Sky Imager results now being generated to validate these models with empirical data, thereby lending further credibility to GBL System Concepts.

Tavis, M.T.; Levinson, S.W.; Parker, K.M.

1990-03-12

343

Towards a quantification of ocean wave heights off the west coast of Ireland using land based seismic data  

NASA Astrophysics Data System (ADS)

Ocean gravity waves are driven by atmospheric pressure systems. Their interactions with one another and reflection off coastlines generate pressure changes at the sea floor. These pressure fluctuations are the cause of continuous background seismic noise known as microseisms. The levels of microseism activity vary as a function of the sea state and increase during periods of intensive ocean wave activity. In 2011 a seismic network was deployed along the west coast of Ireland to continuously record microseisms generated in the Atlantic Ocean, as part of the Wave Observation (WaveObs) project based in University College Dublin. This project aims to determine the characteristics of the causative ocean gravity waves through calibration of the microseism data with ocean buoy data. In initial tests we are using a Backpropagation Feed-forward Artificial Neural Network (BP ANN) to establish the underlying relationships between microseisms and ocean waves. ANNs were originally inspired by studies of the mammalian brain and nervous system and are designed to learn by example. If successful these tools could then be used to estimate ocean wave heights and wave periods using a land-based seismic network and complement current wave observations being made offshore by marine buoys. Preliminary ANN results are promising with the network successfully able to reconstruct trends in ocean wave heights and periods. Microseisms can provide significant information about oceanic processes. With a deeper understanding of how these processes work there is potential for 1) locating and tracking the evolution of the largest waves in the Atlantic and 2) reconstructing the wave climate off the west coast of Ireland using legacy seismic data on a longer time scale than is currently available using marine based observations.

Donne, S.; Bean, C. J.; Lokmer, I.; Lambkin, K.; Creamer, C.

2012-12-01

344

Ground-based remote sensing of thin clouds in the Arctic  

NASA Astrophysics Data System (ADS)

This paper describes a method for using interferometer measurements of downwelling thermal radiation to retrieve the properties of single-layer clouds. Cloud phase is determined from ratios of thermal emission in three "micro-windows" at 862.5 cm-1, 935.8 cm-1, and 988.4 cm-1 where absorption by water vapour is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in the first two of these micro-windows, constrained by the transmission through clouds of primarily stratospheric ozone emission at 1040 cm-1. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius re, visible optical depth ?, number concentration N, and water path WP are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement programme (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with both ground-based microwave radiometer measurements of liquid water path and a method that uses combined shortwave and microwave measurements to retrieve re, ? and N. Compared to other retrieval methods, advantages of this technique include its ability to characterise thin clouds year round, that water vapour is not a primary source of retrieval error, and that the retrievals of microphysical properties are only weakly sensitive to retrieved cloud phase. The primary limitation is the inapplicability to thicker clouds that radiate as blackbodies and that it relies on a fairly comprehensive suite of ground based measurements.

Garrett, T. J.; Zhao, C.

2013-05-01

345

Dynamical and Microphysical Characteristics of Arctic Clouds during BASE.  

NASA Astrophysics Data System (ADS)

In this study, observations from aircraft, Doppler radar, and LANDSAT are used to better understand dynamical and microphysical characteristics of low-level Arctic clouds for climate change studies. Observations during the Beaufort and Arctic Storms Experiment were collected over the southern Beaufort Sea and the northern Mackenzie River Basin during 1 September-14 October 1994. Measurements from the cases of 8 September and 24-25 September are analyzed. In situ observations were made by instruments mounted on a Convair-580 research aircraft. Reflectivity and radial winds were obtained from an X-band Doppler radar located near Inuvik. The reflectivity field from LANDSAT observations concurrent with the aircraft and radar observations was also obtained. Dynamical activity, representing vertical air velocity (wa) and turbulent fluxes, is found to be larger in cloud regions. The sizes of coherent structures (e.g., cells) are from 0.1 to 15 km as determined by wavelet analysis and time series of aircraft data. This size is comparable with LANDSAT and Doppler radar-derived cell sizes. Reflectivity in embedded cells for the 8 September case was larger than that of single convective cells for the 24-25 September case. The effective radius for ice crystals (droplets) ranged from 37(7.5) m to 70(9.5) m for both cases. Using observations, parameterization of the ice crystal number concentration (Ni) is obtained from a heat budget equation. Results showed that Ni is a function of wa, radiative cooling, particle size, and supersaturation. The large-scale models may have large uncertainties related to microphysical and dynamical processes (e.g., particle size and vertical air velocity, respectively), which can directly or indirectly influence radiative processes. Overall, the results suggest that the microphysical and dynamical properties of Arctic clouds need to be further explored for climate change studies.

Gultepe, I.; Isaac, G.; Hudak, D.; Nissen, R.; Strapp, J. W.

2000-04-01

346

Maskless imaging of dense samples using pixel super-resolution based multi-height lensfree on-chip microscopy  

PubMed Central

Lensfree in-line holographic microscopy offers sub-micron resolution over a large field-of-view (e.g., ~24 mm2) with a cost-effective and compact design suitable for field use. However, it is limited to relatively low-density samples. To mitigate this limitation, we demonstrate an on-chip imaging approach based on pixel super-resolution and phase recovery, which iterates among multiple lensfree intensity measurements, each having a slightly different sample-to-sensor distance. By digitally aligning and registering these lensfree intensity measurements, phase and amplitude images of dense and connected specimens can be iteratively reconstructed over a large field-of-view of ~24 mm2 without the use of any spatial masks. We demonstrate the success of this multi-height in-line holographic approach by imaging dense Papanicolaou smears (i.e., Pap smears) and blood samples.

Greenbaum, Alon; Ozcan, Aydogan

2012-01-01

347

Maskless imaging of dense samples using pixel super-resolution based multi-height lensfree on-chip microscopy.  

PubMed

Lensfree in-line holographic microscopy offers sub-micron resolution over a large field-of-view (e.g., ~24 mm2) with a cost-effective and compact design suitable for field use. However, it is limited to relatively low-density samples. To mitigate this limitation, we demonstrate an on-chip imaging approach based on pixel super-resolution and phase recovery, which iterates among multiple lensfree intensity measurements, each having a slightly different sample-to-sensor distance. By digitally aligning and registering these lensfree intensity measurements, phase and amplitude images of dense and connected specimens can be iteratively reconstructed over a large field-of-view of ~24 mm2 without the use of any spatial masks. We demonstrate the success of this multi-height in-line holographic approach by imaging dense Papanicolaou smears (i.e., Pap smears) and blood samples. PMID:22330550

Greenbaum, Alon; Ozcan, Aydogan

2012-01-30

348

Automatic Atlas Based Electron Density and Structure Contouring for MRI-based Prostate Radiation Therapy on the Cloud  

NASA Astrophysics Data System (ADS)

Our group have been developing methods for MRI-alone prostate cancer radiation therapy treatment planning. To assist with clinical validation of the workflow we are investigating a cloud platform solution for research purposes. Benefits of cloud computing can include increased scalability, performance and extensibility while reducing total cost of ownership. In this paper we demonstrate the generation of DICOM-RT directories containing an automatic average atlas based electron density image and fast pelvic organ contouring from whole pelvis MR scans.

Dowling, J. A.; Burdett, N.; Greer, P. B.; Sun, J.; Parker, J.; Pichler, P.; Stanwell, P.; Chandra, S.; Rivest-Hénault, D.; Ghose, S.; Salvado, O.; Fripp, J.

2014-03-01

349

Determination of Planetary Boundary Layer Height from Ground Based Wind Profiler and Lidar Measurements using the Covariance Wavelet Transform (CWT)  

NASA Astrophysics Data System (ADS)

This thesis documents the application of the Covariance Wavelet Transform (CWT) to lidar and, for the first time to our knowledge, wind profiler data to examine the possibility of accurate and continuous planetary boundary layer height (PBLH) measurements on short temporal resolution (one and fifteen minute averages respectively). Comparisons between PBLHs derived from the Elastic Lidar Facility (ELF) through application of the CWT and daytime radiosonde launches from Beltsville and RFK Stadium as part of the September 2009 NOAA/ARL and NCEP field study show an R2 = 0.84 correlation. PBLHs from ELF aided in diagnosing issues with the automatic PBLH calculation from Aircraft Communications Addressing and Reporting System (ACARS) profiles in the Real-Time Mesoscale Analysis used by plume dispersion modelers. Determining the mixing in the PBL was one goal of a study of the spatial and diurnal variations of the PBL height over Maryland for July 2011, during NASA's Earth Venture mission DISCOVER-AQ. A semi-automated PBLH detection algorithm utilizing the CWT for wind profiler data was developed. This algorithm was tested on data from the 915 MHz wind profiler at Beltsville, Maryland, and compared against PBLHs derived from ground based radiosondes measured at Beltsville. Comparisons were also done between PBLHs derived from ground based lidars at UMBC and Beltsville. Results from the comparison show an R 2 = 0.89, 0.92, and 0.94 correlation between the radiosonde PBLHs and the lidars and wind profiler PBLHs, respectively. Accurate determination of the PBLH by applying the CWT to lidar and wind profilers will allow for improved air quality forecasting and understanding of regional pollution dynamics.

Compton, Jaime Cole

350

Satellite-derived cloud climatology over high elevation areas based on circulation types: A 2007 analysis of the Tatra Mountains  

NASA Astrophysics Data System (ADS)

Mountain ecosystems are unique due to their valuable nature and their specific interaction with the atmosphere. Nowhere else do clouds interact directly with the terrestrial surface as often as on mountains. Cloud water deposition may play a key role in the hydrological cycle, but when a cloud is populated with acidic ions, cloud pollution deposition may lead to ecosystem damage. The investigation of this process required the total amount of clouds, which is closely related to the circulation schemes that reflect the direction of polluted air advection, among other data. In this study, Moderate-Resolution Imaging Spectroradiometer (MODIS) cloud mask data were used instead of the traditional (surface based) information to obtain a continuous spatial distribution of the total cloud amount over the Tatra Mountains in 2007. The daily means of the total cloud amount were grouped according to the locally oriented atmospheric circulation type classification. The final maps indicated situations of atmospheric flow blocking phenomenon and a cloud amount rise that is typical of this process. Simultaneously, with the application of a digital elevation model (DEM), the cloud amount change with regard to the terrain elevation was calculated and characterised for each circulation type. The possibility of inversion detection was accented. Utilisation of both horizontal and vertical cloud amount information within predefined circulation types helps to improve the determination of hazardous zones of cloud pollution deposition in mountains.

Kotarba, Andrzej Z.

351

Ship-Track Clouds, Aerosol, and Ship Dynamic Effects; A Climate Perspective from Ship-Based Measurements  

SciTech Connect

Ship-track clouds are marine boundary layer clouds that form behind ocean ships and are observed from satellites in the visible and near infrared. Ship-track clouds provide a rare opportunity to connect aerosol cloud condensation nuclei (CCN) emissions and observable changes in marine stratiform clouds. A very small change in the reflectivity of these eastern Pacific and Atlantic clouds (about 4%) provides a climate feedback of similar magnitude to doubling CO{sub 2} (increasing cloud reflectivity corresponds to global cooling). The Department of Energy sponsored research from 1991 to 1995 to study ship-track clouds including two ocean-based experiments in the summers of 1991 and 1994. These experiments showed that ship-track cloud properties were often more complex those related to a reduction of droplet size with an increase in number associated with increasing CCN from the ship's plume. The clouds showed evidence of morphological changes more likely to be associated with cloud dynamic effects either initiated by the increased CCN or directly by the ship's heat output or turbulent air wake. The fact that marine stratiform clouds, that are susceptible to ship track formation, are starved for both CCN and convective turbulence complicates the separation of the two effects.

Porch, W.M.

1998-10-13

352

Nowcasting of cloud cover with MSG  

NASA Astrophysics Data System (ADS)

In this poster, an algorithm is shown to detect water and ice clouds seperately and forecast their developement for the next timesteps. It is based on Meteosat SEVIRI (Spinning Enhanced Visible and Infrared Imager) data from almost all channels with a timestep of 15 minutes. In order to derive cloud cover, optical depth and height of ice clouds the "Cirrus Optical properties derived from CALIOP and SEVIRI during day and night" (COCS) algorithm (Kox 2012) was used. For the determination of water clouds a cloud mask was developed. For a most accurate forecast the detected clouds are divided into two groups, convective and advective, and afterwards treated seperately. The forecast of advective clouds basically takes place with the pyramidal matcher ("optical flow" technique, Zinner et al. 2008) by determining a motion vector field from two consecutive images. The clouds are then classified as objects with similar properties (optical depth, temperature) and a forecast for each object separately is then performed. For the detection of convective clouds the tracking and nowcasting algorithm Cb-TRAM (CumulonimBus TRacking And Monitoring, Zinner et al. 2008) is used, which divides convection into three stages. The further development und thus the forecast of these clouds is dependent of the current stage. Appications to selected case studies will be shown.

Sirch, Tobias; Bugliaro, Luca

2014-05-01

353

Clouds Roll in for Martian Winter  

NASA Technical Reports Server (NTRS)

Using its left navigation camera, the Mars Exploration Rover Opportunity sought to capture some clouds on its 153rd sol on Mars (June 28, 2004). The presence of morning clouds in the area of Endurance Crater was established by spacecraft orbiting Mars. Mars has three kinds of clouds: dust clouds low in the atmosphere; water clouds near the surface up to heights of 20 kilometers (about 12 miles); and carbon dioxide clouds at very high altitudes.

Just as on Earth, clouds, especially water clouds, are good tracers of the weather. Based on orbital data, more clouds are expected during the martian winter. As this change occurs, the rover's cameras and miniature thermal emission spectrometer will track other changes that occur as the clouds accumulate.

The rovers provide a unique opportunity to examine the lower portion of Mars' atmosphere. The lower atmosphere is difficult to characterize from orbit, but it is critical because that is where the atmosphere interacts with the surface. Since the rovers landed, the science team has been using the rover's miniature thermal emission spectrometer instrument to see the weather at this bottom layer.

2004-01-01

354

2D Radiative Processes Near Cloud Edges  

NASA Technical Reports Server (NTRS)

Because of the importance and complexity of dynamical, microphysical, and radiative processes taking place near cloud edges, the transition zone between clouds and cloud free air has been the subject of intense research both in the ASR program and in the wider community. One challenge in this research is that the one-dimensional (1D) radiative models widely used in both remote sensing and dynamical simulations become less accurate near cloud edges: The large horizontal gradients in particle concentrations imply that accurate radiative calculations need to consider multi-dimensional radiative interactions among areas that have widely different optical properties. This study examines the way the importance of multidimensional shortwave radiative interactions changes as we approach cloud edges. For this, the study relies on radiative simulations performed for a multiyear dataset of clouds observed over the NSA, SGP, and TWP sites. This dataset is based on Microbase cloud profiles as well as wind measurements and ARM cloud classification products. The study analyzes the way the difference between 1D and 2D simulation results increases near cloud edges. It considers both monochromatic radiances and broadband radiative heating, and it also examines the influence of factors such as cloud type and height, and solar elevation. The results provide insights into the workings of radiative processes and may help better interpret radiance measurements and better estimate the radiative impacts of this critical region.

Varnai, T.

2012-01-01

355

Measuring Height without a Stadiometer  

PubMed Central

Objectives To compare whether four methods to measure or estimate height among wheelchair users result in significantly different estimates and to determine which method is most accurate. Design Height data were obtained for 141 wheelchair users. Height estimates included asking for self-report and measuring recumbent length, knee height, and armspan. All analyses were conducted separately for men and women. A two-group confirmatory factor analysis assessed which measure provided the best estimate of height in this population. It also tested the measurement invariance of the four height estimates between men and women and whether there were significant differences across these estimates within each sex. Results CFA findings indicated that the four measures yielded significantly different height estimates and BMI values for both men and women. For both sexes, armspan resulted in the longest estimate and measured recumbent length the shortest, with the reverse pattern for BMI values. The common variance estimates were outstanding for recumbent length (92%) and knee height (>83%) and very good for self-report (>75%), while the common variance for armspan was poor (<42%). Conclusions The measurement method used to estimate height yields significantly different values for both height and BMI among wheelchair users who cannot stand to be measured using a stadiometer. Recumbent length yields the most accurate height estimate for wheelchair users. However, when logistical and practical considerations pose difficulties for obtaining this measure, height estimates based on knee height and self-report may provide reasonable alternatives.

Froehlich-Grobe, Katherine; Nary, Dorothy E.; Van Sciver, Angela; Lee, Jaehoon; Little, Todd D.

2011-01-01

356

Cloud Computing  

Microsoft Academic Search

Cloud computing is an emerging computing and business model where users can gain access to their applications from anywhere\\u000a through their connected devices. The proliferation of intelligent mobile devices, high speed wireless connectivity, and rich\\u000a browser-based Web 2.0 interfaces have made this shared network-based cloud computing model possible. Cloud Computing is very\\u000a much driven by the increasingly unmanageable IT complexity.

George Wang

2009-01-01

357

An intercomparison of radar-based liquid cloud microphysics retrievals and implications for model evaluation studies  

NASA Astrophysics Data System (ADS)

This paper presents a statistical comparison of three cloud retrieval products of the Atmospheric Radiation Measurement (ARM) program at the Southern Great Plains (SGP) site from 1998 to 2006: MICROBASE, University of Utah (UU), and University of North Dakota (UND) products. The probability density functions of the various cloud liquid water content (LWC) retrievals appear to be consistent with each other. While the mean MICROBASE and UU cloud LWC retrievals agree well in the middle of cloud, the discrepancy increases to about 0.03 gm-3 at cloud top and cloud base. Alarmingly large differences are found in the droplet effective radius (re) retrievals. The mean MICROBASE re is more than 6 ?m lower than the UU re, whereas the discrepancy is reduced to within 1 ?m if columns containing raining and/or mixed-phase layers are excluded from the comparison. A suite of stratified comparisons and retrieval experiments reveal that the LWC difference stems primarily from rain contamination, partitioning of total liquid later path (LWP) into warm and supercooled liquid, and the input cloud mask and LWP. The large discrepancy among the re retrievals is mainly due to rain contamination and the presence of mixed-phase layers. Since rain or ice particles are likely to dominate radar backscattering over cloud droplets, the large discrepancy found in this paper can be thought of as a physical limitation of single-frequency radar approaches. It is therefore suggested that data users should use the retrievals with caution when rain and/or mixed-phase layers are present in the column.

Huang, D.; Zhao, C.; Dunn, M.; Dong, X.; Mace, G. G.; Jensen, M. P.; Xie, S.; Liu, Y.

2012-06-01

358

Long-term impacts of aerosols on vertical development of cloud and precipitation  

SciTech Connect

Aerosols alter cloud density and the radiative balance of the atmosphere. This leads to changes in cloud microphysics and atmospheric stability, which can either suppress or foster the development of clouds and precipitation. The net effect is largely unknown, but depends on meteorological conditions and aerosol properties. Here, we examine the long-term impact of aerosols on the vertical development of clouds and rainfall frequencies, using a 10-year dataset of aerosol, cloud and meteorological variables collected in the Southern Great Plains in the United States. We show that cloud-top height and thickness increase with aerosol concentration measured near the ground in mixed-phase clouds-which contain both liquid water and ice-that have a warm, low base. We attribute the effect, which is most significant in summer, to an aerosol-induced invigoration of upward winds. In contrast, we find no change in cloud-top height and precipitation with aerosol concentration in clouds with no ice or cool bases. We further show that precipitation frequency and rain rate are altered by aerosols. Rain increases with aerosol concentration in deep clouds that have a high liquid-water content, but declines in clouds that have a low liquid-water content. Simulations using a cloud-resolving model confirm these observations. Our findings provide unprecedented insights of the long-term net impacts of aerosols on clouds and precipitation.

Li Z.; Liu Y.; Niu, F.; Fan, J.; Rosenfeld, D.; Ding, Y.

2011-11-13

359

Solar coupling to clouds through the global electric circuit  

NASA Astrophysics Data System (ADS)

Earth's global electric circuit extends from the planet's surface to the Ionosphere, coupling the two regions by permitting vertical current flow. The upper and lower horizontal edges of non-thunderstorm layer clouds acquire charge as a consequence of this current flow, due to the sharp vertical gradient in electrical conductivity that exists between the cloud and clear air regions. Such cloud edge charging results in electrification of cloud droplets, which can influence some cloud microphysical processes and potentially provides one source of variability in the macroscopic properties of clouds. Above the Earth's surface, the atmosphere's electrical conductivity is mainly from ionisation due to Galactic Cosmic Rays (GCRs), which vary with solar activity on many different timescales. Solar modulation of GCRs allows the global electric circuit to convey a solar influence to the lower atmosphere, and, potentially to some meteorological phenomena through modulation of cloud properties through electrified cloud edges. Evidence for a microphysical response to the global circuit at a horizontal cloud boundary is supported by the presence of a diurnal oscillation in the height of the cloud base in the both the Arctic and Antarctic during polar night, which is similar in phase to that of the Carnegie curve in global atmospheric electricity. In order to improve knowledge of possible atmospheric electrical effects on layer clouds, a campaign of experiments with new instrumentation has been undertaken, taking advantage of in-situ measurements. These have been made from a free balloon platform, using specially developed disposable instrumentation capable of measuring charge and optical cloud properties inside non-thunderstorm clouds. The combined sensor package monitors the cloud and electrical properties simultaneously, using a solar radiation sensor, cloud droplet sensor and a charge sensor, providing a new approach to obtaining high vertical resolution measurements of cloud boundaries. These measurements will be discussed in terms of the typical distribution of charge present in layer clouds, and the potential implications of the charging observed on cloud microphysical processes.

Nicoll, K.; Harrison, R.

2013-12-01

360

Targeting and impacts of AgI cloud seeding based on rain chemical composition and cloud top phase characterization  

NASA Astrophysics Data System (ADS)

During four winters when cloud seeding took place, precipitation samples were collected at three stations in the catchment area of the Sea of Galilee (target stations) and in one station west of the seeding line (control station). Chemical analyses were carried out on more than 4000 rain samples in order to determine the major and trace metal compositions and enrichment factors of Ag (EF) with respect to Al, where Al is used as a tracer for natural dust. In addition, satellite images were analyzed to characterize the cloud phase and the temperature of the tops of the rain clouds using the EUMETSAT second generation geostationary satellite. Our results show that the seeding agent (AgI) arrives to the target stations, as indicated by significantly higher EFAg values of Ag there compared to the control station. Furthermore, we found higher EFAg values in precipitation samples from mixed-phase clouds compared to precipitation from warm or fully glaciated clouds. This difference was observed only at the target stations. Therefore, our results are consistent with the hypothesis that AgI contributes actively to precipitation formation processes in mixed-phase clouds, where ice content is controlled by ice nuclei (IN) concentration. This is in accordance with the conventional wisdom that AgI should be mostly active in such clouds, but not in clouds that are already naturally glaciated or in warm clouds, and it supports previous statistical studies which claimed that cloud seeding enhanced rainfall in Northern Israel.

Zipori, Assaf; Rosenfeld, Daniel; Shpund, Jacob; Steinberg, David M.; Erel, Yigal

2012-10-01

361

TPM: cloud-based tele-PTSD monitor using multi-dimensional information.  

PubMed

An automated system that can remotely and non-intrusively screen individuals at high risk for Post-Traumatic Stress Disorder (PTSD) and monitor their progress during treatment would be desired by many Veterans Affairs (VAs) as well as other PTSD treatment and research organizations. In this paper, we present an automated, cloud-based Tele-PTSD Monitor (TPM) system based on the fusion of multiple sources of information. The TPM system can be hosted in a cloud environment and accessed through landline or cell phones, or on the Internet through a web portal or mobile application (app). PMID:23400205

Xu, Roger; Mei, Gang; Zhang, Guangfan; Gao, Pan; Pepe, Aaron; Li, Jiang

2013-01-01

362

A cloud-based x73 ubiquitous mobile healthcare system: design and implementation.  

PubMed

Based on the user-centric paradigm for next generation networks, this paper describes a ubiquitous mobile healthcare (uHealth) system based on the ISO/IEEE 11073 personal health data (PHD) standards (X73) and cloud computing techniques. A number of design issues associated with the system implementation are outlined. The system includes a middleware on the user side, providing a plug-and-play environment for heterogeneous wireless sensors and mobile terminals utilizing different communication protocols and a distributed "big data" processing subsystem in the cloud. The design and implementation of this system are envisaged as an efficient solution for the next generation of uHealth systems. PMID:24737958

Ji, Zhanlin; Ganchev, Ivan; O'Droma, Máirtín; Zhang, Xin; Zhang, Xueji

2014-01-01

363

A Cloud-Based X73 Ubiquitous Mobile Healthcare System: Design and Implementation  

PubMed Central

Based on the user-centric paradigm for next generation networks, this paper describes a ubiquitous mobile healthcare (uHealth) system based on the ISO/IEEE 11073 personal health data (PHD) standards (X73) and cloud computing techniques. A number of design issues associated with the system implementation are outlined. The system includes a middleware on the user side, providing a plug-and-play environment for heterogeneous wireless sensors and mobile terminals utilizing different communication protocols and a distributed “big data” processing subsystem in the cloud. The design and implementation of this system are envisaged as an efficient solution for the next generation of uHealth systems.

Ji, Zhanlin; O'Droma, Mairtin; Zhang, Xin; Zhang, Xueji

2014-01-01

364

A Wing Pod-based Millimeter Wave Cloud Radar on HIAPER  

NASA Astrophysics Data System (ADS)

One of the attractive features of a millimeter wave radar system is its ability to detect micron-sized particles that constitute clouds with lower than 0.1 g m-3 liquid or ice water content. Scanning or vertically-pointing ground-based millimeter wavelength radars are used to study stratocumulus (Vali et al. 1998; Kollias and Albrecht 2000) and fair-weather cumulus (Kollias et al. 2001). Airborne millimeter wavelength radars have been used for atmospheric remote sensing since the early 1990s (Pazmany et al. 1995). Airborne millimeter wavelength radar systems, such as the University of Wyoming King Air Cloud Radar (WCR) and the NASA ER-2 Cloud Radar System (CRS), have added mobility to observe clouds in remote regions and over oceans. Scientific requirements of millimeter wavelength radar are mainly driven by climate and cloud initiation studies. Survey results from the cloud radar user community indicated a common preference for a narrow beam W-band radar with polarimetric and Doppler capabilities for airborne remote sensing of clouds. For detecting small amounts of liquid and ice, it is desired to have -30 dBZ sensitivity at a 10 km range. Additional desired capabilities included a second wavelength and/or dual-Doppler winds. Modern radar technology offers various options (e.g., dual-polarization and dual-wavelength). Even though a basic fixed beam Doppler radar system with a sensitivity of -30 dBZ at 10 km is capable of satisfying cloud detection requirements, the above-mentioned additional options, namely dual-wavelength, and dual-polarization, significantly extend the measurement capabilities to further reduce any uncertainty in radar-based retrievals of cloud properties. This paper describes a novel, airborne pod-based millimeter wave radar, preliminary radar measurements and corresponding derived scientific products. Since some of the primary engineering requirements of this millimeter wave radar are that it should be deployable on an airborne platform, occupy minimum cabin space and maximize scan coverage, a pod-based configuration was adopted. Currently, the radar system is capable of collecting observations between zenith and nadir in a fixed scanning mode. Measurements are corrected for aircraft attitude changes. The near-nadir and zenith pointing observations minimize the cross-track Doppler contamination in the radial velocity measurements. An extensive engineering monitoring mechanism is built into the recording system status such as temperature, pressure, various electronic components' status and receiver characteristics. Status parameters are used for real-time system stability estimates and correcting radar system parameters. The pod based radar system is mounted on a modified Gulfstream V aircraft, which is operated and maintained by the National Center for Atmospheric Research (NCAR) on behalf of the National Science Foundation (NSF). The aircraft is called the High-Performance Instrumented Airborne Platform for Environmental Research (HIAPER) (Laursen et al., 2006). It is also instrumented with high spectral resolution lidar (HSRL) and an array of in situ and remote sensors for atmospheric research. As part of the instrument suite for HIAPER, the NSF funded the development of the HIAPER Cloud Radar (HCR). The HCR is an airborne, millimeter-wavelength, dual-polarization, Doppler radar that serves the atmospheric science community by providing cloud remote sensing capabilities for the NSF/NCAR G-V (HIAPER) aircraft. An optimal radar configuration that is capable of maximizing the accuracy of both qualitative and quantitative estimated cloud microphysical and dynamical properties is the most attractive option to the research community. The Technical specifications of cloud radar are optimized for realizing the desired scientific performance for the pod-based configuration. The radar was both ground and flight tested and preliminary measurements of Doppler and polarization measurements were collected. HCR observed sensitivity as low as -37 dBZ at 1 km range and resolved linear depolarization ratio (LDR) si

Vivekanandan, Jothiram; Tsai, Peisang; Ellis, Scott; Loew, Eric; Lee, Wen-Chau; Emmett, Joanthan

2014-05-01

365

Ground Based Retrievals of Cloud Properties for Liquid, Glaciated and Mixed Phase Conditions  

NASA Astrophysics Data System (ADS)

Cirrus cloud microphysical data from recent field programs using new instruments tend to minimize or remove the problem of ice particle shattering. These measurements suggest that in most instances, the anomalously high concentrations of small ice crystals reported in earlier in situ measurements are absent. These earlier measurements of small crystals indicated an abrupt increase in concentration for ice particle lengths around 60 ?m and smaller, resulting in a "small particle mode." In addition, a new methodology we developed for satellite and ground-based remote sensing indicates that this small mode is either absent or lower in amplitude than earlier aircraft measurements have indicated. Remote sensing results presented on our website (http://www.dri.edu/Projects/Mitchell/) address both anvil and in situ synoptic cirrus in tropical and mid-latitude regions. This leads us to hypothesize that, in general, ice particle size distributions (PSD) are monomodal. This study applies this hypothesis to mixed phase clouds to estimate the ice water path (IWP) and liquid water path (LWP). When our remote sensing method indicates the cloud PSD as bimodal, the small mode is attributed to liquid water while the large mode is attributed to ice particles. Data from Mixed-Phase Arctic Cloud Experiment (M-PACE), conducted at the north slope of Alaska (winter 2004), have been used to test this new method for retrieving the LWP and IWP. The framework of the retrieval algorithm consists of the modified anomalous diffraction approximation (MADA) for mixed phase cloud optical properties, a radar reflectivity-ice microphysics relationship and a temperature-dependent ice PSD scheme. Cloud thermal emission measurements made by the ground-based Atmospheric Emitted Radiance Interferometer (AERI) yield information on the total water path (TWP) while reflectivity measurements from the Millimeter Cloud Radar (MMCR) in combination with the ice PSD slope are used to derive the IWP. This provides one estimate of the LWP/TWP fraction. Another estimate is obtained by applying the principle of photon tunneling or wave resonance to radiances at 11 and 12 ?m, which allows us to infer the magnitude or absence of a small mode for the retrieved PSD. Combining this small mode information with the PSD scheme describing the larger ice particle concentrations yields the retrieved PSD. While this is a work in progress, the anticipated products from this AERI-radar retrieval scheme are the IWP/IWC, LWP/TWP fraction, and LWP for mixed phase clouds and IWP/IWC, PSD slope and effective diameter for cirrus clouds. This information can be extremely useful in characterizing cloud microphysical propertied in Global Climate Models (GCMs). For example, Arctic clouds are often mixed phase and play a major role in Arctic climate, and need to be characterized in GCMs. Moreover, the PSD slope can be used to estimate ice sedimentation rates, a critical parameter affecting cirrus cloud lifetime, IWP and coverage. The fact that (1) IWP retrieved from the MMCR radar was generally consistent with the AERI TWP in glaciated regions and that (2) these retrievals were independent and based on very different physics appears promising for using this approach to approximate IWP and LWP in mixed phase clouds. This technique appears particularly useful for characterization of liquid and mixed phase clouds having TWP < 100 gm-2, a range where traditional methods have exhibited insufficient accuracy.

Mishra, S.; Mitchell, D. L.; Deslover, D.

2008-12-01

366

Retrieval of mixing height and dust concentration with lidar ceilometer  

NASA Astrophysics Data System (ADS)

The Vaisala ceilometers CT25K and CL31 are eye-safe single lens lidar systems reporting attenuated backscatter profiles; they often operate 24 h a day in fully automated, hands-off operation mode. These profiles can be used for more than just cloud-base height determination. In dry weather situations, there is a fairly good correlation between the ceilometer near-range backscatter and in situ PM10 concentration readings. The comparison of mixing height values based on soundings and on ceilometer backscattering profiles indicates that ceilometers are suitable instruments for determining the convective mixing height. Its enhanced optics and electronics enables the CL31 ceilometer to detect fine boundary-layer structures whose counterparts are seen in temperature profiles.

Münkel, Christoph; Eresmaa, Noora; Räsänen, Janne; Karppinen, Ari

2007-07-01

367

Remote sensing of cloud optical properties from ground-based measurements of transmittance: A feasibility study  

SciTech Connect

The authors present a retrieval technique for the influence of cloud optical depth from data obtained by a ground-based multichannel radiometer for use in climate-related studies. The basic steps of the analysis procedure are considered, including accurate calculations of the atmosphere and cloud properties. An approach is described that uses observed and model-simulated transmittances rather than irradiances and that does not depend on an absolute calibration of the instrument. This approach, which specifically deals with the transmittances, also offers substantial computational advantages. The resulting algorithm is applied (but not limited) to the measurements of incoming solar irradiance by a particular ground-based instrument, the so-called Multi-Filter Rotating Shadowband Radiometer (MFRSR). Sample results of inferred cloud optical depth obtained from MFRSR measurements in Fairbanks, Alaska, are presented. 27 refs., 13 figs., 2 tabs.

Leontieva, E.; Stamnes, K. [Univ. of Alaska, Fairbanks, AK (United States)] [Univ. of Alaska, Fairbanks, AK (United States)

1996-11-01

368

A cloud computing based platform for sleep behavior and chronic diseases collaborative research.  

PubMed

The objective of this study is to propose a Cloud Computing based platform for sleep behavior and chronic disease collaborative research. The platform consists of two main components: (1) a sensing bed sheet with textile sensors to automatically record patient's sleep behaviors and vital signs, and (2) a service-oriented cloud computing architecture (SOCCA) that provides a data repository and allows for sharing and analysis of collected data. Also, we describe our systematic approach to implementing the SOCCA. We believe that the new cloud-based platform can provide nurse and other health professional researchers located in differing geographic locations with a cost effective, flexible, secure and privacy-preserved research environment. PMID:24943526

Kuo, Mu-Hsing; Borycki, Elizabeth; Kushniruk, Andre; Huang, Yueh-Min; Hung, Shu-Hui

2014-01-01

369

Curb-Based Street Floor Extraction from Mobile Terrestrial LIDAR Point Cloud  

NASA Astrophysics Data System (ADS)

Mobile terrestrial laser scanners (MTLS) produce huge 3D point clouds describing the terrestrial surface, from which objects like different street furniture can be generated. Extraction and modelling of the street curb and the street floor from MTLS point clouds is important for many applications such as right-of-way asset inventory, road maintenance and city planning. The proposed pipeline for the curb and street floor extraction consists of a sequence of five steps: organizing the 3D point cloud and nearest neighbour search; 3D density-based segmentation to segment the ground; morphological analysis to refine out the ground segment; derivative of Gaussian filtering to detect the curb; solving the travelling salesman problem to form a closed polygon of the curb and point-inpolygon test to extract the street floor. Two mobile laser scanning datasets of different scenes are tested with the proposed pipeline. The results of the extracted curb and street floor are evaluated based on a truth data. The obtained detection rates for the extracted street floor for the datasets are 95% and 96.53%. This study presents a novel approach to the detection and extraction of the road curb and the street floor from unorganized 3D point clouds captured by MTLS. It utilizes only the 3D coordinates of the point cloud.

Ibrahim, S.; Lichti, D.

2012-07-01

370

Model-Based Estimation of Forest Canopy Height in Red and Austrian Pine Stands Using Shuttle Radar Topography Mission and Ancillary Data: a Proof-of-Concept Study  

SciTech Connect

In this paper, accurate tree stand height retrieval is demonstrated using C-band Shuttle Radar Topography Mission (SRTM) height and ancillary data. The tree height retrieval algorithm is based on modeling uniform tree stands with a single layer of randomly oriented vegetation particles. For such scattering media, the scattering phase center height, as measured by SRTM, is a function of tree height, incidence angle, and the extinction coefficient of the medium. The extinction coefficient for uniform tree stands is calculated as a function of tree height and density using allometric equations and a fractal tree model. The accuracy of the proposed algorithm is demonstrated using SRTM and TOPSAR data for 15 red pine and Austrian pine stands (TOPSAR is an airborne interferometric synthetic aperture radar). The algorithm yields root-mean-square (rms) errors of 2.5-3.6 m, which is a substantial improvement over the 6.8-8.3-m rms errors from the raw SRTM minus National Elevation Dataset Heights.

Brown Jr., C G; Sarabandi, K; Pierce, L E

2007-04-06

371

A point cloud segmentation method based on vector estimation and color clustering  

Microsoft Academic Search

For automatic processing of point clouds, the segmentation is a key but difficult step. Many researchers have tried to develop segmentation methods including edge-based segmentation, surface-based segmentation and color-based segmentation, and so on. In this paper, we present a point data segmentation method based on normal vector estimation and color clustering. The main workflow of this method is made by

Qingming Zhan; Liang Yu; Yubing Liang

2010-01-01

372

Height control of laser metal-wire deposition based on iterative learning control and 3D scanning  

NASA Astrophysics Data System (ADS)

Laser Metal-wire Deposition is an additive manufacturing technique for solid freeform fabrication of fully dense metal structures. The technique is based on robotized laser welding and wire filler material, and the structures are built up layer by layer. The deposition process is, however, sensitive to disturbances and thus requires continuous monitoring and adjustments. In this work a 3D scanning system is developed and integrated with the robot control system for automatic in-process control of the deposition. The goal is to ensure stable deposition, by means of choosing a correct offset of the robot in the vertical direction, and obtaining a flat surface, for each deposited layer. The deviations in the layer height are compensated by controlling the wire feed rate on next deposition layer, based on the 3D scanned data, by means of iterative learning control. The system is tested through deposition of bosses, which is expected to be a typical application for this technique in the manufacture of jet engine components. The results show that iterative learning control including 3D scanning is a suitable method for automatic deposition of such structures. This paper presents the equipment, the control strategy and demonstrates the proposed approach with practical experiments.

Herali?, Almir; Christiansson, Anna-Karin; Lennartson, Bengt

2012-09-01

373

Physics-Based Visualization of Dense Natural Clouds. II. Cloud-Rendering Algorithm  

Microsoft Academic Search

We discuss the representation of aerosol-scattering properties, boundary information, and the use of these results in line-of-sight rendering applications for visualization of a modeled atmosphere based on a discrete ordinates three-dimensional radiative-transport method. The outputs of the radiative-transfer model provide spatial and angular distributions of limiting path radiance, given an input density distribution and external illumination conditions. We discuss the

Sean G. O'Brien; David H. Tofsted

1998-01-01

374

The interdependence of continental warm cloud properties derived from unexploited solar background signal in ground-based lidar measurements  

NASA Astrophysics Data System (ADS)

We have extensively analysed the interdependence between cloud optical depth, droplet effective radius, liquid water path (LWP) and geometric thickness for stratiform warm clouds using ground-based observations. In particular, this analysis uses cloud optical depths retrieved from untapped solar background signal that is previously unwanted and needs to be removed in most lidar applications. Combining these new optical depth retrievals with radar and microwave observations at the Atmospheric Radiation Measurement (ARM) Climate Research Facility in Oklahoma during 2005-2007, we have found that LWP and geometric thickness increase and follow a power-law relationship with cloud optical depth regardless of the presence of drizzle; LWP and geometric thickness in drizzling clouds can be generally 20-40% and at least 10% higher than those in non-drizzling clouds, respectively. In contrast, droplet effective radius shows a negative correlation with optical depth in drizzling clouds, while it increases with optical depth and reaches an asymptote of 10 ?m in non-drizzling clouds. This asymptotic behaviour in non-drizzling clouds is found in both droplet effective radius and optical depth, making it possible to use simple thresholds of optical depth, droplet size, or a combination of these two variables for drizzle delineation. This paper demonstrates a new way to enhance ground-based cloud observations and drizzle delineations using existing lidar networks.

Chiu, J. C.; Holmes, J. A.; Hogan, R. J.; O'Connor, E. J.

2014-04-01

375

Dual-FOV Raman and Doppler lidar studies of aerosol-cloud interactions: Simultaneous profiling of aerosols, warm-cloud properties, and vertical wind  

NASA Astrophysics Data System (ADS)

For the first time, colocated dual-field of view (dual-FOV) Raman lidar and Doppler lidar observations (case studies) of aerosol and cloud optical and microphysical properties below and within thin layered liquid water clouds are presented together with an updraft and downdraft characterization at cloud base. The goal of this work is to investigate the relationship between aerosol load close to cloud base and cloud characteristics of warm (purely liquid) clouds and the study of the influence of vertical motions and turbulent mixing on this relationship. We further use this opportunity to illustrate the applicability of the novel dual-FOV Raman lidar in this field of research. The dual-FOV lidar combines the well-established multiwavelength Raman lidar technique for aerosol retrievals and the multiple-scattering Raman lidar technique for profiling of the single-scattering extinction coefficient, effective radius, number concentration of the cloud droplets, and liquid water content. Key findings of our 3 year observations are presented in several case studies of optically thin altocumulus layers occurring in the lower free troposphere between 2.5 and 4 km height over Leipzig, Germany, during clean and polluted situations. For the clouds that we observed, the most direct link between aerosol proxy (particle extinction coefficient) and cloud proxy (cloud droplet number concentration) was found at cloud base during updraft periods. Above cloud base, additional processes resulting from turbulent mixing and entrainment of dry air make it difficult to determine the direct impact of aerosols on cloud processes.

Schmidt, Jörg; Ansmann, Albert; Bühl, Johannes; Baars, Holger; Wandinger, Ulla; Müller, Detlef; Malinka, Aleksey V.

2014-05-01

376

Two Cloud-Based Cues for Estimating Scene Structure and Camera Calibration.  

PubMed

We describe algorithms that use cloud shadows as a form of stochastically structured light to support 3D scene geometry estimation. Taking video captured from a static outdoor camera as input, we use the relationship of the time series of intensity values between pairs of pixels as the primary input to our algorithms. We describe two cues that relate the 3D distance between a pair of points to the pair of intensity time series. The first cue results from the fact that two pixels that are nearby in the world are more likely to be under a cloud at the same time than two distant clouds. We describe methods for using this cue to estimate focal length and scene structure. The second cue is based on the motion of shadow clouds across the scene; this cue results in a set of linear constraints on scene structure. These constraints have an inherent ambiguity, which we show how to overcome by combining the cloud motion cue with the spatial cue. We evaluate our method on several time lapses of real outdoor scenes. PMID:23509185

Jacobs, Nathan; Abrams, Austin; Pless, Robert

2013-03-01

377

A Tag Cloud-Based Visualization for Geo-Referenced Text Information  

NASA Astrophysics Data System (ADS)

Large amounts of geo-referenced text information such as messages from microblog websites are continuously becoming more popular. In this paper, we introduce a new visualization method based on tag clouds for geo-referenced text information. We process large amounts of geo-referenced text, using several visual metaphors including tag clouds, for the exploration of information on maps, instead of using just conventional cartographic approaches. The results show that this method can be useful for presentation and exploration of such geo-referenced text information.

Li, X.; Hua, Y.-X.; Zhao, J.-X.; Wang, L.-N.; Wang, P.

2013-11-01

378

The cloud radiative effect on the atmospheric energy budget and global mean precipitation  

NASA Astrophysics Data System (ADS)

This study seeks to explain the effects of cloud on changes in atmospheric radiative absorption that largely balance changes in global mean precipitation under climate change. The partial radiative perturbations (PRPs) due to changes in cloud and due to the effects of the pre-existing climatological cloud distribution on non-cloud changes, known as "cloud masking", are calculated when atmospheric CO2 concentration is doubled for the HadSM3 and MIROC models and for a large ensemble of parameter perturbed models based on HadSM3. Because the effect of cloud on changes in atmospheric shortwave absorption is almost negligible, longwave fluxes are analysed alone. We find that the net effects of cloud masking and cloud PRP on atmospheric absorption are both substantial. For the tropics, our results are reviewed in light of hypotheses put forward to explain cloud and radiative flux changes. We find that the major effects of clouds on radiation change are linked to known physical processes that are quite consistently simulated by models. Cloud top height changes are quite well described by the fixed anvil temperature hypothesis of Hartmann and Larson; cloud base heights change little, remaining near the same pressure. Changes in cloud geographical location and cloud amount are significant, but play a smaller role in driving radiative flux changes. Finally, because clouds are a large source of modelling uncertainty, we consider whether resolving errors in cloud simulation could reconcile modelled global mean precipitation trends of about 1-3 %{K}^{-1} with some estimates of observed trends of 7 %{K}^{-1} or more. This would require the radiative effect of clouds to change from one that increases atmospheric radiative absorption by about 0.5 {Wm}^{-2} {K}^{-1} to one that decreases it by -3.5 {Wm}^{-2} {K}^{-1} . Based on our results, this seems difficult to achieve within our current rationale for the tropics at least.

Lambert, F. Hugo; Webb, Mark J.; Yoshimori, Masakazu; Yokohata, Tokuta

2014-05-01

379

Resource allocation for cloud-based free viewpoint video rendering for mobile phones  

Microsoft Academic Search

Free viewpoint video (FVV) \\/ Free viewpoint TV (FTV) on mobile devices over cellular networks is very challenging due to the requirement for large bandwidth and limitations in computation and battery life on mobile phones. To address such challenges, in this paper we propose a cloud-based FVV \\/ FTV rendering framework for mobile devices over cellular networks. In this framework,

Dan Miao; Wenwu Zhu; Chong Luo; Chang Wen Chen

2011-01-01

380

Exploring Architecture Options for a Federated, Cloud-based System Biology Knowledgebase  

SciTech Connect

This paper evaluates various cloud computing technologies and resources for building a system biology knowledge base system. This system will host a huge amount of data and contain a flexible sets of workflows to operate on these data. It will enable system biologist to share their data and algorithms to allow research results to be reproduced, shared, and reused across the system biology community.

Gorton, Ian; Liu, Yan; Yin, Jian

2010-12-02

381

The framework of the fourth party mobile integrated payment platform based on cloud computing  

Microsoft Academic Search

This paper presents a framework for the fourth party mobile integrated payment platform based on cloud computing. The purposes of this paper are as follows: to solve the problem of departments segmentation during mobile payment development, to realize the barrier-free communication and integration of mobile payment industrial Chains, to cut down customer attrition cause by low usability of mobile payment.

Xu Young; Hu Qiqi

2010-01-01

382

Satellite approach based on cloud cover classification: Estimation of hourly global solar radiation from meteosat images  

Microsoft Academic Search

Hourly global solar irradiation data useful for the design of solar energy conversion systems is generated using a new satellite based model called SICIC (solar irradiation from cloud image classification). It is a model built by processing high resolution visible Meteosat images and ground measurements of solar radiation flux collected in various locations of France during the 1994\\/95 period. Taking

A. Mefti; A. Adane; M. Y. Bouroubi

2008-01-01

383