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1

Passive method for cloud base height detection  

NASA Astrophysics Data System (ADS)

Clouds cover a surface of Earth on the average on 50 % and are one of the major parameter of climate formation. Besides, knowledge of a local overcast condition play main role in aviation safety. The passive method of cloud base height detection with use of two spatially carried matrix photodetectors is offered. The cloud base height is detected by a triangulation method. This method is used in a geodesy and stereophotogrammetria. The essence of a method consists that on knowing distance between two points of monitoring and knowing corners of a direction on observing object, it is possible to define distance up to this object. For this case the same point of overcast is accepted for a marker and an angular coordinates of the marker is calculated separately for each photodetector. Besides, the given method allows to define not only height, but also a direction and speed of clouds movement.

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

2006-11-01

2

A novel technique for extracting clouds base height using ground based imaging  

NASA Astrophysics Data System (ADS)

The height of a cloud in the atmospheric column is a key parameter in its characterization. Several remote sensing techniques (passive and active, either ground-based or on space-borne platforms) and in-situ measurements are routinely used in order to estimate top and base heights of clouds. In this article we present a novel method that combines thermal imaging from the ground and sounded wind profile in order to derive the cloud base height. This method is independent of cloud types, making it efficient for both low boundary layer and high clouds. In addition, using thermal imaging ensures extraction of clouds' features during daytime as well as at nighttime. The proposed technique was validated by comparison to active sounding by ceilometers (which is a standard ground based method), to lifted condensation level (LCL) calculations, and to MODIS products obtained from space. As all passive remote sensing techniques, the proposed method extracts only the height of the lowest cloud layer, thus upper cloud layers are not detected. Nevertheless, the information derived from this method can be complementary to space-borne cloud top measurements when deep-convective clouds are present. Unlike techniques such as LCL, this method is not limited to boundary layer clouds, and can extract the cloud base height at any level, as long as sufficient thermal contrast exists between the radiative temperatures of the cloud and its surrounding air parcel. Another advantage of the proposed method is its simplicity and modest power needs, making it particularly suitable for field measurements and deployment at remote locations. Our method can be further simplified for use with visible CCD or CMOS camera (although nighttime clouds will not be observed).

Hirsch, E.; Agassi, E.; Koren, I.

2011-01-01

3

A novel technique for extracting clouds base height using ground based imaging  

NASA Astrophysics Data System (ADS)

The height of a cloud in the atmospheric column is a key parameter in its characterization. Several remote sensing techniques (passive and active, either ground-based or on space-borne platforms) and in-situ measurements are routinely used in order to estimate top and base heights of clouds. In this article we present a novel method that combines thermal imaging from the ground and sounded wind profile in order to derive the cloud base height. This method is independent of cloud types, making it efficient for both low boundary layer and high clouds. In addition, using thermal imaging ensures extraction of clouds' features during daytime as well as at nighttime. The proposed technique was validated by comparison to active sounding by ceilometers (which is a standard ground based method), to lifted condensation level (LCL) calculations, and to MODIS products obtained from space. As all passive remote sensing techniques, the proposed method extracts only the height of the lowest cloud layer, thus upper cloud layers are not detected. Nevertheless, the information derived from this method can be complementary to space-borne cloud top measurements when deep-convective clouds are present. Unlike techniques such as LCL, this method is not limited to boundary layer clouds, and can extract the cloud base height at any level, as long as sufficient thermal contrast exists between the radiative temperatures of the cloud and its surrounding air parcel. Another advantage of the proposed method is its simplicity and modest power needs, making it particularly suitable for field measurements and deployment at remote locations. Our method can be further simplified for use with visible CCD or CMOS camera (although nighttime clouds will not be observed).

Hirsch, E.; Agassi, E.; Koren, I.

2010-10-01

4

Cloud Base Height and Wind Speed Retrieval through Digital Camera Based Stereo Vision  

Microsoft Academic Search

Clouds are an important factor in Earth's climate system. In general, the height of the cloud determines if the cloud consists of water droplets or ice crystals which have large consequences on the radiative properties of the clouds. Also, the height plays a role on the interaction between aerosols and clouds. Furthermore, the height of low clouds is very important

F. M. Janeiro; F. Wagner; P. M. Ramos

2010-01-01

5

Intercomparison of Ground-Based Radar and Satellite Cloud-Top Height Retrievals for Overcast Single-Layered Cloud Fields  

Microsoft Academic Search

The objective of this paper is to assess the accuracy of the Semi-Analytical CloUd Retrieval Algorithm (SACURA) that retrieves cloud-top heights (CTHs) using hyperspectral SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) onboard Environmental Satellite measurements for overcast single-layer cloud fields. Intercomparisons with ground-based 35-GHz millimeter wave cloud radar CTHs were performed for 14 dates during 2003-2007 at the U.S.

Alexander A. Kokhanovsky; Catherine M. Naud; Abhay Devasthale

2009-01-01

6

Inferring Low Cloud Base Heights at Night for Aviation Using Satellite Infrared and Surface Temperature Data  

NASA Astrophysics Data System (ADS)

A nighttime image product that depicts areas of the lowest cloud base heights has been developed by combining brightness temperature data from the Geostationary Operational Environmental Satellite (GOES) Imager InfraRed (IR) bands centered at 3.9 µm and 10.7 µm, with hourly shelter temperatures from surface observing sites and offshore marine buoys. A dependent data sample showed a good correlation between the surface temperature minus IR cloud top temperature differences versus measured cloud base heights. Histogram analysis indicated that a temperature difference of less than 4-C related to a > 50% frequency of ceilings below 1000 ft above ground level, the threshold for Instrument Flight Rules (IFR). Using this result as a model, an experimental Low Cloud Base image product was developed that highlights regions of likely IFR ceilings. Validation of the Low Cloud Base product for two separate periods resulted in Probabilities of Detection of 67% and 72% and False Alarm Rates of 6% and 11%, respectively. Some regional variation observed could be related to the relative frequency of multi-layered overcast conditions. The biggest factor leading to underdetection of IFR ceilings by the GOES Low Cloud Base product is the presence of overlying clouds, including thin cirrus contamination. The GOES Low Cloud Base product shows potential for use as guidance for aviation meteorologists over both continental and marine areas.

Ellrod, Gary P.; Gultepe, Ismail

2007-06-01

7

The computation of cloud base height from paired whole-sky imaging cameras  

SciTech Connect

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 most important effect determining the magnitude of possible climate responses to human activity. Of particular value to reducing the uncertainties associated with cloud-radiation interactions is the measurement of cloud base height (CBH), both because it is a dominant factor in determining the infrared radiative properties of clouds with respect to the earth`s surface and lower atmosphere and because CBHs are essential to measuring cloud cover fraction. We have developed a novel approach to the extraction of cloud base height from pairs of whole sky imaging (WSI) cameras. The core problem is to spatially register cloud fields from widely separated WSI cameras; this complete, triangulation provides the CBH measurements. The wide camera separation (necessary to cover the desired observation area) and the self-similarity of clouds defeats all standard matching algorithms when applied to static views of the sky. To address this, our approach is based on optical flow methods that exploit the fact that modern WSIs provide sequences of images. We will describe the algorithm and present its performance as evaluated both on real data validated by ceilometer measurements and on a variety of simulated cases.

Allmen, M.C.; Kegelmeyer, W.P. Jr.

1994-03-01

8

An assessment of Multiangle Imaging Spectroradiometer (MISR) stereo-derived cloud top heights and cloud top winds using ground-based radar, lidar, and microwave radiometers  

Microsoft Academic Search

(1) In this article stereoscopically derived cloud top heights and cloud winds estimated from the Multiangle Imaging Spectroradiometer (MISR) are assessed. MISR is one of five instruments on board the NASATerra satellite. The cloud top height assessment is based on a comparison of more than 4 years of MISR retrievals with that derived from ground-based radar and lidar systems operated

Roger T. Marchand; Thomas P. Ackerman; Catherine Moroney

2007-01-01

9

An assessment of Multiangle Imaging Spectroradiometer (MISR) stereo-derived cloud top heights and cloud top winds using ground-based radar, lidar, and microwave radiometers  

Microsoft Academic Search

In this article stereoscopically derived cloud top heights and cloud winds estimated from the Multiangle Imaging Spectroradiometer (MISR) are assessed. MISR is one of five instruments on board the NASA Terra satellite. The cloud top height assessment is based on a comparison of more than 4 years of MISR retrievals with that derived from ground-based radar and lidar systems operated

Roger T. Marchand; Thomas P. Ackerman; Catherine Moroney

2007-01-01

10

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

Microsoft Academic Search

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

Hugh Joseph Christopher Pasika

2000-01-01

11

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

Microsoft Academic Search

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

Hugh Joseph Christopher Pasika

1999-01-01

12

Cloud base heights retrieved during night-time conditions with MODIS data  

Microsoft Academic Search

The capability to retrieve cloud base heights was developed under the US National Polar?orbiting Operational Environmental Satellite System (NPOESS) programme as one of 27 data products to be created from data collected by the Visible Infrared Imager Radiometer Suite (VIIRS). First launch of the VIIRS sensor, which is the high?resolution Earth imager of the NPOESS programme, comes on National Aeronautics

Keith Hutchison; Eric Wong; S. C. Ou

2006-01-01

13

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

14

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

15

Coupling Between Cloud Base Height and Land Surface Processes in Lowland Amazonia  

NASA Astrophysics Data System (ADS)

Investigating the coupling between vegetation and climate in lowland Amazonia is critical to understanding the importance of tropical forests to the region's hydrological cycle. Recent modelling studies illustrate the adverse consequences of land-use changes on cloud formation in tropical montane cloud forests, with deforestation resulting in an increasing cloud base height, or lifting condensation level (LCL). Similar circumstances may apply to lowland Amazonia; however, little research has been directed toward establishing the importance of feedback processes between LCL and vegetation in this region. By deriving the change in LCL under different climate scenarios, our aim is to quantify the relationship between LCL and vegetation cover in order to distinguish natural from anthropogenic components of land-atmosphere processes. Using the simulated surface temperature and specific humidity values generated by the Hadley Centre's coupled general circulation model HadCM3LC, we compute Amazonian LCL for five time periods: Last Glacial Maximum (LGM), Younger Dryas (YD), Pre-Industrial, Present Day and Future (IPCC IS92a scenario). Our results indicate that average LCL values for Present Day, Pre-Industrial and YD are similar, whereas LGM and Future values both exceed Present Day LCL. We analyze the relationship between LCL, evapotranspiration, precipitation and change in vegetation cover for each time period. The results of this analysis will be used to assess the impact of lowland deforestation on naturally-driven regional convective cloud formation. This project follows as part of an on-going research program aimed at exploring Amazonian forest-climate feedbacks over both short and long timescales.

Pinto, E. R.; Shin, Y.; Jones, C. D.; Cowling, S. A.

2005-12-01

16

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

17

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

18

Validation of SCIAMACHY O2 A band cloud heights using Cloudnet radar/lidar measurements  

NASA Astrophysics Data System (ADS)

For the first time two SCIAMACHY O2 A band cloud height products are validated using ground-based radar/lidar measurements between January 2003 and December 2011. The products are the ESA 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 one hour centered at the SCIAMACHY overpass time to achieve an optimal temporal and spatial match. In total we have about 220 cases of single layer clouds and 200 cases of multi-layer clouds. The FRESCO cloud height and ESA L2 cloud top height are compared with the Cloudnet cloud top height and Cloudnet cloud middle height. 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 0.44 km higher than the Cloudnet cloud top height, with a standard deviation of 3.07 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 -0.14 km with a standard deviation of 1.88 km. 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, which is 24 % percent of the data. 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, which is 85 % percent of the data. The results are similar for multi-layer clouds, but the percentage of cases having a bias within 1 km is smaller than for single layer clouds. Since globally about 60 % of all clouds are low clouds and 42 % are single-layer low clouds, we expect that globally for a large percentage of cases the FRESCO cloud height would be close to the cloud middle height.

Wang, P.; Stammes, P.

2013-10-01

19

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

20

Research of Confirming Height Rules of Human Characteristic Positions Based on 3D Point-Cloud Data  

Microsoft Academic Search

In this research, Point-cloud diagrams can be obtained by using 3D body scanner and then characteristic positions of the body (such as waist, abdomen and buttocks) can be confirmed. Then height of characteristic positions can be measured from diagrams by the software of Image-ware. The correlation relationship between height of characteristic positions and height can be analyzed by the software

Hai-yan Kong; Bing-fei Gu; Jun-qiang Su; Guo-lian Liu

2010-01-01

21

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

NASA Astrophysics Data System (ADS)

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 heights and subsequently calculates the spatial displacements of cloud images. Optimal parameterization of the piecewise linear approximation is achieved using the shuffled complex evolution (SCE) algorithm. Because the proposed method simplifies the stereoscopic analysis, it allows for an easy implementation of stereoscopic technique on desktop computers. When compared to the standard isotherm matching approaches, the proposed method yielded higher correlation between GOES 8 and GOES 9 scan-simultaneous images after the parallax adjustment. The validity of the linear approximation was tested against temperature profiles obtained from the multiple ground sounding measurements from the Tropical Rainfall Measuring Mission/Texas and Florida Underflights (TRMM/TEFLUN) experiments. The results of this comparison demonstrated good fit, particularly within the troposphere, between the optimized relationship and atmospheric sounding measurements. The data produced by this method, including cloud top temperatures and heights, atmospheric temperature profiles for cloudy sky areas, and spatial displacement-adjusted cloud images, can be useful for weather/climate and atmospheric studies. In particular, the displacement-adjusted cloud images can be critical to develop high-resolution satellite rainfall estimates, which are urgently needed by mesoscale atmospheric modeling and studies, severe weather monitoring, and heavy precipitation and flash flood forecasting. Limitations of the proposed method are also identified and discussed.

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

2000-06-01

22

RADIOACTIVE CLOUDS AT GREAT HEIGHTS  

Microsoft Academic Search

The results of high-altitude measurements made at Gottingen with a ; single counter tube from Oct. 15 to 29, 1962, at heights from 16 to 25 km are ; reported. Counting rates much higher than normal were observed. The counting ; rates in excess of the usual cosmic background were determined as a function of ; the height. The results

E. Keppler; G. Pfotzer

1963-01-01

23

Cloud-Top Height Estimation by Geostationary Satellite Split-Window Measurements using CloudSat Measurements  

NASA Astrophysics Data System (ADS)

Estimation of cloud-top height and visible optical thickness of upper-tropospheric clouds by brightness temperature (TB) measurements of geostationary satellite at two infrared split-window wavelengths was conducted. These cloud parameters were estimated by regressing the measurements of 94-GHz cloud radar onboard CloudSat satellite in terms of TB at 10.8 um (T11) and its difference from TB at 12 um (?T = T11 - T12) measured by geostationary satellite MTSAT-1R. Estimation by geostationary satellite measurements are fairly useful in field campaigns aiming mesoscale cloud systems, where cloud-top heights are compared with the vertical profiles of ground-based measurements such as wind and cloud condensates in a short time interval. Hamada et al. (2008) conducted the estimation of cloud-top height by T11 and ?T measured by GMS-5, using ship-borne cloud radar measurements. However, their ground-based result was limited to the non-rainy clouds, since cloud radar signal is heavily attenuated by precipitation particles. Spaceborne radar measurements enables an estimation of cloud-top height without concern for the existence of precipitation. We examined the dependences of the estimates of cloud-top height on latitude, season, satellite zenith angle, day-night, and land-sea differences. It was shown that these dependences were considered as being uniform in tropics, except for the region with large satellite zenith angle. The dependences on latitude and season were negligible in tropics, while they became the most significant factor affecting the estimates at higher latitudes. Estimation of visible optical thickness was also conducted, although limited to the non-rainy high clouds. The distributions of estimates in TB-?T space were qualitatively consistent with those expected from a simplified radiative transfer equation, although the standard deviations of measurements were slightly large. Since the CloudSat conducts cloud radar observations on a global scale, the method adopted in this study can easily be applied to other current geostationary satellites with split-window channels, yielding hourly estimation map of cloud-top and optical thickness in global scale. We are planning to provide the near real-time product at our Website. Estimates (shading and thin solid contours) and standard deviations of samples (dashed contours) for cloud-top height by T11 and ?T.

Hamada, A.; Nishi, N.

2009-12-01

24

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

25

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

26

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

27

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

NASA Astrophysics Data System (ADS)

At the Earth's L1 Lagrangian point, the Deep Space Climate Observatory (DSCOVR) would see the whole sunlit half of the Earth and would provide simultaneous data on cloud and aerosol properties from 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, which are designed for cloud height retrievals. In this talk, we will present the progress on EPIC cloud height retrieval using Oxygen A and B band. As the first step, a study on the effect of cloud phase, particle size, optical depth, extinction coefficient, cloud fraction, sun-view geometry, and surface type on the cloud height determination is conducted. Second, based on the simple Lambertian cloud reflectance model, two cloud pressure retrieval algorithms are developed: 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, a cloud height retrieval model that is suitable for operational use is implemented. Test results with the data from the EPIC simulator will be presented.

Yang, Y.; Marshak, A.; Lyapustin, A.; Wang, Y.; Mao, J.; Meyer, K.; Herman, J. R.

2011-12-01

28

Development of a Cloud-Top Height Estimation Method by Geostationary Satellite Split-Window Measurements Trained with CloudSat Data  

NASA Astrophysics Data System (ADS)

Estimation of cloud-top height and visible optical thickness of upper-tropospheric clouds by brightness temperature (TB) measurements of geostationary satellite at two infrared split-window wavelengths was conducted. These cloud parameters were estimated by regressing the measurements of 94-GHz cloud radar onboard CloudSat satellite in terms of TB at 10.8 um (T11) and its difference from TB at 12 um (?T = T11 -T12) measured by geostationary satellite MTSAT-1R. Estimation by geostationary satellite measurements are fairly useful in field campaigns aiming mesoscale cloud systems, where cloud-top heights are compared with the vertical profiles of ground-based measurements such as wind and cloud condensates in a short time interval. Hamada et al. (2008) conducted the estimation of cloud-top height by T11 and ?T measured by GMS-5, using ship-borne cloud radar measurements. However, their ground-based result was limited to the non-rainy clouds, since cloud radar signal is heavily attenuated by precipitation particles. Spaceborne radar measurements enables an estimation of cloud-top height without concern for the existence of precipitation. We examined the dependences of the estimates of cloud-top height on latitude, season, satellite zenith angle, day-night, and land-sea differences. It was shown that these dependences were considered as being uniform in tropics, except for the region with large satellite zenith angle. The dependences on latitude and season were negligible in tropics, while they became the most significant factor affecting the estimates at higher latitudes. Estimation of visible optical thickness was also conducted, although limited to the non-rainy high clouds. The distributions of estimates in TB-?T space were qualitatively consistent with those expected from a simplified radiative transfer equation, although the standard deviations of measurements were slightly large. The near real-time products has already been provided on our Website (http://www-clim.kugi.kyoto-u.ac.jp/hamada/ctop/). Since the CloudSat conducts cloud radar observations on a global scale, the method adopted in this study can easily be applied to other current geostationary satellites with split-window channels, yielding hourly estimation map of cloud-top and optical thickness in global scale. We will show the results also using Meteosat Second Generation measurements.

Hamada, Atsushi; Nishi, Noriyuki; Inoue, Toshiro

2010-05-01

29

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...

30

On the Variation with Height of the Top Brightness of Precipitating Convective Clouds.  

National Technical Information Service (NTIS)

As part of a program to estimate rain from satellite observations, and to test the program's assumption that the highest clouds are the brightest, a correlation between cloud height and cloud brightness in the South Florida area was made 43 days during th...

C. G. Griffith W. L. Woodley

1973-01-01

31

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

32

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

33

Assessment of multispectral ATSR2 stereo cloud-top height retrievals  

Microsoft Academic Search

The Along-Track Scanning Radiometer 2 (ATSR2) instrument has a dual view capability that allows for stereo height retrievals. Stereo heights were retrieved for selected scenes over the United Kingdom Chilbolton Facility for Atmospheric and Radio Research and the United States Atmospheric Radiation Measurement program Southern Great Plains site from 1997 to 2000. Stereo cloud-top heights obtained with the 11 ?m and

Catherine Naud; Jan-Peter Muller; Eugene E. Clothiaux

2006-01-01

34

Stratocumulus Cloud-Top Height Estimates and Their Climatic Implications  

Microsoft Academic Search

A depth-dependent boundary layer lapse rate was empirically deduced from 156 radiosondes released during 6 month-long research cruises to the southeast Pacific sampling a variety of stratocumulus con- ditions. The lapse rate dependence on boundary layer height is weak, decreasing from a best-fit of 7.6 K km 1 to 7.2 K km 1 as the boundary layer deepens from 800

Paquita Zuidema; David Painemal; Simon de Szoeke; Chris Fairall

2009-01-01

35

Height  

Center for Drug Evaluation (CDER)

... Height. FDA Data Element Number. CDER Data Element Number. C-GEN-10212. Data Element Name. Height. Description. ... More results from www.fda.gov/drugs/developmentapprovalprocess/formssubmissionrequirements

36

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

37

CloudSat-constrained cloud ice water path and cloud top height retrievals from MHS 157 and 183.3 GHz radiances  

NASA Astrophysics Data System (ADS)

Ice water path (IWP) and cloud top height (ht) are two of the key variables to determine cloud radiative and thermodynamical properties in the climate models. Large uncertainty remains among IWP measurements from satellite sensors, in large part due to the assumptions made for cloud microphysics in these retrievals. In this study, we develop a fast algorithm to retrieve IWP from the 157, 183.3 ± 3 and 190.3 GHz radiances of Microwave Humidity Sounder (MHS) such that the MHS cloud ice retrieval is consistent with CloudSat IWP measurements. This retrieval is obtained by constraining the forward models between collocated-and-coincident measurements of CloudSat IWP and MHS cloud-induced radiance depression (Tcir) at these channels. The empirical forward model is represented by a look-up-table (LUT) of Tcir-IWP relationships as a function of ht and frequency channel. With ht simultaneously retrieved, the IWP is found to be more accurate. The useful range of the MHS IWP retrieval is between 0.5 and 10 kg m-2, and agrees well with CloudSat in terms of normalized probability density function (PDF). Compared to the empirical model, current radiative transfer models (RTMs) still have significant uncertainties in characterizing the observed Tcir-IWP relationships. Therefore, the empirical LUT method developed here remains as an effective approach to retrieving ice cloud properties from the MHS-like microwave channels.

Gong, J.; Wu, D. L.

2013-09-01

38

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

39

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

NASA Astrophysics Data System (ADS)

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 to GOES sounder data are tested. Comparisons between the daytime, nighttime and CO2-slicing cloud top heights and the surface retrievals yield mean differences of -0.84 +/- 1.48 km, -0.56 +/- 1.31 km, and -1.30 +/- 2.30 km, respectively, for all clouds. The errors generally increase with increasing cloud altitude and decreasing optical thickness. These results, which highlight some of the challenges associated with passive satellite cloud height retrievals, are being used to guide development of a blended LaRC/CO2-slicing cloud top height product with accuracies suitable for assimilation into weather forecast models.

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

2008-07-01

40

Rise of Volcanic Eruption Clouds: Relationship between Cloud Height and Eruption Intensity.  

National Technical Information Service (NTIS)

The rise of eruption clouds is produced by the upward momentum and thermal buoyancy of volcanic dust and gas, processes which play important roles in other phenomena. The expansion of a turbulent jet in free flow is controlled by the rate at which the for...

M. Settle

1976-01-01

41

N2Cloud: Cloud based neural network simulation application  

Microsoft Academic Search

We present N2Cloud, a novel Cloud-based neural network simulation system, which provides and exchanges neural network knowledge and simulation resources to and between arbitrary users on a world-wide basis following the Web 2.0 principle. N2Cloud enables the exchange of knowledge, as neural network objects and paradigms, by a virtual organization environment and delivers ample resources by exploiting the Cloud computing

Altaf Ahmad Huqqani; Xin Li; Peter Paul Beran; Erich Schikuta

2010-01-01

42

10 Years of Height Resolved, Cloud-Track, Vector Winds from MISR  

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 nearly 10 years of height-resolved, cloud-track, vector winds using a single, globally consistent algorithm. The MISR cloud-track winds are reported globally on mesoscale domains of 70.4 km × 70.4 km and referenced to stereoscopically derived heights above the earth ellipsoid, which have a nominal vertical resolution of approximately 500 m. Importantly, from the standpoint of climate research, the stereo height assignment and wind retrieval are largely insensitive to instrument calibration changes because the pattern matcher relies only on relative brightness values, rather than the absolute magnitude of the brightness. We will describe comparisons with other wind datasets, including geostationary cloud drift winds, scatterometer surface winds, and reanalysis model 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, because the global winds are driven primarily by the global (im)balance of heating, monitoring variations in the winds over 10 years promises to yield important insights into the processes related to the hydrologic cycle and transport of heat and water vapor, such as the Madden-Julian Oscillation (MJO) and the El Niño Southern Oscillation (ENSO).

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

2009-12-01

43

Correlating Polar Stratospheric Cloud Occurrence at the South Pole with Transport and Polar Geopotential Height Anomalies  

NASA Astrophysics Data System (ADS)

In a recent paper, we describe the macrophysical and thermodynamic properties of polar stratospheric clouds (PSC) at the South Pole based on continuous eye-safe lidar measurements made over five seasons (2000, 2003-2006). In this paper, we describe the relationship between PSC occurrence and the propensity for transport within the austral polar vortex. The southern lower-stratospheric polar airmass may be approximated as a closed system from May to September. Saturation vapor pressures for background concentrations of sulfuric and nitric acid and water vapor are reached either through radiational cooling or isentropic lift. Once nucleated, PSC acquire fall-velocities that remove these compounds from these heights. Satellite measurements (e.g., MLS) depict the widening proximity of the depleted airmass through the polar night. Yet, our measurements show that PSC occurrence can occur up to 20 km late in the season, which suggests replenishment of these species in air originating near the edges of the vortex. We examine 120-h back-trajectories during July and August and temperature histories to identify conditions and circumstances favorable to this occurring. Furthermore, we describe geopotential height anomalies averaged along 60° - 90° S, and compared to a twenty-year mean, as a proxy for the dynamic character of the polar vortex. Negative/positive anomalies indicate a strong/weak and deep/shallow vortex where its circulation inhibits/promotes meridional transport, replenishment and the likelihood of PSC at South Pole. We test this hypothesis using our dataset and reach conclusions on the influence of the polar vortex on total PSC observed each season, which, in turn, may influence the severity of annual ozone losses.

Campbell, J. R.; Sassen, K.

2007-12-01

44

Analysis of tropical cloud systems using a new cloud-top height data by geostationary satellite split-window measurements trained with CloudSat data  

NASA Astrophysics Data System (ADS)

Lookup tables for estimating the cloud-top height (CTOP) and visible optical thickness of upper-tropospheric clouds by the infrared brightness temperature (TB) at 10.8 ?m (T11) and its difference from TB at 12 ?m (DT11-12) measured by geostationary satellites are developed (Hamada and Nishi 2010, JAMC). These lookup tables were constructed by regressing the cloud radar measurements by the CloudSat satellite over the infrared measurements by the Japanese geostationary multifunctional transport satellite MTSAT-1R and MTSAT-2. The calculated CTOP is available at http://database.rish.kyoto-u.ac.jp/arch/ctop/ since July 2005. A merit of this dataset is that standard deviations of measurements around the estimates were also available as an indicator of the ambiguity in the estimates. The data have good precision for tropical cirrus clouds that have large DT11-12 values and suitable for analyses of cloud systems with well-developed cirrus clouds. We made correction for the satellite view angle and can offer the data over almost all tropical regions where the satellites can observe (20S-20N, 80E-160W for MTSAT-1R and 85E-155W for MTSAT-2). We analyzed zonally elongated cloud band extending 3000 km around ITCZ. It was first tightly concentrated at the ITCZ latitude and then spread meridionally into the two parallel zonal cloud bands. They kept moving meridionally away even after the cumulonimbi that could make divergence wind were hardly seen around the ITCZ. This phenomenon attracted attention during January 1993, the intensive observation period (IOP) of the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). Since there were not enough rainfall and cloud height information at that time, it was not clear why meridional separation starts simultaneously in the wide zonal region and what causes the continuous meridional separation over a day. In this study, we detected some typical cases in 2007, covered with our CTOP data. We examined detail of the separation with our CTOP data and Global Satellite Mapping of Precipitation (GSMaP; Kubota et al. 2007, IEEE Trans. Geosci. Remote Sens) data: precipitation estimation dataset made with microwave radiometers including Tropical Rainfall Measuring Mission/Microwave Imager (TRMM/TMI). We found that the separated cloud bands had little precipitation regions (larger than 1mm/hour) and CTOP was above 12 km. The facts show that the bands consist of the cirriform clouds passively advected by larger-scale wind. However, there are little active cumulus systems, which generally create horizontal divergence in the cirrus height, between and within the cloud bands, when examining GSMaP data and optical thickness estimation in the CTOP data. Though we do not have conclusive idea for this separation mechanism, one plausible candidate is a westward-moving equatorial trapped inertial gravity wave. It was observed around these cloud bands and can make meridional divergence without cumulus activity.

Nishi, N.; Hamada, A.; Ohigawa, M.; Shige, S.

2011-12-01

45

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

46

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

47

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.

48

Operational generation of AVHRR-based cloud products for Europe and the Arctic at EUMETSAT's Satellite Application Facility on Climate Monitoring (CM-SAF)  

NASA Astrophysics Data System (ADS)

The Satelite Application Facility on Climate Monitoring has implemented a new processing environment for AVHRR-based climate monitoring products. AVHRR measurements from NOAA-17, NOAA-18 and MetOp-A are utilized to generate daily and monthly means of several cloud parameters for Europe and the Inner Arctic: Cloud fraction, cloud types, cloud phase, cloud top height, cloud optical thickness and cloud liquid water path.

Kaspar, F.; Hollmann, R.; Lockhoff, M.; Karlsson, K.-G.; Dybbroe, A.; Fuchs, P.; Selbach, N.; Stein, D.; Schulz, J.

2009-04-01

49

Simple eye-safe lidar for cloud height measurement and small forest fire detection  

NASA Astrophysics Data System (ADS)

A simple and robust eye-safe lidar was developed on the basis of a rangefinder optical scheme comprising an Er:glass laser which generates 8 mJ pulses of 1540-nm radiation with the pulse repetition rate of 0.17 Hz and a 38-mm-diameter telescope. Reliable measurements of the cloud height up to 3700 m and early forest-fire detection with a range of 3000 m were experimentally demonstrated. Theoretical estimations indicate that using an optical scheme built around a 10 Hz Er:glass lasers and 150 mm light gathering optics early forest fire detection in a range up to 6500 m can be achieved.

Lavrov, A.; Utkin, A. B.; Vilar, R.

2010-07-01

50

Evaluation of single field-of-view cloud top height retrievals from hyperspectral infrared sounder radiances with CloudSat and CALIPSO measurements  

NASA Astrophysics Data System (ADS)

Accurate cloud top height retrievals from hyperspectral infrared (IR) sounder radiances are needed for weather and climate prediction. To account for the nonlinearity of the cloud parameters with respect to the IR radiances, a one-dimensional variational retrieval algorithm is used to derive the cloud top heights (CTHs) from the Atmospheric Infrared Sounder (AIRS) radiances on a single field-of-view basis. The CTHs are evaluated by comparison with the measurements from radar and lidar instruments onboard the Earth Observing System (EOS) CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. Using the retrievals from a global 3 day dataset, it is found that the variational algorithm compared with the regression algorithm could reduce the variability of the difference between the AIRS and active measurements by 1 km. And the biases of AIRS CTHs range from +1.5 to -1.4 km and from +1.6 to -3.8 km, depending on the Cloud Profiling Radar (CPR) and CALIPSO CTHs between 3 and 18 km, respectively. Globally, the AIRS CTH is overestimated (underestimated) when the CTH from active measurements is below (above) 5 km. The bias decreases from -1.9 to -0.8 km, and the variability decreases from 2.8 to about 1.6 km with the increase of the CALIPSO cloud optical thickness from 0.1 to 2.5. It also reveals that the AIRS CTHs agree better with the CPR than the CALIPSO.

Yao, Zhigang; Li, Jun; Weisz, Elisabeth; Heidinger, Andrew; Liu, Chian-Yi

2013-08-01

51

Study on the cloud layer height and properties in Hefei observed by lidar  

NASA Astrophysics Data System (ADS)

A co-axial transmission elastic-backscattered lidar aiming to detect the optical properties of the clouds is presented in this paper. The modular co-axial design can guarantee the consistency of the transmitting part and the receiving part. In practice a specific diaphragm is used to suppress the stray light of the primary mirror and background light to improve SNR of the backscattered signal in the daytime. So the near ground signal must be corrected with the appropriate overlap factor. A Licel transient recorder is used for data acquisition in analog and photon counting combined in one acquisition system. With the 15 MHz sampling rate, the spatial resolution of 10 m can be attained. The control over the transient recorder and the treatment of the data is performed on a PC. After getting the correctional backscattered signal, retrieving and analyzing the extinction coefficient profile, the cloud base, cloud peak and related optical parameters of the clouds can be confirmed. In order to testify the feasibility of our lidar, it was implemented with a Finland ceilometer Vaisala simultaneously in May in 2008 in Hefei. Results show the lidar system is stable and the data is reliable.

Chen, Zhenyi; Liu, Wenqing; Zhang, Yujun; He, Junfeng; Ruan, Jun; Li, Sheng; Cui, Yiben

2010-05-01

52

Verification of global cloud top heights and thermodynamic phase classification as derived fromSCIAMACHY visible and near infrared limb spectra  

NASA Astrophysics Data System (ADS)

The determination of global cloud top heights (CTH) and cloud thermodynamic phase (CTP) using SCIAMACHY limb measurements in the visible and near infrared wavelength range is presented in this paper. Knowledge of the effective CTH is an important input parameter for limb trace gas retrievals to extend the detection limit towards the troposphere. Use of CTH information reduces the error above clouds significantly as was shown in theoretical studies. The cloud thermodynamic phase is important for both cloud modeling and cloud properties remote sensing. Therefore a threshold method has been designed to determine the quantities CTH and CTP for the limb viewing geometry for tropospheric clouds. Furthermore polar stratospheric clouds and noctilucent clouds can be detected with this method. The height resolution with about 3.3 km is coarse due to the limb scanning concept of SCIAMACHY. This study will give first verification results with independent measurements.

Eichmann, Kai-Uwe; Bovensmann, Heinrich; Meringer, Markus; von Savigny, Christian; Kokhanovsky, Alexander

53

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

54

Vehicle Classification Based on the Radar Measurement of Height Profiles  

Microsoft Academic Search

The problem of classifying road vehicles according to vehicle type is considered. The proposed solution is based on using vehicle height and length and height profiles obtained by a microwave (MW) radar sensor. We show that if the radar sensor satisfies certain requirements, then a precise feature vector can be extracted, and simple deterministic algorithms can be applied to determine

Iidar Urazghildiiev; Rolf Ragnarsson; Pierre Ridderström; Anders Rydberg; Eric Ojefors; Kjell Wallin; Per Enochsson; Magnus Ericson; Göran Löfqvist

2007-01-01

55

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

56

Building outline detection based on height and intensity information of airborne laser scanning data  

NASA Astrophysics Data System (ADS)

Urban environment is extremely complex due to a multitude of features with different heights and structures. Traditional methods available to extract information regarding the buildings by using optical remote sensing images are highly labor-intensive and time-consuming. This paper developed a new method to detect building outlines based on height and intensity information of Airborne LiDAR data. Texture, relative height and intensity characteristics were first extracted from the LiDAR point cloud. Then, Support Vector Data Description was used to detect buildings with training knowledge. Finally, building outlines were obtained after data post process including small region removal, raster to vector conversion and so on. Experiments show the method proposed in this study is reliable and could be widely used in other urban areas.

Wang, Chengyi; Liang, Fuyuan; Zheng, Yi

2011-11-01

57

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

58

Contract-based cloud architecture  

Microsoft Academic Search

Cloud Computing as a service on demand architecture has become a topic of interest in the last few years. The outsourcing of duties and infrastructure to external parties enables new services to be established quickly and with low financial risk. These services also can be scaled on demand. Nevertheless, several issues such as security and legality should be considered before

Maxim Schnjakin; Rehab Alnemr; Christoph Meinel

2010-01-01

59

The effects of cloud inhomogeneities upon radiative fluxes, and the supply of a cloud truth validation dataset. Semiannual progress report, 1 July-31 December 1992  

SciTech Connect

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, R.M.

1993-01-01

60

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

61

The ESA Cloud CCI project: Generation of Multi Sensor consistent Cloud Properties with an Optimal Estimation Based Retrieval Algorithm  

NASA Astrophysics Data System (ADS)

The ultimate objective of the ESA Climate Change Initiative (CCI) Cloud project is to provide long-term coherent cloud property data sets exploiting and improving on the synergetic capabilities of past, existing, and upcoming European and American satellite missions. The synergetic approach allows not only for improved accuracy and extended temporal and spatial sampling of retrieved cloud properties better than those provided by single instruments alone but potentially also for improved (inter-)calibration and enhanced homogeneity and stability of the derived time series. Such advances are required by the scientific community to facilitate further progress in satellite-based climate monitoring, which leads to a better understanding of climate. Some of the primary objectives of ESA Cloud CCI Cloud are (1) the development of inter-calibrated radiance data sets, so called Fundamental Climate Data Records - for ESA and non ESA instruments through an international collaboration, (2) the development of an optimal estimation based retrieval framework for cloud related essential climate variables like cloud cover, cloud top height and temperature, liquid and ice water path, and (3) the development of two multi-annual global data sets for the mentioned cloud properties including uncertainty estimates. These two data sets are characterized by different combinations of satellite systems: the AVHRR heritage product comprising (A)ATSR, AVHRR and MODIS and the novel (A)ATSR - MERIS product which is based on a synergetic retrieval using both instruments. Both datasets cover the years 2007-2009 in the first project phase. ESA Cloud CCI will also carry out a comprehensive validation of the cloud property products and provide a common data base as in the framework of the Global Energy and Water Cycle Experiment (GEWEX). The presentation will give an overview of the ESA Cloud CCI project and its goals and approaches and then continue with results from the Round Robin algorithm comparison exercise carried out at the beginning of the project which included three algorithms. The purpose of the exercise was to assess and compare existing cloud retrieval algorithms in order to chose one of them as backbone of the retrieval system and also identify areas of potential improvement and general strengths and weaknesses of the algorithm. Furthermore the presentation will elaborate on the optimal estimation algorithm subsequently chosen to derive the heritage product and which is presently further developed and will be employed for the AVHRR heritage product. The algorithm's capabilities to coherently and simultaneously process all radiative input and yield retrieval parameters together with associated uncertainty estimates will be presented together with first results for the heritage product. In the course of the project the algorithm is being developed into a freely and publicly available community retrieval system for interested scientists.

Jerg, M.; Stengel, M.; Hollmann, R.; Poulsen, C.

2012-04-01

62

Lifting Condensation Level and Its Relation to Convective Cloud Base.  

National Technical Information Service (NTIS)

This thesis explores the relationship between the lifting condensation level (LCL) and the height and time of convective cloud formation. Data collected from several different sources during the BLX83 field program is utilized. Sounding data is used to in...

N. P. Wilde

1984-01-01

63

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

64

Aircraft Microphysical Documentation from Cloud Base to Anvils of Hailstorm Feeder Clouds in Argentina  

Microsoft Academic Search

Documentation during January and February 2000 of the structure of severe convective storms in Men- doza, Argentina, with a cloud-physics jet aircraft penetrating the major feeder clouds from cloud base to the 45°C isotherm level is reported. Complementary radar, satellite, and radiosonde measurements are in- corporated into the study. The main research goal was the description of the microphysical evolution

Daniel Rosenfeld; William L. Woodley; Terrence W. Krauss; Viktor Makitov

2006-01-01

65

Chemical and physical characterisation of low clouds: results from the FEBUKO ground-based cloud experiment.  

PubMed

Clouds play an immense role in transport and transformation of atmospheric trace species. In the joint project FEBUKO (Field investigations of budgets and conversions of particle phase organics in tropospheric cloud processes) the microphysics and chemistry of different types of aerosols, the role of aerosol chemical composition for cloud formation as well as the chemical transformation in cloud processes have been investigated by means of ground-based cloud experiments at Mt. Schmücke in the Thuringian Forest (Germany). The groups involved used a wide range of measurements of trace gases, aerosol particles and cloud droplets at three sites to study their sources and sinks, especially those in cloud. Although kind and behaviour of organic substances were of special interest (e.g., organic acids, peroxides, organic carbon, soot) attention was paid to the role of inorganic soluble material being the main part of the cloud condensation nuclei. In this paper we present selected results from the first experiment in autumn 2001. PMID:14994644

Acker, Karin; Wieprecht, Wolfgang; Möller, Detlev

2003-12-01

66

Total body height estimation using sacrum height in Anatolian Caucasians: multidetector computed tomography-based virtual anthropometry  

Microsoft Academic Search

Objective  Estimation of total body height is a major step when a subject has to be identified from his\\/her skeletal structures. In the\\u000a presence of decomposed skeletons and missing bones, estimation is usually based on regression equation for intact long bones.\\u000a If these bones are fragmented or missing, alternative structures must be used. In this study, the value of sacrum height

Hakki Muammer Karakas; Osman Celbis; Ahmet Harma; Banu Alicioglu

2011-01-01

67

Statistical analysis of an LES shallow cumulus cloud ensemble using a cloud tracking algorithm  

NASA Astrophysics Data System (ADS)

A technique for the tracking of individual clouds in a Large Eddy Simulation (LES) is presented. We use this technique on an LES of a shallow cumulus cloud field based upon the Barbados Oceanographic and Meteorological Experiment (BOMEX) to calculate statistics of cloud height, lifetime, and other physical properties for individual clouds in the model. We also examine the question of nature versus nurture in shallow cumulus clouds: do properties at cloud base determine the upper-level properties of the clouds (nature), or are cloud properties determined by the environmental conditions they encounter (nurture). We find that clouds which ascend through an environment that has been pre-moistened by previous cloud activity are no more likely to reach the inversion than clouds that ascend through a drier environment. Cloud base thermodynamic properties are uncorrelated with upper-level cloud properties, while mean fractional entrainment and detrainment rates display moderate correlations with cloud properties up to the inversion. Conversely, cloud base area correlates well with upper-level cloud area and maximum cloud height. We conclude that cloud thermodynamic properties are primarily influenced by entrainment and detrainment processes, cloud area and height are primarily influenced by cloud base area, and thus nature and nurture both play roles in the dynamics of BOMEX shallow cumulus clouds.

Dawe, J. T.; Austin, P. H.

2012-01-01

68

Statistical analysis of a LES shallow cumulus cloud ensemble using a cloud tracking algorithm  

NASA Astrophysics Data System (ADS)

A technique for the tracking of individual clouds in a Large Eddy Simulation (LES) is presented. We use this technique on a LES of a shallow cumulus cloud field based upon the Barbados Oceanographic and Meteorological Experiment (BOMEX) to calculate statistics of cloud height, lifetime, and other physical properties for individual clouds in the model. We also examine the question of nature versus nurture in shallow cumulus clouds: do properties at cloud base determine the upper-level properties of the clouds (nature), or are cloud properties determined by the environmental conditions they encounter (nurture). We find that clouds which ascend through an environment that has been pre-moistened by previous cloud activity are no more likely to reach the inversion than clouds that ascend through a drier environment. Cloud base thermodynamic properties are uncorrelated with upper-level cloud properties, while mean fractional entrainment and detrainment rate displays moderate correlations with cloud properties up to the inversion. Conversely, cloud base area correlates well with upper-level cloud area and maximum cloud height. We conclude that cloud thermodynamic properties are primarily influenced by entrainment and detrainment processes, cloud area and height are primarily influenced by cloud base area, and thus nature and nurture both play roles in the dynamics of BOMEX shallow cumulus clouds.

Dawe, J. T.; Austin, P. H.

2011-08-01

69

Ontology-Based Resource Management for Cloud Computing  

Microsoft Academic Search

\\u000a Resource management is a challenging issue in cloud computing. This paper aims to allocate requested jobs to cloud resources\\u000a suitable for cloud user requirements. To achieve the aim, this paper proposes an ontology-based job allocation algorithm for\\u000a cloud computing to perform inferences based on semantic meanings. We extract resource candidates depending on user requirements\\u000a and allocate a job to the

Yong Beom Ma; Sung-Ho Jang; Jong Sik Lee

2011-01-01

70

Weight-Height Standards Based on World War II Experience  

Microsoft Academic Search

From data on height and weight (nude) of registrants for military service during World War II, relationships have been established between weight and height. From these relationships, which may be considered representative of the male population from 18 to 37 years of age, three weight-height tables have been prepared for White, Negro, and Total (White and Negro combined) men, for

Bernard D. Karpinos

1958-01-01

71

A client-based privacy manager for cloud computing  

Microsoft Academic Search

A significant barrier to the adoption of cloud services is that users fear data leakage and loss of privacy if their sensitive data is processed in the cloud. In this paper, we describe a client-based privacy manager that helps reduce this risk, and that provides additional privacy-related benefits. We assess its usage within a variety of cloud computing scenarios. We

Miranda Mowbray; Siani Pearson

2009-01-01

72

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

73

Enhancing privacy in cloud computing via policy-based obfuscation  

Microsoft Academic Search

In this paper, we describe a privacy manager for cloud computing that controls policy-based obfuscation and de-obfuscation\\u000a of personal, sensitive, or confidential data within cloud service provision. By these means, cloud computing users may reduce\\u000a the risk of their private data being stolen or misused, and in addition assistance may be given to cloud computing providers\\u000a in helping them conform

Miranda Mowbray; Siani Pearson; Yun Shen

74

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

NASA Astrophysics Data System (ADS)

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 precipitation, and glaciation. Not all zones need appear in a given cloud system. Application to maritime clouds shows, from base to top, zones of coalescence, rainout, a shallow mixed-phase region, and glaciation starting at -10°C or even warmer. In contrast, continental clouds have a deep diffusional growth zone above their bases, followed by coalescence and mixed-phase zones, and glaciation at -15° to -20°C. Highly continental clouds have a narrow or no coalescence zone, a deep mixed-phase zone, and glaciation occurring between -20° and -30°C. Limited aircraft validation for the satellite inferences over Israel, Thailand, and Indonesia is available.Substantial transformation in the microphysical and precipitation forming processes is observed by this method in convective clouds developing in air masses moving from the sea inland. These changes appear to be related to the modification of the maritime air mass as it moves inland and becomes more continental. Further transformations are observed in air masses moving into areas affected by biomass burning smoke or urban air pollution, such that coalescence, and thus precipitation, is suppressed even in deep tropical clouds. It follows that natural and anthropogenic aerosols can substantially modify clouds not only in pristine environments, as was already demonstrated by the ship tracks, but they can also incur profound impact on cloud microstructure and precipitation in more continental environments, leading to substantial weather modification in densely populated areas.

Rosenfeld, Daniel; Lensky, Itamar M.

1998-11-01

75

A voxel-based lidar method for estimating crown base height for deciduous and pine trees  

Microsoft Academic Search

The overall goal of this study was to develop methods for assessing crown base height for individual trees using airborne lidar data in forest settings typical for the southeastern United States. More specific objectives are to: (1) develop new lidar-derived features as multiband height bins and processing techniques for characterizing the vertical structure of individual tree crowns; (2) investigate several

Sorin C. Popescu; Kaiguang Zhao

2008-01-01

76

Modeling Cloud Phase Fraction Based on In-situ Observations in Stratiform Clouds  

NASA Astrophysics Data System (ADS)

Mixed-phase clouds influence weather and climate in several ways. Due to the fact that they exhibit very different optical properties as compared to ice or liquid only clouds, they play an important role in the earth's radiation balance by modifying the optical properties of clouds. Precipitation development in clouds is also enhanced under mixed-phase conditions and these clouds may contain large supercooled drops that freeze quickly in contact with aircraft surfaces that may be a hazard to aviation. The existence of ice and liquid phase clouds together in the same environment is thermodynamically unstable, and thus they are expected to disappear quickly. However, several observations show that mixed-phase clouds are relatively stable in the natural environment and last for several hours. Although there have been some efforts being made in the past to study the microphysical properties of mixed-phase clouds, there are still a number of uncertainties in modeling these clouds particularly in large scale numerical models. In most models, very simple temperature dependent parameterizations of cloud phase fraction are being used to estimate the fraction of ice or liquid phase in a given mixed-phase cloud. In this talk, two different parameterizations of ice fraction using in-situ aircraft measurements of cloud microphysical properties collected in extratropical stratiform clouds during several field programs will be presented. One of the parameterizations has been tested using a single prognostic equation developed by Tremblay et al. (1996) for application in the Canadian regional weather prediction model. The addition of small ice particles significantly increased the vapor deposition rate when the natural atmosphere is assumed to be water saturated, and thus this enhanced the glaciation of simulated mixed-phase cloud via the Bergeron-Findeisen process without significantly affecting the other cloud microphysical processes such as riming and particle sedimentation rates. After the water vapor pressure in mixed-phase cloud was modified based on the Lord et al. (1984) scheme by weighting the saturation water vapor pressure with ice fraction, it was possible to simulate more stable mixed-phase cloud. It was also noted that the ice particle concentration (L>100 ?m) in mixed-phase cloud is lower on average by a factor 3 and as a result the parameterization should be corrected for this effect. After accounting for this effect, the parameterized ice fraction agreed well with observed mean ice fraction.

Boudala, F. S.; Isaac, G. A.

2005-12-01

77

Height-resolved Scaling Properties of Tropospheric Water Vapour based on Airborne Lidar Observations  

NASA Astrophysics Data System (ADS)

Two-dimensional vertical water vapour cross sections of the free troposphere between altitudes of 2 and 10 km, measured by nadir-viewing airborne differential-absorption lidar with high spatial resolution, were analyzed using structure functions up to the fifth order. We found scale invariance, i.e. a power-law dependency of structure function on length scale, for scales between 5 and 100 km, for the horizontal time series of water vapour mixing ratio. In contrast to one-dimensional in situ measurements, the two-dimensional water vapor lidar observations allow height-resolved analyses of power-law scaling exponents at a vertical resolution of 200 m. The data reveal significantly different scaling properties above and below an air-mass boundary. They stem from three very dissimilar aircraft campaigns: COPS/ETReC over middle and southern Europe in summer 2007, T-PARC around Japan mostly over sea in late summer 2008, and T-IPY around Spitsbergen over sea in winter 2008. After discarding flight segments with low lidar signals or large data gaps, and after averaging horizontally to a resolution of between 1 and 5 km to obtain a high signal to noise ratio, structure functions were computed for 20 flights at various heights, adding up to a length of more than 300,000 km. The power-law scaling exponents of the structure functions do not show significant latitudinal, seasonal or land/sea dependency, but they do differ between air masses influenced by moist convection and air masses aloft, not influenced. A classification of the horizontal water vapour time series into two groups according to whether the series occurred above or below the level of nearby convective cloud tops could be performed by detecting the cloud top height from the lidar backscatter signal in the corresponding flight segment. We found that the scaling exponents can be divided into two groups depending on the respective air mass: The smoothness of the time series, expressed by the first-order scaling exponent, varies from less than 0.5 in the low-level convectively influenced air masses to values greater than 0.5 and most frequently near 0.6 in the higher-level air above the convective cloud tops. The time series' intermittency, expressed by the variation of the scaling exponent with increasing order, is larger in convectively influenced air masses. These differences in variability strongly suggest that convection provides a source of moisture variability on small scales. Our results show that the high horizontal and vertical resolution of lidar observations allows a characterisation of the scale dependency of the water vapour field at scales close to and smaller than the smallest resolved scales in modern weather and climate models. This provides both a reference for validation of high resolution models and a basis for the design of stochastic or pdf-based parameterisations of clouds and convection.

Kiemle, Christoph; Fischer, Lucas; Craig, George C.

2013-04-01

78

A study of the morphology of winter sprites in the Hokuriku area of Japan in relation to cloud charge height  

NASA Astrophysics Data System (ADS)

Continuous observations of sprites in the Hokuriku area of Japan were performed from two optical sites during the three winter periods. The purpose of this observation is to study the major effect in the appearance of sprites and in determining the morphology of sprites (columns or carrots). Detailed analysis is performed based on the estimation of the height of -10 °C at the time of sprite occurrence. When the height of -10 °C is lower than 1800 m, the occurrence of sprites is infrequent, and the dominant shape is column. Then when it is increased (1800-3000 m), a new situation takes place, namely the occurrence of sprites is very enhanced and more spectacular shapes like carrots tend to be frequently observed in addition to column sprites. These sprite characteristics are first compared with those of parent lightning in the Hokuriku area and with our latest computer simulations on sprite initiation.

Myokei, K.; Matsudo, Y.; Asano, T.; Suzuki, T.; Hobara, Y.; Michimoto, K.; Hayakawa, M.

2009-04-01

79

Research on Digital Library Platform Based on Cloud Computing  

Microsoft Academic Search

\\u000a Cloud computing is a new computing model. The emergence and development of cloud computing have a great effect on the development\\u000a and application of digital library. Based on the analysis of the problem in the existing digital library, a new digital library\\u000a platform architecture model based on cloud computing is put forward. The model consists of four lays: infrastructure layer,

Lingling Han; Lijie Wang

80

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

2012-10-10

81

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

82

Satellite cloud image retrieval based on deformable circle model  

Microsoft Academic Search

In order to build a content-based cloud image retrieval system, a deformable circle model is proposed to represent cloud shape. After a description of the model and shape decomposition process, a hierarchical similarity rule is presented. Then comparative experiments with some conventional contented-based image retrieval methods are carried out, which leads to a finding that the retrieval performance of our

Yuan-Xiang Li; Yan-Bing Li; Zhong-Liang Jing

2007-01-01

83

Model based building height retrieval from single SAR images  

Microsoft Academic Search

With the improvements of spaceborne and airborne SAR system resolution, the applications of radar remote sensing has been extended to building 3D geometric information retrieval and reconstruction from urban SAR images, which is the foundation of build-up areas reconstruction and urban analysis. This paper mainly focuses on the problem of building height estimation from a single high resolution (HR) SAR

Li-bing Jiang; Zhuang Wang; Wen-xian Yu

2011-01-01

84

Unified approach to prediction of propagation over buildings for all ranges of base station antenna height  

Microsoft Academic Search

Theoretical results for the dependence on base station antenna height of the average received signal for mobiles at street level are presented. The results apply to residential and commercial sections of cities and to all ranges of antenna height from well above to below that of the surrounding buildings. Assuming all buildings to be of equal heights, the range dependence

Leandro Rocha Maciel; Henry L. Bertoni; Howard H. Xia

1993-01-01

85

Topside ionospheric scale height analysis and modelling based on radio occultation measurements  

Microsoft Academic Search

The knowledge of the scale height in the topside ionosphere region remains rather poor due to the insufficient observations carried so far. To advance this knowledge, presented here is a new method of retrieving the topside ionospheric scale height based on radio occultation observations onboard low-earth-orbiting satellites. The scale height, well known for its dependence on the temperatures and masses

S. M. Stankov; N. Jakowski

2006-01-01

86

Cloud Based Processing of Large Photometric Surveys  

NASA Astrophysics Data System (ADS)

Astronomy, as is the case with many scientific domains, has entered the realm of being a data rich science. Nowhere is this reflected more clearly than in the growth of large area surveys, such as the recently completed Sloan Digital Sky Survey (SDSS) or the Dark Energy Survey, which will soon obtain PB of imaging data. The data processing on these large surveys is a major challenge. In this paper, we demonstrate a new approach to this common problem. We propose the use of cloud-based technologies (e.g., Hadoop MapReduce) to run a data analysis program (e.g., SExtractor) across a cluster. Using the intermediate key/value pair design of Hadoop, our framework matches objects across different SExtractor invocations to create a unified catalog from all SDSS processed data. We conclude by presenting our experimental results on a 432 core cluster and discuss the lessons we have learned in completing this challenge.

Farivar, R.; Brunner, R. J.; Santucci, R.; Campbell, R.

2013-10-01

87

Testing the Parameterizations of Cloud Base Mass-Flux for Shallow Cumulus Clouds using Cloud Radar Observations  

NASA Astrophysics Data System (ADS)

Shallow cumulus clouds have significant impact on the vertical distributions of heat and moisture and on surface energy fluxes over land through their effect on incoming shortwave radiation. The present resolutions of General Circulation Model (GCM) and Numerical weather prediction (NWP) models are not fine enough to simulate shallow clouds directly, leaving not much choice other than parameterizations evaluated using either Large Eddy Simulation (LES) and observations. The representation of these clouds in numerical models is an important and challenging issue in model development, because of its potential impacts on near-surface weather and long-term climate simulations. Recent studies through LES have shown that the mass flux is the important parameter for determining the characteristics of cumulus transports within cloud layer. Based on LES results and scaling arguments, substantial efforts have been made to parameterize the cloud base mass flux to improve the interactions between the subcloud and cloud layer. Despite these efforts, what factors control the mass flux and how the interaction between subcloud and cloud layers should be parameterized is not fully understood. From the observational perspective, studies have been done using aircraft and remote sensing platform to address the above issue; there have been insufficient observations to develop detailed composite studies under different conditions. The Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) in Southern Great Plains (SGP) offers unique long-term measurements from cloud radars (35 and 94 GHz) along with synergetic measurements to address the above problem of non-precipitating shallow cumulus clouds over the SGP region. Doppler velocities from the cloud radar are processed to remove the insect contamination using a fuzzy-logic approach before they are used for the mass-flux calculation. The present observations are used to validate the existing mass-flux relations used in parameterizations. The possible factors [such as, effect of wind shear, transition layer strength, lower tropospheric relative humidity, large-scale vertical velocity and stability (CAPE and CIN)] that affects the mass-flux in addition to the convective velocity (w*) are studied using sounding and ECMWF model dataset. Furthermore, the data are classified based on time of the day, and for various cloud fractions and composite profiles are calculated to define the differences for different regimes.

Chandra, A.; Kollias, P.; Albrecht, B. A.; Zhu, P.; Klein, S. A.; Zhang, Y.

2010-12-01

88

Satellite cloud image texture feature extraction based on Gabor wavelet  

Microsoft Academic Search

In recent years, multi-resolution, multi-channel texture analysis algorithm get extensive attention, and become the important development direction of the texture analysis. According to the satellite cloud images, this paper put forward the cloud classification method based on texture feature of 2D-Gabor wavelet. Experiments show that the 2D-Gabor wavelet texture features can achieve better classification of clouds, take this method compared

Desheng Fu; Lijuan Xu

2011-01-01

89

Contented-Based Satellite Cloud Image Processing and Information Retrieval  

Microsoft Academic Search

Satellite cloud image is a kind of useful image which includes abundant information, for acquired this information, the image\\u000a processing and character extraction method adapt to satellite cloud image has to be used. Content-based satellite cloud image\\u000a processing and information retrieval (CBIPIR) is a very important problem in image processing and analysis field. The basic\\u000a character, like color, texture, edge

Yanling Hao; Wei Shangguan; Yi Zhu; Yanhong Tang

2007-01-01

90

Effects of Multiple Scattering on Attenuation-Based Retrievals of Stratiform Rainfall from CloudSat  

Microsoft Academic Search

An attenuation-based method to retrieve vertical profiles of rainfall rates from height derivatives\\/ gradients of CloudSat nadir-pointing W-band reflectivity measurements is discussed. This method takes advantage of the high attenuation of W-band frequency signals in rain and the low variability of nonat- tenuated reflectivity due to strong non-Rayleigh scattering from rain drops. The retrieval uncertainties could reach 40%-50%. The suggested

Sergey Y. Matrosov; Alessandro Battaglia; Peter Rodriguez

2008-01-01

91

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.

92

Definition of "banner clouds" based on time lapse movies  

NASA Astrophysics Data System (ADS)

Banner clouds appear on the leeward side of a mountain and resemble a banner or a flag. This article provides a comprehensive definition of "banner clouds". It is based primarily on an extensive collection of time lapse movies, but previous attempts at an explanation of this phenomenon are also taken into account. The following ingredients are considered essential: the cloud must be attached to the mountain but not appear on the windward side; the cloud must originate from condensation of water vapour contained in the air (rather than consist of blowing snow); the cloud must be persistent; and the cloud must not be of convective nature. The definition is illustrated and discussed with the help of still images and time lapse movies taken at Mount Zugspitze in the Bavarian Alps.

Schween, J. H.; Kuettner, J.; Reinert, D.; Reuder, J.; Wirth, V.

2007-04-01

93

Defintion of "banner clouds" based on time lapse movies  

NASA Astrophysics Data System (ADS)

Banner clouds appear on the leeward side of a mountain and resemble a banner or a flag. This article provides a comprehensive definition of "banner clouds". It is based primarily on an extensive collection of time lapse movies, but previous attempts at an explanation of this phenomenon are also taken into account. The following ingredients are considered essential: the cloud must be attached to the mountain but not appear on the windward side; the cloud must originate from condensation of water vapour contained in the air (rather than consist of blowing snow); the cloud must be persistent; and the cloud must not be of convective nature. The definition is illustrated and discussed with the help of still images and time lapse movies taken at Mount Zugspitze in the Bavarian Alps.

Schween, J. H.; Kuettner, J.; Reinert, D.; Reuder, J.; Wirth, V.

2006-10-01

94

Combined Satellite- and Surface-Based Observations of Clouds.  

NASA Astrophysics Data System (ADS)

A new method for combining satellite and surface-based cloud observations into a self-consistent three-dimensional field is presented. This method derives the probabilities of the cloud states, which are most consistent with all of the observations and assumptions concerning the nature and relative uncertainties of the observations. It is applied to a three-layer atmosphere using monthly satellite- and surface-based cloud observations. The reconstructions of the observed fields usually lead to modifications of the surface-observed low cloud amount of less than 0.008 fractional cloud cover. Over the ocean the satellite-view low cloud amounts are usually decreased by between 0.06 and 0.12 for most of the middle latitudes and southeastern tropical Pacific. Over land the adjustments in the satellite low cloud amounts are generally smaller. The method leads to increases in satellite high cover of between 0.03 and 0.09 over most regions, and increases in middle cloud cover of up to around 0.03 over the subtropical oceans. Comparisons between derived total cloud cover and that calculated with the commonly used random and mixed overlap assumptions suggest that the mixed assumption generally better fits the results. On the whole there is overall fairly good agreement between the percent low cloud relative to total cloud cover in the reconstructed observations and a global climate model, but the model has a far larger percentage of high clouds nearly everywhere, especially in the tropical convective regions and over the Indian subcontinent.

Weare, Bryan C.

1999-03-01

95

Temporal adaptive neural network-based satellite cloud imagery classification  

Microsoft Academic Search

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

Bin Tian

1998-01-01

96

Search Engine Prototype System Based on Cloud Computing  

NASA Astrophysics Data System (ADS)

With the development of Internet, IT support systems need to provide more storage space and faster computing power for Internet applications such as search engine. The emergence of cloud computing can effectively solve these problems. We present a search engine prototype system based on cloud computing platform in this paper.

Han, Jinyu; Hu, Min; Sun, Hongwei

97

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

98

Cloud statistics measured with a ground-based Infrared Cloud Imager  

Microsoft Academic Search

The Infrared Cloud Imager (ICI) is a ground-based instrument for measuring spatial cloud statistics. ICI uses an uncooled microbolometer detector array to record downwelling infrared atmospheric emission in the 8-14 mum spectral band with 320times240 pixels. The ICI system has been deployed at Poker Flat Research Range near Fairbanks, Alaska, at Barrow, Alaska, and in central Oklahoma. With a water

Joseph A. Shaw; Brentha Thurairajah; Kohei Mizutani

2004-01-01

99

Clouds: An Internet Based Lesson Plan  

NSDL National Science Digital Library

This site facilitates a classroom activity in which students create a hypothesis on cloud formation and then conduct online research to either validate or refute their initial hypothesis. The activity begins with a brief laboratory experiment that demonstrates cloud formation and asks students to generate a hypothesis on how clouds form. The activity then switches to students conducting Internet research. Finally, small groups of students will create reports summarizing the cloud formation process, and each group will present their report to the class. Students are then encouraged to compare their final reports with the initial hypothesis created by the class. Students can also track and research local weather patterns, and study how technology is utilized in predicting weather.

Hassard, Jack

100

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 ...

101

Microwave propagation characteristics depending on base-station antenna height in an urban area  

Microsoft Academic Search

We have conducted propagation experiments assuming the environment of low base station antenna height and, hence, microcells in an urban area and have reported their results. In this report, we report the results of a propagation experiment in the microwave band that is conducted with transmission base station antennas installed at height sufficiently higher or lower than the surrounding building

K. Sakawa; H. Masui; M. Ishii; H. Shimizu; T. Kobayashi

2001-01-01

102

Characteristics of Borneo and Sumatra fire plume heights and smoke clouds and their impact on regional El Niño-induced drought  

NASA Astrophysics Data System (ADS)

During the dry season, anthropogenic fires in tropical forests and peatlands in equatorial Asia produce regionally expansive smoke clouds. We estimated the altitude of smoke clouds from these fires, characterized the sensitivity of these clouds to regional drought and El Niño variability, and investigated their effect on climate. We used the MISR satellite product and MISR INteractive eXplorer (MINX) software to estimate the heights of 382 smoke plumes (smoke with a visible surface source and transport direction) on Borneo and 143 plumes on Sumatra for 2001—2009. In addition, we estimated the altitudes of 10 smoke clouds (opaque regions of smoke with no detectable surface source or transport direction) on Borneo during 2006. Most smoke plumes (84%) were observed during El Niño events (2002, 2004, 2006, and 2009); this is consistent with higher numbers of active fire detections and larger aerosol optical depths observed during El Niño years. Annually averaged plume heights on Borneo were positively correlated to the Oceanic Niño Index (ONI), an indicator of El Niño (r2 = 0.53), and the mean plume height for all El Niño years was 772.5 ± 15.9m, compared to 711.4 ± 28.7m for non-El Niño years. The median altitude of the 10 smoke clouds observed on Borneo during 2006 was 1313m, considerably higher than the median of nearby smoke plumes (787m). The difference in height between individual plumes and regional smoke clouds may be related to deeper planetary boundary layers and injection heights later in the afternoon (after the 10:30am MISR overpass) or other atmospheric mixing processes that occur on synoptic timescales. We investigated the climate response to these expansive smoke clouds using the Community Atmosphere Model (CAM). Climate responses to smoke from two 30 year simulations were compared: one simulation was forced with fire emissions typical of a dry (El Niño) burning year, while the other was forced with emissions typical of a low (La Niña) burning year. Fire aerosols reduced net shortwave radiation at the surface during August-October by an average of 10% in the region encompassing most of Sumatra and Borneo (90°E-120°E, 5° S-5°N). The reductions in net radiation cooled both sea surface temperature (0.5 ± 0.3°C) and land air temperature (0.4 ± 0.2°C) during these months. Tropospheric heating from black carbon (BC) absorption increased substantially (20.5 ± 9.3 W m-2) and was balanced by an overall reduction in latent heating in the mid-troposphere. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9 ± 0.6 mm d-1 (10%). The vulnerability of ecosystems to fire was enhanced because the decreases in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño.

Tosca, Michael; Randerson, James; Zender, Cs; Flanner, Mg; Nelson, Dl; Diner, Dj; Rasch, Pj; Logan, Ja

2010-05-01

103

An Inversion Method of Significant Wave Height Based on Radial Basis Function Neural Network  

Microsoft Academic Search

In view of the question that traditional significant wave height inversion method of ocean wave don't have high precision and its applicable scope is limited, a significant wave height inversion method based on radial basis function neural network is proposed. Assume significant wave height has a linear relationship with the radar image signal-to-noise ratio's square root, radial basis function neural

Liqiang Liu; Zhichao Fan; Chunyan Tao; Yuntao Dai

2011-01-01

104

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

105

Is School-Based Height and Weight Screening of Elementary Students Private and Reliable?  

ERIC Educational Resources Information Center

The Institute of Medicine recommends school-based body mass index (BMI) screening as an obesity prevention strategy. While school nurses have provided height/weight screening for years, little has been published describing measurement reliability or process. This study evaluated the reliability of height/weight measures collected by school nurses…

Stoddard, Sarah A.; Kubik, Martha Y.; Skay, Carol

2008-01-01

106

Is School-Based Height and Weight Screening of Elementary Students Private and Reliable?  

ERIC Educational Resources Information Center

|The Institute of Medicine recommends school-based body mass index (BMI) screening as an obesity prevention strategy. While school nurses have provided height/weight screening for years, little has been published describing measurement reliability or process. This study evaluated the reliability of height/weight measures collected by school nurses…

Stoddard, Sarah A.; Kubik, Martha Y.; Skay, Carol

2008-01-01

107

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

108

The Construction and Realization of the Intelligent NIPS Based on the Cloud Security  

Microsoft Academic Search

The cloud security is a safe mode applied super Internet based on the cloud computing, also a new technology and the trend of development on network security. On the basis of outlining the cloud security's superiority, key technologies and the IPS technology, this paper proposes a new cloud security-based intelligent NIPS structure, function, characteristic and difference from general NIPS, finally

Jia Tiejun; Wang Xiaogang

2009-01-01

109

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

110

Height Compensation Using Ground Inclination Estimation in Inertial Sensor-Based Pedestrian Navigation  

PubMed Central

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.

Park, Sang Kyeong; Suh, Young Soo

2011-01-01

111

The Research of Soft Component Library Based on Cloud Computing  

Microsoft Academic Search

Aimed at the problems that have appeared in the component library (CL) development at present, this paper introduces a distributed CL system based on cloud computing technology. The architecture and retrieval model of this system are also introduced. It can nicely meet the need of component retrieval for component requester through many distributed component base.

Hongyan Zhao; Yingjun Zhang; Jiangfeng Liu

2011-01-01

112

Studies of base-station antenna height effects on mobile radio  

Microsoft Academic Search

As is well known, a base-station antenna height gain factor of 6 dB\\/octave has been predicted theoretically for signal path loss over flat ground and has been verified by measured data. However, the 6-dB\\/octave rule for antenna height effect cannot be used to predict signal strength for terrain contours if the terrain is not flat. A model has been developed

W. C. Y. Lee

1980-01-01

113

Mobile path loss characteristics for low base station antenna height in different forest densities  

Microsoft Academic Search

This paper presents studies of propagation in a suburban forest based on a measurement campaign at a frequency of 1.8 GHz. We investigated how tree density affected path loss-distance and the fast fading characteristic depending on the base tree size and base station antenna height in a range of 3, 4, and 5 m above ground while the receiving antenna

S. Phaiboon; S. Somkuarnpanit

2006-01-01

114

Characteristics of Borneo and Sumatra fire plume heights and smoke clouds and their impact on regional El Niño-induced drought  

NASA Astrophysics Data System (ADS)

During the dry season, anthropogenic fires burn the tropical forests and peatlands of equatorial Asia and produce regionally expansive smoke clouds. We estimated the altitude of smoke from these fires, characterized the sensitivity of this smoke to regional drought and El Niño variability, and investigated its effect on climate. We used the MISR satellite product and MISR INteractive eXplorer (MINX) software to estimate the heights of 382 smoke plumes (smoke with a visible surface source and transport direction) on Borneo and 121 plumes on Sumatra for 2001-2009. In addition, we estimated the altitudes of 10 smoke clouds (opaque regions of smoke with no detectable surface source or transport direction) on Borneo for 2006. Most smoke plumes (80%) were observed during El Niño events (2002, 2004, 2006, 2009); this is consistent with higher aerosol optical depths observed during El Niño-induced drought. Annually averaged plume heights on Borneo were positively correlated to the Oceanic Niño Index (ONI), an indicator of El Niño (r2 = 0.53). The mean plume height for all El Niño years was 765.8 ± 19.7m, compared to 711.4 ± 28.7 for non-El Niño years. The median altitude of all 10 smoke clouds observed on Borneo during 2006 was 1313m, compared to a median 787m for smoke plume grid cells. The area covered by all smoke plumes from 2006 corresponded to approximately three individual smoke clouds. We investigated the climate response to these expansive smoke clouds using the Community Atmosphere Model (CAM). Climate variables from two 30 year simulations were compared: one simulation was forced with fire emissions typical of a dry (El Niño) burning year, while the other was forced with emissions typical of a low (La Niña) burning year. Fire aerosols reduced net shortwave radiation at the surface during August-October by an average of 10% in the region encompassing most of Sumatra and Borneo (90°E-120°E, 5°S-5°N). The reductions in net radiation cooled both ocean (0.5 ± 0.3°C) and land (0.4 ± 0.2°C) temperatures during these months. Tropospheric heating from black carbon (BC) absorption increased substantially (20.5 ± 9.3 W m-2), but was balanced by an overall reduction in latent heating. The combination of decreased SSTs and increased atmospheric heating reduced regional precipitation by 0.9 ± 0.6 mm d-1 (10%). This implies that the vulnerability of ecosystems to fire was increased because the reductions in precipitation exceeded those for evapotranspiration. Together, the satellite and modeling results imply a possible positive feedback loop in which anthropogenic burning in the region intensifies drought stress during El Niño.

Tosca, Michael; Randerson, James; Zender, Charles; Flanner, Mark; Nelson, David; Diner, David; Rasch, Phil; Logan, Jennifer

2010-05-01

115

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

116

Do parental heights influence pregnancy length?: a population-based prospective study, HUNT 2  

PubMed Central

Background The objective of this study was to examine the association of maternal and paternal height with pregnancy length, and with the risk of pre- and post-term birth. In addition we aimed to study whether cardiovascular risk factors could explain possible associations. Methods Parents who participated in the Nord-Trøndelag Health Study (HUNT 2; 1995–1997) were linked to offspring data from the Medical Birth Registry of Norway (1997–2005). The main analyses included 3497 women who had delivered 5010 children, and 2005 men who had fathered 2798 pregnancies. All births took place after parental participation in HUNT 2. Linear regression was used to estimate crude and adjusted differences in pregnancy length according to parental heights. Logistic regression was used to estimate crude and adjusted associations of parental heights with the risk of pre- and post-term births. Results We found a gradual increase in pregnancy length by increasing maternal height, and the association was essentially unchanged after adjustment for maternal cardiovascular risk factors, parental age, offspring sex, parity, and socioeconomic measures. When estimated date of delivery was based on ultrasound, the difference between mothers in the lower height quintile (<163 cm cm) and mothers in the upper height quintile (? 173 cm) was 4.3 days, and when estimated date of delivery was based on last menstrual period (LMP), the difference was 2.8 days. Shorter women (< 163 cm) had lower risk of post-term births, and when estimated date of delivery was based on ultrasound they also had higher risk of pre-term births. Paternal height was not associated with pregnancy length, or with the risks of pre- and post-term births. Conclusions Women with shorter stature had shorter pregnancy length and lower risk of post-term births than taller women, and when EDD was based on ultrasound, they also had higher risk of preterm births. The effect of maternal height was generally stronger when pregnancy length was based on second trimester ultrasound compared to last menstrual period. The association of maternal height with pregnancy length could not be explained by cardiovascular risk factors. Paternal height was neither associated with pregnancy length nor with the risk of pre- and post-term birth.

2013-01-01

117

Ground-based measurements of local cloud cover  

NASA Astrophysics Data System (ADS)

Clouds are believed to reflect temporal climate changes through variations in their amounts, characteristics, and occurrence. In addition, they reflect both weather and climate in a region. In this work, a methodology to determine the local cloud cover (LCC) is proposed using sky images obtained from a ground-based instrument. Three years of sky images from an urban, tropical site were obtained and analyzed through that methodology. Monthly average LCC varied from 3 to 96 %, while seasonal average values were 68 % for summer, 54 % for spring, 46 % for fall, and 23 % for winter. LCC results show a clear seasonal dependence and a fair agreement ( r 2 = 0.72) with satellite data, which typically underestimate the cloud cover in relation to LCC. Our analysis also suggests the possibility of a measurable link between LCC and natural events like the El Niño Southern Oscillation.

Silva, Abel Antônio; de Souza Echer, Mariza Pereira

2013-05-01

118

A Cloud-based Approach to Medical NLP  

PubMed Central

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.

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

2011-01-01

119

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

2011-10-22

120

Cloud computing based ETL technique using Warehouse Intermediate Agents  

Microsoft Academic Search

The decentralized and distributed business management increases the need to trade information between different parties. The aim of this research is to provide a technique that enables data integration using ETL technique in a cloud computing environment to be offered as a service. This enables scalability and cost saving. The technique developed is based on Warehouse Intermediate Agents (WIA) to

Ahmed I. Saada; Ghada A. El Khayat; Shawkat K. Guirguis

2011-01-01

121

Doppler Turbulence Measurements in an Evaporating 'Stalactite' Cloud Base Zone.  

National Technical Information Service (NTIS)

The evaporating base of an ice crystal cloud deck is commonly marked by mammata-form vertical appendages which have come to be called 'stalactites'. Because this zone is cooled by evaporation from above, its lower portion becomes convectively unstable and...

D. Atlas R. S. Sekhon R. J. Serafin

1972-01-01

122

A cloud based SIM DRM scheme for the mobile internet  

Microsoft Academic Search

With the rapid growth of the mobile industry, a considerable amount of mobile applications and services are available. Meanwhile, pirates and illegal distributions of digital contents have become serious issues. Digital Rights Management (DRM) aims at protecting digital contents from being abused through regulating the usage of digital contents. In this paper, a cloud based SIM DRM scheme, called CS-DRM,

Peng Zou; Chaokun Wang; Zhang Liu; Jianmin Wang; Jia-Guang Sun

2010-01-01

123

Dynamic hosting management of web based applications over clouds  

Microsoft Academic Search

Dynamic Application Hosting Management (DAHM) allows clouds to dynamically host applications in data centers at different locations based on: (i) spatio-temporal variation of energy price, (ii) data center computing and cooling energy efficiency, (iii) Virtual Machine (VM) migration cost for the applications, and (iv) any SLA violations due to migration overhead or network delay. DAHM is complementary to dynamic workload

Zahra Abbasi; Tridib Mukherjee; Georgios Varsamopoulos; Sandeep K. S. Gupta

2011-01-01

124

Cloud Classification Based on Self-Organizing Feature Map and Probabilistic Neural Network  

Microsoft Academic Search

For overcoming the shortcoming of single ANN classifier being difficult used to identify and classify complex clouds, based on the multi-spectrum samples of stationary meteorology satellite cloud pictures, by computing and analysing the gray-grads and texture characters of satellite cloud picture samples, and picking-up some suitable cloud classification factors, a synthetic optimization SOM-PNN cloud classifier was designed and established. Firstly,

Ren Zhang; Yanlei Wang; Wei Liu; Weijun Zhu; Jiguang Wang

2006-01-01

125

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

126

Retrieval of cloud geometrical properties using satellite remote sensing data  

NASA Astrophysics Data System (ADS)

It is of great interest to investigate the radiative features on the cloud optical, microphysical, and geometrical properties of clouds that play crucial role in the climate system. Here, top height, base height, and geometrical thickness of cloud layer are considered as cloud geometrical properties. Previous studies show that information of some spectral regions including oxygen A-band, enables us to retrieve cloud geometrical properties as well as optical thickness, effective particle radius of cloud. In this study, an algorithm was developed to retrieve simultaneously cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer with the spectral information of visible, near infrared, thermal infrared, and oxygen A-band channels. This algorithm was applied to the GLI dataset on board ADEOS-II satellite that has been launched recently. The preliminary results are not so strange and to be validated in future, comparing to the in-situ observations.

Kuji, Makoto; Nakajima, Teruyuki; Mukai, Sonoyo

2004-02-01

127

A Novel Network Layout for CDMA Cellular Networks with Optimal Base Station Antenna Height and Downtilt  

Microsoft Academic Search

The target of this paper is to show the optimal base station antenna height and downtilt for a novel network layout, and to compare the performance of the novel network layout to a traditional layout. The optimum performance is derived by analyzing the maximum cell area which provides the minimum service probability over the analysis area. The results of the

Jarkko Itkonen; Balázs P. Tuzson; Jukka Lempiäinen

2006-01-01

128

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

2011-08-09

129

An Approach for Image and Height Calibration for Borescope Based Surface Characterization  

NASA Astrophysics Data System (ADS)

When the topology of a surface is characterized using triangulation with a structured light beam, the image quality and mapping charge coupled device (CCD) pixel offset to a height variation assumes utmost importance. A typical optical is adversely affected by the distortions in the images introduced by the optical components. In this specific case, the optical system employs a borescope that introduces distortions visible even to a naked untrained eye. One reason for this is the view angle of the borescope and the other is the presence of the lenses in the borescope. For borescopes to be used for quantitative characterization purposes, these distortions need to be corrected. Mapping the offset in the CCD chip into a height variation is a popular approach for triangulation. In this presentation, we will introduce an algorithm on how we remove the distortions from borescope images, and how we perform a height calibration for determining the surface topology through a borescope based system.

Inanc, Feyzi

2006-03-01

130

A new retrieval for cloud liquid water path using a ground-based microwave radiometer and measurements of cloud temperature.  

SciTech Connect

A new method to retrieve cloud liquid water path using 23.8 and 31.4 GHz microwave radiometer brightness temperature measurements is developed. This method does not depend on climatological estimates of either the mean radiating temperature of the atmosphere T{sub mr} or the mean cloud liquid water temperature T{sub cloud}. Rather, T{sub mr} is estimated from surface temperature and relative humidity measurements, while T{sub cloud} is estimated using millimeter-wave cloud radar data, together with atmospheric temperature profiles obtained from either radiosonde or rapid update cycle (RUC) model output. Simulations demonstrate that the new retrieval method significantly reduces the biases in the liquid water path estimates that are apparent in a site-specific retrieval based on monthly stratified, local climatology. An analysis of the liquid water path estimates produced by the two retrievals over four case study days illustrates trends and retrieval performances consistent with the model simulations.

Liljegren, J. C.; Clothiaux, E. E.; Mace, G. G.; Kato, S.; Dong, X.; Environmental Research; Pennsylvania State Univ.; Univ. of Utah; Hampton Univ.

2001-07-16

131

Classification of Cloud Types Through Infrared APT Imagery  

NSDL National Science Digital Library

This activity is designed to teach students about the different classes of clouds, as well as how they are classified. Students will learn about classification by performing their own classification of clouds based on information given them by instructors. Students will also use infrared ATP images to study clouds by height, temperature, and appearance.

Costulis, P.

2002-09-30

132

A simple cloud-based energy balance model to estimate dew  

Microsoft Academic Search

Two energy balance (EB) analyses, based on two different methods to estimate the downward long wave radiation, were used to model dew duration. Model I utilized cloud cover and cloud altitude to calculate sky temperatures whereas model II was based only on cloud cover to estimate sky apparent emissivity. The models were validated with hourly data from on-site weather station

A. C. Madeira; K. S. Kim; S. E. Taylor; M. L. Gleason

2002-01-01

133

Policy-Based Event-Driven Services-Oriented Architecture for Cloud Services Operation & Management  

Microsoft Academic Search

Cloud based services, by their nature, are distributed and traditional operation and management processes that often exert centralized control are not suited for cloud services operation and management. This paper introduces a Policy-based Event-driven Service-oriented Architecture (PESA) that enables the manageability of these loosely coupled services distributed across multiple public or private clouds or a hybrid cloud. PESA allows the

Pankaj Goyal; Rao Mikkilineni

2009-01-01

134

Ground-Based Observations of Cloud Features on Uranus  

Microsoft Academic Search

NSFCAM observations at 1.7 ?m in 1998 and 1999 recorded the first discrete cloud features to appear in ground-based digital images of Uranus and the brightest such feature ever observed. The differential contributions of these northern hemisphere features to Uranus' disk-integrated brightness range from 0.8±0.2% and 0.11±0.3% for two 1998 features, to 4.9±0.7% for one 1999 feature, which is four

L. A. Sromovsky; J. R. Spencer; K. H. Baines; P. M. Fry

2000-01-01

135

Impromptu Clusters for Near-Interactive Cloud-Based Services  

Microsoft Academic Search

Abstract We introduce Impromptu Clusters (ICs), a new ab- straction that makes,it possible to leverage cloud-based clusters to execute short-lived parallel tasks, for ex- ample,Internet services that use parallelism to deliver near-interactive responses. ICs are particularly relevant for resource-intensive web,applications in areas such as bioinformatics, graphics rendering, computational fi- nance, and search. In an IC, an application encapsulated inside a

H. Andrés Lagar-cavilla; Joseph Whitney; Adin Scannell; Stephen M. Rumble; Eyal De Lara; Michael Brudno; M. Satyanarayanan

136

Aerosol particles from tropical convective systems: 2. Cloud bases  

Microsoft Academic Search

Aerosol particles were collected at the altitudes of cloud bases during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida Area Cirrus Experiment (CRYSTAL-FACE) and analyzed using transmission electron microscopy. The particles consist of ammonium sulfate (45–90% by number), sea salt (5–45%), mineral dust (1–20%), and anthropogenic materials such as soot and fly ash (<3%). Ammonium sulfate particles have

Tomoko Kojima; Peter R. Buseck; J. Michael Reeves

2005-01-01

137

A global survey of aerosol-liquid water cloud overlap based on four years of CALIPSO-CALIOP data  

NASA Astrophysics Data System (ADS)

The presence of aerosols over highly reflective liquid water cloud tops poses a big challenge in simulating their radiative impacts. Particularly, absorbing aerosols, such as smoke, may have significant impact in such situations and even change the sign of net radiative forcing. Until now, it was not possible to obtain information on such overlap events realistically from the existing passive satellite sensors. However, the CALIOP instrument onboard NASA's CALIPSO satellite allows us to examine these events with an unprecedented accuracy. Using four years of collocated CALIPSO 5 km Aerosol and Cloud Layer Version 3 Products (June 2006-May 2010), we quantify, for the first time, the macrophysical characteristics of overlapping aerosol and water cloud layers globally. We investigate seasonal variability in these characteristics over six latitude bands to understand the hemispheric differences. We compute a) the percentage cases when such overlap is seen globally and seasonally when all aerosol types are included (AAO case) in the analysis, b) the joint histograms of aerosol layer base height and cloud layer top height, and c) the joint histograms of aerosol and cloud geometrical thicknesses in such overlap cases. We also investigate frequency of smoke aerosol-cloud overlap (SAO case). The results show a distinct seasonality in overlap frequency in both AAO and SAO cases. Globally, the frequency is highest during JJA months in AAO case, while for the SAO case, it is highest in SON months. The seasonal mean overlap frequency can regionally exceed 20% in AAO case and 10% in SAO case. There is a tendency that the vertical separation between aerosol and cloud layers increases from high to low latitude regions in the both hemispheres. In about 5-10% cases the vertical distance between aerosol and cloud layers is less than 100 m, while about in 45-60% cases it less than a kilometer in the annual means for different latitudinal bands. The frequency of occurrence of thicker aerosol layers gradually increases from poles to tropics. In about 70-80% cases, aerosol layers are less than a kilometer thick, while in about 18-22% cases they are 1-2 km thick. The frequency of aerosol layers 2-3 km thick is about 4-5% in the tropical belts during overlap events. The results further highlight spatial and temporal variations in aerosol-liquid water cloud overlap and suggest that the frequency of occurrence of such overlap events is far from being negligible globally.

Devasthale, A.; Thomas, M. A.

2010-09-01

138

Preliminary comparison of CloudSAT-derived microphysical quantities with ground-based measurements for mixed-phase cloud research in the Arctic  

NASA Astrophysics Data System (ADS)

The omnipresent existence of thin, mixed-phase clouds in northern polar latitudes presents special challenges to CloudSAT as it attempts to map radiatively relevant cloudiness around the globe. In this work, retrieved cloud properties of Arctic mixed-phase clouds observed simultaneously in Eureka, Canada by ground-based cloud radar and lidar, and by the CloudSAT Cloud-Profiling Radar (CPR) are compared. Through these comparisons, we evaluate the efficacy of identification of precipitation and assignment of cloud type by the 2B-CLDCLASS product, as well as the accuracy of microphysical retrievals from the 2B-CWC-RO product. These preliminary comparisons result in the following findings with regard to the CloudSAT retrievals: (1) The cloud detection algorithm worked well, detecting all clouds observed from surface based sensors. (2) Precipitation was not well identified, and was often mislabeled as cloud. (3) Both liquid and ice particle number densities retrieved by CloudSAT are found to be 1 to 2 orders of magnitude too high when compared to surface-based retrievals and previous studies of these cloud types. (4) CloudSAT particle effective sizes are often too large, with the exception of the largest particles, which are misidentified as liquid. (5) Water contents show the best agreement between the two retrieval types, as well as with measured values from outside studies. All comparisons were completed for raw liquid and ice retrievals, as well as for "composite" retrievals that partition liquid and ice contributions to measured reflectivity through a temperature-dependent algorithm. Differences found for these limited cases imply that careful analysis is required for application of these cloud products to mixed-phase cloud research. Furthermore, these differences help highlight specific assumptions within the CloudSAT algorithms that are in need of improvement to complete mixed-phase cloud retrievals.

de Boer, Gijs; Tripoli, Gregory J.; Eloranta, Edwin W.

2008-04-01

139

Automatically locating the typhoon center based on satellite cloud image  

Microsoft Academic Search

An automatic locating algorithm is presented for typhoon center locating using cloud motion wind vectors derived from the satellite cloud images. The cloud motion wind vectors are obtained by implementing template matching to a pair of interrelated satellite cloud images with stated time interval. The template matching is a process to find the child image that corresponds to the given

Zhengguang Liu; Juntao Xue; Yuanfei Yu; Bing Wu; Gary Shen

2004-01-01

140

Arctic Cloud Microphysics Retrievals from Surface-Based Remote Sensors at SHEBA  

Microsoft Academic Search

An operational suite of ground-based, remote sensing retrievals for producing cloud microphysical prop- erties is described, assessed, and applied to 1 yr of observations in the Arctic. All measurements were made in support of the Surface Heat Budget of the Arctic (SHEBA) program and First International Satellite Cloud Climatology Project Regional Experiment (FIRE) Arctic Clouds Experiment (ACE) in 1997-98. Retrieval

Matthew D. Shupe; Taneil Uttal; Sergey Y. Matrosov

2005-01-01

141

Thin apps store for smart phones based on private cloud infrastructure  

Microsoft Academic Search

A novel approach to implement cloud computing for smart phone devices has been presented based on Eucalyptus, an open source cloud-computing framework that provides infrastructure as a service (IaaS). It has full support of Virtualization and is Amazon Web Services interface compatible. A private cloud has been designed using Eucalyptus to develop a smart phone application store. The architecture, physical

Ashish Tanwer; Abhishek Tayal; Muzahid Hussain; Parminder Singh Reel

2010-01-01

142

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

143

Evaluation Method of the Industry's Innovation Capacity Based on Cloud Model  

Microsoft Academic Search

With Innovative capital perspective, the proportion of R & D personnel, R & D intensity, R & D productivity and per capita number of patents are constructed as the industry's innovation capacity evaluation indexes. Using cloud theoretical framework, the evaluation method of industry's innovation capacity based on cloud model is built. Through the backward cloud algorithm, this method combines qualitative

Li Shan; Xu Shenghua

2010-01-01

144

HEIGHTS PROGRAM.  

ERIC Educational Resources Information Center

|THE "HEIGHTS" PROGRAM, AS PART OF THE GREAT CITIES SCHOOL IMPROVEMENT PROGRAM, IS BASED ON THE BELIEF THAT MUCH CAN BE DONE TO CHANGE THE PATTERNS OF ASPIRATION, ACHIEVEMENT, AND ADJUSTMENT WHICH CULTURALLY DEPRIVED YOUTH TEND TO FOLLOW. TRADITIONAL GOALS OF EDUCATION WILL BE FOLLOWED, BUT THE TEACHERS AND STAFF WILL HAVE AT THEIR DISPOSAL A…

POTTER, LOUIS A.

145

Relative surface variation as a function of base station antenna heights at WiMAX Cell  

Microsoft Academic Search

This article gives calculation of the relative surface variation, for WiMAX cell, in percentage for covering particular modo of signal as a function of the WiMAX base station antenna heights. The first part of this paper gives a short description of WiMAX technology. Second part shows transmission modes in the WiMAX air interface, followed in the third part by mathematical

Winton Afric; Branka Zovko-Cihlar; Mislav Grgic

2008-01-01

146

A 12-channel VMEbus-based pulse-height analysis module  

SciTech Connect

The author describes a 12-channel VMEbus-based pulse-height analysis board that was designed for use in a high-rate, multidetector, gamma-ray imaging system. This module was designed to minimize dead-time losses and to allow all key parameters to be software controlled. Gamma-ray detectors are connected directly to this module, eliminating the need for additional electronics.

Arnone, G.J.

1993-12-01

147

A load-adapative cloud resource scheduling model based on ant colony algorithm  

Microsoft Academic Search

Dynamic scheduling cloud resources according to the change of the load are key to improve cloud computing on-demand service capabilities. This paper proposes a load-adaptive cloud resource scheduling model based on ant colony algorithm. By real-time monitoring virtual machine of performance parameters, once judging overload, it schedules fast cloud resources using ant colony algorithm to bear some load on the

Xin Lu; Zilong Gu

2011-01-01

148

Global aerosol effects on convective clouds  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols affect cloud properties, and thereby the radiation balance of the planet and the water cycle. The influence of aerosols on clouds is dominated by increase of cloud droplet and ice crystal numbers (CDNC/ICNC) due to enhanced aerosols acting as cloud condensation and ice nuclei. In deep convective clouds this increase in CDNC/ICNC is hypothesised to increase precipitation because of cloud invigoration through enhanced freezing and associated increased latent heat release caused by delayed warm rain formation. Satellite studies robustly show an increase of cloud top height (CTH) and precipitation with increasing aerosol optical depth (AOD, as proxy for aerosol amount). To represent aerosol effects and study their influence on convective clouds in the global climate aerosol model ECHAM-HAM, we substitute the standard convection parameterisation, which uses one mean convective cloud for each grid column, with the convective cloud field model (CCFM), which simulates a spectrum of convective clouds, each with distinct values of radius, mixing ratios, vertical velocity, height and en/detrainment. Aerosol activation and droplet nucleation in convective updrafts at cloud base is the primary driver for microphysical aerosol effects. To produce realistic estimates for vertical velocity at cloud base we use an entraining dry parcel sub cloud model which is triggered by perturbations of sensible and latent heat at the surface. Aerosol activation at cloud base is modelled with a mechanistic, Köhler theory based, scheme, which couples the aerosols to the convective microphysics. Comparison of relationships between CTH and AOD, and precipitation and AOD produced by this novel model and satellite based estimates show general agreement. Through model experiments and analysis of the model cloud processes we are able to investigate the main drivers for the relationship between CTH / precipitation and AOD.

Wagner, Till; Stier, Philip

2013-04-01

149

Volcanic plume height measured by seismic waves based on a mechanical model  

USGS Publications Warehouse

In August 2008 an unmonitored, largely unstudied Aleutian volcano, Kasatochi, erupted catastrophically. Here we use seismic data to infer the height of large eruptive columns such as those of Kasatochi based on a combination of existing fluid and solid mechanical models. In so doing, we propose a connection between a common, observable, short-period seismic wave amplitude to the physics of an eruptive column. To construct a combined model, we estimate the mass ejection rate of material from the vent on the basis of the plume height, assuming that the height is controlled by thermal buoyancy for a continuous plume. Using the estimated mass ejection rate, we then derive the equivalent vertical force on the Earth through a momentum balance. Finally, we calculate the far-field surface waves resulting from the vertical force. The model performs well for recent eruptions of Kasatochi and Augustine volcanoes if v, the velocity of material exiting the vent, is 120-230 m s-1. The consistency between the seismically inferred and measured plume heights indicates that in these cases the far-field ~1 s seismic energy radiated by fluctuating flow in the volcanic jet during the eruption is a useful indicator of overall mass ejection rates. Thus, use of the model holds promise for characterizing eruptions and evaluating ash hazards to aircraft in real time on the basis of far-field short-period seismic data. This study emphasizes the need for better measurements of eruptive plume heights and a more detailed understanding of the full spectrum of seismic energy radiated coeruptively.

Prejean, Stephanie G.; Brodsky, Emily E.

2011-01-01

150

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

151

Comparison of CERES-MODIS and CloudSat/CALIPSO cloud properties with DOE ARM AMF measurements at Shouxian, China  

NASA Astrophysics Data System (ADS)

Cloud properties derived from both the CERES-MODIS SSF Ed-2B products and CloudSat/CALIPSO level 2B products have been compared with Department of Energy, Atmospheric Radiation Measurements Mobile Facility (DOE AMF) measurements taken at the Shouxian site (32.55N, 116.78E), China during the period Oct. 15-Dec. 15 of 2008. The AMF data, such as cloud base/top heights and liquid water path are averaged over a 1-h interval centered at the time of each satellite overpass, and the CERES-MODIS and CloudSat/CALIPSO cloud properties are averaged within a 1x1 degree grid box centered at the Shouxian site. A total of 41 satellite overpasses have been selected for this study. The preliminary results show that most of the cloud effective heights derived from CERES-MODIS agree very well with the ARM cloud radar-lidar observations. However, some discrepancies in cloud LWP exist between MODIS and ARM AMF observations. For CERES-MODIS data, the median and mean of cloud effective heights are 6.6 and 6.9 km, respectively. The median and mean of cloud-base height observed by AMF cloud radar are 4.4 and 4.1 km, they are 8.5 and 7.9 km for cloud-top height. During the ARM AMF deployment, four cloud systems have been observed by both surface and satellite and used to improve our understanding to the cloud formation, growth, and dissipation process. For the observed four cloud systems, we will investigate the effect of CCN loading on the different stage of cloud process, and/or show how the satellite observations can improve our knowledge of the evolving process of clouds. The vertical profiles of cloud properties observed by both CloudSat/CALIPSO and ARM cloud radar are also compared where the peak reflectivity heights measured by CloudSat/CALIPSO are ~ 0.5 km lower than that measured by the ARM radar/lidar for both high level clouds and low level clouds.

Qiu, Y.; Dong, X.; Xi, B.; Minnis, P.

2010-12-01

152

Intuitive Terrain Reconstruction Using Height Observation-Based Ground Segmentation and 3D Object Boundary Estimation  

PubMed Central

Mobile robot operators must make rapid decisions based on information about the robot’s surrounding environment. This means that terrain modeling and photorealistic visualization are required for the remote operation of mobile robots. We have produced a voxel map and textured mesh from the 2D and 3D datasets collected by a robot’s array of sensors, but some upper parts of objects are beyond the sensors’ measurements and these parts are missing in the terrain reconstruction result. This result is an incomplete terrain model. To solve this problem, we present a new ground segmentation method to detect non-ground data in the reconstructed voxel map. Our method uses height histograms to estimate the ground height range, and a Gibbs-Markov random field model to refine the segmentation results. To reconstruct a complete terrain model of the 3D environment, we develop a 3D boundary estimation method for non-ground objects. We apply a boundary detection technique to the 2D image, before estimating and refining the actual height values of the non-ground vertices in the reconstructed textured mesh. Our proposed methods were tested in an outdoor environment in which trees and buildings were not completely sensed. Our results show that the time required for ground segmentation is faster than that for data sensing, which is necessary for a real-time approach. In addition, those parts of objects that were not sensed are accurately recovered to retrieve their real-world appearances.

Song, Wei; Cho, Kyungeun; Um, Kyhyun; Won, Chee Sun; Sim, Sungdae

2012-01-01

153

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

Microsoft Academic Search

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

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

2009-01-01

154

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

155

Cloud Security Service Providing Schemes Based on Mobile Internet Framework  

Microsoft Academic Search

This paper deals with the issues about dynamic cloud security services in mobile internet framework, where some important differences compared with traditional cloud security service exist, such as the complexity, mobility, openness and instability of the user groups. In view of these features, different enterprises and users may have different demands for cloud security services. Therefore, in order to provide

Lian-chi Zhou; Chun-di Xiu

2012-01-01

156

A cloud computing based 12-lead ECG telemedicine service  

PubMed Central

Background Due to the great variability of 12-lead ECG instruments and medical specialists’ interpretation skills, it remains a challenge to deliver rapid and accurate 12-lead ECG reports with senior cardiologists’ decision making support in emergency telecardiology. Methods We create a new cloud and pervasive computing based 12-lead Electrocardiography (ECG) service to realize ubiquitous 12-lead ECG tele-diagnosis. Results This developed service enables ECG to be transmitted and interpreted via mobile phones. That is, tele-consultation can take place while the patient is on the ambulance, between the onsite clinicians and the off-site senior cardiologists, or among hospitals. Most importantly, this developed service is convenient, efficient, and inexpensive. Conclusions This cloud computing based ECG tele-consultation service expands the traditional 12-lead ECG applications onto the collaboration of clinicians at different locations or among hospitals. In short, this service can greatly improve medical service quality and efficiency, especially for patients in rural areas. This service has been evaluated and proved to be useful by cardiologists in Taiwan.

2012-01-01

157

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

158

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

159

Spatial statistics of likely convective clouds in CloudSat data  

NASA Astrophysics Data System (ADS)

Spatial characteristics of cloud objects derived from 14 months of CloudSat data are analyzed with the aim of understanding global statistics for atmospheric convection. This study uses meteorological fields provided by NASA's Modern Era Reanalysis for Research and Applications (MERRA) and the European Center's ERA-Interim reanalysis to determine environmental conditions for the cloud objects. Width and aspect ratio statistics for clouds of likely convective origin are presented. Cloud object heights are compared with predictions from entraining plume models. A major finding of this study is that actual cloud depths are usually more than 50% smaller than those predicted by the plume models. This holds for a range of entrainment rate specifications, including rates based on observed cloud widths. A technique for isolating "mature" convective clouds based on their shape is proposed. When this technique is used to select objects, the comparison with the entraining plume model improves dramatically. Another result from this analysis is power law behavior in the cloud width distribution derived from CloudSat objects. After accounting for the difference between one-dimensional and two-dimensional sampling, the slope of the CloudSat distribution appears consistent with that found in earlier studies' cloud imagery. However, when clouds are selected using a minimum depth criterion, the resulting population is sharply peaked at widths close to this minimum depth. Finally, a weakly trimodal distribution of convective cloud depths is found, consistent with results from Johnson et al. (1999).

Bacmeister, J. T.; Stephens, G. L.

2011-02-01

160

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

161

Comparison of CERES-MODIS stratus cloud properties with ground-based measurements at the DOE ARM Southern Great Plains site  

NASA Astrophysics Data System (ADS)

Overcast stratus cloud properties derived for the Clouds and the Earth's Radiant Energy System (CERES) project using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) data are compared with observations taken at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern Great Plains site from March 2000 through December 2004. Retrievals from ARM surface-based data were averaged over a 1-h interval centered at the time of each satellite overpass, and the CERES-MODIS cloud properties were averaged within a 30 km × 30 km box centered on the ARM SGP site. Two data sets were analyzed: all of the data (ALL), which include multilayered, single-layered, and slightly broken stratus decks and a subset, single-layered unbroken decks (SL). The CERES-MODIS effective cloud heights were determined from effective cloud temperature using a lapse rate method with the surface temperature specified as the 24-h mean surface air temperature. For SL stratus, they are, on average, within the ARM radar-lidar estimated cloud boundaries and are 0.534 ± 0.542 km and 0.108 ± 0.480 km lower than the cloud physical tops and centers, respectively, and are comparable for day and night observations. The mean differences and standard deviations are slightly larger for ALL data, but not statistically different to those of SL data. The MODIS-derived effective cloud temperatures are 2.7 ± 2.4 K less than the surface-observed SL cloud center temperatures with very high correlations (0.86-0.97). Variations in the height differences are mainly caused by uncertainties in the surface air temperatures, lapse rates, and cloud top height variability. The biases are mainly the result of the differences between effective and physical cloud top, which are governed by cloud liquid water content and viewing zenith angle, and the selected lapse rate, -7.1 K km-1. On the basis of a total of 43 samples, the means and standard deviations of the differences between the daytime Terra and surface retrievals of effective radius re, optical depth, and liquid water path for SL stratus are 0.1 ± 1.9 ?m (1.2 ± 23.5%), -1.3 ± 9.5 (-3.6 ± 26.2%), and 0.6 ± 49.9 gm-2 (0.3 ± 27%), respectively, while the corresponding correlation coefficients are 0.44, 0.87, and 0.89. For Aqua, they are 0.2 ± 1.9 ?m (2.5 ± 23.4%), 2.5 ± 7.8 (7.8 ± 24.3%), and 28.1 ± 52.7 gm-2 (17.2 ± 32.2%), as well as 0.35, 0.96, and 0.93 from a total of 21 cases. The results for ALL cases are comparable. Although a bias in re was expected because the satellite retrieval of effective radius only represents the top of the cloud, the surface-based radar retrievals revealed that the vertical profile of re is highly variable with smaller droplets occurring at cloud top in some cases. The larger bias in optical depth and liquid water path for Aqua is due, at least partially, to differences in the Terra and Aqua MODIS visible channel calibrations. Methods for improving the cloud top height and microphysical property retrievals are suggested.

Dong, Xiquan; Minnis, Patrick; Xi, Baike; Sun-Mack, Sunny; Chen, Yan

2008-02-01

162

Cloud droplet size distributions in low-level stratiform clouds  

SciTech Connect

A database of stratus cloud droplet size distribution parameters, derived from in situ data reported in the existing literature, was created, facilitating intercomparison among datasets and quantifying typical values and their variability. From the datasets, which were divided into marine and continental groups, several parameters are presented, including the total number concentration, effective diameter, mean diameter, standard deviation of the droplet diameters about the mean diameter, and liquid water content, as well as the parameters of modified gamma and lognormal distributions. In light of these results, the appropriateness of common assumptions used in remote sensing of cloud droplet size distributions is discussed. For example, vertical profiles of mean diameter, effective diameter, and liquid water content agreed qualitatively with expectations based on the current paradigm of cloud formation. Whereas parcel theory predicts that the standard deviation about the mean diameter should decrease with height, the results illustrated that the standard deviation generally increases with height. A feature common to all marine clouds was their approximately constant total number concentration profiles; however, the total number concentration profiles of continental clouds were highly variable. Without cloud condensation nuclei spectra, classification of clouds into marine and continental groups is based on indirect methods. After reclassification of four sets of measurements in the database, there was a fairly clear dichotomy between marine and continental clouds, but a great deal of variability within each classification. The relevant applications of this study lie in radiative transfer and climate issues, rather than in cloud formation and dynamics. Techniques that invert remotely sensed measurements into cloud droplet size distributions frequently rely on a priori assumptions, such as constant number concentration profiles and constant spectral width. The results of this paper provide a basis for evaluating the sensitivity of these techniques. In particular, there were large enough differences in observed droplet spectral widths to significantly affect remotely sensed determinations of cloud microphysics.

Miles, N.L.; Verlinde, J.; Clothiaux, E.E.

2000-01-15

163

P1.20 RETRIEVAL OF CLOUD DROPLET CONCENTRATION OF LIQUID-WATER CLOUDS FROM GROUND BASED REMOTE SENSING OBSERVATION  

Microsoft Academic Search

The environment in which clouds develop is cru- cial for the cloud microphysics and therefore the cloud radiative properties. The impact of aerosols on cli- mate via modification of cloud radiative properties is called the aerosol indirect effect. Twomey (1977) rec- ognized the connection between increasing concentra- tion of aerosols acting as cloud condensation nuclei and thus increasing cloud droplet

Ela Grzeszczak; Hanna Pawlowska; Reinout Boers; Henk Klein Baltink

164

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

165

The Atmospheric Infrared Sounder Version 6 cloud products  

NASA Astrophysics Data System (ADS)

The Version 6 cloud products of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) instrument suite are described. The cloud top temperature, pressure, and height and effective cloud fraction are now reported at the AIRS field of view (FOV) resolution. Significant improvements in cloud height assignment over Version 5 are shown with pixel-scale comparisons to cloud vertical structure observed by the CloudSat 94 GHz radar and the Cloud-Aerosol LIdar with Orthogonal Polarization (CALIOP). Cloud thermodynamic phase (ice, liquid, and unknown phase), ice cloud effective diameter (De), and ice cloud optical thickness (?) are derived using an optimal estimation methodology for AIRS FOVs, and global distributions for January 2007 are presented. The largest values of ? are found in the storm tracks and near convection in the Tropics, while De is largest on the equatorial side of the midlatitude storm tracks in both hemispheres, and lowest in tropical thin cirrus and the winter polar atmosphere. Over the Maritime Continent the diurnal cycle of ? is significantly larger than for the total cloud fraction, ice cloud frequency, and De, and is anchored to the island archipelago morphology. Important differences are described between northern and southern hemispheric midlatitude cyclones using storm center composites. The infrared-based cloud retrievals of AIRS provide unique, decadal-scale and global observations of clouds over the diurnal and annual cycles, and captures variability within the mesoscale and synoptic scales at all latitudes.

Kahn, B. H.; Irion, F. W.; Dang, V. T.; Manning, E. M.; Nasiri, S. L.; Naud, C. M.; Blaisdell, J. M.; Schreier, M. M.; Yue, Q.; Bowman, K. W.; Fetzer, E. J.; Hulley, G. C.; Liou, K. N.; Lubin, D.; Ou, S. C.; Susskind, J.; Takano, Y.; Tian, B.; Worden, J. R.

2013-06-01

166

Assessment of variability in continental low stratiform clouds based on observations of radar reflectivity  

Microsoft Academic Search

The variability of overcast low stratiform clouds observed over the ARM Climate Research Facility Southern Great Plains (ACRF SGP) site is analyzed, and an approach to characterizing subgrid variability based on assumed statistical distributions is evaluated. The analysis is based on a vast (>1000 hours) radar reflectivity database collected by the Millimeter-Wave Cloud Radar at ACRF SGP site. The radar

Zena N. Kogan; David B. Mechem; Yefim L. Kogan

2005-01-01

167

Influences of barrier height and space charge on DC breakdown in BaTiO3-based ceramic capacitors  

Microsoft Academic Search

DC breakdown in BaTiO3-based multilayer ceramic capacitors (MLCs) was studied. An abnormal depressed dc breakdown region near the Curie temperature of BaTiO3 was observed. It was found that the crystal microstructure of BaTiO3-based ceramic in Curie temperature region transformed from the ferroelectric tetragonal phase to the paraelectric cubic phase while the barrier height increases. We assumed the increasing barrier height

Yuanxiang Zhou; Zixia Cheng; Ping Yan; Xidong Liang; Zhicheng Guan

2001-01-01

168

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

169

Edge features extraction from 3D laser point cloud based on corresponding images  

NASA Astrophysics Data System (ADS)

An extraction method of edge features from 3D laser point cloud based on corresponding images was proposed. After the registration of point cloud and corresponding image, the sub-pixel edge can be extracted from the image using gray moment algorithm. Then project the sub-pixel edge to the point cloud in fitting scan-lines. At last the edge features were achieved by linking the crossing points. The experimental results demonstrate that the method guarantees accurate fine extraction.

Li, Xin-feng; Zhao, Zi-ming; Xu, Guo-qing; Geng, Yan-long

2013-09-01

170

Dealing with clouds from space-based ultraspectral IR observations  

NASA Astrophysics Data System (ADS)

Hyperspectral infrared sounders with nadir observations are limited by the cloud cover It is critical to detect the clouds in satellite measurements and to accurately retrieve the atmospheric and surface parameters with cloud contamination measurements An inversion scheme has been developed dealing with cloudy as well as cloud-free radiances observed with ultraspectral infrared sounders to simultaneously retrieve surface atmospheric thermodynamic and cloud microphysical parameters A fast radiative transfer model which applies to the clouded atmosphere is used for atmospheric profile and cloud parameter retrieval A one-dimensional 1-d variational multi-variable inversion solution is used to iteratively improve the background state defined by an eigenvector-regression-retrieval The solution is iterated in order to account for non-linearity in the 1-d variational solution NPOESS Airborne Sounder Testbed -- Interferometer NAST-I retrievals are compared with coincident observations obtained from dropsondes and the nadir-pointing Cloud Physics Lidar CPL This work was motivated by the need to obtain solutions for atmospheric soundings from infrared radiances observed for every individual field of view regardless of cloud cover from future ultraspectral geostationary satellite sounding instruments such as the Geosynchronous Imaging Fourier Transform Spectrometer GIFTS and the Hyperspectral Environmental Suite HES However this retrieval approach can also be applied to the ultraspectral sounding instruments to fly on polar satellites such

Zhou, D.; Smith, W.; Liu, X.; Larar, A.; Mango, S.; Huang, H.-L.

171

Determination of Cloud Vertical Structure from Upper-Air Observations.  

NASA Astrophysics Data System (ADS)

A method is described to use rawinsonde data to estimate cloud vertical structure, including cloud-top and cloud-base heights, cloud-layer thickness, and the characteristics of multilayered clouds. Cloud-layer base and top locations are identified based on three criteria: maximum relative humidity in a cloud of at least 87%, minimum relative humidity of at least 84%, and relative humidity jumps exceeding 3% at cloud-layer top and base, where relative humidity is with respect to liquid water at temperatures greater than or equal to 0°C and with respect to ice at temperatures less than 0°C. The analysis method is tested at 30 ocean sites by comparing with cloud properties derived from other independent data sources. Comparison of layer-cloud frequencies of occurrence with surface observations shows that rawinsonde observations (RAOBS) usually detect the same number of cloud layers for low and middle clouds as the surface observers, but disagree more for high-level clouds. There is good agreement between the seasonal variations of RAOBS-determined top pressure of the highest cloud and that from the International Satellite Cloud Climate Project (ISCCP) data. RAOBS-determined top pressures of low and middle clouds agree better with ISCCP, but RAOBS often fail to detect very high and thin clouds. The frequency of multilayered clouds is qualitatively consistent with that estimated from surface observations. In cloudy soundings at these ocean sites, multilayered clouds occur 56% of the time and are predominately two layered. Multilayered clouds are most frequent (70%) in the Tropics (10°S 10°N) and least frequent at subtropical eastern Pacific stations. The frequency of multilayered clouds is higher in summer than in winter at low-latitude stations (30°S 30°N), but the opposite variation appears at the two subtropical stations. The frequency distributions of cloud top, cloud base, and cloud-layer thickness and cloud occurrence as a function of height are also presented. The lowest layer of multilayered cloud systems is usually located in the atmospheric boundary layer.

Wang, Junhong; Rossow, William B.

1995-10-01

172

GROUND-BASED CLOUD IMAGES AND SKY RADIANCES IN THE VISIBLE AND NEAR INFRARED REGION FROM WHOLE SKY IMAGER MEASUREMENTS  

Microsoft Academic Search

Automatic cloud documentation from the ground is one of the basic tools to set up cloud climatologies with high resolution in space and time. Ground-based cloud data are of specific importance to study the role of clouds on the radiation balance of the earth's surface and the lower atmosphere. They can also provide ground-truth information for satellite-retrieved cloud parameters. A

Uwe Feister; Janet Shields; Monette Karr; Richard Johnson; Klaus Dehne; Michael Woldt

173

Cloud Super-Cooled Liquid Water Estimation from Satellite Data  

NASA Astrophysics Data System (ADS)

An automated algorithm for estimating cloud super-cooled liquid water (SLW) from satellite data was developed to perform cloud surveys for assessing potential precipitation enhancement. The algorithm produces spatial cloud SLW column distributions by utilizing many of the Moderate Resolution Imaging Spectroradiometer (MODIS) derived cloud products in addition to parameterizations developed to estimate vertical cloud thickness and fractional cloud liquid water content. Vertically derived cloud SLW is integrated to produce column totals. Sensitivity studies identified differences up to 30% in SLW content from individual changes in the minimum cloud optical depth threshold, vertical cloud thickness estimation, moist adiabatic lapse rate, and cloud liquid fraction parameterization constants. Corrections to MODIS cloud water path artifacts also reduced the estimated SLW content by 10% to 50%. Validation of the cloud base height and temperature estimates and derived total column SLW has begun using ground data from the Atmospheric Radiation Measurement North Slope Alaska site and CloudSat radar derived cloud products. Results thus far indicate that the algorithm may underestimate important cloud properties such as cloud thickness and cloud liquid water content which, in turn, may lead to an underestimation of cloud SLW. Comparisons of the algorithm’s vertical estimates of cloud SLW to aircraft data taken during the Indirect and Semi-Direct Aerosol Campaign (ISDAC) in northern Alaska yield very good results. National Center for Environmental Prediction reanalysis data was sampled along with annual MODIS datasets in both dry and wet years over the state of New Mexico to identify specific environmental indicators. Although cloud coverage was similar between the two periods, cloud SLW was found to be 60% greater and the number of days in which the 500 mb level wind was predominantly westerly increased by 12% during the wet year. The parameters with the highest correlation to cloud SLW were the 700 mb to the 500 mb level relative humidity.

Roskovensky, J. K.; Ivey, M.; Porch, W.; Beavis, N.; Herrman, R.

2010-12-01

174

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

175

Monitoring Insiders Activities in Cloud Computing Using Rule Based Learning  

Microsoft Academic Search

One of the essential but formidable tasks in cloud computing is to detect malicious attacks and their types. A cloud provider's constraints or inability in monitoring its employees, and lack of transparency, may make the detection process even harder. We found these insiders' activities form similar pattern in the monitoring systems as some other cyber attacks because these also uses

A. B. M. Shawkat Ali; Saleh A. Wasimi

2011-01-01

176

Based on Private Matching and Min-attribute Generalization for Privacy Preserving in Cloud Computing  

Microsoft Academic Search

When our private data are out-sourced in cloud computing, we should guarantee the confidentiality and search ability of the private data. However, nowadays privacy preserving issues in the cloud have not been carefully explored at current stage. To relieve individuals' concerns of their data privacy, this paper explores a new approach based on private matching and min-attribute generalization to solve

Jian Wang; Jiajin Le

2010-01-01

177

HASBE: A Hierarchical Attribute-Based Solution for Flexible and Scalable Access Control in Cloud Computing  

Microsoft Academic Search

Cloud computing has emerged as one of the most influential paradigms in the IT industry in recent years. Since this new computing technology requires users to entrust their valuable data to cloud providers, there have been increasing security and privacy concerns on outsourced data. Several schemes employing attribute-based encryption (ABE) have been proposed for access control of outsourced data in

Zhiguo Wan; Jun'e Liu; Robert H. Deng

2012-01-01

178

The Research and Application of Content-Based Satellite Cloud Image Retrieval  

Microsoft Academic Search

Content-based satellite cloud image retrieval is a very important problem in image processing and analysis field. Traditional image retrieval method has some limitation, for realized image retrieval accurately and quickly, the CBIR method is an adaptive method. For achieved good retrieval result, some of the pretreatment method of the satellite cloud image was used, and the experiment effect was shown.

Wei ShangGuan; YanLing Hao; YanHong Tang; Yi Zhu

2007-01-01

179

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

180

Atlas and Catalog of Dark Clouds Based on the 2 Micron All Sky Survey  

NASA Astrophysics Data System (ADS)

This paper presents an atlas and catalog of dark clouds derived based on the 2 Micron All Sky Survey Point Source Catalog (2MASS PSC). Color excess maps of E (J - H) and E (H - KS) as well as extinction maps of AJ, AH, and AKS covering all of the sky have been produced at the 1' grid with a changing angular resolution (˜1'-12'), depending on the regions in the sky. Maps drawn at the lower 15' grid with a fixed 1° resolution were also derived for various sets of threshold magnitudes in the J, H, and KS bands to estimate the background star colors and star densities needed to derive the color excess and extinction maps. The maps obtained in this work are presented on various scales in a series of figures that can be used as an atlas of dark clouds for general research purposes. On the basis of the E (J - H) and AJ maps drawn at the 1' grid, we have carried out a systematic survey for dark clouds all over the sky. In total, we identified 7614 dark clouds, and measured the coordinates, extents, and AV values for each of them. We also searched for their counterparts in a previously published catalog of dark clouds based on the optical photographic plates DSS (Dobashi et al. 2005, PASJ, 57, S1). These cloud parameters, including the information of the counterparts, are compiled into a new catalog of dark clouds. The atlas and catalog organized in this paper mainly trace relatively dense regions in dark clouds, revealing a number of dense cloud cores leading to star formation, while those presented by Dobashi et al. (2005) based on the optical database are more suited to trace less-dense regions and to reveal the global extents of dark clouds. These two datasets are complementary, and all together, they are useful to picture the structures of dark clouds in various density ranges.

Dobashi, Kazuhito

2011-01-01

181

Airborne remote sensing of cloud radiative smoothing during the Baltex Bridge Cloud campaign  

NASA Astrophysics Data System (ADS)

Based on airborne observations during the Baltex Bridge Cloud (BBC) campaign in September 2001, the impact of two layer cloud systems, gas absorption and surface albedo on cloud radiative smoothing is investigated. Multispectral nadir radiance measurements have been conducted which cover the visible and near infrared wavelength range. The observed radiances are transformed into Fourier space where ranges of scale-invariance are identified. Associated slopes and scale breaks are determined and used to characterize the impacts on cloud radiative smoothing. The results reveal that an increase of gas absorption reduces the small scale slope and the scale break due to a decreasing likelihood of horizontal photon transport. Another impact is that the increasing gas absorption reduces the cloud surface interaction, which is indicated by an increase of the large scale slope. An increasing surface albedo results in large scale cloud radiative smoothing and is associated with a decrease of the large scale slope. This effect depends on the cloud height and the cloud morphology. Two layer cloud systems exhibit a similar behaviour in Fourier space as large surface albedos beneath a single cloud deck. It is argued that the impact of two layer cloud systems on large scale cloud radiative smoothing may not be typical for two layer clouds.

Schröder, Marc; Bennartz, Ralf; Fischer, Jürgen; Ruhtz, Thomas

2004-11-01

182

Learning-based computing techniques in geoid modeling for precise height transformation  

NASA Astrophysics Data System (ADS)

Precise determination of local geoid is of particular importance for establishing height control in geodetic GNSS applications, since the classical leveling technique is too laborious. A geoid model can be accurately obtained employing properly distributed benchmarks having GNSS and leveling observations using an appropriate computing algorithm. Besides the classical multivariable polynomial regression equations (MPRE), this study attempts an evaluation of learning based computing algorithms: artificial neural networks (ANNs), adaptive network-based fuzzy inference system (ANFIS) and especially the wavelet neural networks (WNNs) approach in geoid surface approximation. These algorithms were developed parallel to advances in computer technologies and recently have been used for solving complex nonlinear problems of many applications. However, they are rather new in dealing with precise modeling problem of the Earth gravity field. In the scope of the study, these methods were applied to Istanbul GPS Triangulation Network data. The performances of the methods were assessed considering the validation results of the geoid models at the observation points. In conclusion the ANFIS and WNN revealed higher prediction accuracies compared to ANN and MPRE methods. Beside the prediction capabilities, these methods were also compared and discussed from the practical point of view in conclusions.

Erol, B.; Erol, S.

2013-03-01

183

Vertical structure of ice cloud layers from CloudSat and CALIPSO measurements and comparison to NICAM simulations  

NASA Astrophysics Data System (ADS)

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 253 K 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

2013-09-01

184

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

185

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

186

New-Knowledge-View Based Ontology Cloud Model  

Microsoft Academic Search

In this article, an ontology cloud model and its corresponding definition and operation is brought forward. The new-knowledge-view and pragmatic which leads to virginity and creativity of knowledge is embodied in this model, and the knowledgepsilas characters including uncertainty, inconsistency, time-varying and sociality, regularity is well expressed in this model too. As a result, Knowledge modeling by ontology-cloud model is

Jiang Zhu; Wenhua Wang

2008-01-01

187

Facial plastic surgery area acquisition method based on point cloud mathematical model solution.  

PubMed

It is one of the hot research problems nowadays to find a quick and accurate method of acquiring the facial plastic surgery area to provide sufficient but irredundant autologous or in vitro skin source for covering extensive wound, trauma, and burnt area. At present, the acquisition of facial plastic surgery area mainly includes model laser scanning, point cloud data acquisition, pretreatment of point cloud data, three-dimensional model reconstruction, and computation of area. By using this method, the area can be computed accurately, but it is hard to control the random error, and it requires a comparatively longer computation period. In this article, a facial plastic surgery area acquisition method based on point cloud mathematical model solution is proposed. This method applies symmetric treatment to the point cloud based on the pretreatment of point cloud data, through which the comparison diagram color difference map of point cloud error before and after symmetry is obtained. The slicing mathematical model of facial plastic area is got through color difference map diagram. By solving the point cloud data in this area directly, the facial plastic area is acquired. The point cloud data are directly operated in this method, which can accurately and efficiently complete the surgery area computation. The result of the comparative analysis shows the method is effective in facial plastic surgery area. PMID:24036743

Li, Xuwu; Liu, Fei

2013-09-01

188

A robust threshold-based cloud mask for the HRV channel of MSG SEVIRI  

NASA Astrophysics Data System (ADS)

A robust threshold-based cloud mask for the high-resolution visible (HRV) channel (1 × 1 km2) of the METEOSAT SEVIRI instrument is introduced and evaluated. It is based on operational EUMETSAT cloud mask for the low resolution channels of SEVIRI (3 × 3 km2), which is used for the selection of suitable thresholds to ensure consistency with its results. The aim of using the HRV channel is to resolve small-scale cloud structures which cannot be detected by the low resolution channels. We find that it is of advantage to apply thresholds relative to clear-sky reflectance composites, and to adapt the threshold regionally. Furthermore, the accuracy of the different spectral channels for thresholding and the suitability of the HRV channel are investigated for cloud detection. The case studies show different situations to demonstrate the behaviour for various surface and cloud conditions. Overall, between 4 and 24% of cloudy low-resolution SEVIRI pixels are found to contain broken clouds in our test dataset depending on considered region. Most of these broken pixels are classified as cloudy by EUMETSAT's cloud mask, which will likely result in an overestimate if the mask is used as estimate of cloud fraction.

Bley, S.; Deneke, H.

2013-03-01

189

Measuring the accuracy of self-reported height and weight in a community-based sample of young people  

PubMed Central

Background Self-reported anthropometric data are commonly used to estimate prevalence of obesity in population and community-based studies. We aim to: 1) Determine whether survey participants are able and willing to self-report height and weight; 2) Assess the accuracy of self-reported compared to measured anthropometric data in a community-based sample of young people. Methods Participants (16–29 years) of a behaviour survey, recruited at a Melbourne music festival (January 2011), were asked to self-report height and weight; researchers independently weighed and measured a sub-sample. Body Mass Index was calculated and overweight/obesity classified as ?25kg/m2. Differences between measured and self-reported values were assessed using paired t-test/Wilcoxon signed ranks test. Accurate report of height and weight were defined as <2cm and <2kg difference between self-report and measured values, respectively. Agreement between classification of overweight/obesity by self-report and measured values was assessed using McNemar’s test. Results Of 1405 survey participants, 82% of males and 72% of females self-reported their height and weight. Among 67 participants who were also independently measured, self-reported height and weight were significantly less than measured height (p=0.01) and weight (p<0.01) among females, but no differences were detected among males. Overall, 52% accurately self-reported height, 30% under-reported, and 18% over-reported; 34% accurately self-reported weight, 52% under-reported and 13% over-reported. More females (70%) than males (35%) under-reported weight (p=0.01). Prevalence of overweight/obesity was 33% based on self-report data and 39% based on measured data (p=0.16). Conclusions Self-reported measurements may underestimate weight but accurately identified overweight/obesity in the majority of this sample of young people.

2012-01-01

190

Measurement of solder ball height and shape defects using a visible supercontinuum based line scan interferometer  

Microsoft Academic Search

We identify shape defects on ~300 ?m high solder balls by measuring the 3D profile over +\\/-20 degrees down the ball surface. A broadband line scan interferometer enables measurement of ball height with 125 nm axial resolution.

Malay Kumar; Mohammed N. Islam; Fred L. Terry Jr; Douglas Davidson; Carl Aleksoff

2010-01-01

191

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

192

Surface Cloud Observations for Radiation, Climatology and Incorporation Into Satellite-Based Nephanalyses.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. An investigation of the potential value of surface cloud observations has been undertaken with special regard to their role in surface radiation modelling, global cloud climatologies and as an aid in satellite cloud retrieval. This type of data, for so long considered to be an inadequate source of cloud information, can now be recognised as contributing much to climate modelling (which requires accurate global cloud statistics). Surface cloud observations have been evaluated on a variety of spatial scales in order to highlight specific applications. The range of methods for obtaining cloud parameters from satellite radiances and from the ground is discussed. Intercomparison of satellite and surface retrievals shows that close agreement is often reached in terms of large scale cloud amounts, but that surface observations can provide valuable small scale information in situations where the satellite algorithm may fall. All-sky camera images have been used to illustrate the difficulties of reporting low optical depth cloud accurately from the surface and also to demonstrate how total and layered amounts can be observed with greater precision. The parameterisation of surface radiation fluxes is shown to be highly dependent on conventional cloud data and an analysis of high temporal resolution all-sky imagery has revealed how rapid changes in cloudiness may affect the performance of radiation models over different time scales. The use of climatological cloud type contingency probabilities in improving the 3-dimensional nature of satellite cloud retrievals has been examined. From a preliminary analysis of raw surface observations, it appears that the vertical association of cloud types exhibits a complex spatial and possibly seasonal dependency, requiring further investigation before such a scheme could be used to calibrate satellite retrievals. The main theme of this work, exploiting conventional cloud data to improve the results of satellite algorithms, is extended to include climatological examples of the U.S.A.F. 3D -Nephanalysis. Comparison of these against preliminary results from the International Satellite Cloud Climatology Project (ISCCP) show good agreement, whilst some unexpected discrepancies have been identified when comparing the ISCCP and surface climatologies. Overall, the benefits gained by incorporation of ground-based observations into global cloudiness evaluation derived primarily from satellite algorithms have been demonstrated.

Goodman, Alan Howard

193

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

Microsoft Academic Search

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

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

2005-01-01

194

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" where absorption by water vapor is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in two micro-windows, constrained by the transmission through clouds of stratospheric ozone emission. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius, visible optical depth, number concentration, and water path are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement program (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with ground-based microwave radiometer measurements of liquid water path. Compared to other retrieval methods, advantages of this technique include its ability to characterize thin clouds year round, that water vapor 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.

Garrett, T. J.; Zhao, C.

2012-11-01

195

Scale Dependence of Variability in Stratiform Clouds Based on Millimeter Wave Could Radar  

SciTech Connect

Internal variability of stratiform clouds is manifested on grid scales ranging from cloud resolving models to general circulation models, and its accurate formulation is one of the most important tasks in improvement of model predictions. Understanding cloud variability on different scales will help to develop and improve subgrid-scale cloud parameterizations. Information about variability is also crucial when dealing with retrieval of microphysical information from observations of volume averaged reflectivity parameters, since neglecting variability can lead to substantial biases in estimation of retrieved microphysical variables. The Atmospheric Radiation Measurement Program (ARM) operates millimeter wave cloud radar (MMCR) at the ARM Climate Research Facility over the Southern Great Plains (ACRF SGP) that provides a unique opportunity to obtain continuous observations in order to address issues of cloud variability. These data contain information on spatial and/or temporal short- and long-range correlations in cloudiness, enabling scale-by-scale (scaling) analyses over a range of hundreds of meters to hundreds of kilometers. The objective of this study is to conduct an analysis based on radar reflectivity observations of clouds over the ACRF SGP site with special emphasis on boundary layer clouds, and the effect of drizzle.

Kogan, Z.N.; Kogan, Y.L.; Mechem, D.B.

2005-03-18

196

Segmentation-based filtering and object-based feature extraction from airborne LiDAR point cloud data  

NASA Astrophysics Data System (ADS)

Three dimensional (3D) information about ground and above-ground features such as buildings and trees is important for many urban and environmental applications. Recent developments in Light Detection And Ranging (LiDAR) technology provide promising alternatives to conventional techniques for acquiring such information. The focus of this dissertation research is to effectively and efficiently filter massive airborne LiDAR point cloud data and to extract main above-ground features such as buildings and trees in the urban area. A novel segmentation algorithm for point cloud data, namely the 3D k mutual nearest neighborhood (kMNN) segmentation algorithm, was developed based on the improvement to the kMNN clustering algorithm by employing distances in 3D space to define mutual nearest neighborhoods. A set of optimization strategies, including dividing dataset into multiple blocks and small size grids, and using distance thresholds in x and y, were implemented to improve the efficiency of the segmentation algorithm. A segmentation based filtering method was then employed to filter the generated segments, which first generates segment boundaries using Voronoi polygon and dissolving operations, and then labels the segments as ground and above-ground based on their size and relative heights to the surrounding segments. An object-based feature extraction approach was also devised to extract buildings and trees from the above-ground segments based on object-level statistics derived, which were subject to a rule based classification system developed by either human experts or an inductive machine-learning algorithm. Case studies were conducted with four different LiDAR datasets to evaluate the effectiveness and efficiency of the proposed approaches. The proposed segmentation algorithm proved to be not only effective in separating ground and above-ground measurements into different segments, but also efficient in processing large datasets. The segmentation based filtering and object based feature extraction approaches have also demonstrated effectiveness in labeling the segments into ground and above-ground and in extracting buildings and trees from the above-ground segments. When incorporating spectral information from remote sensing imagery with the LiDAR data, the accuracy for feature extraction was further increased.

Chang, Jie

197

Plume Height Analysis of the 2009 Redoubt Eruption: A Comparison of MISR, AVHRR, and MODIS Data  

NASA Astrophysics Data System (ADS)

The eruption of Mt. Redoubt (March 2009) in the Alaskan-Aleutian volcanic chain brought attention to a major discrepancy between the different methods of ash cloud height determination used in a real-time operational setting. This discrepancy has implications for the use of satellite data (often the only monitoring tool available for remote volcanoes) to assess an ash cloud’s altitude and provide input to determine its future location through dispersion model forecasts. During Redoubt’s eruption, the satellite temperature method (which uses ash cloud temperatures from satellite imagery compared to atmospheric temperature profiles) consistently produced lower heights than ground-based radar, with the difference between the heights as great as 6 to 8 km (~50% difference). This poses a problem for scientists tracking the cloud, as it is unclear which sensor provides the most accurate height to use as input for dispersion models that predict ash cloud movement. Any inaccuracy in the height of the cloud can produce an inaccurate trajectory for the cloud’s motion. An accurate trajectory is necessary to assess hazards and relay information to the aviation community. A study of many of the height determination methods available to constrain plume altitude is underway (including ground-based radar, the temperature method, the displacement method, stereo methods, and pilot reports). Included in this study is a comparison of the Multi-angle Imaging SpectroRadiometer (MISR) sensor with two sensors that the Alaska Volcano Observatory uses for operational monitoring: the Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS). Stereo methods, using the MISR INteractive eXplorer (MINX) software, are used to constrain plume altitude from MISR data. Satellite temperature methods are used to constrain plume altitude from AVHRR and MODIS data. The results of this comparison show that the three sensors and their corresponding methods are able to detect the same layer in the ash cloud, and produce comparable heights, despite the fact that the sensors have different spectral and spatial resolution and operate in different wavelengths. This result suggests that the lower-altitude layer constrained by satellite temperature methods must correspond to an actual physical feature in the cloud, and that the higher-altitude layer seen by radar must correspond to a separate physical feature in the cloud. This presentation will present the height comparisons and discuss possible explanations for the different physical features in the plume.

Ekstrand, A. L.; Webley, P.; Dehn, J.; Nelson, D. L.; Garay, M. J.; Dean, K. G.

2010-12-01

198

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

199

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

200

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

201

Improving the Scalability of Cloud-Based Resilient Database Servers  

Microsoft Academic Search

\\u000a Many rely now on public cloud infrastructure-as-a-service for database servers, mainly, by pushing the limits of existing\\u000a pooling and replication software to operate large shared-nothing virtual server clusters. Yet, it is unclear whether this\\u000a is still the best architectural choice, namely, when cloud infrastructure provides seamless virtual shared storage and bills\\u000a clients on actual disk usage.\\u000a \\u000a \\u000a This paper addresses this

Lu ´ is Soares

2011-01-01

202

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

203

Aerosol effect on cloud droplet size as monitored from surface-based remote sensing over East China Sea region  

Microsoft Academic Search

The effect of increased aerosol concentrations on the low-level, non-precipitating, ice-free stratus clouds is examined using a suite of surface-based remote sensing systems. Cloud droplet effective radius and liquid water path are retrieved using cloud radar and microwave radiometer. Collocated measurements of aerosol scattering coefficient, size distribution and cloud condensation nuclei (CCN) concentrations were used to examine the response of

G. Pandithurai; T. Takamura; J. Yamaguchi; K. Miyagi; T. Takano; Y. Ishizaka; S. Dipu; A. Shimizu

2009-01-01

204

An alternative approach for the prediction of significant wave heights based on classification and regression trees  

Microsoft Academic Search

In this study, the performances of classification and regression trees for the prediction of significant wave heights were investigated. The data set used in this study is comprised of 5 years of wave and wind data gathered from a deep water location in Lake Michigan. Training and testing data include wind speed and wind direction as the input variables and significant

J. Mahjoobi; A. Etemad-Shahidi

2008-01-01

205

Exploiting virtualization for delivering cloud-based IPTV services  

Microsoft Academic Search

Cloud computing is a new infrastructure environ- ment that delivers on the promise of supporting on-demand services in a flexible manner by scheduling bandwidth, storage and compute resources on the fly. IPTV services like Video On Demand (VoD) and Live broadcast TV requires substantial bandwidth and compute resources to meet the real time re- quirements and to handle the very

Vaneet Aggarwal; Xu Chen; Vijay Gopalakrishnan; Rittwik Jana; K. K. Ramakrishnan; Vinay A. Vaishampayan

2011-01-01

206

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

207

SEMANTIC FEATURE BASED REGISTRATION OF TERRESTRIAL POINT CLOUDS  

Microsoft Academic Search

As an active remote sensing technique, Terrestrial Laser Scanning (TLS) is popular for constructing detailed 3D models of complex objects. To create a complete 3D scene, TLS point clouds scanned from multiple positions need to be registered to the same coordinate system. Conventional registration methods demand significant amount of manual work. Recent studies use geometric features (points, lines and planes)

A. Thapa; S. Pu; M. Gerke

208

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

209

Gossip-based resource management for cloud environments  

Microsoft Academic Search

We address the problem of resource management for a large-scale cloud environment that hosts sites. Our contribution centers around outlining a distributed middleware architecture and presenting one of its key elements, a gossip protocol that meets our design goals: fairness of resource allocation with respect to hosted sites, efficient adaptation to load changes and scalability in terms of both the

Fetahi Wuhib; Rolf Stadler; Mike Spreitzer

2010-01-01

210

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

211

Design and testing of a new aircraft-based cloud water sampling system  

NASA Astrophysics Data System (ADS)

Experimental studies of cloud processing mechanisms necessitate the collection of representative samples of cloud water for chemical analysis. In order to provide samples from clouds that are inaccessible from ground-based sampling stations, a new aircraft-based cloud water collection system has been developed. The objective of the design process was to produce an automated collector that can acquire well-characterized cloud water samples and is portable between multiple research aircraft. Issues such as cloud drop shatter and re-entrainment, system size and weight, and material compatibility with the anticipated chemical analyses were considered during the design process. The new cloud water collection system utilizes an axial-flow cyclone to centrifugally separate cloud drops from the air stream. An analysis of the axial-flow cyclone was performed with a finite volume based computational fluid dynamics (CFD) code. The predicted continuous phase (air) velocity field indicates that the cyclone generates a strong rotational flow field with a tangential velocity of 85 m s-1. Trajectory simulations predict that entrained cloud drops move rapidly to the wall of the axial-flow cyclone where they can be removed for storage. Collection efficiency as a function of drop size was ascertained and the 50% cut diameter was determined to be approximately 8 microns. An experimental laboratory calibration involving monodisperse fluorescein-tagged drops was performed to verify the numerical modeling results. The system was deployed during the Dynamics and Chemistry of Marine Stratocumulus, Phase II (DYCOMS-II) field project in July 2001. The DYCOMS-II campaign served as an evaluation program for the system as well as an opportunity to study the chemical composition of stratocumulus clouds in the remote marine environment. Over the course of the project, 50 samples were obtained during nine flights. Sample pH was measured on-site after each flight. Peroxide, formaldehyde, S(IV), trace metals and major ions (Cl-, NO3 -, SO42-, Na+, NH4+, K+, Ca2+, and Mg2+) were preserved on site and analyzed after the field campaign. The analyses were used to characterize the composition of the sampled clouds and to investigate cloud processing mechanisms, including the potential for rapid aqueous phase oxidation of S(IV) to sulfate.

Straub, Derek John

2002-01-01

212

Forecasting for Grid and Cloud Computing On-Demand Resources Based on Pattern Matching  

Microsoft Academic Search

Abstract: The Cloud phenomenon,brings along the cost-saving benefit of dynamic scaling. Knowledge in advance is necessary as the virtual resources that Cloud computing uses have a setup time that is not negligible. We propose a new approach to the problem of workload prediction based on identifying similar past occurrences to the current short-term workload history. We present in detail the

Eddy Caron; Frédéric Desprez; Adrian Muresan

2010-01-01

213

Cloud Phase Determination Using Ground-Based AERI Observations at SHEBA  

Microsoft Academic Search

ABSTRACT A new,technique for ascertaining the thermodynamic,cloud phase from high-spectral-resolution ground-based infrared measurements,made,by the Atmospheric,Emitted Radiance Interferometer (AERI) is presented. This technique takes advantage,of the differences in the index of refraction of ice and water between,11 and 19 mm. The differences in the refractive indices translate into differences in cloud emissivity at the various wavelengths, which are used to determine

D. D. Turner; S. A. Ackerman; B. A. Baum; H. E. Revercomb; P. Yang

2003-01-01

214

Determination of cloud vertical structure from upper air observations and its effects on atmospheric circulation in a GCM  

NASA Astrophysics Data System (ADS)

The GISS GCM is used to investigate effects of macro- scale cloud vertical structure (CVS), including cloud base and top heights and layer thicknesses, and the characteristics of multi-layered clouds, on atmospheric circulations. Clouds suppress Hadley circulations in the transient state, but intensify them in the equilibrium state. The existence of multi-layered clouds is more important than top heights of the highest cloud layers for Hadley circulations. Vertical gradients of clouds are more important than their horizontal gradient for circulations. The results suggest the importance of cloud top radiative cooling and base warming within clouds for circulations and thus the requirement of resolving such structure for observations and GCMs. Clouds affect atmospheric circulations by directly modifying radiative cooling and indirectly imposing opposing effects on latent heating mainly through modulating atmospheric thermodynamics. A method was developed to use rawinsonde humidity profiles to estimate cloud layer base and top locations based on the fact of high relative humidity (RH) within clouds and sudden RH jumps at cloud boundaries. The analysis method has been applied in a 20-year (1976-1995) global daily rawinsonde dataset to create a 20-year global CVS dataset, and has been validated by comparing RAOBS-determined CVS properties with other independent data sources. RAOBS can sample all low and middle clouds and determine their boundaries accurately. However, RAOBS might oversample 10% of all clouds globally which might be clear moisture layers, and miss high and thin clouds by 5%. Global and annual mean cloud top and base heights, layer thickness and separation distance between two consecutive multiple cloud layers are 4.26 km MSL, 2.87 km MSL, 1.39 km and 2.1 km, respectively. Globally, multi-layered clouds occur 46% of the time and are predominately two- layered. The lowest layer of multi-layered cloud systems is usually located in the atmospheric boundary layer. Clouds over ocean occur more frequently at low levels and are thinner, but are more often formed in multiple layers than clouds over land. Average cloud top and base heights decrease with latitudes in each hemisphere, and are higher in summer than in winter. Multi-layered clouds exist most frequently in the tropics but least in the subtropics, and there are more multi-layered clouds in summer than in winter. CVS also exhibits significant regional variations.

Wang, Junhong

1997-08-01

215

Height estimates using AATSR dual view  

NASA Astrophysics Data System (ADS)

We describe a height estimate algorithm based on radiances measured at the top of the atmosphere (TOA) by the Advanced Along Track Scanning Radiometer (AATSR) aboard the ENVISAT satellite. The algorithm is designed to estimate volcanic ash plume top heights, but it can be used for other high contrast features as well, such as dust and smoke plumes, meteorological clouds or surface features. The algorithm is designed to be fully automatic, which allows it to be run in parallel with various retrieval algorithms used in Helsinki, such as aerosol and cloud optical depth retrievals and ash plume concentration retrievals. Information on the feature height is important for choosing the correct retrieval parameters, and could be used for example in dispersion calculations. The center wavelengths of the AATSR visible (VIS) and near-infrared (NIR) channels are 0.555, 0.659, 0.865, 1.61 ?m. The AATSR thermal channels are centered at 3.7, 11, and 12 ?m and provide brightness temperature data. The visible channels can be used for aerosol optical depth (AOD) retrievals, while the thermal channels are useful in ash or dust detection. The AATSR instrument has two views, a nadir view and a 55° forward view. The stereo view is used to estimate the feature height. A spatial correlation algorithm can be used to collocate the views, and the resulting parallax gives a height estimate with nominal accuracy of 1 km. Statistical methods are used to assess the quality of retrieved heights and to filter out unreliable data. The stereo view is also used in the AOD retrieval, with the AATSR dual view (ADV) algorithm, which does not require a priori knowledge of the surface reflectance.

Virtanen, Timo; Kolmonen, Pekka; Sogacheva, Larisa; Sundström, Anu-Maija; Rodriguez, Edith; Atlaskina, Ksenia; Hannukainen, Meri; Saponaro, Giulia; de Leeuw, Gerrit

2013-04-01

216

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

217

Snow surface height change in Dome-A from 2003 to 2008 based on ICESat/GLAS and DEM generated from GPS  

NASA Astrophysics Data System (ADS)

Dome A is the summit in Antarctic ice sheet. In this paper, snow accumulation from 2003 to 2008 in this area of about 20 km×20 km was derived for the first time with ICESat/GLAS data and local DEM, produced with GPS data collected in 2008. Four tracks data covering this region from 2003 to 2009 were selected for later use. This paper primarily introduced the method and final results. To get high quality ICESat/GLAS data, quality-control measures were firstly taken to exclude those highly saturated footprints or those affected by cloud. Secondly, an improved method to obtain Snow Surface-Height Changes (SSHC) based on GPS DEM and GLAS data was put forward. The basic principle is to convert ICESat data from elevation data with datum of Topex/Poseidon to relative elevation data with datum of a local DEM. Thirdly, Snow Surface Height Change (SSHC) tendency in a grid of 300 m×300 m was calculated if footprints in the grid were from more than six different campaigns (Figure 1). Fourthly, the tendency of SSHC in Dome-A region from 2003 to 2008 was given as an average of all grid data and snow accumulation rate of about 3.2±1.2 cm a-1 is derived, corresponding to 0.6±0.2 cm w e a-1. Snow accumulation from automatic weather station (AWS) data from 2005 to 2008 is used to make comparison with that from GLAS data at a buffer area of 2 km centered at the Dome-A AWS. Correlation coefficient between them is 0.80 for two GLAS tracks when a 9-day average of AWS data was adopted. The lower correlation coefficient may be owing to location difference because AWS is not covered by any ICESat footprints.

Wang, X.; Cheng, X.; Gong, P.; Li, Z.; Huang, H.; Hui, F.; Li, X.

2011-12-01

218

Aerosol-cloud-drizzle interactions in warm boundary layer clouds using ground-based measurements from Atlantic and continental European sites  

NASA Astrophysics Data System (ADS)

Aerosol impacts the climate directly through scattering and absorbing radiation, and indirectly through altering properties of clouds and precipitation. With increasing ambient aerosol concentration, it is agreed that the redistribution of cloud water to more numerous, but smaller cloud droplets suppresses precipitation. However, the magnitude of precipitation suppression is uncertain, and the response of total cloud water to aerosol concentration remains poorly observed and understood. To better understand how aerosols regulate macro- and microphysical properties of boundary-layer clouds, and to establish statistical relationships of aerosol-cloud-precipitation interactions, we analyze high-temporal resolution observations from the Atmospheric Radiation Measurement (ARM) Mobile Facility deployments in Germany in 2007 and in the Azores during 2009-2010. Through synergy between ground-based aerosol observing systems, active and passive remote sensing instruments, we will show how the drizzle rate at cloud base varies with aerosol concentration. We will also demonstrate how the probability of precipitation and the precipitation susceptibility respond to ambient aerosol concentration, and whether these responses agree with results from state-of-the-art satellite observations and climate models.

Mann, Julian; Chiu, Christine; Hogan, Robin; O'Connor, Ewan

2013-04-01

219

Profiles of cloud fraction and water content deduced from ground-based solar radiation measurements  

NASA Astrophysics Data System (ADS)

Ground-based measured solar radiation fluxes are used to derive simultaneously cloud water content and cloud fraction cover. In this paper we present a new method for prognostically inferring cloud microphysical properties based on previous work of Chou and Suarez. A look up table method combined with simulated annealing process is associated with the Chou and Suarez radiation transfer model called CLIRAD-SW. This model which is of great sensitivity has been validated for several atmospheres. Calculations here are conducted for an equivalent period of one year of measurement realized by the MINREST-LRE program for the Yaoundé meteorological station during the year 1984 and are focused on the previously derived average solar days similar to those proposed by Klein and more representative of the monthly solar radiation profile. In order to reduce computational time, mean values of liquid, mixed phase and ice cloud effective radius are used according to those proposed by Chou M.D. As part of our retrieving method, diffuse and global fluxes calculated for each set of cloud and aerosol microphysical characteristics are compared with the fluxes measured during the corresponding period. The obtained results are in very good agreement with those fluxes with relative errors ranging from 0.001% to 1.9% for diffuse flux and from 0.0009% to 2% for global flux. Mean cloud fraction profile obtained was generally well correlated with seasons whereas the correlation of cloud water content with seasons was not very good. However, the characteristic trend was in good agreement with the change in seasons. The overall agreement observed suggests that the method is capable of characterizing cloud water content and fraction for the given period of the day and the year although the lack of in situ measurements was a limitation for a valuable verification of the accuracy of the method.

Akana Nguimdo, L.; Njomo, D.

2010-11-01

220

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

221

Long-term impacts of aerosols on the vertical development of clouds and precipitation  

NASA Astrophysics Data System (ADS)

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, Zhanqing; Niu, Feng; Fan, Jiwen; Liu, Yangang; Rosenfeld, Daniel; Ding, Yanni

2011-12-01

222

Imputation of single-tree attributes using airborne laser scanning-based height, intensity, and alpha shape metrics  

Microsoft Academic Search

Forest inventories based on single-tree interpretation of airborne laser scanning (ALS) data often rely on an allometric estimation chain in which inaccuracies in the estimates of the diameter at breast height (DBH) propagate to other characteristics of interest such as the stem volume. Our purpose was to test nearest neighbor imputation by the k-Most Similar Neighbor (k-MSN) and the Random

Jari Vauhkonen; Ilkka Korpela; Matti Maltamo; Timo Tokola

2010-01-01

223

Accuracy of Body Mass Index Categories Based on Self-Reported Height and Weight Among Women in the United States  

Microsoft Academic Search

Objective The purpose of this study was to assess the accuracy of BMI categories based on self-reported height and weight in adult\\u000a women. Methods BMI categories from self-reported responses were compared to categories measured during physical examination from women,\\u000a age 18 or older, who participated in the National Health and Examination Survey, 1999–2004. We first examined strength of\\u000a agreement using

Benjamin M. Craig; Alexandra K. Adams

2009-01-01

224

Estimation of daily cloud-free, snow-covered areas from MODIS based on variational interpolation  

NASA Astrophysics Data System (ADS)

NASA's MODIS global snow-covered area (SCA) products are one of the mission's major objectives that frequently contain cloud hindrances, which degrade their practical usability. Many techniques have been developed to mitigate the problem but with no assurance of eliminating all of the clouds. An image-processing algorithm with its kernel based on the variational interpolation theorem is developed to automatically obtain cloud-free dynamic SCA maps from MODIS. Two cases consisting of "accumulation" and "melting" phases are processed and validated using observations at 121 ground-snow sensors over the Sierra Nevada Mountains in California. The results show that the algorithm cleared all the cloud hindrance over the period of study. In terms of accuracy, the retrieved cloud-free snow cover for the accumulation case had an average omission error of around 22.5% and average commission error of around 2.1%, as compared to all available ground sensors. These high percentages of errors basically came from the input data of Terra and Aqua, which had omission errors of 14.3% and 20.2% (and the commission errors of ˜0.5%), respectively. For the melting case, when there were fewer clouds and hence more sensors available, the errors of omission and commission between the algorithm and direct observations from Terra and Aqua were close to each other (5.7-5.0% for omission and 0% for commission).

Xia, Qing; Gao, Xiaogang; Chu, Wei; Sorooshian, Soroosh

2012-09-01

225

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

226

GEWEX Cloud System Study (GCSS) cirrus cloud working group: modelling case development based on 9 March 2000 ARM SGP observations  

NASA Astrophysics Data System (ADS)

The GCSS working group on cirrus focuses on inter-comparison of model simulations for models ranging from very detailed microphysical and dynamical models through to general circulation models (GCMs). In the previous GCSS inter-comparison, it was a surprise to the modeling community how much of a range there was in ice water path predictions by different cirrus models for such idealized cases. There was some grouping according to the complexity of models; however, there were no observations with which to distinguish between model performance. The aim of the current GCSS cirrus inter-comparison is to base the study on a rigorously observed case study. In this way, the case may be used to identify which models in the inter-comparison are performing well and highlight areas for model development as well as provide a base case for future models to compare against when being developed or when testing new developments within existing models. In this paper, we present the case development for the current GCSS working group study on cirrus cloud. This paper summarizes how the case was developed and based on the 9 March 2000 Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) intensive observation period (IOP). To our knowledge, this case offers the most detailed case study for cirrus comparison available, with extensive effort to derive the most appropriate large scale forcing as possible which is such a significant determinant of clouds. We anticipate this will offer significant improvement over past comparisons which have mostly been loosely based on observations. Notably this study makes use of retrievals of observations of ice water content, ice number concentration, and fall velocity, thus offering several constraints to evaluate model performance. The case study is developed utilizing various observations including ARM SGP remote sensing including the Millimeter cloud radar (MMCR), radiometers, radiosondes, aircraft observations, satellite observations, objective analysis and complemented with results from the Rapid Update Cycle (RUC) model output and bespoke gravity wave simulations using the 3-dimensional velocities over mountains (3DVOM) model. An initial modelling assessment of the case has been shown using the UK Met Office Large Eddy Simulation Model (LEM) which supports the use of this case for the full inter-comparison study.

Yang, H.; Dobbie, S.; Mace, G. G.; Ross, A.; Quante, M.

2011-10-01

227

Comparison of precipitation observations from a prototype space-based cloud radar and ground-based radars  

NASA Astrophysics Data System (ADS)

A prototype space-based cloud radar has been developed and was installed on an airplane to observe a precipitation system over Tianjin, China in July 2010. Ground-based S-band and Ka-band radars were used to examine the observational capability of the prototype. A cross-comparison algorithm between different wavelengths, spatial resolutions and platform radars is presented. The reflectivity biases, correlation coefficients and standard deviations between the radars are analyzed. The equivalent reflectivity bias between the S- and Ka-band radars were simulated with a given raindrop size distribution. The results indicated that reflectivity bias between the S- and Ka-band radars due to scattering properties was less than 5 dB, and for weak precipitation the bias was negligible. The prototype space-based cloud radar was able to measure a reasonable vertical profile of reflectivity, but the reflectivity below an altitude of 1.5 km above ground level was obscured by ground clutter. The measured reflectivity by the prototype space-based cloud radar was approximately 10.9 dB stronger than that by the S-band Doppler radar (SA radar), and 13.7 dB stronger than that by the ground-based cloud radar. The reflectivity measured by the SA radar was 0.4 dB stronger than that by the ground-based cloud radar. This study could provide a method for the quantitative examination of the observation ability for space-based radars.

Liu, Liping; Zhang, Zhiqiang; Yu, Danru; Yang, Hu; Zhao, Chonghui; Zhong, Lingzhi

2012-11-01

228

Retrieval of cloud geometrical properties using ADEOS-II/GLI data for radiation budget studies  

NASA Astrophysics Data System (ADS)

Clouds play a crucial role in the climate system. The investigation of their radiative properties on the cloud optical, microphysical, and geometrical characteristics is of great interest. Here, top height, base height, and geometrical thickness of cloud layer are considered as cloud geometrical properties. Several studies show that information of some spectral regions including oxygen A-band, enables us to retrieve the cloud geometrical properties as well as the optical thickness and the effective particle radius of cloud. In this study, an algorithm was developed to retrieve simultaneously the cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer with the spectral information of visible, near infrared, thermal infrared, and oxygen A-band channels. This algorithm was applied to ADEOS-II / GLI. For the preparation of global analysis, we look into the look up tables for the sensitivity of cloud optical thickness, particle size, top height, and geometrical thickness. This study will expand to the global analysis and is anticipated to contribute to the earth climate studies in terms of cloud optical, microphysical, and geometrical properties.

Kuji, Makoto; Nakajima, Teruyuki

2005-10-01

229

Contemporary study of cloud computing environment  

Microsoft Academic Search

Cloud computing is an emerging model of business computing. It is basically a model that helps to provide on-demand network access from a shared pool that consists of client computers, distributed servers, cloud storage, applications and cloud services to the consumers. Cloud computing is definitely more than the internet. It is touching the new heights in the modern era. Cloud

Vinay Kukreja; Jaiteg Singh; Anju Sharma

2011-01-01

230

Validation of CERES-MODIS Arctic cloud properties using CloudSat/CALIPSO and ARM NSA observations  

NASA Astrophysics Data System (ADS)

The traditional passive satellite studies of cloud properties in the Arctic are often affected by the complex surface features present across the region. Nominal visual and thermal contrast exists between Arctic clouds and the snow- and ice-covered surfaces beneath them, which can lead to difficulties in satellite retrievals of cloud properties. However, the addition of active sensors to the A-Train constellation of satellites has increased the availability of validation sources for cloud properties derived from passive sensors in the data-sparse high-latitude regions. In this study, Arctic cloud fraction and cloud heights derived from the NASA CERES team (CERES-MODIS) have been compared with CloudSat/CALIPSO and DOE ARM NSA radar-lidar observations over Barrow, AK, for the two-year period from 2007 to 2008. An Arctic-wide comparison of cloud fraction and height between CERES-MODIS and CloudSat/CALIPSO was then conducted for the same time period. The CERES-MODIS cloud properties, which include cloud fraction and cloud effective heights, were retrieved using the 4-channel VISST (Visible Infrared Solar-Infrared Split-window Technique) [Minnis et al.,1995]. CloudSat/CALIPSO cloud fraction and cloud-base and -top heights were from version RelB1 data products determined by both the 94 GHz radar onboard CloudSat and the lidar on CALIPSO with a vertical resolution of 30 m below 8.2 km and 60 m above. To match the surface and satellite observations/retrievals, the ARM surface observations were averaged into 3-hour intervals centered at the time of the satellite overpass, while satellite observations were averaged within a 3°x3° grid box centered on the Barrow site. The preliminary results have shown that all observed CFs have peaks during April-May and September-October, and dips during winter months (January-February) and summer months (June-July) during the study period of 2007-2008. ARM radar-lidar and CloudSat/CALIPSO show generally good agreement in CF (0.79 vs. 0.74), while CERES-MODIS derived values are much lower (0.60). CERES-MODIS derived cloud effective height (2.7 km) falls between the CloudSat/CALIPSO derived cloud base (0.6 km) and top (6.4 km) and the ARM ceilometers and MMCR derived cloud base (0.9 km) and radar derived cloud top (5.8 km). When extended to the entire Arctic, although the CERES-MODIS and Cloudsat/CALIPSO derived annual mean CFs agree within a few percents, there are significant differences over several regions, and the maximum cloud heights derived from CloudSat/CALIPSO (13.4 km) and CERES-MODIS (10.7 km) show the largest disagreement during early spring.

Giannecchini, K.; Dong, X.; Xi, B.; Minnis, P.; Kato, S.

2011-12-01

231

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

232

Physics-based visualization of dense natural clouds. I. Three-dimensional discrete ordinates radiative transfer.  

PubMed

A technique is developed to model radiative transfer in three-dimensional natural clouds with a standard discrete ordinates finite-element method modified to evaluate cell-surface-averaged radiances. A log-least-squares-based scale transformation is used to improve the discrete phase-function model. We handle dense media by assuming constant diffuse radiances over input faces to cubic cells, allowing analytical forms for transmittance factors. Transmission equations are combined with diffuse volumetric single-scattering calculations to support evaluations of cell energy balance. Energy not accounted for volumetrically is treated with surface-based effects. Results produced show accurate flux computations at over 30 optical depths per modeled cell. Comparisons with nonuniform cloud Monte Carlo calculations show less than 1% rms error and correlations greater than 0.999 for cases in which cloud-density fluctuations are resolved. PMID:18301609

Tofsted, D H; O'Brien, S G

1998-11-20

233

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

NASA Astrophysics Data System (ADS)

Arctic clouds strongly influence the regional radiation balance, temperature, melting of sea ice, and freezing of sea water. Despite their importance, there is a lack of systematic and reliable observations of Arctic clouds. The CloudSat satellite launched in 2006 with a 94 GHz Cloud Profiling Radar (CPR) may contribute to close this gap. Here we compare one of the key parameters, the cloud liquid water path (LWP) retrieved from CloudSat observations and from microwave radiometer (MWR) data taken during the ASCOS (Arctic Summer Cloud Ocean Study) cruise of the research vessel Oden from August to September 2008. Over the 45 days of the ASCOS cruise, collocations closer than 3 h and 100 km were found in only 9 d, and collocations closer than 1 h and 30 km in only 2 d. The poor correlations in the scatter plots of the two LWP retrievals can be explained by the patchiness of the cloud cover in these two days (August 5th and September 7th), as confirmed by coincident MODIS (Moderate-resolution Imaging Spectroradiometer) images. The averages of Oden-observed LWP values are systematically higher (40-70 g m-2) than the corresponding CloudSat observations (0-50 g m-2). These are cases of generally low LWP with presumably small droplets, and may be explained by the little sensitivity of the CPR to small droplets or by the surface clutter.

Liu, Shuang; Heygster, Georg; Zhang, Suping

2010-12-01

234

Mixing height determination by tethered balloon-based particle soundings and modeling simulations  

NASA Astrophysics Data System (ADS)

Vertical profiles of particle number concentration, potential temperature and relative humidity were measured in the Po Valley using an optical particle counter and a portable meteorological station attached to a tethered balloon. The field campaign covered the period 2006-2008, providing an extended dataset of vertical profiles in both stable and convective boundary-layer conditions. These vertical profiles were used to estimate an experimentally retrieved mixing height (MH).The MM5 meteorological model was also used to simulate the atmospheric dispersion characteristics for the same period, using a variety of different boundary-layer and land surface parameterization schemes (Medium-Range Forecast; high-resolution Blackadar; Gayno-Seaman; and Pleim-Chang). The model simulated MHs were compared among themselves, and then with that measured from balloon soundings. MRF parameterization represented the best compromise solution to simulate increasing MHs in the Po Valley. The MM5 simulations showed the regional character of meteorological forcing on PM ground-concentrations in the Po Valley.

Ferrero, L.; Riccio, A.; Perrone, M. G.; Sangiorgi, G.; Ferrini, B. S.; Bolzacchini, E.

2011-10-01

235

Use of Cloud Model Microphysics for Passive Microwave-Based Precipitation Retrieval: Significance of Consistency between Model and Measurement Manifolds  

Microsoft Academic Search

Precipitation estimation from passive microwave radiometry based on physically based profile retrieval algorithms must be aided by a microphysical generator providing structure information on the lower portions of the cloud, consistent with the upper-cloud structures that are sensed. One of the sources for this information is mesoscale model simulations involving explicit or parameterized microphysics. Such microphysical information can be then

Giulia Panegrossi; Stefano Dietrich; Frank S. Marzano; Alberto Mugnai; Eric A. Smith; Xuwu Xiang; Gregory J. Tripoli; Pao K. Wang; J. P. V. Poiares Baptista

1998-01-01

236

Cloud Control  

ERIC Educational Resources Information Center

|Your learning curriculum needs a new technological platform, but you don't have the expertise or IT equipment to pull it off in-house. The answer is a learning system that exists online, "in the cloud," where learners can access it anywhere, anytime. For trainers, cloud-based coursework often means greater ease of instruction resulting in greater…

Weinstein, Margery

2012-01-01

237

A threshold-based cloud mask for the high-resolution visible channel of Meteosat Second Generation SEVIRI  

NASA Astrophysics Data System (ADS)

A threshold-based cloud mask for the high-resolution visible (HRV) channel (1 × 1 km2) of the Meteosat SEVIRI (Spinning Enhanced Visible and Infrared Imager) instrument is introduced and evaluated. It is based on operational EUMETSAT cloud mask for the low-resolution channels of SEVIRI (3 × 3 km2), which is used for the selection of suitable thresholds to ensure consistency with its results. The aim of using the HRV channel is to resolve small-scale cloud structures that cannot be detected by the low-resolution channels. We find that it is of advantage to apply thresholds relative to clear-sky reflectance composites, and to adapt the threshold regionally. Furthermore, the accuracy of the different spectral channels for thresholding and the suitability of the HRV channel are investigated for cloud detection. The case studies show different situations to demonstrate the behavior for various surface and cloud conditions. Overall, between 4 and 24% of cloudy low-resolution SEVIRI pixels are found to contain broken clouds in our test data set depending on considered region. Most of these broken pixels are classified as cloudy by EUMETSAT's cloud mask, which will likely result in an overestimate if the mask is used as an estimate of cloud fraction. The HRV cloud mask aims for small-scale convective sub-pixel clouds that are missed by the EUMETSAT cloud mask. The major limit of the HRV cloud mask is the minimum cloud optical thickness (COT) that can be detected. This threshold COT was found to be about 0.8 over ocean and 2 over land and is highly related to the albedo of the underlying surface.

Bley, S.; Deneke, H.

2013-10-01

238

Occurrence of lower cloud albedo in ship tracks  

NASA Astrophysics Data System (ADS)

The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, cloud regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air), nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.

Chen, Y.-C.; Christensen, M. W.; Xue, L.; Sorooshian, A.; Stephens, G. L.; Rasmussen, R. M.; Seinfeld, J. H.

2012-05-01

239

Occurrence of lower cloud albedo in ship tracks  

NASA Astrophysics Data System (ADS)

The concept of geoengineering by marine cloud brightening is based on seeding marine stratocumulus clouds with sub-micrometer sea-salt particles to enhance the cloud droplet number concentration and cloud albedo, thereby producing a climate cooling effect. The efficacy of this as a strategy for global cooling rests on the extent to which aerosol-perturbed marine clouds will respond with increased albedo. Ship tracks, quasi-linear cloud features prevalent in oceanic regions impacted by ship exhaust, are a well-known manifestation of the effect of aerosol injection on marine clouds. We present here an analysis of the albedo responses in ship tracks, based on in situ aircraft measurements and three years of satellite observations of 589 individual ship tracks. It is found that the sign (increase or decrease) and magnitude of the albedo response in ship tracks depends on the mesoscale cloud structure, the free tropospheric humidity, and cloud top height. In a closed cell structure (cloud cells ringed by a perimeter of clear air), nearly 30% of ship tracks exhibited a decreased albedo. Detailed cloud responses must be accounted for in global studies of the potential efficacy of sea-spray geoengineering as a means to counteract global warming.

Chen, Y.-C.; Christensen, M. W.; Xue, L.; Sorooshian, A.; Stephens, G. L.; Rasmussen, R. M.; Seinfeld, J. H.

2012-09-01

240

Architecture of Web-EDA system based on Cloud computing and application for project management of IC design  

Microsoft Academic Search

Cloud computing is usually defined to deliver infrastructure, platform and software as services, which is available as a pay-as-you-go model for users. A paradigm of Cloud computing for EDA service is presented in this paper, and a hierarchical architecture of Web-EDA system implemented with Cloud computing is described in detail. Based on this proposed system structure, we developed a prototype

Xiaopeng Lin; Yiyang Li; Huaiyu Dai; Donghui Guo

2010-01-01

241

Cloud field classification based upon high spatial resolution textural features. 2. Simplified vector approaches  

NASA Astrophysics Data System (ADS)

The huge volume of data being collected in global climate studies makes it necessary to develop efficient automatic data analysis methods. While most cloud classification algorithms are based upon multispectral signatures, there is growing use of textural features. The results given in Part 1 of this study demonstrate that textural features computed from the Gray Level Cooccurrence Matrix (GLCM) approach produce high cloud classification accuracies. The present study compares classification results derived from two vector approaches, Sum and Difference Histogram (SADH) and Gray Level Difference Vector (GLDV), with those from the GLCM approach. It is found that the SADH approach produces accuracies equivalent to those obtained using GLCM, but with greater ability to resolve error clusters; also, there is a 30% savings in run time and a 50% savings in storage requirements. The GLDV approach suffers a slight degradation in classification accuracy but has a 40% savings in run time and an 87% savings in storage requirements. Textural features are not highly sensitive to moderate variations in cloud threshold selection. However, the whole cloud, rather than only the brightest portions of the cloud, produce the highest classification accuracies. A very important result is that spatial information content and classification accuracy are preserved even at lower radiometric resolutions with effective gray levels of 16. means that significantly low resolution digitized versions of satellite imagery retain essentially the full spatial information content of the original digital data. Substitution of digitized imagery can significantly reduce the expense of many remote sensing studies.

Chen, D. W.; Sengupta, S. K.; Welch, R. M.

1989-10-01

242

On the optimal method for evaluating cloud products from passive satellite imagery using CALIPSO-CALIOP data: example investigating the CM SAF CLARA-A1 dataset  

NASA Astrophysics Data System (ADS)

A method for detailed evaluation of a new satellite-derived global 28 yr cloud and radiation climatology (Climate Monitoring SAF Clouds, Albedo and Radiation from AVHRR data, named CLARA-A1) from polar-orbiting NOAA and Metop satellites is presented. The method combines 1 km and 5 km resolution cloud datasets from the CALIPSO-CALIOP (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation - Cloud-Aerosol Lidar with Orthogonal Polarization) cloud lidar for estimating cloud detection limitations and the accuracy of cloud top height estimations. Cloud detection is shown to work efficiently for clouds with optical thicknesses above 0.30 except for at twilight conditions when this value increases to 0.45. Some misclassifications of cloud-free surfaces during daytime were revealed for semi-arid land areas in the sub-tropical and tropical regions leading to up to 20% overestimated cloud amounts. In addition, a substantial fraction (at least 20-30%) of all clouds remains undetected in the polar regions during the polar winter season due to the lack of or an inverted temperature contrast between Earth surfaces and clouds. Subsequent cloud top height evaluation took into account the derived information about the cloud detection limits. It was shown that this has fundamental importance for the achieved results. An overall bias of -274 m was achieved compared to a bias of -2762 m when no measures were taken to compensate for cloud detection limitations. Despite this improvement it was concluded that high-level clouds still suffer from substantial height underestimations, while the opposite is true for low-level (boundary layer) clouds. The validation method and the specifically collected satellite dataset with optimal matching in time and space are suggested for a wider use in the future for evaluation of other cloud retrieval methods based on passive satellite imagery.

Karlsson, K.-G.; Johansson, E.

2013-05-01

243

An automatic registration algorithm for the scattered point clouds based on the curvature feature  

NASA Astrophysics Data System (ADS)

Object modeling by the registration of multiple range images has important applications in reverse engineering and computer vision. In order to register multi-view scattered point clouds, a novel curvature-based automatic registration algorithm is proposed in this paper, which can solve the registration problem with partial overlapping point clouds. For two sets of scattered point clouds, the curvature of each point is estimated by using the quadratic surface fitting method. The feature points that have the maximum local curvature variations are then extracted. The initial matching points are acquired by computing the Hausdorff distance of curvature, and then the circumference shape feature of the local surface is used to obtain the accurate matching points from the initial matching points. Finally, the rotation and translation matrix are estimated by the quaternion, and an iterative algorithm is used to improve the registration accuracy. Experimental results show that the algorithm is effective.

He, Bingwei; Lin, Zeming; Li, Y. F.

2013-03-01

244

Nature of the ultraviolet absorber in the venus clouds: inferences based on pioneer venus data.  

PubMed

Several photometric measurements of Venus made from the Pioneer Venus orbiter and probes indicate that solar near-ultraviolet radiation is being absorbed throughout much of the main cloud region, but little above the clouds or within the first one or two optical depths. Radiative transfer calculations were carried out to simulate both Pioneer Venus and ground-based data for a number of proposed cloud compositions. This comparison rules out models invoking nitrogen dioxide, meteoritic material, and volatile metals as the source of the ultraviolet absorption. Models involving either small ( approximately 1 micrometer) or large ( approximately 10 micrometers) sulfur particles have some serious difficulties, while ones invoking sulfur dioxide gas appear to be promising. PMID:17778908

Pollack, J B; Ragent, B; Boese, R; Tomasko, M G; Blamont, J; Knollenberg, R G; Esposito, L W; Stewart, A I; Travis, L

1979-07-01

245

X-RIME: Cloud-Based Large Scale Social Network Analysis  

Microsoft Academic Search

As an important technique in modern sociology, social network analysis has gained a lot of attention from many disciplines, and been used as important complements to traditional statistics and data analysis. In order to make it affordable for analysts with massive and fast growing networks, we present X-RIME, a cloud-based library for large scale social network analysis. We propose an

Wei Xue; JuWei Shi; Bo Yang

2010-01-01

246

Research on library management system for CDs attached to books based on Cloud Computing  

Microsoft Academic Search

Nowadays, all of library management systems for CDs attached to books are running independently: independent devices, independent systems, and making CD images independently. That brings huge waste of investment and labor. In this paper, we redesign the management system for CDs attached to books based on Cloud Computing. By comparing and analyzing the two systems, we can see that the

Honghai Kan; Zhimin Yang; Yue Wang; Nana Qi

2010-01-01

247

Efficient point clouds based scatter correction for fully 3D PET  

Microsoft Academic Search

A novel way to perform scatter correction for Positron Emission Tomography by using point clouds representation is presented. The scatter correction method is based on single scatter simulation. The strategy of scatter point sampling during scatter calculation will affect the accuracy of scatter correction directly and the number of sampled scatter points determines the computation complexity. Compared with regular voxel

Fei Gao; Jingjia Xu; Huafeng Liu; Pengcheng Shi

2010-01-01

248

Satellite Cloud Image Segmentation Based on the Improved Normalized Cuts Model  

Microsoft Academic Search

We propose a novel approach for satellite cloud image segmentation based on the improved Normalized Cuts Model. We extracted three important features from the multi-channel grayscale information and the texture features of satellite image, by the statistical analyses of the surface observation. Having set up the weight matrix by those features, we use the spectral graph theoretic framework of normalized

Fei Wenlong; Lv Hong; Wei Zhihui

2009-01-01

249

Classification of satellite cloud imagery based on multi-feature texture analysis and neural networks  

Microsoft Academic Search

The aim of this work was to develop a system based on modular neural networks and multi-feature texture analysis that facilitates the automated interpretation of cloud images. This speeds up the interpretation process and provides continuity in the application of satellite imagery for weather forecasting. A series of infrared satellite images from the geostationary satellite METEOSAT7 were employed. Nine different

Christina I. Christodoulou; Silas C. Michaelides; Constantinos S. Pattichis; Kyriakos Kyriakou

2001-01-01

250

A comparison between ground-based observations of noctilucent clouds and Aura satellite data  

Microsoft Academic Search

A comparison is made between ground-based observations of noctilucent clouds (NLCs), obtained with a network of automated digital cameras, and Aura satellite data (the MLS instrument). The Aura data (water vapor and temperature) demonstrate reasonable values around the summer mesopause fostering NLC formation in June through August, when supersaturated air conditions occur. The temperature decrease leads, in general, to amplification

P. Dalin; N. Pertsev; A. Dubietis; M. Zalcik; A. Zadorozhny; M. Connors; I. Schofield; T. McEwan; I. McEachran; S. Frandsen; O. Hansen; H. Andersen; V. Sukhodoev; V. Perminov; R. Balciunas; V. Romejko

2011-01-01

251

The Roles of Cloud Drop Effective Radius and LWP in Determining Rain Properties in Marine Stratocumulus  

SciTech Connect

Numerical simulations described in previous studies showed that adding cloud condensation nuclei to marine stratocumulus can prevent their breakup from closed into open cells. Additional analyses of the same simulations show that the suppression of rain is well described in terms of cloud drop effective radius (re). Rain is initiated when re near cloud top is around 12-14 um. Cloud water starts to get depleted when column-maximum rain intensity (Rmax) exceeds 0.1 mm h-1. This happens when cloud-top re reaches 14 um. Rmax is mostly less than 0.1 mm h-1 at re<14 um, regardless of the cloud water path, but increases rapidly when re exceeds 14 um. This is in agreement with recent aircraft observations and theoretical observations in convective clouds so that the mechanism is not limited to describing marine stratocumulus. These results support the hypothesis that the onset of significant precipitation is determined by the number of nucleated cloud drops and the height (H) above cloud base within the cloud that is required for cloud drops to reach re of 14 um. In turn, this can explain the conditions for initiation of significant drizzle and opening of closed cells providing the basis for a simple parameterization for GCMs that unifies the representation of both precipitating and non-precipitating clouds as well as the transition between them. Furthermore, satellite global observations of cloud depth (from base to top), and cloud top re can be used to derive and validate this parameterization.

Rosenfeld, Daniel; Wang, Hailong; Rasch, Philip J.

2012-07-04

252

Validity of Web-Based Self-Reported Weight and Height: Results of the Nutrinet-Sant? Study  

PubMed Central

Background With the growing scientific appeal of e-epidemiology, concerns arise regarding validity and reliability of Web-based self-reported data. Objective The objectives of the present study were to assess the validity of Web-based self-reported weight, height, and resulting body mass index (BMI) compared with standardized clinical measurements and to evaluate the concordance between Web-based self-reported anthropometrics and face-to-face declarations. Methods A total of 2513 participants of the NutriNet-Santé study in France completed a Web-based anthropometric questionnaire 3 days before a clinical examination (validation sample) of whom 815 participants also responded to a face-to-face anthropometric interview (concordance sample). Several indicators were computed to compare data: paired t test of the difference, intraclass correlation coefficient (ICC), and Bland–Altman limits of agreement for weight, height, and BMI as continuous variables; and kappa statistics and percent agreement for validity, sensitivity, and specificity of BMI categories (normal, overweight, obese). Results Compared with clinical data, validity was high with ICC ranging from 0.94 for height to 0.99 for weight. BMI classification was correct in 93% of cases; kappa was 0.89. Of 2513 participants, 23.5% were classified overweight (BMI?25) with Web-based self-report vs 25.7% with measured data, leading to a sensitivity of 88% and a specificity of 99%. For obesity, 9.1% vs 10.7% were classified obese (BMI?30), respectively, leading to sensitivity and specificity of 83% and 100%. However, the Web-based self-report exhibited slight underreporting of weight and overreporting of height leading to significant underreporting of BMI (P<.05) for both men and women: –0.32 kg/m2 (SD 0.66) and –0.34 kg/m2 (SD 1.67), respectively. Mean BMI underreporting was –0.16, –0.36, and –0.63 kg/m2 in the normal, overweight, and obese categories, respectively. Almost perfect agreement (ie, concordance) was observed between Web-based and face-to-face report (ICC ranged from 0.96 to 1.00, classification agreement was 98.5%, and kappa 0.97). Conclusions Web-based self-reported weight and height data from the NutriNet-Santé study can be considered as valid enough to be used when studying associations of nutritional factors with anthropometrics and health outcomes. Although self-reported anthropometrics are inherently prone to biases, the magnitude of such biases can be considered comparable to face-to-face interview. Web-based self-reported data appear to be an accurate and useful tool to assess anthropometric data.

Peneau, Sandrine; Touvier, Mathilde; Julia, Chantal; Galan, Pilar; Hercberg, Serge; Kesse-Guyot, Emmanuelle

2013-01-01

253

GEWEX Cloud System Study (GCSS) cirrus cloud working group: development of an observation-based case study for model evaluation  

NASA Astrophysics Data System (ADS)

The GCSS working group on cirrus focuses on an inter-comparison of model simulations ranging from very detailed microphysical and dynamical models through to general circulation models (GCMs). The past GCSS cirrus cloud inter-comparison highlighted the wide range in modelling results that was a surprise to the modelling community. That inter-comparison was idealised and, therefore, a key issue was that it did not benefit from observations to help distinguish between model performances. In this work, we aim to address this key issue by developing an observationally based case study to be used for the GCSS cirrus modelling inter-comparison study. We focused on developing a case that had sufficient observations with which to evaluate models, to help identify which models in the inter-comparison are performing well and highlight areas for model development. Furthermore, it will provide a base case for future model comparisons or testing of new or updated models. This paper outlines the modelling case development and the inter-comparison results will be presented in a follow-on paper. The case was based on the 9 March 2000 Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) during an intensive observation period (IOP). The case was developed utilising various observations including ARM SGP remote sensing including the MilliMeter Cloud Radar (MMCR), radiometers, radiosondes, aircraft observations, satellite observations, objective analysis and complemented with results from the Rapid Update Cycle (RUC) model as well as bespoke gravity wave simulations used to provide the best estimate for large scale forcing. The retrievals of ice water content, ice number concentration and fall velocity provide several constraints to evaluate model performances. Initial testing of the case has been reported using the UK Met Office Large Eddy Simulation Model (LEM) which suggests the case is appropriate for the model inter-comparison study. To our knowledge, this case offers the most detailed case study for cirrus comparison available and we anticipate this will offer significant benefits over past comparisons which have mostly been loosely based on observations.

Yang, H.; Dobbie, S.; Mace, G. G.; Ross, A.; Quante, M.

2012-06-01

254

Mystery clouds  

NASA Astrophysics Data System (ADS)

‘Mystery clouds,’ recently observed to cover the earth's northern hemisphere, have caused speculation as to their origin. Apparently, they could be fallout from a nuclear explosion or from a meteor impact. A more likely probability is that the clouds are layers of fine particulates, probably a sulfuric acid water mist, released from volcanic eruptions. M.P. McCormick of the Langley Research Center, speaking in regard to its possible volcanic origin, stated ‘It had to be one that had little local damage but moved material high enough to get into the stratosphere, where it [could] travel around the world. Historically, information on the height of volcanic eruptions has proven unreliable due to, among other things, the difficulty of accurately observing them at night or through cloud cover.’

Bell, Peter M.

255

Aerosol and Cloud Properties during the Cloud Cheju ABC Plume -Asian Monsoon Experiment (CAPMEX) 2008: Linking between Ground-based and UAV Measurements  

NASA Astrophysics Data System (ADS)

Cheju Atmospheric Brown Cloud (ABC) Plume-Monsoon Experiment (CAPMEX), comprehsensive ground-based measurements and a series of data-gathering flights by specially equipped autonomous unmanned aerial vehicles (AUAVs) for aerosol and cloud, had conducted at Jeju (formerly, Cheju), South Korea during August-September 2008, to improve our understanding of how the reduction of anthropogenic emissions in China (so-called “great shutdown” ) during and after the Summer Beijing Olympic Games 2008 effcts on the air quliaty and radiation budgets and how atmospheric brown clouds (ABCs) influences solar radiation budget off Asian continent. Large numbers of in-situ and remote sensing instruments at the Gosan ABC observatory and miniaturized instruments on the aircraft measure a range of properties such as the quantity of soot, size-segregated aerosol particle numbers, total particle numbers, size-segregated cloud droplet numbers (only AUAV), aerosol scattering properties (only ground), aerosol vertical distribution, column-integrated aerosol properties, and meteorological variables. By integrating ground-level and high-elevation AUAV measurements with NASA-satellite observations (e.g., MODIS, CALIPSO), we investigate the long range transport of aerosols, the impact of ABCs on clouds, and the role of biogenic and anthropogenic aerosols on cloud condensation nuclei (CCN). In this talk, we will present the results from CAPMEX focusing on: (1) the characteristics of aerosol optical, physical and chemical properties at Gosan observatory, (2) aerosol solar heating calculated from the ground-based micro-pulse lidar and AERONET sun/sky radiometer synergy, and comparison with direct measurements from UAV, and (3) aerosol-cloud interactions in conjunction with measurements by satellites and Gosan observatory.

Kim, S.; Yoon, S.; Venkata Ramana, M.; Ramanathan, V.; Nguyen, H.; Park, S.; Kim, M.

2009-12-01

256

Cloud field identification for earth radiation budget studies. Part II: Cloud field classification for the ScaRaB radiometer  

SciTech Connect

The radiometer ScaRaB (scanner for radiation balance) has two narrowband channels (0.5-0.7 and 10.5-12.5 {mu}m) in addition to the two broadband channels (0.2-4 and 0.2-50 {mu}m) necessary for earth radiation budget (ERB) measurements in order to improve cloud detection. Most automatic cloud classifications were developed with measurements of very good spatial resolution (200 m to 5 km). Earth radiation budget experiments (ERBE), on the other hand, work at a spatial resolution of about 50 km (at nadir), and therefore a cloud field classification adapted to this scale must be investigated. For this study, ScaRaB measurements are simulated by collocated Advanced Very High Resolution Radiometer (AVHRR) ERBE data. The best-suited variables for a global cloud classification are chosen using as a reference cloud types determined by an operationally working threshold algorithm applied to AVHRR measurements at a reduced spatial resolution of 4 km over the North Atlantic. Cloud field types are then classified by an algorithm based on the dynamic clustering method. More recently, the authors have carried out a global cloud field identification using cloud parameters extracted by the 3I (improved initialization inversion) algorithm, from High-Resolution Infrared Sounder (HIRS) - Microwave Sounding Unit (MSU) data. This enables the authors first to determine mean values of the variables best suited for cloud field classification and then to use a maximum-likelihood method for the classification. The authors find that a classification of cloud fields is still possible at a spatial resolution of ERB measurements. Roughly, one can distinguish three cloud heights and two effective cloud amounts (combination of cloud emissivity and cloud cover). However, only by combining flux measurements (ERBE) with cloud field classifications from sounding instruments (HIRS/MSU) can differences in radiative behavior of specific cloud fields be evaluated accurately. 29 refs., 14 figs., 3 tabs.

Stubenrauch, C.J.; Seze, G.; Scott, N.A.; Chedin, A. [Laboratoire de Meteorologie Dynamique du CNRS, Palaiseau (France)] [and others

1996-03-01

257

Automatic registration of multi-view 3D laser point cloud based on image registration and ameliorated ICP Algorithm  

NASA Astrophysics Data System (ADS)

In the process of the registration of multi-view point cloud, it's difficult to extract the feature points at present. In view of this condition, the article advances a new automatic registration method of multi-view point cloud based on Image Registration and ICP Algorithm. After the registration of point cloud and corresponding image, the feather can be extracted from the image that has plenty of textures compared with the point cloud. And it's beneficial to improve the precision and efficiency for the next registration. The experimental results demonstrate that the new method guarantees accurate fine registration.

Zhao, Ziming; Hao, Xiangyang; Zhao, Song; Su, Yintai

2011-06-01

258

Cloud Field Identification for Earth Radiation Budget Studies. Part II: Cloud Field Classification for the ScaRaB Radiometer.  

NASA Astrophysics Data System (ADS)

Gaining a better understanding of the influence of clouds on the earth's energy budget requires a cloud classification that takes into account cloud height, thickness, and cloud cover. The radiometer ScaRaB (scanner for radiation balance), which was launched in January 1994, has two narrowband channels (0.5 0.7 and 10.5 12.5 µm) in addition to the two broadband channels (0.2 4 and 0.2 50 µm) necessary for earth radiation budget (ERB) measurements in order to improve cloud detection. Most automatic cloud classifications were developed with measurements of very good spatial resolution (200 m to 5 km). Earth radiation budget experiments (ERBE), on the hand, work at a spatial resolution of about 50 km (at nadir), and therefore a cloud field classification adapted to this scale must be investigated. For this study, ScaRaB measurements are simulated by collocated Advanced Very High Resolution Radiometer (AVHRR) ERBE data. The best-suited variables for a global cloud classification are chosen using as a reference cloud types determined by an operationally working threshold algorithm applied to AVHRR measurements at a reduced spatial resolution of 4 km over the North Atlantic. Cloud field types are then classified by an algorithm based on the dynamic clustering method. More recently, the authors have carried out a global cloud field identification using cloud parameters extracted by the 3I (improved initialization inversion) algorithm, from High-Resolution Infrared Sounder (HIRS)-Microwave Sounding Unit (MSU) data. This enables the authors first to determine mean values of the variables best suited for cloud field classification and then to use a maximum-likelihood method for the classification. The authors find that a classification of cloud fields is still possible at a spatial resolution of ERB measurements. Roughly, one can distinguish three cloud heights and two effective cloud amounts (combination of cloud emissivity and cloud cover). However, only by combining flux measurements (ERBE) with cloud field classifications from sounding instruments (HIRS/MSU) can differences in radiative behavior of specific cloud fields be evaluated accurately.

Stubenrauch, C. J.; Seze, G.; Scott, N. A.; Chedin, A.; Desbois, M.; Kandel, R. S.

1996-03-01

259

A validation study of SCIAMACHY cloud products  

NASA Astrophysics Data System (ADS)

Since clouds play an essential role in the Earth's climate system, it is important to understand the cloud characteristics as well as their distribution on a global scale using satellite observa-tions. One of the main scientific objectives of SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on ENVISAT is the retrieval of cloud parameters which are also relevant for the study of tropospheric constituents. On the one hand, SCIAMACHY has to be sensitive to low variations in trace gas concentra-tions which means the ground pixel size has to be large enough. On the other hand, such a large pixel size leads to the problem that SCIAMACHY spectra are not well suitable to de-rive a reliable cloud fraction that can be used as input parameter for subsequent retrievals of cloud properties or vertical trace gas columns. Therefore, we use MERIS/ENVISAT spectral measurements with its high spatial resolution as sub-pixel information for the determination of MerIs Cloud fRaction fOr Sciamachy (MICROS). Since MERIS covers an even broader swath width than SCIAMACHY, no problems with spatial and temporal matches of measurements occur. This enables the derivation of a SCIAMACHY cloud fraction with an accuracy much higher as compared with other current cloud fractions that are based on SCIAMACHY's PMD (Polarization Measurement Device) data. We present our new developed MICROS algorithm based on the threshold approach as well as a qualitative validation of our results with MERIS satellite imageries for different locations, especially with respect to bright surfaces such as snow/ice and sands. Moreover, the SCIA-MACHY cloud fractions derived with MICROS serve as input parameter for the satellite cloud retrieval algorithm SACURA (Semi-Analytical CloUd Retrieval Algorithm) in order to retrieve cloud optical thickness, cloud top height, liquid water path, effective radius and cloud albedo for SCIAMACHY. These cloud properties are intercompared with other current cloud products which have been derived for SCIAMACHY as well as for other spaceborne or ground based instruments.

Martinecz, Cornelia; Kokhanovsky, Alexander; Vountas, Marco; Rozanov, Vladimir; Burrows, John P.

260

Measurement of total and condensed water mixing ratios in warm-based cumulus clouds by a jet engine evaporation technique  

Microsoft Academic Search

A technique has been developed for measuring total water mixing ratio and condensed water mixing ratio in warm-based convective clouds. The jet engine compressor on a Learjet 24 is employed as an evaporator to convert all cloud condensate to vapour and the vapour density in the compressed (bleed) air is measured with a Lyman-alpha humidiometer.

G. Morgan; B. J. Morrison; G. K. Mather

1989-01-01

261

A spectral method for retrieving cloud optical thickness and effective radius from surface-based transmittance measurements  

Microsoft Academic Search

We introduce a new multispectral method for the retrieval of optical thickness and effective radius from cloud transmittance, which is less sensitive to effective radius than cloud reflectance. Based on data from the moderate spectral resolution observations of the Solar Spectral Flux Radiometer (SSFR) and Shortwave Spectroradiometer (SWS), we use the spectral shape of transmitted radiance as a means of

P. J. McBride; K. S. Schmidt; P. Pilewskie; A. S. Kittelman; D. E. Wolfe

2011-01-01

262

Comparison of Satellite and Ground-based Measurements of Polar Mesospheric Clouds  

NASA Astrophysics Data System (ADS)

Polar Mesospheric Clouds (PMCs) are tenuous ice clouds that form near the cold (<150K) summer mesopause region (80-85 km). From the ground, these clouds are seen during twilight hours as Noctilucent or "night shining" Clouds (NLCs) and are typically seen from latitudes from 50° to 65°. Observations by the Solar Backscatter Ultraviolet (SBUV) instruments on the NOAA satellites have shown that the occurrence and brightness of NLCs have been increasing over the last several decades prompting speculation concerning their possible role in climate change. Recently the Aeronomy of Ice in the Mesosphere (AIM) satellite was launched (April 2007) and is the first satellite dedicated to the study of NLCs. In this presentation, we compare SBUV and AIM PMC observations with ground-based image data collected during two campaigns from Edmonton, Canada (June 30-July 17, 2007) and Delta Junction, Alaska (July 29- August 17, 2007). Four nights of data are presented where coincident measurements were obtained by AIM, SBUV and ground-based imagers. The results show good spatial or temporal agreement, but rarely both, and illustrate the importance of coordinated measurements for better understanding the geographic and local time variability of PMCs.

Barker-Tvedtnes, J.; Taylor, M.; Deland, M.

2008-12-01

263

Cloud parcel modelling of CCN activation in megacity air based on observations from Beijing and Guangzhou  

NASA Astrophysics Data System (ADS)

The other team members are P. Achtert (3), M. Hu (4), M. Shao (4), and Y.H. Zhang (4). The activation of cloud condensation nuclei (CCN) determines the initial number of cloud droplets, and thus influences the evolution of the cloud and formation of precipitation. Characterizing the CCN activation process by parcel model studies with detailed cloud microphysics and dynamics provides useful information for parameterizing the activation process in meso-scale and global-scale models. During the CAREBEIJING 2006 campaign in Beijing and the PRIDE-PRD2006 campaign in Guangzhou, fast condensational growth of particles was frequently observed and the CCN size distribution was sometimes dominated by the growing nucleation mode (Aitken Mode) rather than by the accumulation mode. In this study we investigated the implications of the experimental findings using a cloud parcel model with detailed spectral cloud microphysics and with the ΰ-Köhler model approach for efficient and realistic description of the effective hygroscopicity and CCN activity of aerosol particles. The number of droplets formed at the cloud base was examined for a wide range of updraft velocities and aerosol particle number concentrations. Moreover, the impact of aerosol hygroscopicity, size distribution and giant CCN were also evaluated. References: Reutter, P., Trentmann, J., Su, H., Simmel M., Rose, D., Wernli, H., Andreae, M. O., and Pöschl, U.: Activation of aerosol particles as cloud condensation nuclei (CCN) under smoky and pyro-convective conditions, manuscript in preparation, 2009 Rose, D., Gunthe, S. S., Mikhailov, E., Frank, G. P., Dusek, U., Andreae, M. O., and Pöschl, U.: Calibration and measurement uncertainties of a continuous-flow cloud condensation nuclei counter (DMT-CCNC): CCN activation of ammonium sulfate and sodium chloride aerosol particles in theory and experiment, Atmos. Chem. Phys., 8, 1153-1179, 2008. Rose, D., Nowak, A., Achtert, P., Wiedensohler, A., Hu, M., Shao, M., Zhang, Y., Andreae, M. O., and Pöschl, U.: Cloud condensation nuclei in polluted air and biomass burning smoke near the mega-city Guangzhou, China - Part 1: Size-resolved measurements and implications for the modeling of aerosol particle hygroscopicity and CCN activity, Atmos. Chem. Phys. Discuss., 8, 17343-17392, 2008. Simmel, M. and Wurzler, S.: Condensation and activation in sectional cloud microphysical models., Atmospheric Research 80(2-3): 218-236., 2006. Wiedensohler, A., Cheng, Y. F., Nowak, A., Wehner, B., Achtert, P., Berghof, M., Birmili, W., Wu, Z. J., Hu, M., Zhu, T., Takegawa, N., Kita, K., Kondo, Y., Lou, S. R., Hofzumahaus, A., Holland, F., Wahner, A., Gunthe, S., Rose, D., and Pöschl, U.: Rapid Aerosol Particle Growth and Increase of Cloud Condensation Nucleus (CCN) Activity by Secondary Aerosol Formation: a Case Study for Regional Air Pollution in North Eastern China, J. Geophys. Res., submitted, 2008

Su, H.; Reutter, P.; Trentmann, J.; Rose, D.; Gunthe, S.; Simmel, M.; Nowak, A.; Wiedensohler, A.; Zhu, T.; Pöschl, U.

2009-04-01

264

Retrieval of cloud geometrical properties using ADEOS-II/GLI data  

NASA Astrophysics Data System (ADS)

It is of great interest to investigate the radiative properties on the cloud optical, microphysical, and geometrical properties of clouds that play crucial role in the climate system. Here, top height, base height, and geometrical thickness of cloud layer are considered as cloud geometrical properties. Several studies show that information of some spectral regions including oxygen A-band, enables us to retrieve the cloud geometrical properties as well as the optical thickness, the effective particle radius of cloud. In this study, an algorithm was developed to retrieve simultaneously the cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer with the spectral information of visible, near infrared, thermal infrared, and oxygen A-band channels. This algorithm was applied to ADEOS-II / GLI dataset so as to retrieve global distribution of cloud geometrical properties. The retrieved results around Japan are not strange and to be validated with other observation in the near future. This study will expand to the global analysis and be anticipated to contribute to the earth climate studies in terms of cloud optical, microphysical, and geometrical properties.

Kuji, Makoto; Nakajima, Teruyuki

2004-11-01

265

Climatological characteristics of cloud distribution and planetary boundary layer structure in Jakarta, Indonesia revealed by lidar observation  

NASA Astrophysics Data System (ADS)

For two years we observed the vertical distribution of clouds and aerosols in Jakarta, Indonesia, with ground-based Mie scattering lidars. A histogram of the cloud base height shows a notable maximum at an altitude of approximately 5 km, especially in the wet season. The planetary boundary layer height we inferred from the upper boundary of the aerosol layer was approximately 1.5-2 km in the wet season and 2-3 km in the dry season.

Sugimoto, Nobuo; Matsui, Ichiro; Shimizu, Atsushi; Pinandito, Mego; Sugondo, Santoso

266

A comparison of AMIP II model cloud layer properties with ISCCP D2 estimates  

NASA Astrophysics Data System (ADS)

The cloud amounts and liquid and ice water paths as a function of height in five Atmospheric Model Intercomparison Project (AMIP) II models have been compared to International Satellite Cloud Climatology Project (ISCCP) d2 observations. The model layer data have been transformed to the ISCCP low, mid and height cloud amount and vertically integrated water values. In addition a simple radiative transfer model has been used to transform both model output and ISCCP cloud amount and water contents into top of atmosphere albedos for the low, mid and high cloud fractions. Overall, most models represent moderately well the spatial, seasonal and interannual variability of total cloud albedo, which is largely a function of the total cloud amount. The models also tend to predict moderately well the spatial, seasonal, and interannual variability of cloud fraction, but fail to display the observed spatial, and especially, seasonal and interannual variability in cloud water path. In particular nearly all models have mid and low cloud water path variabilities, which are much larger than those observed in the ISCCP observations. This increased cloud water path variability seems to compensate partially for smaller underestimates of cloud fraction variability in most models. Furthermore, variations in cloud amount and cloud water path are much more often negatively correlated in models than in the observations. A simple estimate of the influence of cloud overlap suggests that monthly mean model cloud layers are less stacked in the vertical in models than in an observational estimate based upon a combination of satellite and ground-based observations.

Weare, B. C.

267

3D reconstruction using projection of virtual height line based on dynamic programming  

Microsoft Academic Search

3D reconstruction is the base of mobile robot navigation. And it is necessary to provide the environment information for robots effectively and rapidly. The traditional 3D reconstruction method relies on the dense disparity map which requires high computing ability, and there is large redundant data in the reconstructed 3D data. Unlike traditional methods, the proposed method needn't obtain the disparity

Huahua Chen; Yifei Jiang; Jianwu Zhang

2010-01-01

268

Wideband channel modeling for line-of-sight microcellular environment with low base station antenna height  

Microsoft Academic Search

In high-speed wireless data transmission, the most significant problem is severe frequency-selective fading. Consequently, obtaining information on the propagation delay is very important and precise modeling of a radio channel is essential in designing mobile multimedia communications systems. Empirical wideband channel models with a low base station antenna are proposed for the line-of-sight microcellular environment. The models determine the delay

Kazunnasa TAIRA; Shinya SEKIZAWA; Yoshihiro HASE

1998-01-01

269

Microwave and Millimeter Wave Characteristics and Attenuation of Clouds over some Malaysian Equatorial Stations  

NASA Astrophysics Data System (ADS)

Based on radar range height indicator (RHI) measurements, cloud characteristics in relation to radiowave propagation over three locations in different geographical region in western Malaysia have been presented. It is seen that low cloud occurrence over these locations are quite significant. Cloud attenuation and noise temperature can result in serious degradation of telecommunication link performances. This paper presents cloud coverage in different months, 0°C isotherm height and cloud attenuation results at 12 GHz, 20 GHz, 36 GHz, 50 GHz, 70 GHz and 100 GHz over measurement site. The low level cloud over the measurement sites has been found to occur for many days and nights and particularly in the months of April to May and October to December. Such results are useful for satellite communication and remote sensing application in Malaysia.

Mandeep, J. S.; Hassan, S. I. S.

2008-03-01

270

Analysis of global radiation budgets and cloud forcing using three-dimensional cloud nephanalysis data base. Master's thesis  

SciTech Connect

A one-dimensional radiative transfer model was used to compute the global radiative budget at the top of the atmosphere (TOA) and the surface for January and July. 1979. The model was also used to determine the global cloud radiative forcing for all clouds and for high and low cloud layers. In the computations. the authors used the monthly cloud data derived from the Air Force Three-Dimensional Cloud Nephanalysis (3DNEPH). These data were used in conjunction with conventional temperature and humidity profiles analyzed during the 1979 First GARP (Global Atmospheric Research Program) Global Experiment (FGGE) year. Global surface albedos were computed from available data and were included in the radiative transfer analysis. Comparisons of the model-produced outgoing solar and infrared fluxes with those derived from Nimbus 7 Earth Radiation Budget (ERS) data were made to validate the radiative model and cloud cover. For reflected solar and emitted infrared (IR) flux, differences within 20 w/sq m meters were shown.

Mitchell, B.

1990-12-01

271

Joint occurrence period of wind speed and wave height based on both service term and risk probability  

NASA Astrophysics Data System (ADS)

Return periods calculated for different environmental conditions are key parameters for ocean platform design. Many codes for offshore structure design give no consideration about the correlativity among multi-loads and over-estimate design values. This frequently leads to not only higher investment but also distortion of structural reliability analysis. The definition of design return period in existing codes and industry criteria in China are summarized. Then joint return periods of different ocean environmental parameters are determined from the view of service term and danger risk. Based on a bivariate equivalent maximum entropy distribution, joint design parameters are estimated for the concomitant wave height and wind speed at a site in the Bohai Sea. The calculated results show that even if the return period of each environmental factor, such as wave height or wind speed, is small, their combinations can lead to larger joint return periods. Proper design criteria for joint return period associated with concomitant environmental conditions will reduce structural size and lead to lower investment of ocean platforms for the exploitation of marginal oil field.

Dong, Sheng; Fan, Dunqiu; Tao, Shanshan

2012-12-01

272

A high performance cloud-based protein-ligand docking prediction algorithm.  

PubMed

The potential of predicting druggability for a particular disease by integrating biological and computer science technologies has witnessed success in recent years. Although the computer science technologies can be used to reduce the costs of the pharmaceutical research, the computation time of the structure-based protein-ligand docking prediction is still unsatisfied until now. Hence, in this paper, a novel docking prediction algorithm, named fast cloud-based protein-ligand docking prediction algorithm (FCPLDPA), is presented to accelerate the docking prediction algorithm. The proposed algorithm works by leveraging two high-performance operators: (1) the novel migration (information exchange) operator is designed specially for cloud-based environments to reduce the computation time; (2) the efficient operator is aimed at filtering out the worst search directions. Our simulation results illustrate that the proposed method outperforms the other docking algorithms compared in this paper in terms of both the computation time and the quality of the end result. PMID:23762864

Chen, Jui-Le; Tsai, Chun-Wei; Chiang, Ming-Chao; Yang, Chu-Sing

2013-05-14

273

Inference of cirrus cloud properties using satellite-observed visible and infrared radiances. Part II: verification of theoretical cirrus radiative properties  

SciTech Connect

A methodology is developed to apply a parameterization of radiative transfer calculations to satellite analyses of cirrus clouds. Cloud heights and optical depths are derived from visible and infrared window measurements taken during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE). Geostationary satellite retrievals are compared to lidar-derived cloud heights and retrievals from a polar-orbiting satellite taken at different angles to determine which theoretical models of scattering phase function and single-scattering albedo best represent actual cirrus clouds. Models using small hexagonal ice crystals with a diameter of 20 [mu]m (C20) and a size distribution of slightly larger hexagonal ice crystals representing a cirrostratus (CS) cloud produce the best results. The resulting mean cloud heights are within [+-]0.3 km of the lidar results and have instantaneous uncertainties of [+-]1.3 km. Mean cloud heights derived using a model based on water droplets with a 10-Am effective radius (ID) and a model based on a distribution of large ice crystals (CU) are 1.3 km less than the lidar heights. The cloud height biases are due to overestimates of the cloud optical depths that are as much as 1.7 times greater than the C20 values. Reflectance patterns computed with the ice crystal models are consistent with the dual-satellite, multiangle observations of optical depth. The C20 model produced the least bias (3%) of the models, while the CU model yielded the greatest (12%). The ID-model optical depths derived using the geostationary satellite were 67% less than those from the polar-orbiting satellite. It is concluded that interpretation of cirrus reflectance with water-droplet models leads to biased results. This finding has important implications for the cirrus cloud properties derived by the ISCCP. The cloud-height and optical depth biases can be minimized using C20 or CS models. 20 refs., 11 figs., 4 tabs.

Minnis, P. (NASA Langley Research Center, Hampton, VA (United States)); Heck, P.W.; Young, D.F. (Lockheed Engineering and Sciences Company, Hampton, VA (United States))

1993-05-01

274

A Comparison of the Optical Pulse Characteristics of Intracloud and Cloud-to-Ground Lightning as Observed above Clouds  

Microsoft Academic Search

The time-resolved optical waveforms at 777.4 nm and electric-field changes produced by intracloud and cloud-to-ground lightning flashes were measured above clouds from a U2 airplane (flying at a height of 20 km) at the same time that ground-based measurements of lightning were obtained from a mobile laboratory and a regional lightning location network. The U2 optical pulse trains are examined

Steven J. Goodman; Hugh J. Christian; W. David Rust

1988-01-01

275

Estimating final height from parental heights and sex in Taiwanese.  

PubMed

We have developed a simple function for accurately estimating target height for use in evaluating growth and growth-promoting therapies in Taiwanese children. The heights of parents and their adult offspring born in the 1970s were determined in 1229 healthy families who accompanied another family member to our pediatric clinic. We directly measured the heights of the population-based cohort of adult offspring. The heights of their parents were based on self-report. Both the parents and their offspring were healthy. The increases in height between the two generations were 1.49-3.19 cm for boys and 2.03-2.61 cm for girls. These increases lie between those reported for Chinese children in Hong Kong (4.2-4.8 cm) and children in Sweden (0.7-1.0 cm). Final height was underestimated using the corrected midparental height method and was overestimated using the final parental height model developed from Swedish data. We developed a new linear model by fitting our data: boy height = 79.3 + 0.56 (midparental height); girl height = 35.2 + 0.76 (midparental height). The intercept and slope of the model are similar to those reported for Swedish girls but not to those reported for Swedish boys. Use of the new equations derived from our data may increase the accuracy of estimates of target height in Taiwanese children. The intermediate position of our fairly representative Taiwanese sample in both final height and generational increases in final height may reflect an intermediate stage between the Swedes and Hong Kong Chinese in the secular trend of heights. PMID:18078201

Su, Pen-Hua; Wang, Shu-Li; Chen, Jia-Yuh

2007-06-01

276

Clouds and Shortwave Fluxes at Nauru. Part I: Retrieved Cloud Properties  

SciTech Connect

The datasets currently being collected at the Atmospheric Radiation Measurement (ARM)Program's sites on the islands of Nauru and Manus represent the longest time series of ground based cloud measurements available in the tropical western Pacific region. This paper presents statistics of retrieved microphysical properties of non-precipitating liquid and ice clouds and estimates of the shortwave cloud radiative effect from 12 months of data collected at the Nauru site between June 1999 and May 2000. Non-precipitating liquid clouds observed at Nauru were primarily shallow cumulus with bases less than 1 km. Of the retrieved liquid clouds, 90% had liquid water path less than 100 grams per square meter. The average retrieved effective radius was 9.9 microns, however limitations in the sensitivity of the two-channel microwave radiometer led to large uncertainties in retrieved effective radius and liquid water content for the shallow clouds typically seen at Nauru. The frequency of liquid c loud detection, height of liquid cloud base, and magnitude of the shortwave cloud radiative effect showed a clear diurnal cycle, which is most likely related to the island effect and the existence of the Nauru cloud plume. An average shortwave radiative cloud effect of -55.4 watts per square meter was estimated over the study period, which is significantly lower than studies during the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA-COARE). Differences in clear sky modeling do not seem large enough to account for this difference, indicating that there was probably less cloud over Nauru during the current study period than during TOGA-COARE, which is consistent with the phase of the El-Nino Southern Oscillation (ENSO) during the two periods.

McFarlane, Sally A.; Evans, K. F.

2004-03-01

277

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

278

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 the production of standing waves in the water column 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. 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. 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 North-East 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, Sarah; Bean, Chris; Lokmer, Ivan; Creamer, Columba; Lambkin, Keith

2013-04-01

279

Validation of a radiosonde-based cloud layer detection method against a ground-based remote sensing method at multiple ARM sites  

NASA Astrophysics Data System (ADS)

Cloud vertical structure is a key quantity in meteorological and climate studies, but it is also among the most difficult quantities to observe. In this study, we develop a long-term (10 years) radiosonde-based cloud profile product for the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP), Tropical Western Pacific (TWP), and North Slope of Alaska (NSA) sites and a shorter-term product for the ARM Mobile Facility (AMF) deployed in Shouxian, Anhui Province, China (AMF-China). The AMF-China site was in operation from 14 May to 28 December 2008; the ARM sites have been collecting data for over 15 years. The Active Remote Sensing of Cloud (ARSCL) value-added product (VAP), which combines data from the 95-GHz W-band ARM Cloud Radar (WACR) and/or the 35-GHz Millimeter Microwave Cloud Radar (MMCR), is used in this study to validate the radiosonde-based cloud layer retrieval method. The performance of the radiosonde-based cloud layer retrieval method applied to data from different climate regimes is evaluated. Overall, cloud layers derived from the ARSCL VAP and radiosonde data agree very well at the SGP and AMF-China sites. At the TWP and NSA sites, the radiosonde tends to detect more cloud layers in the upper troposphere.

Zhang, Jinqiang; Li, Zhanqing; Chen, Hongbin; Cribb, Maureen

2013-01-01

280

Research on trust-based access control model in cloud computing  

Microsoft Academic Search

In this paper we propose a trust-based dynamic access control model for cloud computing environment inspired by the GTRBAC model, where the users can validate their legal identities and acquire their access control privileges for the resources according to the role information and the trust-degree in the lightweight certificates. The trust-degree in the certificate can be calculated by the direct

Zhanjiang Tan; Zhuo Tang; Renfa Li; Ahmed Sallam; Liu Yang

2011-01-01

281

Implementation of MapReduce-based image conversion module in cloud computing environment  

Microsoft Academic Search

In recent years, the rapid advancement of the Internet and the growing number of people using social networking services (SNSs) have facilitated the sharing of multimedia data. However, multimedia data processing techniques such as transcoding and transmoding impose a considerable burden on the computing infrastructure as the amount of data increases. Therefore, we propose a MapReduce-based image-conversion module in cloud

Hyeokju Lee; Myoungjin Kim; Joon Her; Hanku Lee

2012-01-01

282

CUT SIZE MINIMIZATION AND CLOUD ELEMENT BREAK-UP IN A GROUND-BASED CVI  

Microsoft Academic Search

A ground-based Counterflow Virtual Impactor (CVI) was optimized to achieve nearly complete in situ segregation of cloud droplets and ice crystals (with subsequent evaporation, releasing dissolved gaseous and non-volatile material) from their surrounding carrier gas and interstitial aerosol particles. With a one-dimensional numerical model, the CVI cut size D50 was reduced to 4?m from 7?m in an earlier design (Anderson

Alfons Schwarzenbo; Jost Heintzenberg

2000-01-01

283

NASA-Langley web-based operational real-time cloud retrieval products from geostationary satellites  

NASA Astrophysics Data System (ADS)

At NASA Langley Research Center (LaRC), radiances from multiple satellites are analyzed in near real-time to produce cloud products over many regions on the globe. These data are valuable for many applications such as diagnosing aircraft icing conditions and model validation and assimilation. This paper presents an overview of the multiple products available, summarizes the content of the online database, and details web-based satellite browsers and tools to access satellite imagery and products.

Palikonda, Rabindra; Minnis, P.; Spangenberg, D. A.; Khaiyer, M. M.; Nordeen, M. L.; Ayers, J. K.; Nguyen, L.; Yi, Y.; Chan, P. K.; Trepte, Q. Z.; Chang, F.-L.; Smith, W. L., Jr.

2006-12-01

284

IONEX: A meshfree ion extraction code based on ``particle in cloud of points'' concept  

NASA Astrophysics Data System (ADS)

Ion Extraction (IONEX) is an ion extraction modeling code, developed at FAR-TECH, Inc., based on the meshless particle-in-cloud-of-points concept. IONEX self-consistently solves motion equations for ions and Poisson's equation for the electrostatic field, assuming a Boltzmann distribution for the electrons. IONEX is capable of handling multiple species and is graphical user interface-driven. The two-dimensional version is benchmarked with IGUN. The basic algorithm and sample runs are presented.

Galkin, S. A.; Grubert, J. E.; Cluggish, B. P.; Barov, N.; Kim, J. S.

2010-02-01

285

Utility-based resource allocation for virtual machines in Cloud computing  

Microsoft Academic Search

One of the challenges of Infrastructure-as-a-Service Clouds is how to dynamically allocate resources to virtual machines such that quality of service constraints are satisfied and operating costs are minimized. The tradeoff between these two conflicting goals can be expressed by a utility function. In this paper, a two-tier resource management approach based on adequate utility functions is presented, consisting of

Dorian Minarolli; Bernd Freisleben

2011-01-01

286

Low clouds and fog along the South-Western African coast — Satellite-based retrieval and spatial patterns  

NASA Astrophysics Data System (ADS)

The spatial and temporal patterns of fog and low clouds along the South-Western African coast are characterized based on an evaluation of Meteosat SEVIRI satellite data. A technique for the detection of fog/low clouds in the region is introduced, and validated using 1 year of CALIOP cloud lidar products, showing reliable performance. The frequency of fog and low cloud in the study area is analyzed by systematic application of the technique to all available Meteosat SEVIRI scenes from 2004 to 2009, for 7:00 UTC and 14:00 UTC. The highest frequencies are encountered in the area around Walvis Bay, with a peak in the summer months. Fog and low clouds clear by 14:00 UTC almost everywhere over land. Supplementary data are available at doi:10.1594/PANGAEA.755427.

Cermak, Jan

2012-10-01

287

Turbulence and mass-transports in stratocumulus clouds  

NASA Astrophysics Data System (ADS)

Boundary layer (BL) stratocumulus clouds are an important factor in the earth's radiation budget due to their high albedo and low cloud top heights. Continental BL stratocumulus clouds are closely coupled to the diurnal cycle and the turbulence in the BL affecting the surface energy and moisture budgets. In this study the turbulence and mass-transport structures in continental BL stratocumulus clouds are studied using data from the Atmospheric Radiation Measurements (ARM)'s Southern Great Plains (SGP) observing facility located at Lamont, Oklahoma. High temporal (4 sec) and spatial (45 m) resolution observations from a vertically pointing 35 GHz cloud Doppler radar were used to obtain the in-cloud vertical velocity probability density function (pdf) in the absence of precipitation size hydrometeors. A total of 70 hours of radar data were analyzed to report half-hourly statistics of vertical velocity variance, skewness, updraft fraction, downdraft and velocity binned mass-flux at five cloud depth normalized levels. The variance showed a general decrease with increase in height in the cloud layer while the skewness is weakly positive in the cloud layer and negative near cloud top. The updraft fraction decreases with height with the decrease mainly occurring in the upper half of the cloud layer. The downdraft fraction increases with decrease in height with the increase being almost linear. The velocity of eddies responsible for maximum mass-transport decreases from of 0.4 ms-1 near cloud base to 0.2 ms-1 near cloud top. The half-hour periods were then classified based on the surface buoyancy flux as stable or unstable and it was found that the variance near cloud top is higher during the stable periods as compared to the unstable periods. Classification was also made based on the cloud depth to BL depth ratio (CBR) being greater or less than 0.3. The variance profile was similar for the classification while the skewness was almost zero during periods with CBR less 0.3 and positive during periods with CBR greater than 0.3. A 14 hour period of stratocumulus cloud on March 25, 2005 was analyzed to study the diurnal changes in the turbulence structure and mass transports. The variance near cloud base during the day time when the BL turbulence is primarily due to surface buoyancy production was higher than during the nighttime when the BL turbulence is driven by radiative cooling near the cloud top. Output from a one dimensional radiative transfer model was analyzed to study the vertical structure of the radiative fluxes. A radiative velocity scale analogous to the surface convective velocity scale is proposed to assess the relative importance of radiative cooling near cloud top in generating turbulence compared with the surface buoyancy production. An attempt was also made to calculate the hourly liquid water flux by combining the high temporal resolution (20 sec) liquid water content estimates from the radar reflectivity and a microwave radiometer with the radar observed vertical velocity. The liquid water flux was found to peak at a level below the cloud top and show a divergence with height that was similar to that from model simulations.

Ghate, Virendra P.

288

Comparison of satellite-derived and observer-based determinations of cloud cover amount at the SGP CART site  

SciTech Connect

Cloud-climate feedback is one of the most important factors in predicting the timing and magnitude of global climate change and its regional effects. Recent satellite measurements indicate that global effects of clouds on solar and infrared radiation are large. The experimental objective of the Atmospheric Radiation Measurement (ARM) Program is to characterize, empically, the radiative processes in the Earth`s atmosphere with improved resolution and accuracy. Therefore, the effective treatment of cloud formation and cloud properties is crucial for reliable climate prediction. This study focuses on the analysis of cloud cover data for the ARM Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) site central facility. The data set was obtained from the Advanced Very High Resolution Radiometer (AVHRR) on National Oceanic and Atmospheric Administration (NOAA) Satellites 11 and 12, and cloud observations made by SGP CART site operators. Such an analysis provides a basis for future evaluations with whole-sky cameras and provides a means of assessing the reliability of surface-based observations of cloud cover at the SGP CART site.

Liaw, Y.P. [North Central College, Naperville, IL (United States). Dept. of Physics; Cook, D.R.; Sisterson, D.L.; Gao, W. [Argonne National Lab., IL (United States)

1995-06-01

289

Ground-based all-sky mid-infrared and visible imagery for purposes of characterizing cloud properties  

NASA Astrophysics Data System (ADS)

This paper describes the All Sky Infrared Visible Analyzer (ASIVA), a multi-purpose visible and infrared sky imaging and analysis instrument whose primary function is to provide radiometrically calibrated imagery in the mid-infrared (mid-IR) atmospheric window. This functionality enables the determination of diurnal hemispherical cloud fraction (HCF) and estimates of sky/cloud temperature from which one can derive estimates of cloud emissivity and cloud height. This paper describes the calibration methods and performance of the ASIVA instrument with particular emphasis on data products being developed for the meteorological community. Data presented here were collected during a field campaign conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Climate Research Facility from 21 May to 27 July 2009. The purpose of this campaign was to determine the efficacy of IR technology in providing reliable nighttime HCF data. Significant progress has been made in the analysis of the campaign data over the past several years and the ASIVA has proven to be an excellent instrument for determining HCF as well as several other important cloud properties.

Klebe, D. I.; Blatherwick, R. D.; Morris, V. R.

2013-08-01

290

Aerosol and Cloud Observations at an Ocean Platform  

NASA Astrophysics Data System (ADS)

A number of recent observational studies have focused upon the microphysical properties of clouds and aerosols in the presence of broken low-level clouds, since this is a natural environment for studying aerosol and cloud interactions. We examine the aerosol properties over the Chesapeake Lighthouse using surface datasets from the CERES Ocean Validation Experiment (COVE) and cloud properties from the Geostationary Operational Environmental Satellites (GOES) imagery. (Note that COVE is a unique location for satellite-surface studies because it is a small platform surrounded by ocean, 25 km off of the East Coast U.S.). We focus our study on cases with cloud base heights less than 2 km (i.e., boundary layer clouds) and no overlying cirrus. Then we compare aerosol properties in conditions of low cloud fraction to aerosol properties in conditions of high cloud fraction that occur earlier or later on the same day. Our results indicate that the aerosol optical depth is greater at times with low-level cloud fractions greater than 50 percent than at other times on the same day. Conversely, the Angstrom exponent (500/870) is smaller at times with low-level cloud fractions greater than 50 percent than at other times on the same day.

Fabbri, B. E.; Schuster, G. L.; Minnis, P.; Palikonda, R.

2009-12-01

291

Macrophysical properties of tropical cirrus clouds from the CALIPSO satellite and from ground-based micropulse and Raman lidars  

NASA Astrophysics Data System (ADS)

Lidar observations of cirrus cloud macrophysical properties over the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program Darwin, Australia, site are compared from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, the ground-based ARM micropulse lidar (MPL), and the ARM Raman lidar (RL). Comparisons are made using the subset of profiles where the lidar beam is not fully attenuated. Daytime measurements using the RL are shown to be relatively unaffected by the solar background and are therefore suited for checking the validity of diurnal cycles. RL and CALIPSO cloud fraction profiles show good agreement while the MPL detects significantly less cirrus, particularly during the daytime. Both MPL and CALIPSO observations show that cirrus clouds occur less frequently during the day than at night at all altitudes. In contrast, the RL diurnal cycle is significantly different from zero only below about 11 km; where it is of opposite sign (i.e., more clouds during the daytime). For cirrus geometrical thickness, the MPL and CALIPSO observations agree well and both data sets have significantly thinner clouds during the daytime than the RL. From the examination of hourly MPL and RL cirrus cloud thickness and through the application of daytime detection limits to all CALIPSO data, we find that the decreased MPL and CALIPSO cloud thickness during the daytime is very likely a result of increased daytime noise. This study highlights the significant improvement the RL provides (compared to the MPL) in the ARM program's ability to observe tropical cirrus clouds and will help improve our understanding of these clouds. The RL also provides a valuable ground-based lidar data set for the evaluation of CALIPSO observations.

Thorsen, Tyler J.; Fu, Qiang; Comstock, Jennifer M.; Sivaraman, Chitra; Vaughan, Mark A.; Winker, David M.; Turner, David D.

2013-08-01

292

Canopy BRF simulation of forest with different crown shape and height in larger scale based on Radiosity method  

NASA Astrophysics Data System (ADS)

Radiosity method is based on the computer simulation of 3D real structures of vegetations, such as leaves, branches and stems, which are composed by many facets. Using this method we can simulate the canopy reflectance and its bidirectional distribution of the vegetation canopy in visible and NIR regions. But with vegetations are more complex, more facets to compose them, so large memory and lots of time to calculate view factors are required, which are the choke points of using Radiosity method to calculate canopy BRF of lager scale vegetation scenes. We derived a new method to solve the problem, and the main idea is to abstract vegetation crown shapes and to simplify their structures, which can lessen the number of facets. The facets are given optical properties according to the reflectance, transmission and absorption of the real structure canopy. Based on the above work, we can simulate the canopy BRF of the mix scenes with different species vegetation in the large scale. In this study, taking broadleaf trees as an example, based on their structure characteristics, we abstracted their crowns as ellipsoid shells, and simulated the canopy BRF in visible and NIR regions of the large scale scene with different crown shape and different height ellipsoids. Form this study, we can conclude: LAI, LAD the probability gap, the sunlit and shaded surfaces are more important parameter to simulate the simplified vegetation canopy BRF. And the Radiosity method can apply us canopy BRF data in any conditions for our research.

Song, Jinling; Qu, Yonghua; Wang, Jindi; Wan, Huawei; Liu, Xiaoqing

2007-08-01

293

Clouds, Wind and the Biogeography of Central American Cloud Forests: Remote Sensing, Atmospheric Modeling, and Walking in the Jungle  

NASA Astrophysics Data System (ADS)

Cloud forests stand at the core of the complex of montane ecosystems that provide the backbone to the multinational Mesoamerican Biological Corridor, which seeks to protect a biodiversity conservation "hotspot" of global significance in an area of rapidly changing land use. Although cloud forests are generally defined by frequent and prolonged immersion in cloud, workers differ in their feelings about "frequent" and "prolonged", and quantitative assessments are rare. Here we focus on the dry season, in which the cloud and mist from orographic cloud plays a critical role in forest water relations, and discuss remote sensing of orographic clouds, and regional and atmospheric modeling at several scales to quantitatively examine the distribution of the atmospheric conditions that characterize cloud forests. Remote sensing using data from GOES reveals diurnal and longer scale patterns in the distribution of dry season orographic clouds in Central America at both regional and local scales. Data from MODIS, used to calculate the base height of orographic cloud banks, reveals not only the geographic distributon of cloud forest sites, but also striking regional variation in the frequency of montane immersion in orographic cloud. At a more local scale, wind is known to have striking effects on forest structure and species distribution in tropical montane ecosystems, both as a general mechanical stress and as the major agent of ecological disturbance. High resolution regional atmospheric modeling using CSU RAMS in the Monteverde cloud forests of Costa Rica provides quantitative information on the spatial distribution of canopy level winds, insight into the spatial structure and local dynamics of cloud forest communities. This information will be useful in not only in local conservation planning and the design of the Mesoamerican Biological Corridor, but also in assessments of the sensitivity of cloud forests to global and regional climate changes.

Lawton, R.; Nair, U. S.

2011-12-01

294

The NASA CloudSat Education Network  

NASA Astrophysics Data System (ADS)

CloudSat, a NASA Earth System Science Pathfinder Mission, will launch into orbit the world's most advanced weather radar designed to measure properties of clouds that are essential for accurate understanding of Earth's weather and climate processes. Providing the first vertical profiles of global measurements of cloud thickness, height, water and ice content and a wide range of precipitation data linked to cloud development, CloudSat measurements will fill a critical gap in understanding how clouds affect climate. Any mission of this nature requires extensive ground-based reference data. The CloudSat Education Network provides the opportunity for schools around the world to partner with the CloudSat Science Team and the NASA-sponsored GLOBE Program. The Network will link together scientists, students, teachers, and their communities to give students meaningful, authentic and contemporary science education experiences. Student activities and learning outcomes are being developed to meet both general education outcomes and specific standards or objectives from school curricula. The main focus of the knowledge development component of the project is to help students better understand long-term climate change and the climatic processes that maintain the Earth's Energy balance. Student research with CloudSat/GLOBE data will be strongly encouraged. Scientists will receive research-quality data in support of the mission and in return will interact with teachers and their students to promote interest in science. Participation in the network throughout the duration of the project will be monitored and schools will be asked to maintain levels of participation in order to give CloudSat scientists a solid consistent base of data to support their research. The preferred base level of participation is the reporting of cloud, temperature and precipitation data according to modified GLOBE protocols approximately every 16 days coinciding with the CloudSat satellite overpass. The CloudSat Education Network when fully complete will contain 100-150 schools from target sites around the world. Countries interested in participating include Canada, Thailand, New Zealand, Australia, India, Cameroon, Croatia, Germany, Estonia, Switzerland, Dominican Republic, and the United States. Most already have participating CloudSat Education Network schools.

Krumm, D. K.

2006-05-01

295

A survey and analysis of cloud model-based security for computing secure cloud bursting and aggregation in renal environment  

Microsoft Academic Search

Cloud Computing has emerged as a major information and communications technology trend and has been proved as a key technology for market development and analysis for the users of several field. The practice of computing across two or more data centers separated by the Internet is growing in popularity due to an explosion in scalable computing demands. However, one of

Pritesh Jain; Dheeraj Rane; Shyam Patidar

2011-01-01

296

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

297

Addressing security, collaboration, and usability with tactical edge mobile devices and strategic cloud-based systems  

NASA Astrophysics Data System (ADS)

Success in the future battle space is increasingly dependent on rapid access to the right information. Faced with a shrinking budget, the Government has a mandate to improve intelligence productivity, quality, and reliability. To achieve increased ISR effectiveness, leverage of tactical edge mobile devices via integration with strategic cloud-based infrastructure is the single, most likely candidate area for dramatic near-term impact. This paper discusses security, collaboration, and usability components of this evolving space. These three paramount tenets outlined below, embody how mission information is exchanged securely, efficiently, with social media cooperativeness. Tenet 1: Complete security, privacy, and data integrity, must be ensured within the net-centric battle space. This paper discusses data security on a mobile device, data at rest on a cloud-based system, authorization and access control, and securing data transport between entities. Tenet 2: Lack of collaborative information sharing and content reliability jeopardizes mission objectives and limits the end user capability. This paper discusses cooperative pairing of mobile devices and cloud systems, enabling social media style interaction via tagging, meta-data refinement, and sharing of pertinent data. Tenet 3: Fielded mobile solutions must address usability and complexity. Simplicity is a powerful paradigm on mobile platforms, where complex applications are not utilized, and simple, yet powerful, applications flourish. This paper discusses strategies for ensuring mobile applications are streamlined and usable at the tactical edge through focused features sets, leveraging the power of the back-end cloud, minimization of differing HMI concepts, and directed end-user feedback.teInput=

Graham, Christopher J.

2012-05-01

298

Combined observational and modeling based study of the relationship between aerosols and super-cooled cloud fraction  

NASA Astrophysics Data System (ADS)

Recent observational and modeling studies indicate that aerosols may have a strong effect on Earth's energy budget via their influence on mixed-phase clouds. Global climate studies have predicted aerosol interaction with mixed-phase clouds to warm the current climate, but estimates are uncertain because mixed-phase cloud processes in GCMs are highly parameterized and have to date been poorly constrained by satellite data. Here, we present global and regional distributions of the frequency of supercooled cloud water and its link to aerosols from two global climate models (GCMs), compared to a new satellite data set. Both GCMs link ice formation at temperatures between -40 and 0 degrees C to the simulated concentrations of aerosols with ice nucleating ability (IN), assigning different freezing efficiencies to the different insoluble aerosol species (mineral dust, bio-aerosols and soot). Consequently, both models generally simulate an anti-correlation between aerosol abundance and supercooled liquid water in clouds, a finding that was recently qualitatively confirmed by satellite observations. By studying the relationship between aerosols and the supercooled cloud fraction (SCF) from the GCMs and from the NASA spaceborne lidar instrument CALIOP (cloud-aerosol lidar with orthogonal polarization), we get strong indications of how aerosols may influence mixed-phase clouds. Furthermore, based on the guidance from the satellite data, we perform global sensitivity simulations of the radiative effects associated with aerosol influence on mixed-phase clouds. We argue that with the new validation of SCF and its link to aerosols, GCM estimates of aerosol effects on climate via their influence on mixed-phase clouds may become more reliable.

Storelvmo, T.; Lohmann, U.; Choi, Y.

2011-12-01

299

A Governance Model for Cloud Computing  

Microsoft Academic Search

As Cloud Computing begins to move beyond the pure hype stage and into the beginning of mainstream adoption, adopting cloud-based services or moving application services to the cloud brings a number of new risks, including: Cloud availability, Cloud security, Erosion of data integrity, and so on. However, for enterprise which require visibility, trust and control over cloud-based services. To maximize

Zhiyun Guo; Meina Song; Junde Song

2010-01-01

300

Application of a multifilter shadowband radiometer and microwave radiometer for ground based evaluation of aerosol-cloud interactions  

NASA Astrophysics Data System (ADS)

The quantification of the first direct aerosol cloud interaction mechanism requires simultaneous observations of cloud water drop properties as well as aerosol properties below the cloud. The simultaneous measurement of both these properties is very difficult from space borne systems and efforts to develop ground remote sensing measurements are critical. To measure the cloud properties, we make use of an approach which combines a Microwave radiometer and a MFRSR radiometer for simultaneous Cloud Optical Depth (COD) and Liquid Water Path (LWP). From these measurements, effective droplet diameter can be estimated assuming the homogeneity of the cloud. In using the diffuse flux, we confirm that for COD > 2 and solar zenith angles < 60, the standard MFRSR correction can be applied with errors < 1%. In addition, we develop a method whereby regional retrieval of Microphysical properties from multispectral extinction measurements can be made based on NN based methods trained on full sky scans. Also, we discuss the uncertainty in the inferred COD due to various input parameters in the formation of Look-Up-Tables and present preliminary data sets for evaluation. Finally, we discuss methods to extract useful aerosol information during partly cloudy conditions that can be used to better define the state of the aerosol prior to cloud interaction.

Gross, Barry; Cordero, Lina; He, Julia; Madhalvan, Bomidi; Moshary, Fred; Ahmed, Sam

2011-10-01

301

Cloud Security with Virtualized Defense and Reputation-Based Trust Mangement  

Microsoft Academic Search

Internet clouds work as service factories built around Web-scale data centers. The elastic cloud resources and huge datasets processed are subject to security breaches, privacy abuses, and copyright violations. Provisioned cloud resources on-demand are especially vulnerable to cyber attacks. The cloud platforms built by Google, IBM, and Amazon all reveal this weaknesses. We propose a new approach to integrating virtual

Kai Hwang; S. Kulkareni; Yue Hu

2009-01-01

302

Toward dynamic and attribute based publication, discovery and selection for cloud computing  

Microsoft Academic Search

Cloud computing is an emerging paradigm where computing resources are offered over the Internet as scalable, on-demand (Web) services. While cloud vendors have concentrated their efforts on the improvement of performance, resource consumption and scalability, other cloud characteristics have been neglected. On the one hand cloud service providers face difficult problems of publishing services that expose resources, and on the

Andrzej Goscinski; Michael Brock

2010-01-01

303

Monitoring for aerosol effects on southeast Pacific stratocumulus clouds from ship and space  

NASA Astrophysics Data System (ADS)

Satellite (primarily MODIS) and shipboard measurements from 6 month-long cruises to the climatically important southeast Pacific stratocumulus region are used to elucidate regional cloud properties. The focus is on the cloud top height, geometrical cloud thickness, and cloud droplet number concentrations. The latter two cloud properties in combination can distinguish the first or Twomey aerosol indirect effect separately from aerosol effects on the cloud macrophysical properties. The comparison of the satellite-derived to the shipboard-derived cloud geometrical thickness is used to define an effective condensation rate within adiabatic clouds. The comparison between a satellite-derived cloud droplet number concentration and the shipboard accumulation-mode aerosol concentration contains too much error to define a best-fit effective cloud droplet size distribution width, but does show a consistent relationship between the two parameters. Comparisons of the MODIS cloud top temperature to the sounding inversion base temperature reveal a mean underestimate by 1.3 K by the MODIS values, and effectively larger boundary-layer lapse rates consistent with increased boundary-layer decoupling within the deeper boundary layers. Monthly-mean satellite-derived spatial plots were constructed for each of the 6 cruises. These reveal a local ridging of the cloud top heights along 20S coincident with the cruise tracks. The monthly- mean cloud droplet number concentration spatial pattern does not vary much between the months and years examined, suggesting the aerosol impact on the near-coastal cloud properties be thought of as a steady-state rather than an episodic influence. Cloud fractions and geometrical thicknesses do vary between the cruise months examined (October 2001, 2005, 2006, and 2007, November 2003, and December 2004).

Zuidema, P.; Painemal, D.; Fairall, C.

2008-05-01

304

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

305

Statistical models of cloud-turbulence interactions  

NASA Astrophysics Data System (ADS)

The application of statistical turbulence theory to the study of atmospheric clouds has a long history that traces back to the pioneering work of L. F. Richardson in the 1920s. At a phenomenological level, both atmospheric clouds and turbulence are now well understood, but analytic theories with the power to predict as well as explain are still lacking. This deficiency is notable because the prediction of statistical cloud change in response to anthropogenic forcing is a preeminent scientific challenge in atmospheric science. In this dissertation, I apply the statistical rigor of new developments in passive scalar theory to problems in cloud physics at small scales O (10 cm), where a white-in-time or delta-correlated closure is asymptotically exact, and at large scales O (100 km) where a statistical approach towards unresolved cloud variability is essential. Using either the delta-correlated model or a self-consistent statistical approach I investigate (i) the preferential concentration or inertial clumping of cloud droplets; (ii) the effect of velocity field intermittency on clumping; (iii) the small-scale spatial statistics of condensed liquid water density and (iv) the large-scale parameterization of unresolved low-cloud physical and optical variability. My investigations, (i) to (iv), lead to the following conclusions: Preferential concentration. Inertial particles (droplets) preferentially concentrate at scales ranging from 60eta at St ? 0.2 to 8eta at St ? 0.6, where eta is the Kolmogorov length and St is the Stokes number. Clumping becomes significant at St ? 0.3. Effect of intermittency. An effective Stokes number, Steff = St( F /3)1/2 where F is the longitudinal velocity-gradient flatness factor (kurtosis) explicitly incorporates velocity-gradient intermittency (i.e. non-Gaussian statistics) into the St-dependence of particle clumping. In the atmospheric boundary-layer, Steff ? 2.7St. Intermittency effects significantly increase the degree of preferential concentration of large cloud droplets. Cloud spatial scaling. Density fluctuations of an inert passive scalar are typically spatially homogeneous, whereas root-mean-square cloud liquid water (ql) fluctuations increase linearly with height above cloud base. As a result, the ql spectral density is axisymmetric and complex. A model of low-cloud viscous-convective statistics where axisymmetric/non-homogeneous production of scalar covariance due to condensation/evaporation is balanced by an axisymmetric rotation reproduces recent experimental measurements [Davis et al., 1999]. Low-cloud optical properties. The assumption of height-independence in unresolved saturation vapour density fluctuations (s) and the introduction of unresolved cloud-top height fluctuations ( z'top ) into a statistical cloud scheme couple parameterized subgrid low-cloud physical and optical variability. Analytic relationships between optical depth, cloud fraction and (s, z'top ) provide a convenient framework for a GCM cloud parameterization that prognoses both the mean and variance of optical depth.

Jeffery, Christopher Andrew M.

306

Fast cloud parameter retrievals of MIPAS/Envisat  

NASA Astrophysics Data System (ADS)

The infrared limb spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Envisat satellite include detailed information on tropospheric clouds and polar stratospheric clouds (PSC). However, no consolidated cloud product is available for the scientific community. Here we describe a fast prototype processor for cloud parameter retrieval from MIPAS (MIPclouds). Retrieval of parameters such as cloud top height, temperature, and extinction are implemented, as well as retrieval of microphysical parameters, e.g. effective radius and the integrated quantities over the limb path (surface area density and volume density). MIPclouds classifies clouds as either liquid or ice cloud in the upper troposphere and polar stratospheric clouds types in the stratosphere based on statistical combinations of colour ratios and brightness temperature differences. Comparison of limb measurements of clouds with model results or cloud parameters from nadir looking instruments is often difficult due to different observation geometries. We therefore introduce a new concept, the limb-integrated surface area density path (ADP). By means of validation and radiative transfer calculations of realistic 2-D cloud fields as input for a blind test retrieval (BTR), we demonstrate that ADP is an extremely valuable parameter for future comparison with model data of ice water content, when applying limb integration (ray tracing) through the model fields. In addition, ADP is used for a more objective definition of detection thresholds of the applied detection methods. Based on BTR, a detection threshold of ADP = 107 ?m2 cm-2 and an ice water content of 10-5 g m-3 is estimated, depending on the horizontal and vertical extent of the cloud. Intensive validation of the cloud detection methods shows that the limb-sounding MIPAS instrument has a sensitivity in detecting stratospheric and tropospheric clouds similar to that of space- and ground-based lidars, with a tendency for higher cloud top heights and consequently higher sensitivity for some of the MIPAS detection methods. For the high cloud amount (HCA, pressure levels below 440 hPa) on global scales the sensitivity of MIPAS is significantly greater than that of passive nadir viewers. This means that the high cloud fraction will be underestimated in the ISCCP dataset compared to the amount of high clouds deduced by MIPAS. Good correspondence in seasonal variability and geographical distribution of cloud occurrence and zonal means of cloud top height is found in a detailed comparison with a climatology for subvisible cirrus clouds from the Stratospheric Aerosol and Gas Experiment II (SAGE II) limb sounder. Overall, validation with various sensors shows the need to consider differences in sensitivity, and especially the viewing geometries and field-of-view size, to make the datasets comparable (e.g. applying integration along the limb path through nadir cloud fields). The simulation of the limb path integration will be an important issue for comparisons with cloud-resolving global circulation or chemical transport models.

Spang, R.; Arndt, K.; Dudhia, A.; Höpfner, M.; Hoffmann, L.; Hurley, J.; Grainger, R. G.; Griessbach, S.; Poulsen, C.; Remedios, J. J.; Riese, M.; Sembhi, H.; Siddans, R.; Waterfall, A.; Zehner, C.

2012-08-01

307

How much water can pollution aerosols hold in the cloud by suppressing warm rain?  

NASA Astrophysics Data System (ADS)

Vertical profiles of aerosols, cloud drop size distribution and hydrometeors were measured by cloud physics airplanes in a wide range of locations in the world and a wide range of aerosol properties. This includes tropical clouds in the Amazon and Indian Monsoon, severe convective clouds in Argentina and the USA, and winter clouds in California and Israel. The aerosol conditions span from pristine maritime to heavy air pollution and smoke from forest fires, and includes large aerosols such as desert dust and sea spray. It is found that heavy air pollution that is dominated by small cloud condensation nuclei (CCN) can suppress the warm rain processes in warm base clouds (cloud base temperature >20C) up to heights of more than 5 km above cloud base, which is well above the freezing level. The warm rain is formed as supercooled rain that freezes and gets rimed into graupel. Such clouds have intense electrical activity. In microphysically highly continental vigorous convective clouds with cold base of 12C, warm rain is also delayed to 5 km above base. The onset of warm rain in these clouds occur at temperatures close to the homogeneous ice nucleation isotherm of -35C and colder. The resultant drizzle forms the embryos of ice hydrometeors. Giant CCN from dust and sea salt initiate the rain faster than would have been expected based on the concentration of small CCN. A relation between CCN concentration and cloud depth for onset of warm rain can be formulated and applied to cloud parameterization in models that do not calculate explicitly the rain forming processes in clouds.

Rosenfeld, D.

2009-12-01

308

Satellite-Based Assessment of the Aerosol Effect on Global Warm Cloud Properties  

Microsoft Academic Search

We present characteristics of global warm cloud properties and warm-rain process in conjunction with the aerosol index (AI) and the lower-tropospheric stability (LTS). The Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) and Visible\\/Infrared Radiance Imager (VIRS) simultaneously derive cloud-top droplet effect radius, column droplet radius, cloud fraction, cloud liquid water path, cloud optical depth, and a warm rain index.

T. Matsui; H. Masunaga; R. A. Pielke; S. M. Kreidenweis; W. Tao; M. Chin; Y. J. Kaufman

2004-01-01

309

Strengthen Cloud Computing Security with Federal Identity Management Using Hierarchical Identity-Based Cryptography  

Microsoft Academic Search

More and more companies begin to provide different kinds of cloud computing services for Internet users at the same time these\\u000a services also bring some security problems. Currently the majority of cloud computing systems provide digital identity for\\u000a users to access their services, this will bring some inconvenience for a hybrid cloud that includes multiple private clouds\\u000a and\\/or public clouds.

Liang Yan; Chunming Rong; Gansen Zhao

2009-01-01

310

SIRTA, a ground-based atmospheric observatory for cloud and aerosol research  

NASA Astrophysics Data System (ADS)

Ground-based remote sensing observatories have a crucial role to play in providing data to improve our understanding of atmospheric processes, to test the performance of atmospheric models, and to develop new methods for future space-borne observations. Institut Pierre Simon Laplace, a French research institute in environmental sciences, created the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA), an atmospheric observatory with these goals in mind. Today SIRTA, located 20km south of Paris, operates a suite a state-of-the-art active and passive remote sensing instruments dedicated to routine monitoring of cloud and aerosol properties, and key atmospheric parameters. Detailed description of the state of the atmospheric column is progressively archived and made accessible to the scientific community. This paper describes the SIRTA infrastructure and database, and provides an overview of the scientific research associated with the observatory. Researchers using SIRTA data conduct research on atmospheric processes involving complex interactions between clouds, aerosols and radiative and dynamic processes in the atmospheric column. Atmospheric modellers working with SIRTA observations develop new methods to test their models and innovative analyses to improve parametric representations of sub-grid processes that must be accounted for in the model. SIRTA provides the means to develop data interpretation tools for future active remote sensing missions in space (e.g. CloudSat and CALIPSO). SIRTA observation and research activities take place in networks of atmospheric observatories that allow scientists to access consistent data sets from diverse regions on the globe.

Haeffelin, M.; Barthès, L.; Bock, O.; Boitel, C.; Bony, S.; Bouniol, D.; Chepfer, H.; Chiriaco, M.; Cuesta, J.; Delanoë, J.; Drobinski, P.; Dufresne, J.-L.; Flamant, C.; Grall, M.; Hodzic, A.; Hourdin, F.; Lapouge, F.; Lemaître, Y.; Mathieu, A.; Morille, Y.; Naud, C.; Noël, V.; O'Hirok, W.; Pelon, J.; Pietras, C.; Protat, A.; Romand, B.; Scialom, G.; Vautard, R.

2005-02-01

311

Computing and Partitioning Cloud Feedbacks using Cloud Property Histograms  

NASA Astrophysics Data System (ADS)

In this study we propose a novel technique for computing cloud feedbacks using histograms of cloud fraction as joint functions of cloud top pressure and optical depth generated by the International Satellite Cloud Climatology Project (ISCCP) simulator, which was incorporated into the climate models that took part in the Cloud Feedback Model Intercomparison Project. We use a radiative transfer model to compute top of atmosphere (TOA) flux sensitivities to cloud fraction perturbations in each bin of the ISCCP simulator histogram, which we refer to as a cloud radiative kernel. Multiplying the cloud radiative kernel histogram with the histogram of actual cloud top fraction changes per unit of global warming simulated by each model produces an estimate of cloud feedback. Both the spatial structures and globally integrated values of cloud feedbacks computed in this manner agree remarkably well with those computed by adjusting the change in cloud radiative forcing for clear-sky effects as in Soden et al. (2008). The technique allows us to quantitatively partition cloud feedbacks into contributions from changes in cloud amount, height, and optical depth. We show that rising clouds are the dominant contributor to the positive LW cloud feedback, and that the extra-tropical contribution is approximately 70% as large as the tropical contribution. In the ensemble mean, the positive impact of rising clouds is 50% larger than the negative impact of reductions in cloud amount on LW cloud feedback, but the degree to which reductions in cloud fraction offset the effect of rising clouds varies considerably across models. In contrast, reductions in cloud fraction make a large and virtually unopposed positive contribution to SW cloud feedback, though the inter-model spread is greater than for any other individual feedback component. In general, models exhibiting greater reductions in subtropical marine boundary layer cloudiness tend to have larger positive SW cloud feedbacks, in agreement with previous studies. Overall reductions in cloud amount have twice as large an impact on SW fluxes as on LW fluxes such that the net cloud amount feedback is moderately positive, with no models analyzed here having a negative net cloud amount feedback. Finally, we find that although global mean cloud optical depth feedbacks are generally smaller than the other components, they are the dominant process at high latitudes, a perhaps surprising result considering one might expect increases in total cloud amount associated with the poleward shift of the storm track to dominate. This locally large negative optical depth feedback arises due to a combination of increased cloud water content and changes in phase from ice to liquid.

Zelinka, M. D.; Klein, S. A.; Hartmann, D. L.

2011-12-01

312

Properties of CM-SAF's cloud products -a statistical analysis  

NASA Astrophysics Data System (ADS)

Clouds have a major impact on the earth radiation budget and contribute significantly to the state of the climate system. Additionally, the space-based retrieval of other atmospheric pa-rameters is highly influenced by clouds. Therefor it is essential to assess the strengths and limitations of the satellite-derived cloud properties as accurately as possible. This study deals with those cloud products, that are operationally generated by the EUMETSAT's Satellite Ap-plication Facility on Climate Monitoring (CM-SAF). 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, sur-face albedo, and atmospheric water vapor, temperature and humidity profiles on a regional and partially on a global scale and thereby focuses on geophysical parameters describing the elements of the energy and water cycle. Since 2005 a threshold technique is used within the CM-SAF to derive various cloud products from satellite data, some are further estimated with an iterative look-up table approach. The properties of CM-SAF's cloud products which are cloud top variables (in here: Cloud Top Height (CTH)), Liquid Water Path (LWP), Cloud Type (CTY), Cloud Optical Thickness (COT) and Cloud Fraction (CFC) are explored and analyzed statistically. The individual products are related to each other via for example two-dimensional frequency distributions in order to verify their consistency. From these statistics average properties for certain classified types are derived, such as LWP-distributions for five different CM-SAF cloud types. Each cloud type can be characterized by an average LWP dis-tribution. Also temporal variations for the cloud properties are studied. The Cloud Top Height product for example shows strong seasonal variations, depending on latitude. Locating the maximal CTH near the equator makes it possible to easily monitor the meridional traveling of the Inter-Tropical Convergence Zone during the the seasons.

Kniffka, Anke; Lockhoff, Maarit; Hollmann, Rainer; Weber, Ralf

313

Simulation of the tropospheric sulfur cycle in a global model with a physically based cloud scheme  

NASA Astrophysics Data System (ADS)

The treatment of the sulfur cycle in the CSIRO global climate model (GCM) is described. It is substantially based on the scheme developed previously for the European Center/Hamburg (ECHAM) model, but the treatment of wet scavenging has been completely rewritten to better reflect the different properties of liquid and frozen precipitation, and the treatment of these in the model's cloud microphysical scheme. The model is able to reproduce the observed finding that wet deposition of sulfur over Europe and North America is larger in summer than in winter, but the seasonal cycle of sulfate over Europe is not well simulated. The latter is improved when the amplitude of the seasonal cycle of European emissions is increased. Below-cloud scavenging makes an important contribution in our scheme: On omitting it, the global sulfate burden increases from 0.67 to 0.93 Tg S. On reverting to the less efficient scavenging treatment used in ECHAM, the global sulfate burden again increases from 0.67 to 0.93 Tg S, and excessive sulfate concentrations are obtained in Europe and North America. Some deficiencies in the simulation are investigated via further sensitivity tests. In particular, during the Arctic winter, the modeled sulfur dioxide (SO2) concentrations are too large, and the modeled sulfate concentrations are too small (as in most global sulfur-cycle models). Recent laboratory experiments suggest that SO2 oxidation in ice clouds is nonnegligible. We obtain a much improved Arctic simulation when a simple treatment of SO2 oxidation in ice clouds is included.

Rotstayn, Leon D.; Lohmann, Ulrike

2002-11-01

314

Microphysical properties of single and mixed-phase Arctic clouds derived from ground-based AERI observations  

Microsoft Academic Search

A novel new approach to retrieve microphysical properties from mixed-phase clouds is presented. This algorithm retrieves cloud optical depth, ice fraction, and the effective size of the water and ice particles from ground-based, high-resolution infrared radiance observations. The theoretical basis is that the absorption coefficient of ice is greater than that of liquid water from 10--13 mum, whereas liquid water

David D. Turner

2003-01-01

315

A spectral method for retrieving cloud optical thickness and effective radius from surface-based transmittance measurements  

Microsoft Academic Search

We introduce a new spectral method for the retrieval of optical thickness and effective radius from cloud transmittance that relies on the spectral slope of the normalized transmittance between 1565 nm and 1634 nm, and on cloud transmittance at a visible wavelength. The standard dual-wavelength technique, which is traditionally used in reflectance-based retrievals, is ill-suited for transmittance because it lacks

P. J. McBride; K. S. Schmidt; P. Pilewskie; A. S. Kittelman; D. E. Wolfe

2011-01-01

316

Management of SOA-Based Context-Aware Applications Hosted in a Distributed Cloud Subject to Percentile Constraints  

Microsoft Academic Search

We consider geographically distributed datacen- ters forming a collectively managed cloud computing sys- tem. Multiple SaaS providers host their SOA-based, context- aware applications in the cloud. Typically, the context-aware applications serve multiple classes of customers (end users) classified on economic considerations, which determine the Quality of Service (QoS) received by each class. This need for differentiated QoS for each customer

Keerthana Boloor; Rada Chirkova; Tiia Salo; Yannis Viniotis

2011-01-01

317

Diagnosis and testing of low-level cloud parameterizations for the NCEP/GFS model using satellite and ground-based measurements  

NASA Astrophysics Data System (ADS)

The objective of this study is to investigate the quality of clouds simulated by the National Centers for Environmental Prediction global forecast system (GFS) model and to examine the causes for some systematic errors seen in the simulations through use of satellite and ground-based measurements. In general, clouds simulated by the GFS model had similar spatial patterns and seasonal trends as those retrieved from passive and active satellite sensors, but large systematic biases exist for certain cloud regimes especially underestimation of low-level marine stratocumulus clouds in the eastern Pacific and Atlantic oceans. This led to the overestimation (underestimation) of outgoing longwave (shortwave) fluxes at the top-of-atmosphere. While temperature profiles from the GFS model were comparable to those obtained from different observational sources, the GFS model overestimated the relative humidity field in the upper and lower troposphere. The cloud condensed water mixing ratio, which is a key input variable in the current GFS cloud scheme, was largely underestimated due presumably to excessive removal of cloud condensate water through strong turbulent diffusion and/or an improper boundary layer scheme. To circumvent the problem associated with modeled cloud mixing ratios, we tested an alternative cloud parameterization scheme that requires inputs of atmospheric dynamic and thermodynamic variables. Much closer agreements were reached in cloud amounts, especially for marine stratocumulus clouds. We also evaluate the impact of cloud overlap on cloud fraction by applying a linear combination of maximum and random overlap assumptions with a de-correlation length determined from satellite products. Significantly better improvements were found for high-level clouds than for low-level clouds, due to differences in the dominant cloud geometry between these two distinct cloud types.

Yoo, Hyelim; Li, Zhanqing; Hou, Yu-Tai; Lord, Steve; Weng, Fuzhong; Barker, Howard W.

2013-09-01

318

A solution to the global height datum problem based on satellite derived global models and the corresponding error budget  

NASA Astrophysics Data System (ADS)

The global height datum problem, that is the determination of biases of different height systems at global scale, is revised and two solutions are proposed. As it is well known, biased heights enter into the computation of terrestrial gravity anomalies, which in turn are used for geoid determination. Hence, these biases enter as secondary or indirect effect also in such a geoid model. In contrast to terrestrial gravity anomalies, gravity and geoid models derived from satellite gravity missions, and in particular GRACE and GOCE, do not suffer from those inconsistencies. Thus, these models can be profitably used in estimating the existing height system biases. Two approaches have been studied. The first one compares the gravity potential coefficients in the range of degrees from 100 to 200 of an unbiased gravity field from GOCE with those of the combined model EGM2008 that in this range are affected by the height biases. The second approach compares height anomalies derived from GNSS ellipsoidal heights and biased normal heights, with anomalies derived from an anomalous potential which combines a satellite-only model up to degree 200 and a high-resolution global model above 200. Numerical tests have been devised to prove the effectiveness of the two methods, in terms of variances of the biases to be estimated. This error budget analysis depends on the observation accuracies as well as of their number and spatial distribution. The impact of the error covariance structure of the GOCE and EGM2008 models has been evaluated together with the impact of the observation network design.

Barzaghi, R.; Gatti, A.; Reguzzoni, M.; Venuti, G.

2012-04-01

319

Radar based remote sensing of cloud liquid water—application of various techniques—a case study  

NASA Astrophysics Data System (ADS)

During the BALTEX BRIDGE Campaign (BBC) of CLIWA-NET, conducted at Cabauw, The Netherlands, from 1 August through 31 September 2001, cloud radar parameters like reflectivity, linear depolarization ratio and Doppler velocities have been observed using a 95 GHz cloud radar. These observations along with other remotely sensed parameters from the ground, have been used to derive the liquid water content of clouds which is one of the most important parameters to be known when the radiative transfer of clouds needs to be calculated. Simultaneously a multi-channel passive microwave radiometer and a lidar ceilometer have been operated close to the radar. While drizzle could be ruled out to have a significant impact on the return signal, corrections due to atmospheric absorption (gaseous) and attenuation due to clouds (mainly loss of signal due to absorption) had to be applied to the radar data. The corrections will be discussed in detail and have been applied to the radar reflectivity profiles before estimating cloud liquid water profiles. After the liquid water content profile has been calculated (for a fixed integrated liquid water path) the maximum in liquid water content of the cloud increased by about 14% and shifted upward within the cloud. The applied corrections bring the liquid water profile closer to adiabatic in the middle and upper part of the cloud. Examples of time series of corrected vertical profiles and average profiles are shown and are discussed. The ground based remotely sensed liquid water profiles show, on average, excellent agreement with simultaneously in situ measured liquid water content from aircraft measurements.

Meywerk, J.; Quante, M.; Sievers, O.

2005-05-01

320

Cloud Altitude Determination of Overshooting Tops in Severe Thunderstorms  

NASA Astrophysics Data System (ADS)

The maximum heights of deep convective clouds and overshooting tops have been analyzed and compared using a combination of space and ground-based measurement systems. Deeply convective cumulonimbus clouds are capable of reaching and penetrating the tropopause. The portions of convective clouds that extend into the stratosphere are known as overshooting tops. Instances of tornado onset have been observed to match or slightly lag the timing of maximum cloud-top altitudes. In addition, precise forecasting and measurement of convective cloud-top heights are of critical importance to the safety and efficiency of commercial aviation flight routings. This study included the use of data from three NASA A-Train satellites, 88-D and TDWR Doppler radar, NAM modeling output, and direct visual sightings. The three polar-orbiting satellites included Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat, and Aqua. CALIPSO and CloudSat return a vertical profile of microphysical parameters as their near-nadir beams intersect clouds. CALIPSO uses a lidar instrument (CALIOP), operating at 532 and 1064 nm, that is capable of detecting aerosol and small cloud particles. CloudSat uses a radar system called Cloud Profiling Radar (CPR), operating at 94 GHz (3.2 mm), that can penetrate thicker clouds, including those with precipitation. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board Aqua provided a 250m resolution map view that permitted identification of the unique texture of overshooting tops. Satellite data and ground-based Doppler radar were co-located and used to compare cloud-top and echo-top measurements and products. In addition to co-located observational data, North American Mesoscale (NAM) model output with maximum 6-hour lead time was analyzed for convective cloud top forecasts. Finally, direct sightings of cloud tops were made at the time of CALIPSO overpasses of New Jersey. Using a surveyor's transit, the angle from the observation spot to the cloud top was measured and the geographic position of the cloud was determined using MODIS images and Google Earth. After cataloging about 125 A-Train intersects of deep convection from January 1 to July 1 of 2011, the maximum convective cloud altitudes were collected from CALIPSO, CloudSat, radar, and modeling data. Our results confirm previous findings that CALIPSO consistently detects cloud tops at a higher altitude than CloudSat. It was also found that CALIPSO cloud tops were consistently higher than Doppler-radar echo tops or NAM cloud tops. However, CALIPSO altitudes were very consistent with altitudes determined by direct sighting. Doppler radar and modeling data often closely matched satellite observations, but on occasion they showed large differences. Careful analysis of the limitations and the biases of these data could improve our understanding of convective cloud-top dynamics and improve in-flight routing decisions for commercial aviation.

Goldberg, R.; Magee, N. B.

2011-12-01

321

Elementary GLOBE Unit: Do You Know that Clouds Have Names?  

NSDL National Science Digital Library

In this book and activities set, the GLOBE Kids share information about the different cloud types by acting out analogies that show what each cloud type looks like and its height in the sky. *Activity 1: Cloud Fun* Students learn about the shape and appearance of cumulus clouds, how to describe them, and what kind of weather is generally happening when these clouds are in the sky. *Activity 2: Cloudscape* Students will be able to identify cloud types using cloud classification names. They will know that the names are based on cloud shape, altitude, and whether they produce precipitation. *Activity 3: To Spread or Not to Spread* Students will be able to identify the three types of contrails and will know that contrails come from airplanes and some contrails become clouds. The Elementary GLOBE unit was designed to introduce K-4 students to the study of Earth System Science. It includes five storybooks and 15 learning activities. The science content provided in the books serves as a springboard to GLOBEâs scientific protocols, and also provides student with an introduction to technology, a basic understanding of the methods of inquiry, and connections to math and literacy skills. Each book has associated hands-on learning activities to support learning exploration.

Hatheway, Becca

2006-01-01

322

Polyp height and width measurement using topographic height map  

NASA Astrophysics Data System (ADS)

The height and width of colonic polyps are important characteristics to evaluate the status and malignancy of polyps. We borrow the idea from geographic information systems to employ topographic height maps to compute the polyp height and width. The height map is generated using a ray-casting algorithm through an orthogonal projection. A concentric index is devised to gauge the quality of the height map and is maximized in a multi-scale spiral spherical search for the optimal projection. We then locate the polyp tip and neck using directional height profiles, and derive height and width measurement based on geometrical analysis. We manually measured the height and width of 58 polyps and performed paired t-tests between manual measurement and height map measurement. The test shows that Pearson correlation is 0.742 and P(T<=t) is 0.01 for height measurement; and Pearson correlation is 0.663 and P(T<=t) is 0.002 for width measurement.

Yao, Jianhua; Frentz, Suzanne; Li, Jiang; Summers, Ronald

2008-04-01

323

A comparison of ship and satellite measurements of cloud properties with global climate model simulations in the southeast Pacific stratus deck  

NASA Astrophysics Data System (ADS)

Here, liquid water path (LWP), cloud fraction, cloud top height, and cloud base height retrieved by a suite of A-train satellite instruments (the CPR aboard CloudSat, CALIOP aboard CALIPSO, and MODIS aboard Aqua) are compared to ship observations from research cruises made in 2001 and 2003-2007 into the stratus/stratocumulus deck over the southeast Pacific Ocean. It is found that CloudSat radar-only LWP is generally too high over this region and the CloudSat/CALIPSO cloud bases are too low. This results in a relationship (LWP~h9) between CloudSat LWP and CALIPSO cloud thickness (h) that is very different from the adiabatic relationship (LWP~h2) from in situ observations. Such biases can be reduced if LWPs suspected to be contaminated by precipitation are eliminated, as determined by the maximum radar reflectivity Zmax>-15 dBZ in the apparent lower half of the cloud, and if cloud bases are determined based upon the adiabatically-determined cloud thickness (h~LWP1/2). Furthermore, comparing results from a global model (CAM3.1) to ship observations reveals that, while the simulated LWP is quite reasonable, the model cloud is too thick and too low, allowing the model to have LWPs that are almost independent of h. This model can also obtain a reasonable diurnal cycle in LWP and cloud fraction at a location roughly in the centre of this region (20° S, 85° W) but has an opposite diurnal cycle to those observed aboard ship at a location closer to the coast (20° S, 75° W). The diurnal cycle at the latter location is slightly improved in the newest version of the model (CAM4). However, the simulated clouds remain too thick and too low, as cloud bases are usually at or near the surface.

Brunke, M. A.; de Szoeke, S. P.; Zuidema, P.; Zeng, X.

2010-07-01

324

THE EFFECT OF CLOUD FRACTION ON THE RADIATIVE ENERGY BUDGET: The Satellite-Based GEWEX-SRB Data vs. the Ground-Based BSRN Measurements  

NASA Astrophysics Data System (ADS)

The NASA GEWEX-SRB (Global Energy and Water cycle Experiment - Surface Radiation Budget) project produces and archives shortwave and longwave atmospheric radiation data at the top of the atmosphere (TOA) and the Earth's surface. The archive holds uninterrupted records of shortwave/longwave downward/upward radiative fluxes at 1 degree by 1 degree resolution for the entire globe. The latest version in the archive, Release 3.0, is available as 3-hourly, daily and monthly means, spanning 24.5 years from July 1983 to December 2007. Primary inputs to the models used to produce the data include: shortwave and longwave radiances from International Satellite Cloud Climatology Project (ISCCP) pixel-level (DX) data, cloud and surface properties derived therefrom, temperature and moisture profiles from GEOS-4 reanalysis product obtained from the NASA Global Modeling and Assimilation Office (GMAO), and column ozone amounts constituted from Total Ozone Mapping Spectrometer (TOMS), TIROS Operational Vertical Sounder (TOVS) archives, and Stratospheric Monitoring-group's Ozone Blended Analysis (SMOBA), an assimilation product from NOAA's Climate Prediction Center. The data in the archive have been validated systemically against ground-based measurements which include the Baseline Surface Radiation Network (BSRN) data, the World Radiation Data Centre (WRDC) data, and the Global Energy Balance Archive (GEBA) data, and generally good agreement has been achieved. In addition to all-sky radiative fluxes, the output data include clear-sky fluxes, cloud optical depth, cloud fraction and so on. The BSRN archive also includes observations that can be used to derive the cloud fraction, which provides a means for analyzing and explaining the SRB-BSRN flux differences. In this paper, we focus on the effect of cloud fraction on the surface shortwave flux and the level of agreement between the satellite-based SRB data and the ground-based BSRN data. The satellite and BSRN employ different measuring methodologies and thus result in data representing means on dramatically different spatial scales. Therefore, the satellite-based and ground-based measurements are not expected to agree all the time, especially under skies with clouds. The flux comparisons are made under different cloud fractions, and it is found that the SRB-BSRN radiative flux discrepancies can be explained to a certain extent by the SRB-BSRN cloud fraction discrepancies. Apparently, cloud fraction alone cannot completely define the role of clouds in radiation transfer. Further studies need to incorporate the classification of cloud types, altitudes, cloud optical depths and so on.

Zhang, T.; Stackhouse, P. W.; Gupta, S. K.; Cox, S. J.; Mikovitz, J. C.; Nasa Gewex Srb

2011-12-01

325

Cloud computing.  

PubMed

In this bimonthly series, the author examines how nurse educators can use Internet and Web-based technologies such as search, communication, and collaborative writing tools; social networking and social bookmarking sites; virtual worlds; and Web-based teaching and learning programs. This article describes how cloud computing can be used in nursing education. PMID:22157990

Wink, Diane M

326

The mechanism of first raindrops formation in deep convective clouds  

NASA Astrophysics Data System (ADS)

formation of first raindrops in deep convective clouds is investigated. A combination of observational data analysis and 2D and 3D simulations of deep convective clouds suggests that the first raindrops form at the top of undiluted or slightly diluted cores. It is shown that droplet size distributions in these regions are wider and contain more large droplets than in diluted volumes. The results of the study suggest that the initial raindrop formation is determined by the basic microphysical processes within ascending adiabatic volumes. It allows one to predict the height of the formation of first raindrops considering the processes of cloud condensation nuclei activation, droplet diffusion growth, and coalescence growth. The results obtained in the study explain observational results through which the in-cloud height of first raindrop formation depends linearly on the droplet number concentration at cloud base. The results also explain why a simple adiabatic parcel model can reproduce this dependence. The present study provides a physical basis for retrieval algorithms of cloud microphysical properties and aerosol properties using satellites. The study indicates that the role of mixing and entrainment in the formation of the first raindrops is not of crucial importance. It is also shown that low variability of effective and mean volume radii along horizontal traverses, as regularly observed by in situ measurements, can be simulated by high-resolution cloud models in which mixing is parameterized by a traditional 1.5 order turbulence closure scheme.

Khain, A.; Prabha, Thara V.; Benmoshe, Nir; Pandithurai, G.; Ovchinnikov, M.

2013-08-01

327

Supercooled Liquid Water Clouds in Utah Winter Mountain Storms: Cloud-seeding Implications of a Remote-Sensing Dataset.  

NASA Astrophysics Data System (ADS)

A polarization lidar, dual-wavelength microwave radiometer, and radiosonde dataset from 19 winter storms studied over the Tushar Mountains in the 1985 and 1987 Utah NOAA cooperative weather modification field campaigns are used to characterize embedded supercooled liquid water (SLW) clouds. The findings show the dominance of barrier-level. mildly supercooled (0° to 10°C) orographic clouds, as identified by the lidar from a midbarrier field site. The combined lidar and radiometer (with liquid water depths greater than or equal to 0.05 mm) data sample indicates an SLW cloud frequency of occurrence of about 73% of the time the lidar was operating, although only 51% of the lidar shots detected SLW clouds because of the frequent presence of range-limiting attenuation from snowfall. A significant development from this study is the application of a new autonomous computer algorithm for identifying SLW clouds store single normalized lidar shots, using only the height derivative of the returned signal and the minimum linear depolarization ratio. In terms of operational AgI cloud-seeding practices, we conclude that it is mainly the upper portions of SLW clouds with relatively warm cloud-base temperatures ( 7°C) that display potential for yielding increased snowfall, since only these clouds regularly produced significant (0.15 mm) radiometric liquid water depths.

Sassen, Kenneth; Zhao, Hongjie

1993-09-01

328

Ground-truthing a satellite-based night-time cloud identification technique at the Pierre Auger Observatory  

NASA Astrophysics Data System (ADS)

Atmospheric conditions are important factors for the cosmic rays detected at the Pierre Auger Observatory. Therefore, we have been accumulating different type of atmospheric data during the last 8 years. This can also be a very interesting source for research for atmospheric scientists. As an illustration of interdisciplinary science, we have used satellite data to identify clouds at night. We developed a method using infrared data from the imager instrument on the GOES-12 satellite. The Pierre Auger Observatory has already installed ground-based instruments, like the Central Laser Facility (CLF), for identifying clouds at night. The Fluorescence Detector (FD) of the Pierre Auger Observatory sees the CLF laser profile and thereby senses the presence of clouds directly above the CLF. For the satellite image pixel encompassing the CLF, we compared cloud identifications with the satellite-based method to those made with the FD observations of CLF laser events. The results of both methods agree. We generate cloud probability maps covering the region of the observatory for all periods of FD operation since 2007. We summarize the cloud cover history of the observatory site as well.

Chirinos, J.

2012-08-01

329

Sensitivity study of cloud/radiation interaction using a second order turbulence radiative-convective model  

SciTech Connect

A high resolution one-dimensional version of a second order turbulence convective/radiative model, developed at the Los Alamos National Laboratory, was used to conduct a sensitivity study of a stratocumulus cloud deck, based on data taken at San Nicolas Island during the intensive field observation marine stratocumulus phase of the First International Satellite Cloud Climatology Program (ISCCP) Regional Experiment (FIRE IFO), conducted during July, 1987. Initial profiles for liquid water potential temperature, and total water mixing ratio were abstracted from the FIRE data. The dependence of the diurnal behavior in liquid water content, cloud top height, and cloud base height were examined for variations in subsidence rate, sea surface temperature, and initial inversion strength. The modelled diurnal variation in the column integrated liquid water agrees quite well with the observed data, for the case of low subsidence. The modelled diurnal behavior for the height of the cloud top and base show qualitative agreement with the FIRE data, although the overall height of the cloud layer is about 200 meters too high.

Kao, C.Y.J.; Smith, W.S.

1993-02-01

330

Sensitivity study of cloud/radiation interaction using a second order turbulence radiative-convective model  

SciTech Connect

A high resolution one-dimensional version of a second order turbulence convective/radiative model, developed at the Los Alamos National Laboratory, was used to conduct a sensitivity study of a stratocumulus cloud deck, based on data taken at San Nicolas Island during the intensive field observation marine stratocumulus phase of the First International Satellite Cloud Climatology Program (ISCCP) Regional Experiment (FIRE IFO), conducted during July, 1987. Initial profiles for liquid water potential temperature, and total water mixing ratio were abstracted from the FIRE data. The dependence of the diurnal behavior in liquid water content, cloud top height, and cloud base height were examined for variations in subsidence rate, sea surface temperature, and initial inversion strength. The modelled diurnal variation in the column integrated liquid water agrees quite well with the observed data, for the case of low subsidence. The modelled diurnal behavior for the height of the cloud top and base show qualitative agreement with the FIRE data, although the overall height of the cloud layer is about 200 meters too high.

Kao, C.Y.J.; Smith, W.S.

1993-01-01

331

Aerosol-Cloud microphysical closure in warm tropical cumulus during CRYSTAL-FACE  

NASA Astrophysics Data System (ADS)

We present a closure study between aerosol and warm-cloud microphysics using field data collected during the NASA CRYSTAL-FACE campaign. CRYSTAL-FACE was conducted in continental and marine environments near southern Florida in July, 2002. Detailed profiles of thirteen cumulus clouds were made by the CIRPAS Twin Otter aircraft, which was equipped with four aerosol sizing systems, two CCN counters operated at 0.4% and 0.7% supersaturation, an Aerodyne aerosol mass spectrometer, a MOUDI filter sampler system, two cloud drop sizing probes, and two turbulence probes. A wide range of CCN (300 to >3500 cm-3) and cloud drop concentrations (200 to >1600 cm-3) provides an ideal case study for aerosol-cloud interactions and the first and second indirect effects. Vertical characterization of the young and mature cumulus clouds are obtained from multiple horizontal passes from below cloud base to cloud top. A detailed adiabatic cloud activation model accurately predicts the cloud drop concentration 100 m above cloud base. The model is constrained by observed updraft velocity and below-cloud aerosol properties (i.e. concentration, size distribution, composition, and supersaturation spectrum). Each cloud contains a core often exceeding 500 m in height in which the equivalent potential temperature follows a moist-adiabatic vertical profile. Effective radius most often follows an adiabatic profile, even in regions where liquid water content and/or equivalent potential temperature are sub-adiabatic. Large cloud-to-cloud variations in the vertical profile of effective radius are primarily driven by below-cloud aerosol concentration and to a lesser degree by cloud dynamics (i.e. vertical velocity). Six of the thirteen clouds are simulated using the RAMS large-eddy-simulation model. RAMS is integrated with bulk and bin microphysical models and is coupled to an offline 3-D radiative transfer model to study the aerosol effects on cloud microphysics and radiative properties. More detailed studies of the evolution of cloud microphysics are conducted using a non-adiabatic cloud activation model that takes as input Lagrangian parcel trajectories computed from the RAMS simulations. The simulations are used to comment on the observed features in the cloud drop size distribution, such as multiple cloud drop modes, the width of the drop distribution, and conditions for the initiation of drizzle.

Conant, W. C.; Lu, M.; Vanreken, T.; Rissman, T.; Varutbangkul, V.; Jonsson, H. H.; Nenes, A.; Jimenez, J. L.; Delia, A. E.; Bahreini, R.; Roberts, G. C.; Flagan, R. C.; Seinfeld, J. H.

2002-12-01

332

Satellite-Based Assessment of the Aerosol Effect on Global Warm Cloud Properties  

NASA Astrophysics Data System (ADS)

We present characteristics of global warm cloud properties and warm-rain process in conjunction with the aerosol index (AI) and the lower-tropospheric stability (LTS). The Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) and Visible/Infrared Radiance Imager (VIRS) simultaneously derive cloud-top droplet effect radius, column droplet radius, cloud fraction, cloud liquid water path, cloud optical depth, and a warm rain index. These cloud properties are clustered by different bins of LTS, and then compared with GOCART-derived AI and MODIS-derived AI values. Results indicate that the characteristics of the aerosol-cloud interactions significant vary between different cloud types and thermodynamic environments. This indicates that the radiative effect and warm-rain process due to aerosols have significant heterogeneous regional climate forcing effects.

Matsui, T.; Masunaga, H.; Pielke, R. A.; Kreidenweis, S. M.; Tao, W.; Chin, M.; Kaufman, Y. J.

2004-12-01

333

A Climatology of Fair-Weather Cloud Statistics at the Atmospheric Radiation Measurement Program Southern Great Plains Site: Temporal and Spatial Variability  

SciTech Connect

In previous work, Berg and Stull (2005) developed a new parameterization for Fair-Weather Cumuli (FWC). Preliminary testing of the new scheme used data collected during a field experiment conducted during the summer of 1996. This campaign included a few research flights conducted over three locations within the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) Southern Great Plains (SGP) site. A more comprehensive verification of the new scheme requires a detailed climatology of FWC. Several cloud climatologies have been completed for the ACRF SGP, but these efforts have focused on either broad categories of clouds grouped by height and season (e.g., Lazarus et al. 1999) or height and time of day (e.g., Dong et al. 2005). In these two examples, the low clouds were not separated by the type of cloud, either stratiform or cumuliform, nor were the horizontal chord length (the length of the cloud slice that passed directly overhead) or cloud aspect ratio (defined as the ratio of the cloud thickness to the cloud chord length) reported. Lane et al. (2002) presented distributions of cloud chord length, but only for one year. The work presented here addresses these shortcomings by looking explicitly at cases with FWC over five summers. Specifically, we will address the following questions: •Does the cloud fraction (CF), cloud-base height (CBH), and cloud-top height (CTH) of FWC change with the time of day or the year? •What is the distribution of FWC chord lengths? •Is there a relationship between the cloud chord length and the cloud thickness?

Berg, Larry K.; Kassianov, Evgueni I.; Long, Charles N.; Gustafson, William I.

2006-03-30

334

Cloud computing security  

Microsoft Academic Search

Cloud computing is a paradigm rapidly being embraced by government and industry as a solution for cost-savings, scalability, and collaboration. While a multitude of applications and services are available commercially for cloud-based solutions, research in this area has yet to fully embrace the full spectrum of potential challenges facing cloud computing. This tutorial aims to provide researchers with a fundamental

Dongwan Shin; William R. Claycomb; Vincent E. Urias

2010-01-01

335

Profiles of Low-Level Stratus Cloud Microphysics Deduced from Ground-Based Measurements  

Microsoft Academic Search

The microwave radiometer-derived cloud liquid water path (LWP) and a profile of radar reflectivity are used to derive a profile of cloud liquid water content (LWC). Two methods (M1 and M2) have been developed for inferring the profile of cloud-droplet effective radius (re) in liquid phase or liquid dominant mixed phase stratocumulus clouds. The M1-inferred re profile is proportional to

Xiquan Dong; Gerald G. Mace

2003-01-01

336

The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius  

NASA Astrophysics Data System (ADS)

A 3-min 3-km rapid scan of the METEOSAT Second Generation geostationary satellite over southern Africa was applied to tracking the evolution of cloud top temperature (T) and particle effective radius (re) of convective elements. The evolution of T-re relations showed little dependence on time, leaving re to depend almost exclusively on T. Furthermore, cloud elements that fully grew to large cumulonimbus stature had the same T-re relations as other clouds in the same area with limited development that decayed without ever becoming a cumulonimbus. Therefore, a snap shot of T-re relations over a cloud field provides the same relations as composed from tracking the time evolution of T and re of individual clouds, and then compositing them. This is the essence of exchangeability of time and space scales, i.e., ergodicity, of the T-re relations for convective clouds. This property has allowed inference of the microphysical evolution of convective clouds with a snap shot from a polar orbiter. The fundamental causes for the ergodicity are suggested to be the observed stability of re for a given height above cloud base in a convective cloud, and the constant renewal of growing cloud tops with cloud bubbles that replace the cloud tops with fresh cloud matter from below.

Lensky, I. M.; Rosenfeld, D.

2005-11-01

337

The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius  

NASA Astrophysics Data System (ADS)

A 3-minute 3-km rapid scan of the METEOSAT Second Generation geostationary satellite over southern Africa was applied to tracking the evolution of cloud top temperature (T) and particle effective radius (re) of convective elements. The evolution of T-re relations showed little dependence on time, leaving re to depend almost exclusively on T. Furthermore, cloud elements that fully grew to large cumulonimbus stature had the same T-re relations as other clouds in the same area with limited development that decayed without ever becoming a cumulonimbus. Therefore, a snap shot of T-re relations over a cloud field provides the same relations as composed from tracking the time evolution of T and re of individual clouds, and then compositing them. This is the essence of exchangeability of time and space scales, i.e., ergodicity, of the T-re relations for convective clouds. This property has allowed inference of the microphysical evolution of convective clouds with a snap shot from a polar orbiter. The fundamental causes for the ergodicity are suggested to be the observed stability of re for a given height above cloud base in a convective cloud, and the constant renewal of growing cloud tops with cloud bubbles that replace the cloud tops with fresh cloud matter from below.

Lensky, I. M.; Rosenfeld, D.

2006-07-01

338

Determination of potential solar power sites in the United States based upon satellite cloud observations  

Microsoft Academic Search

The use of cloud images in the visual spectrum from the SMS\\/GOES geostationary satellites to determine the hourly distribution of sunshine on a mesoscale in the continental United States excluding Alaska is presented. Cloud coverage and density as a function of time of day and season are evaluated through the use of digital data processing techniques. Low density cirrus clouds

H. W. Hiser; H. V. Senn; S. T. Bukkapatnam; K. Akyuzlu

1977-01-01

339

The Research of Satellite Cloud Image Recognition Base on Variational Method and Texture Feature Analysis  

Microsoft Academic Search

Recently, the development of satellite cloud image processing technology has become very quick; the research aspects concentrate on judge the cloud type and classify the cloud mainly. These image processing methods relate to the subject category like image processing and pattern recognition etc; it has become one of the fields of most quickly development in the research of satellite image

Wei Shangguan; Yanling Hao; Zhizhong Lu; Peng Wu

2007-01-01

340

Feeder-Cell Ingestion of Seeding Aerosol from Cloud Base Determined by Tracking Radar Chaff  

Microsoft Academic Search

Questions of delivery, transport, and dispersion of cloud seeding aerosol in a convective feeder cloud are addressed by using radar chaff as a surrogate for aerosol and tracking it with circular-polarization radar. In a case study, a line source of chaff was released by an aircraft at the roots of a growing cloud flanking and feeding into a thunderstorm line.

Roger F. Reinking; Brooks E. Martner

1996-01-01

341

Research on Chinese Character Height Model of Guide Signs Based on 3D Technology and Information Processing Characteristics of Chinese Drivers  

Microsoft Academic Search

Drivers are often not able to recognize the letter in time and sometimes it is a waste of money with too large letters in guide signs. In order to solve this problem, a new Chinese character height model for guide signs has been developed based on 3D technology and the apperceive characteristics of Chinese drivers. The model was built according

Huang Kai; Wang Heng; Tang Jianjuan

2010-01-01

342

Inferring hydroxyl layer peak heights from ground-based measurements of OH(6-2) band integrated emission rate at Longyearbyen (78° N, 16° E)  

Microsoft Academic Search

Measurements of hydroxyl nightglow emissions over Longyearbyen (78° N, 16° E) recorded simultaneously by the SABER instrument onboard the TIMED satellite and a ground-based Ebert-Fastie spectrometer have been used to derive an empirical formula for the height of the OH layer as a function of the integrated emission rate (IER). Altitude profiles of the OH volume emission rate (VER) derived

F. J. Mulligan; M. E. Dyrland; F. Sigernes; C. S. Deehr

2009-01-01

343

Effects of biomass-burning-derived aerosols on precipitation and clouds in the Amazon Basin: a satellite-based empirical study  

NASA Astrophysics Data System (ADS)

Biomass burning in the Amazon provides strong input of aerosols into the atmosphere, with potential effects on precipitation, cloud properties, and radiative balance. However, few studies to date have systematically examined these effects at the scale of the Amazon Basin, over an entire burning season, using available data sets. We empirically study the relationships of aerosol optical depth (?a) versus rainfall and cloud properties measured from satellites over the entire Brazilian Amazon during the dry, biomass burning seasons (August-October) of 2000 and 2003. Elevated ?a was associated with increased rainfall in both 2000 and 2003. With enhanced ?a, cloud cover increased significantly, and cloud top temperature/pressure decreased, suggesting higher cloud tops. The cloud droplet effective radius (Re) exhibited minimal growth with cloud height under background levels of ?a, while distinct increases in Re at cloud top temperatures below -10°C, indicative of ice formation, were observed with aerosol loading. Although empirical correlations do not unequivocally establish the causal link from aerosols, these results are consistent with previous observational and modeling studies that pointed to dynamical effects from aerosols that invigorate convection, leading to higher clouds, enhanced cloud cover, and stronger rainfall. We speculate that changes in precipitation and cloud properties associated with aerosol loading observed in this study could have important radiative and hydrological effects on the Amazonian climate system. The accelerated forest burning for agricultural land clearing and the resulting enhancements in aerosols and rainfall may even partially account for the observed positive trend in Amazonian precipitation over the past several decades.

Lin, J. C.; Matsui, T.; Pielke, R. A.; Kummerow, C.

2006-10-01

344

Ammonia Clouds of Jupiter and Saturn - Here Today, Gone Tomorrow?  

NASA Astrophysics Data System (ADS)

Ground-based, satellite, and spacecraft observations show that, with the exception of some relatively clear regions (belts, hot spots, warm areas), clouds exist everywhere on Jupiter and Saturn. Thermochemical models (Atreya et al., 1999) combined with observational evidence (e.g. Galileo NIMS obiter imaging, Banfield, et al., 1998; Galileo probe data, Atreya et al., 1999, 2003a) suggest that the composition of the upper cloud layer of Jupiter and Saturn is ammonia. Yet, spectrally identifiable ammonia clouds (SIAC) are detected only in certain discrete regions of Jupiter (Baines et al., 2002; Wong, et al., 2003a) and nowhere on Saturn. Less than 1% of Jupiter's area is covered with SIACs according to Galileo NIMS observations (Baines et al., 2002). In this work, we argue that spectral signature of all but the freshly made SIACs is masked by dusting of the ammonia clouds by photochemically produced hydrocarbon haze falling from the stratosphere (Atreya et al., 2003b). We estimate the deposition rate of the coating haze layer to be at least 100 A/year on Jupiter, enough to turn the ammonia cloud into a spectrally grey cloud. The haze particles are composed mostly of condensed polycyclic aromatic hydrocarbons (Wong, et al., 2003b), with smaller contribution from polyyne polymers, nitrile polymers, solid hydrazine and meteoritic dust. Cloud properties including cloud opacity, cloud top height, and the particle size can also be a factor in the lack of detection of ammonia clouds. The lack of spectral identification of Saturn's ammonia clouds can also be explained similarly. References: Atreya et al., Planet. Space Sci., 47, 1243, 1999. Atreya et al., Planet. Space Sci., 51, 105, 2003a. Atreya et al., Jupiter's ammonia clouds-Localized or ubiquitous? Planet. Space Sci., submitted, 2003b. Baines et al., Icarus, 159, 74, 2002. Banfield et al., Icarus, 135, 230, 1998. Wong, M.H., et al., PSS, in press, 2003a. Wong A.S., et al., GRL, 30, art. no. 1447, 2003b.

Atreya, S. K.; Wong, A.

2003-12-01

345

Remote sensing the vertical profile of cloud droplet effective radius, thermodynamic phase, and temperature  

NASA Astrophysics Data System (ADS)

Cloud-aerosol interaction is a key issue in the climate system, affecting the water cycle, the weather, and the total energy balance including the spatial and temporal distribution of latent heat release. Information on the vertical distribution of cloud droplet microphysics and thermodynamic phase as a function of temperature or height, can be correlated with details of the aerosol field to provide insight on how these particles are affecting cloud properties and their consequences to cloud lifetime, precipitation, water cycle, and general energy balance. Unfortunately, today's experimental methods still lack the observational tools that can characterize the true evolution of the cloud microphysical, spatial and temporal structure in the cloud droplet scale, and then link these characteristics to environmental factors and properties of the cloud condensation nuclei. Here we propose and demonstrate a new experimental approach (the cloud scanner instrument) that provides the microphysical information missed in current experiments and remote sensing options. Cloud scanner measurements can be performed from aircraft, ground, or satellite by scanning the side of the clouds from the base to the top, providing us with the unique opportunity of obtaining snapshots of the cloud droplet microphysical and thermodynamic states as a function of height and brightness temperature in clouds at several development stages. The brightness temperature profile of the cloud side can be directly associated with the thermodynamic phase of the droplets to provide information on the glaciation temperature as a function of different ambient conditions, aerosol concentration, and type. An aircraft prototype of the cloud scanner was built and flew in a field campaign in Brazil. The CLAIM-3D (3-Dimensional Cloud Aerosol Interaction Mission) satellite concept proposed here combines several techniques to simultaneously measure the vertical profile of cloud microphysics, thermodynamic phase, brightness temperature, and aerosol amount and type in the neighborhood of the clouds. The wide wavelength range, and the use of multi-angle polarization measurements proposed for this mission allow us to estimate the availability and characteristics of aerosol particles acting as cloud condensation nuclei, and their effects on the cloud microphysical structure. These results can provide unprecedented details on the response of cloud droplet microphysics to natural and anthropogenic aerosols in the size scale where the interaction really happens.

Martins, J. V.; Marshak, A.; Remer, L. A.; Rosenfeld, D.; Kaufman, Y. J.; Fernandez-Borda, R.; Koren, I.; Correia, A. L.; Zubko, V.; Artaxo, P.

2011-09-01

346

Solder joint shape and standoff height prediction and integration with FEA-based methodology for reliability evaluation  

Microsoft Academic Search

Solder joint fatigue failure is a common failure mechanism in semiconductor packages mounted on boards. The thermal expansion mismatch between the package and the board causes cyclic loading on the solder joints during temperature cycling. It is therefore important to model the solder joint shape and standoff height accurately to estimate the reliability of a solder joint assembly. This paper

Sidharth; R. Blish; D. Natekar

2002-01-01

347

Ground-based nitric acid measurements at Arrival Heights, Antarctica, using solar and lunar Fourier transform infrared observations  

Microsoft Academic Search

Nitric acid plays an important role in processes leading to stratospheric ozone loss in polar regions. Spectroscopic absorption measurements of nitric acid have been made during the sunlit part of the Antarctic year at Arrival Heights (78°S, 167°E) since the late 1980s. This paper presents the first extension of these nitric acid measurements through the winter, using the Moon as

S. W. Wood; R. L. Batchelor; A. Goldman; C. P. Rinsland; B. J. Connor; F. J. Murcray; T. M. Stephen; D. N. Heuff

2004-01-01

348

Self-reported body weight and height on admission to hospital: a reliable method in multi-professional evidence-based nutritional care?  

PubMed

Screening patients' nutritional status on admission to hospital is recommended by evidence-based guidelines on malnutrition. In practice, self-reported values for body weight and height are often used by nurses and dieticians. This study assessed the accuracy of self-reported body weight and height and whether these self-reported values might be influenced by the nature of the health-care worker involved. Patients (n = 611) on admission reported their body weight and height to a nurse and a dietician. Reported values were analysed and compared with the measured values. Self-reported values for body weight and height on admission are not always accurate. Patients do report different values to different health-care workers. Self-reported values for body weight to nurses were more accurate as compared with dieticians. Self-reported values for body weight and height are subject to observer bias and should be used with caution in nutritional screening and multi-professional nutritional care. PMID:23009381

Geurden, Bart; Franck, Erik; Van Looy, Luc; Weyler, Joost; Ysebaert, Dirk

2012-10-01

349

Introduction of A Day/Night, Object-Based Quantitative Fog/Low Cloud Detection and Thickness Algorithm for GOES-R  

NASA Astrophysics Data System (ADS)

The GOES-R fog/low cloud detection product is a day/night, object-based algorithm designed to quantitatively identify single layer clouds that produce Instrument Flight Rules (IFR) conditions, defined as having a cloud ceiling below 1000 ft (305 m) above ground level (AGL) or a visibility less than 3 miles. Surface visibility is not available for the GOES-R algorithm so the GOES-R fog product returns a probability that the cloud ceiling is below 1000 ft (305 m) AGL. At night, the 3.9 and 11 ?m channels are used for detection while during the day the 0.65, 3.9, and 11 ?m channels are required. The fog detection algorithm utilizes textural and spectral information, as well as the difference between the cloud radiative temperature and surface temperature. The GOES-R fog/low cloud product also produces an estimation of the fog/low cloud thickness where detected.

Calvert, C. G.; Pavolonis, M. J.

2010-12-01

350

Integrating Cloud-Based Strategies and Tools in Face-to-Face Training Sessions to Increase the Impact of Professional Development  

ERIC Educational Resources Information Center

|This article is based on the premise that face-to-face training can be augmented with cloud-based technology tools, to potentially extend viable training supports as higher education staff and faculty implement new content/skills in their jobs and classrooms. There are significant benefits to harnessing cloud-based tools that can facilitate both…

Gradel, Kathleen; Edson, Alden J.

2012-01-01

351

Confirmation of delayed menarche based on regression evaluation of age at menarche for age at MPV of height in female ball game players.  

PubMed

A general delay in menarche in female athletes has been confirmed based on comparisons of mean ages between athletes and non-athletes; however, it has not been possible to judge such delays individually. If delayed menarche could be evaluated for an individual, the athlete could be advised as to necessary precautions. In this study, the age at maximum peak velocity (MPV) of height, adopted as an index of physical maturation, was identified by the wavelet interpolation method (WIM). The relationship between the age at menarche and age at MPV of height in female athletes and non-athletes was then examined. For the athlete group, health examination records of 90 female ball game players in the first year of university in the Tokai area, all of whom had participated in national level competitions, were reviewed for the period from the first grade of elementary school until the final year of high school (from 1985 to 1996). A similar examination was conducted for the control group, among whom a final group of 78 female non-athletes were selected. The age at menarche was determined by questionnaires, and the longitudinal data for height and weight were obtained from the health examination records. Based on a comparison of the difference between the age at MPV of height and age at menarche in ball game players and the control group, a tendency was seen for the difference between the two ages to narrow as the age at MPV of height rose. A corrected regression evaluation of age at menarche against age at MPV of height was derived in the control group, and the evaluation system was applied to ball game players. The delay in menarche in ball game players could be individually evaluated. PMID:21432163

Fujii, Katsunori; Demura, Schinichi

2005-01-01

352

Lidar observation of PBL clouds: part of the Experimental Cloud Lidar Pilot Study (ECLIPS) phase II  

NASA Astrophysics Data System (ADS)

The clouds play a significant role in the atmosphere particularly in the determination of the radiant balance. Since their type, structure and height considerable influence the transmission, absorption and re-radiation of the IR radiation they are of great importance for the local meteorology and the global climatology. In small spatial scales (micro- and meso- ones) the clouds considerable change in space and time. The ECLIPS (Experimental Cloud Lidar Pilot Study) program in which our lidar group also takes part is well described. In general, the main purpose is a ground-based lidar observation of the clouds simultaneously with the NOAA 10 and NOAA 11 meteorological satellites overpassing the same areas to be performed. Essential lidar data are the recorded profiles from which the information about the clouds height, optical depth and vertical extinction can be derived. The experimental data required for the ECLIPS Phase II measurements were recorded during the period from 21 May to O9 July 1991 at 30 observations by 3 hours each i.e. 1 hour before and 1 hour after the NOAA 10 and NOAA 11 satellites overpasses. The lidar data are completed with certain meteorological information obtained by the conventional means. The presented experiment was conducted using triple- beam aerosol meteorological lidar developed at the Institute of Electronics of Bulgarian Academy of Sciences, which are well described previously.

Kolev, Ivan N.; Parvanov, Orlin; Kaprielov, Boiko; Grigorov, Ivan; Gospodinova, Nadia

1994-12-01

353

A procedure for the automatic estimation of mixed layer height.  

SciTech Connect

The daytime mixed layer results from mechanical and thermal turbulence processes driven by differences in air-surface temperature and moisture. As such, the height of the mixed layer (z{sub i}) is a measure of the effectiveness of energy transfer from the sun to the earth's surface and, in turn, to the lower atmosphere (Stun, 1989). Maximum daytime values for z{sub i} in the region of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) vary from less than 100 m in cloudy, moist, calm, stable conditions to nearly 3 km in clear, dry, unstable conditions. The principal characteristic of the mixed layer is that scalar quantities such as moisture and temperature are mixed throughout. Thus, z{sub i} becomes one of the principal scaling parameters used to describe the structure of the lower planetary boundary layer. Normally, a stable layer (a potential temperature inversion) at the top of the mixed layer interfaces between processes in the lower atmosphere and in the free atmosphere above. The strength of this inversion limits the rate of growth of z{sub i} with time and the vertical transfer of energy and moisture. When and if z{sub i} reaches the condensation level, clouds can form; hence, cloud base height (particularly for fair-weather cumulus clouds) often coincides with z{sub i} later in the day. Although the concept of the mixed layer height is straightforward, its measurement can be relatively difficult, or at least awkward. The most reliable method is an analysis of potential temperature and mixing ratio profiles retrieved from balloon ascents. (The potential temperature changes from constant to increasing with height; the mixing ratio changes from constant to decreasing with height.) Often however, the profiles of temperature and moisture are ambiguous, with multiple inversions or none at all. In addition these profiles supply only a snapshot of the atmospheric structure that may well be unrepresentative of the average, either in time or space. In some instances, the term ''well mixed'' should not be applied to the lower atmosphere at all; during and after precipitation, for instance, the changes in surface and lower atmospheric conditions cause large ambiguities. This paper describes an automatic estimation method using radar profiler data and discusses a one-year climatology of z{sub i} over the SGP CART site.

Coulter, R. L.

1998-04-15

354

A Near-Real-Time Global Geostationary Satellite Cloud and Radiation Retreival System  

NASA Astrophysics Data System (ADS)

Weather prediction models need more quantitative weather information for forecasting and nowcasting. This paper describes a prototype system to provide 3-hourly cloud properties from full-disk geostationary satellites (GEOSat) around the globe. Data from GOES11/12, Meteosat.-9, FY2-C/D and MTSAT is analyzed using a common set of algorithms to derive products including cloud mask, cloud phase, cloud base and top height, optical depth, ice and liquid water path, particle sizes, shortwave albedo and longwave flux. Overlap cloud properties are derived from GOES-12 and Meteosat using the CO2 channel 13.3 um. Active and passive remote sensing data from the surface and other satellites are being used to validate the products. Interactive tools for accessing and viewing the data products are demonstrated. Examples of nowcasting application and assimilation of the cloud products in numerical model are presented and future plans and challenges discussed.

Palikonda, R.; Minnis, P.; Spangenberg, D. A.; Ayers, J. K.; Khaiyer, M. M.; Trepte, Q. Z.; Chang, F.; Heck, P. W.; Chee, T. L.; Nguyen, L.; Nordeen, M.

2009-12-01

355

GPU-Based Cloud Service for Smith-Waterman Algorithm Using Frequency Distance Filtration Scheme  

PubMed Central

As the conventional means of analyzing the similarity between a query sequence and database sequences, the Smith-Waterman algorithm is feasible for a database search owing to its high sensitivity. However, this algorithm is still quite time consuming. CUDA programming can improve computations efficiently by using the computational power of massive computing hardware as graphics processing units (GPUs). This work presents a novel Smith-Waterman algorithm with a frequency-based filtration method on GPUs rather than merely accelerating the comparisons yet expending computational resources to handle such unnecessary comparisons. A user friendly interface is also designed for potential cloud server applications with GPUs. Additionally, two data sets, H1N1 protein sequences (query sequence set) and human protein database (database set), are selected, followed by a comparison of CUDA-SW and CUDA-SW with the filtration method, referred to herein as CUDA-SWf. Experimental results indicate that reducing unnecessary sequence alignments can improve the computational time by up to 41%. Importantly, by using CUDA-SWf as a cloud service, this application can be accessed from any computing environment of a device with an Internet connection without time constraints.

Lee, Sheng-Ta; Hung, Che Lun

2013-01-01

356

Automatic object detection in point clouds based on knowledge guided algorithms  

NASA Astrophysics Data System (ADS)

The modeling of real-world scenarios through capturing 3D digital data has been proven applicable in a variety of industrial applications, ranging from security, to robotics and to fields in the medical sciences. These different scenarios, along with variable conditions, present a challenge in discovering flexible appropriate solutions. In this paper, we present a novel approach based on a human cognition model to guide processing. Our method turns traditional data-driven processing into a new strategy based on a semantic knowledge system. Robust and adaptive methods for object extraction and identification are modeled in a knowledge domain, which has been created by purely numerical strategies. The goal of the present work is to select and guide algorithms following adaptive and intelligent manners for detecting objects in point clouds. Results show that our approach succeeded in identifying the objects of interest while using various data types.

Truong, Hung; Karmacharya, Ashish; Mordwinzew, Waldemar; Boochs, Frank; Chudyk, Celeste; Habed, Adlane; Voisin, Yvon

2013-04-01

357

Relationship of height gradients of passive atmospheric properties to their variances: Applications to the ground-based sensing of profiles  

NASA Astrophysics Data System (ADS)

Ways of relating height profiles of mean atmospheric properties to their variances are compared. Assuming a horizontally homogeneous, time-stationary medium, all methods assert the proportionality of the variance of a property to the variance of the turbulent velocity in the medium, to the square of the height gradient of the mean, and to the inverse Vaisala-Brunt frequency squared. The paper examines the dependence of the proportionality factor on the Richardson number. Finally, the various options for retrieving humidity profiles and refractive index profiles from radar wind Profiler data are discussed, and reasons are given why a system that makes use of the acoustic backscatter as well as the radar backscatter is attractive.

Gossard, E. E.

1992-08-01

358

An explanation of discrepancy in mesospheric temperature trends derived from ground-based LF phase-height observations  

NASA Astrophysics Data System (ADS)

Bremer and Berger (J. Atmos. Solar Terr. Phys. 64 (2002) 805) applied a correction for trends in the NO concentration and ?eff in the interpretation of trends in the low frequency (LF) phase height measurements and obtained results less consistent with model simulations as well as the observed trends in mesospheric temperatures. The correction is shown to be too large most probably due to the application of inappropriate trends in ?eff of Chakrabarty (Adv. Space Res. 20 (1997) 2117), which yield a trend in electron density opposite to that which is observed. The discrepancy between the observational data and model-simulated trends of Bremer and Berger (J. Atoms. Solar. Terr. Phys. 64 (2002) 805) in the LF phase heights can be largely removed. Even more important, the trends in mesospheric temperatures inferred by Bremer and Berger (J. Atmos. Solar Terr. Phys. 64 (2002) 805) from trends in the LF phase heights without the inappropriate correction agree well with the results of analysis of a global set of results on trends in the mesospheric temperatures by Beig et al. (Rev. Geophys. 41 (2003) 1015).

Laštovi?ka, J.

2004-12-01

359

Cloud screening algorithm for AERONET database  

NASA Astrophysics Data System (ADS)

A reasonable cloud screening algorithm is very important to ensure accuracy of aerosol optical thickness determinations from AERONET database. In this paper, a new cloud screening algorithm is developed. The algorithm uses cloud fraction and a so-called scaling height of the tropospheric aerosol, derived from sunphotometer measurements and surface visibility data, to build the screening criterion. The criterion constraints the scaling height varying in some range. In the condition of no cloud day, the variation range is the monthly-mean scaling height plus 3? (?: the standard deviation of scaling height). The larger the cloud fraction is, the smaller the range. The new cloud screening algorithm is used to determine aerosol optical thicknesses from AERONET data measured in Beijing during 2001-2002. According to the application results, the reasonableness of the new algorithm is analyzed.

Qiu, Jinhuan

2005-05-01

360

The NASA CloudSat Education Network  

Microsoft Academic Search

CloudSat, a NASA Earth System Science Pathfinder Mission, will launch into orbit the world's most advanced weather radar designed to measure properties of clouds that are essential for accurate understanding of Earth's weather and climate processes. Providing the first vertical profiles of global measurements of cloud thickness, height, water and ice content and a wide range of precipitation data linked

D. K. Krumm

2006-01-01

361

ESTIMATING CLOUD PARAMETERS FOR NEROS I  

EPA Science Inventory

GOES infrared and visible imagery were combined with surface and upper-air meteorological observations to determine cloud amounts and cloud-top heights over the NEROS grid for the periods 1200, 1500, and 1800 EDT, on 3, 4, and 13 August 1979. Cloud amounts were determined for cum...

362

Mars Water-Ice Clouds and Precipitation  

Microsoft Academic Search

The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights

J. A. Whiteway; L. Komguem; C. Dickinson; C. Cook; M. Illnicki; J. Seabrook; V. Popovici; T. J. Duck; R. Davy; P. A. Taylor; J. Pathak; D. Fisher; A. I. Carswell; M. Daly; V. Hipkin; A. P. Zent; M. H. Hecht; S. E. Wood; L. K. Tamppari; N. Renno; J. E. Moores; M. T. Lemmon; F. Daerden; P. H. Smith

2009-01-01

363

Evaluation of Statistical Distributions for the Parametrization of Subgrid Boundary-Layer Clouds  

NASA Astrophysics Data System (ADS)

In numerical weather prediction and climate models, planetary boundary-layer (PBL) clouds are linked to subgrid-scale processes such as shallow convection. A comprehensive statistical analysis of large-eddy simulations (LES), obtained for warm PBL cloud cases, is carried out in order to characterize the distributions of the horizontal subgrid cloud variability. The production of subgrid clouds is mainly associated with the variability of the total water content. Nevertheless, in the case of PBL clouds, the temperature variability cannot be completely discarded and the saturation deficit, which summarizes both temperature and total water fluctuations, provides a better representation of the cloud variability than the total water content. The probability density functions (PDFs) of LES saturation deficit generally have the shape of a main asymmetric bell-shaped curve with a more or less distinct secondary maximum specific to each type of PBL clouds. Unimodal theoretical PDFs, even those with a flexible skewness, are not sufficient to correctly fit the LES distributions, especially the long tail that appears for cumulus clouds. They do not provide a unified approach for all cloud types. The cloud fraction and the mean cloud water content, diagnosed from these unimodal PDFs, are largely underestimated. The use of a double Gaussian distribution allows correction of these errors on cloud fields and provides a better estimation of the cloud-base and cloud-top heights. Eventually, insights for the design of a subgrid statistical cloud scheme are provided, in particular a new formulation for the weight of the two Gaussian distributions and for the standard deviation of the convective distribution.

Perraud, Emilie; Couvreux, Fleur; Malardel, Sylvie; Lac, Christine; Masson, Valéry; Thouron, Odile

2011-08-01

364

Torrential rainfall responses to vertical wind shear, radiation and ice clouds: A rainfall partitioning analysis based on surface rainfall budget  

NASA Astrophysics Data System (ADS)

The effects of vertical wind shear, radiation and ice clouds on the torrential rainfall event over Jinan, China during July 2007 are investigated through a rainfall partitioning analysis based on surface rainfall budget. All experiments are integrated with an imposed large-scale vertical velocity and zonal wind from the National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS), while vertical wind shear, cloud radiative effects, cloud-radiation interaction and ice clouds are, respectively, suppressed in the sensitivity experiments. The largest change in rainfall contribution from the rainfall with local atmospheric drying, water vapor divergence, and hydrometeor loss/convergence (TfM) caused by the exclusion of vertical wind shear is a decrease associated with the shrink of rainfall area and the decrease in decrease in hydrometeor loss/convergence. The largest change in rainfall contribution from the rainfall with local atmospheric drying, water vapor convergence, and hydrometeor loss/convergence (TFM) caused by the exclusion of ice clouds is an increase associated with the expansion of rainfall area and the enhancements in all rainfall processes. The exclusion of vertical wind shear also causes the increase in rainfall contribution from the rainfall with local atmospheric moistening, water vapor convergence, and hydrometeor loss/convergence (tFM), but the increase is weaker than the decrease in rainfall contribution from TfM. The rainfall contributions from the other rainfall types are less sensitive to these effects than those from the three rainfall types. The cloud radiative effects on rainfall contributions from all rainfall types are weaker than the effects of vertical wind shear and ice clouds.

Zhou, Yushu; Ran, Lingkun

2012-05-01

365

Vertical stratification of tropical cloud properties as determined from satellite  

Microsoft Academic Search

A new retrieval scheme is developed to infer tropical cloud properties and vertical structure, including liquid and ice water content, cloud top and base, and cloud layering. The retrieval scheme utilizes a cloud classification scheme that uses both International Satellite Cloud Climatology Project (ISCCP) cloud top temperature and a microwave index from the special sensor microwave\\/imager (SSM\\/I). Different cloud classes

Rong-Shyang Sheu; Judith A. Curry; Guosheng Liu

1997-01-01

366

Research on private cloud computing based on analysis on typical opensource platform: a case study with Eucalyptus and Wavemaker  

NASA Astrophysics Data System (ADS)

Cloud computing is one of the most popular topics in the IT industry and is recently being adopted by many companies. It has four development models, as: public cloud, community cloud, hybrid cloud and private cloud. Except others, private cloud can be implemented in a private network, and delivers some benefits of cloud computing without pitfalls. This paper makes a comparison of typical open source platforms through which we can implement a private cloud. After this comparison, we choose Eucalyptus and Wavemaker to do a case study on the private cloud. We also do some performance estimation of cloud platform services and development of prototype software as cloud services.

Yu, Xiaoyuan; Yuan, Jian; Chen, Shi

2013-03-01

367

Noctilucent clouds: modern ground-based photographic observations by a digital camera network.  

PubMed

Noctilucent, or "night-shining," clouds (NLCs) are a spectacular optical nighttime phenomenon that is very often neglected in the context of atmospheric optics. This paper gives a brief overview of current understanding of NLCs by providing a simple physical picture of their formation, relevant observational characteristics, and scientific challenges of NLC research. Modern ground-based photographic NLC observations, carried out in the framework of automated digital camera networks around the globe, are outlined. In particular, the obtained results refer to studies of single quasi-stationary waves in the NLC field. These waves exhibit specific propagation properties--high localization, robustness, and long lifetime--that are the essential requisites of solitary waves. PMID:22016249

Dubietis, Audrius; Dalin, Peter; Bal?i?nas, Ri?ardas; ?ernis, Kazimieras; Pertsev, Nikolay; Sukhodoev, Vladimir; Perminov, Vladimir; Zalcik, Mark; Zadorozhny, Alexander; Connors, Martin; Schofield, Ian; McEwan, Tom; McEachran, Iain; Frandsen, Soeren; Hansen, Ole; Andersen, Holger; Grønne, Jesper; Melnikov, Dmitry; Manevich, Alexander; Romejko, Vitaly

2011-10-01

368

A VMM-based intrusion prevention system in cloud computing environment  

Microsoft Academic Search

With the development of information technology, cloud computing becomes a new direction of grid computing. Cloud computing\\u000a is user-centric, and provides end users with leasing service. Guaranteeing the security of user data needs careful consideration\\u000a before cloud computing is widely applied in business. Virtualization provides a new approach to solve the traditional security\\u000a problems and can be taken as the

Hai Jin; Guofu Xiang; Deqing Zou; Song Wu; Feng Zhao; Min Li; Weide Zheng

369

Effective radius of cloud droplets by ground-based remote sensing: Relationship to aerosol  

Microsoft Academic Search

Abstract Enhancement,of cloud ,droplet number ,concentration by anthropogenic, aerosols ,has previously been demonstrated by in-situ measurements, but there remains large uncertainty in the resultant enhancement,of cloud optical depth and reflectivity. Detection of this effect ismade,difficult by the ,large inherent variability in cloud ,liquid water path (LWP); the dominant,influence of LWP on optical ,depth and albedo masks ,any aerosol influences. Here

Byung-Gon Kim; Stephen E. Schwartz; Mark A. Miller; Qilong Min

2003-01-01

370

Cloud detection and classification for earth radiation budget experiments  

NASA Astrophysics Data System (ADS)

In order to get a better understanding of the influence of clouds on the Earth's energy budget, one needs a cloud classification taking into account cloud height, thickness, and cloud cover. The radiometer ScaRaB (scanner for radiation balance), launched in 1993, has in addition to the two broad-band channels (0.2 - 4 micrometers and 0.2 - 50 micrometers ) necessary for earth radiation budget (ERB) measurements, two narrow-band channels (0.5 - 0.7 micrometers and 10.5 - 12.5 micrometers ) in order to improve cloud detection. Most automatic cloud classifications have been developed with measurements of very good spatial resolution (200 m to 5 km). Earth radiation budget experiments, on the other hand, work at a spatial resolution of about 40 km (at nadir), and therefore we investigated a cloud classification algorithm adapted on this scale. The algorithm is based on the dynamic clustering method and uses co-located AVHRR-ERBE data, simulating the ScaRaB measurements. This cloud field classification is compared on one hand to results obtained by a well tested threshold algorithm using AVHRR (advanced very high resolution radiometer) measurements at reduced spatial resolution of 4 km and on the other hand to cloud parameters extracted from HIRS (high resolution infrared sounder)/MSU (microwave sounding unit) data. We find that classification of cloud fields is still possible at a resolution of 40 km, and by combining AVHRR, ERBE, and HIRS/MSU measurements one can undertake interesting studies on the influence of different cloud fields on the Earth radiation budget.

Stubenrauch, Claudia; Seze, Genevieve M.; Scott, N. A.; Chedin, Alain; Desbois, Michel; Kandel, Robert S.

1993-09-01

371

On the sensitivity of cloud effective radius retrieval based on spectral method to bi-modal droplet size distribution: A semi-analytical model  

NASA Astrophysics Data System (ADS)

The bi-spectral solar reflective method is widely used to infer cloud optical thickness (?) and effective radius (re) from satellite cloud reflectance observations. An important assumption often made in this method is that cloud droplet size distribution (DSD) follows the monomodal Gamma or Lognormal distributions, with a fixed variance. However, it is known that the warm rain processes, e.g., collision-coalescence, can broaden cloud DSD and even lead to bi-modal size distribution. In this study, a semi-analytical model is developed to better understand the retrieved re based on the monomodal DSD assumption when the true DSD is bi-modal. The results based on this model agree well with the results from rigorous radiative transfer simulations. The model reveals that the re retrieval based on the monomodal DSD assumption tends to underestimate the re of the true bi-modal DSD. This bias is due to the nonlinear relationship between cloud droplet single-scattering albedo and cloud droplet size. The degree of this underestimation is found to increase with re and the width of the DSD. The model also indicates that the underestimation more strongly affects the 3.7 µm band than in the 2.1 µm band retrievals; leading to smaller 3.7 µm band re retrieval than that based on 2.1 µm. It is also demonstrated through numerical tests that cloud optical thickness retrieval shows little sensitivity to the cloud microphysics assumption and is relatively accurate. This is probably because the asymmetry factor of cloud droplet varies within a relatively small range, and therefore limits the impact of cloud microphysics on ? retrieval. This study has several implications, in particular for understanding the potential impact of drizzle on cloud re retrieval. Future work is needed to evaluate the model in more realistic cloud field.

Zhang, Zhibo

2013-11-01

372

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

Microsoft Academic Search

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%)

Porch

1998-01-01

373

A height resolved global view of dust aerosols from the first year CALIPSO lidar measurements  

Microsoft Academic Search

Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resolved global distribution of dust aerosols is presented for the first time. Results indicate that spring is the most active dust season, during which ~20% and ~12% of areas between 0 and 60°N are influenced by dust at least 10% and 50% of the time, respectively. In

Dong Liu; Zhien Wang; Zhaoyan Liu; Dave Winker; Charles Trepte

2008-01-01

374

Satellite-based assessment of top of atmosphere anthropogenic aerosol radiative forcing over cloud-free oceans  

NASA Astrophysics Data System (ADS)

Most assessments of the direct climate forcing (DCF) of anthropogenic aerosols are from numerical simulations. However, recent advances in remote sensing techniques allow the separation of fine mode aerosols (anthropogenic aerosol is mostly fine aerosol) from coarse mode aerosols (largely marine and dust, which are mostly natural) from satellite data such as the Moderate Resolution Imaging SpectroRadiometer (MODIS). Here, by combining MODIS narrowband measurements with broadband radiative flux data sets from the Clouds and the Earth's Radiant Energy System (CERES), we provide a measurement-based assessment of the global direct climate forcing (DCF) of anthropogenic aerosols at the top of atmosphere (TOA) only for cloud free oceans. The mean TOA DCF of anthropogenic aerosols over cloud-free oceans [60N-60S] is -1.4 +/- 0.9 Wm-2, which is in excellent agreement (mean value of -1.4 Wm-2) with a recent observational study by Kaufman et al. [2005].

Christopher, Sundar A.; Zhang, Jianglong; Kaufman, Yoram J.; Remer, Lorraine A.

2006-08-01

375

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

NASA Astrophysics Data System (ADS)

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 developed and improved continuously. MLH was determined during a one-week-campaign at the airport Mexico City. Air pollutants like NO, NOx, CO and O3 as well as meteorological parameters like wind, temperature and irradiance are measured at the airport in addition to the air quality monitoring network RAMA in Mexico City. The influence of MLH together with wind, temperature and cloudiness upon air pollution is investigated. These continuous MLH and meteorological data are correlated with simultaneous measured air pollutants. The influence of mixing layer height upon air quality is shown.

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

2009-09-01

376

Laser remote sensing of tropospheric aerosols and clouds  

NASA Astrophysics Data System (ADS)

Aerosols and clouds have significant impact on global climate. In this work experimental results from regular lidar investigations of tropospheric aerosols and clouds are presented. Examples of calculated atmospheric backscatter coefficient profiles extracted from four years lidar dataset collected in the city of Sofia (Bulgaria) are offered and analyzed. They illustrate remote detection of aerosol fields and clouds at different altitudes including Saharan dust intrusion over the city and highly situated cirrus clouds. The mass temporal evolution and the spatial distribution of registered atmospheric layers are visualized by 2D-colormaps in height-time coordinates. The ground-based measurements are performed with a newly developed lidar in the Laser Radar Lab, Institute of Electronics, Bulgarian Academy of Sciences. The good parameters of all the laser, telescope, photo-receiving modules and software make it possible the developed lidar to be utilized for carrying out fast and accurate remote atmospheric measurements with high spatial and temporal resolution.

Deleva, Atanaska D.; Avramov, Lachezar A.; Stoyanov, Dimitar V.

2010-10-01

377

Development and comparison of HP41C software to predict solar irradiation of tilted surfaces, based upon cloud cover factors  

Microsoft Academic Search

Summarized is a comparison between predicted and measured solar radiation and cloud cover data from NOAA weather stations and Solar Energy Meterological Research and Training Sites at various locations throughout the US, based upon a semiempirical method which was used recently to generate synthetic insolation data for correlation with measured solar performance under the SUEDE program. This method is unique,

A. D. Nawrocki; S. P. Anderson

1982-01-01

378

Remote observations of eruptive clouds and surface thermal activity during the 2009 eruption of Redoubt volcano  

NASA Astrophysics Data System (ADS)

Volcanoes often erupt explosively and generate a variety of hazards including volcanic ash clouds and gaseous plumes. These clouds and plumes are a significant hazard to the aviation industry and the ground features can be a major hazard to local communities. Here, we provide a chronology of the 2009 Redoubt Volcano eruption using frequent, low spatial resolution thermal infrared (TIR), mid-infrared (MIR) and ultraviolet (UV) satellite remote sensing data. The first explosion of the 2009 eruption of Redoubt Volcano occurred on March 15, 2009 (UTC) and was followed by a series of magmatic explosive events starting on March 23 (UTC). From March 23–April 4 2009, satellites imaged at least 19 separate explosive events that sent ash clouds up to 18 km above sea level (ASL) that dispersed ash across the Cook Inlet region. In this manuscript, we provide an overview of the ash clouds and plumes from the 19 explosive events, detailing their cloud-top heights and discussing the variations in infrared absorption signals. We show that the timing of the TIR data relative to the event end time was critical for inferring the TIR derived height and true cloud top height. The ash clouds were high in water content, likely in the form of ice, which masked the negative TIR brightness temperature difference (BTD) signal typically used for volcanic ash detection. The analysis shown here illustrates the utility of remote sensing data during volcanic crises to measure critical real-time parameters, such as cloud-top heights, changes in ground-based thermal activity, and plume/cloud location.

Webley, P. W.; Lopez, T. M.; Ekstrand, A. L.; Dean, K. G.; Rinkleff, P.; Dehn, J.; Cahill, C. F.; Wessels, R. L.; Bailey, J. E.; Izbekov, P.; Worden, A.

2013-06-01

379

A spectral method for retrieving cloud optical thickness and effective radius from surface-based transmittance measurements  

NASA Astrophysics Data System (ADS)

We introduce a new spectral method for the retrieval of optical thickness and effective radius from cloud transmittance that relies on the spectral slope of the normalized transmittance between 1565 nm and 1634 nm, and on cloud transmittance at a visible wavelength. The standard dual-wavelength technique, which is traditionally used in reflectance-based retrievals, is ill-suited for transmittance because it lacks sensitivity to effective radius, especially for optically thin clouds. Using the spectral slope rather than the transmittance itself enhances the sensitivity of transmittance observations with respect to the effective radius. This is demonstrated by applying it to the moderate spectral resolution observations from the Solar Spectral Flux Radiometer (SSFR) and Shortwave Spectroradiometer (SWS), and by examining the retrieval uncertainties of the standard and the spectral method for data from the DOE ARM Southern Great Plains (SGP) site and a NOAA ship cruise (ICEALOT). The liquid water path (LWP) is derived from the retrieved optical thickness and effective radius, based on two different assumptions about the cloud vertical profile, and compared to the simultaneous observations from a microwave radiometer. Optical thickness and effective radius is also compared to MODIS retrievals. In general, the effective radius uncertainties were much larger for the standard retrieval than for the spectral retrieval, particularly for thin clouds. When defining 2 ?m as upper limit for the tolerable uncertainty of the effective radius, the standard method returned only very few valid retrievals for clouds with an optical thickness below 25. For the analyzed ICEALOT data (mean optical thickness 23), the spectral method provided valid retrievals for 84 % of the data (24 % for the standard method). For the SGP data (mean optical thickness 44), both methods provided a high return of 90 % for the spectral method and 78 % for the standard method.

McBride, P. J.; Schmidt, K. S.; Pilewskie, P.; Kittelman, A. S.; Wolfe, D. E.

2011-07-01

380

A multisensor diagnostic satellite cloud property retrieval scheme  

Microsoft Academic Search

Active sensor data, in the form of lidar and radar cloud vertical boundaries, are used as a priori information to passive sensor satellite retrievals of cloud optical depth and effective particle radius. Correct placement of cloud in the vertical eliminates the need to approximate cloud height from multispectral passive techniques and is shown to improve uncertainties in nighttime retrievals of

S. D. Miller; G. L. Stephens; C. K. Drummond; A. K. Heidinger; P. T. Partain

2000-01-01

381

Cirrus cloud mimic surfaces in the laboratory: organic acids, bases and NOx heterogeneous reactions  

NASA Astrophysics Data System (ADS)

CIRRUS CLOUD MIMIC SURFACES IN THE LABORATORY:ORGANIC ACIDS, BASES AND NOX HETEROGENEOUS REACTIONS. B. ORiordan, J. Sodeau Department of Chemistry and Environment Research Institute, University College Cork, Ireland j.sodeau@ucc.ie /Fax: +353-21-4902680 There are a variety of biogenic and anthropogenic sources for the simple carboxylic acids to be found in the troposphere giving rise to levels as high as 45 ppb in certain urban areas. In this regard it is of note that ants of genus Formica produce some 10Tg of formic acid each year; some ten times that produced by industry. The expected sinks are those generally associated with tropospheric chemistry: the major routes studied, to date, being wet and dry deposition. No studies have been carried out hitherto on the role of water-ice surfaces in the atmospheric chemistry of carboxylic acids and the purpose of this paper is to indicate their potential function in the heterogeneous release of atmospheric species such as HONO. The deposition of formic acid on a water-ice surface was studied using FT-RAIR spectroscopy over a range of temperatures between 100 and 165K. In all cases ionization to the formate (and oxonium) ions was observed. The results were confirmed by TPD (Temperature Programmed Desorption) measurements, which indicated that two distinct surface species adsorb to the ice. Potential reactions between the formic acid/formate ion surface and nitrogen dioxide were subsequently investigated by FT-RAIRS. Co-deposition experiments showed that N2O3 and the NO+ ion (associated with water) were formed as products. A mechanism is proposed to explain these results, which involves direct reaction between the organic acid and nitrogen dioxide. Similar experiments involving acetic acid also indicate ionization on a water-ice surface. The results are put into the context of atmospheric chemistry potentially occuring on cirrus cloud surfaces.

Sodeau, J.; Oriordan, B.

2003-04-01

382

Identification of raining clouds using a method based on optical and microphysical cloud properties from Meteosat second generation daytime and nighttime data  

NASA Astrophysics Data System (ADS)

A new scheme for the delineation of raining and non-raining cloud areas applicable to mid-latitudes from daytime and nighttime multispectral satellite data is developed. The technique is based on optical and microphysical cloud properties using an artificial neural network. The tests have been conducted during the rainy season of 2006/2007. The proposed algorithm uses the spectral parameters of SEVIRI (Spinning Enhanced Visible and Infrared): brightness temperature T IR10.8 and brightness temperature differences ? T IR10.8-IR12.1, ? T IR8.7-IR10.8, ? T IR3.9-IR10.8 and ? T IR3.9-WV7.3 during the nighttime and reflectances R VIS0.6, R NIR1.6, brightness temperature T IR10.8, brightness temperature difference ? T IR8.7-IR10.8 and ? T IR10.8-IR12.0 during the daytime. The algorithm is calibrated by instantaneous meteorological radar using multilayer perceptron. Radar provided the ``ground precipitation truth'' for training and validation. The application shows interesting and encouraging results.

Lazri, Mourad; Ameur, Soltane; Brucker, Jean Michel; Testud, Jacques; Hamadache, Bachir; Hameg, Slimane; Ouallouche, Fethi; Mohia, Yacine

2013-03-01

383

Cloud point phenomena for POE-type nonionic surfactants in imidazolium-based ionic liquids: effect of anion species of ionic liquids on the cloud point.  

PubMed

Cloud point temperatures, T(c), of polyoxyethylene (POE)-type nonionic surfactants in a room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6)), were measured and compared with those previously obtained for the surfactant solution in bmimBF(4). The T(c)s for bmimPF(6) solution are higher than those for bmimBF(4) solution by approx. 40 degrees C. This means that the surfactant molecules are more solvophilic in bmimPF(6) compared to bmimBF(4). The analysis of (1)H NMR chemical shift measurements proved that the higher solvophilicity of the surfactants in bmimPF(6) is attributed to weaker hydrogen-bond interaction between bmim cation and PF6- anion than that between bmim cation and BF4- anion. This interpretation is consistent with the interaction energy parameters derived from the thermodynamic analysis of cloud point curve applying the Flory-Huggins model for phase separation in polymer solution. The present work demonstrates that the property of imidazolium-based ionic liquids as a solvent is determined by a balance of interactions among imidazolium cation, counter anion, and solute molecule. PMID:19486995

Inoue, Tohru; Misono, Takeshi

2009-05-12

384

A Security Framework of Group Location-Based Mobile Applications in Cloud Computing  

Microsoft Academic Search

In this paper, we present a secure frame- work when the location information of mobile terminals is utilized in a cloud computing environment. Because cloud computing provides powerful storage capabil- ity and scalability, many application providers start migrating the data stored in their original databases to outsourced databases (ODB), such as AMAZON SIMPLEDB. However, because of the multiple tenants and

Yu-Jia Chen; Li-Chun Wang

2011-01-01

385

Multi-Dimensional Optimization for Cloud Based Multi-Tier Applications  

ERIC Educational Resources Information Center

|Emerging trends toward cloud computing and virtualization have been opening new avenues to meet enormous demands of space, resource utilization, and energy efficiency in modern data centers. By being allowed to host many multi-tier applications in consolidated environments, cloud infrastructure providers enable resources to be shared among these…

Jung, Gueyoung

2010-01-01

386

Study of the relations between cloud properties and atmospheric conditions using ground-based digital images  

Microsoft Academic Search

The aerosol constituents of the earth atmosphere are of great significance for the radiation budget and global climate of the planet. They are the precursors of clouds that in turn play an essential role in these processes and in the hydrological cycle of the Earth. Understanding the complex aerosol-cloud interactions requires a detailed knowledge of the dynamical processes moving the

Kalinka Bakalova

2008-01-01

387

Modeling studying on ice formation by bacteria in warm-based convective cloud  

Microsoft Academic Search

Bacteria have been recognized as cloud condensation nuclei (CCN), and certain bacteria, commonly found in plants, have exhibited capacity to act as ice nuclei (IN) at temperatures as warm as -2 °C. These ice nucleating bacteria are readily disseminated into the atmosphere and have been observed in clouds at altitudes of several kilometres. It is noteworthy that over 20 years

J. Sun

2005-01-01

388

Providing Network Performance Isolation in VDE-Based Cloud Computing Systems  

Microsoft Academic Search

In a cloud computing system, virtual machines owned by different clients are co-hosted on a single physical machine. It is vital to isolate network performance between the clients for ensuring fair usage of the constrained and shared network resources of the physical machine. Unfortunately, the existing network performance isolation techniques are not effective for cloud computing systems because they are

Vijeta Rathore; Jonghun Yoo; Jaesoo Lee; Seongsoo Hong

2011-01-01

389

Gossip-based resource allocation for green computing in large clouds  

Microsoft Academic Search

We address the problem of resource allocation in a large-scale cloud environment, which we formalize as that of dynamically optimizing a cloud configuration for green computing objectives under CPU and memory constraints. We propose a generic gossip protocol for resource allocation, which can be instantiated for specific objectives. We develop an instantiation of this generic protocol which aims at minimizing

Rerngvit Yanggratoke; Fetahi Wuhib; Rolf Stadler

2011-01-01

390

Towards a Service Lifecycle Based Methodology for Risk Assessment in Cloud Computing  

Microsoft Academic Search

The principles of risk management have been introduced in grid computing to help document and anticipate certain risks and manage them to ensure job executions are successful. Clouds are more complex environments with further concerns like risk, trust, eco-efficiency, green, security or cost. In this paper we present ongoing research work to analyze and address the risk factor in clouds

Mariam Kiran; Ming Jiang; Django J. Armstrong; Karim Djemame

2011-01-01

391

Cloud Coverage Based on All-Sky Imaging and Its Impact on Surface Solar Irradiance  

SciTech Connect

In Lauder, Central Otago, two all-sky imaging systems have been operated for more than one year measuring the total, opaque, and thin cloud fraction as well as an indicator of whether the sun is obscured by clouds. The data provide a basis for investigating the impact of clouds on the surface radiation field. We aligned the all-sky cloud parameters with measurements of global, direct and diffuse surface solar irradiance over the spectral interval from 0.3 to 3 mm. Here we describe results of ongoing analysis of this data set. As a reference for the magnitude of the cloud influence, clear sky irradiance values are estimated as a simple function of solar zenith angle and Earth-Sun distance. The function is derived from a least-square fit to measurements taken when available cloud images show clear sky situations. Averaged over a longer time period, such as a month, cloud fraction and surface irradiance are clearly negatively correlated. Monthly means in the ratio of the measured surface irradiance to the clear-sky value had a correlation coefficient of about -0.9 with means of cloud fraction for the months July 2000 to June 2001. In the present work we analyze reductions in the surface irradiance and also situations where clouds cause radiation values to exceed the expected clear sky amount. Over one year of observations, 1-minute-average radiation measurements exceeding the expected clear sky value by more than 10% were observed with a frequency of 5%. In contr