The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Yi Zhang - One of the best experts on this subject based on the ideXlab platform.
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Simulations of Stratus Clouds over Eastern China in CAM5: Sources of Errors
Journal of Climate, 2014Co-Authors: Yi Zhang, Haoming ChenAbstract:AbstractA previous study by Zhang et al. suggested two biases of the high-resolution configured Community Atmosphere Model, version 5 (CAM5), in simulating Stratus clouds over eastern China, including an underestimation of Stratus occurrence frequency and a spurious low Stratus amount when present (AWP) value center over the Sichuan basin. In this study, the causes for these two problems are further explored.The underestimate of Stratus occurrence frequency in the model is attributed to the bias in large-scale ambient environmental fields. This is confirmed by investigating the differences between two climate counterparts. Results suggest that when the environmental fields in the climate ensemble become more realistic, the simulations of Stratus cloud radiative forcing and cloud fraction are enhanced, mainly caused by a corresponding increase in the Stratus occurrence frequency. The specific sources of the cloud changes between these two ambient climates are then investigated.The presence of a low Stratus...
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Simulations of Stratus Clouds over Eastern China in CAM5: Sensitivity to Horizontal Resolution
Journal of Climate, 2014Co-Authors: Yi Zhang, Haoming ChenAbstract:This paper evaluates the simulations of Stratus clouds over eastern China (EC) in the Community Atmosphere Model, version 5 (CAM5), with an emphasis on the impact of changing horizontal resolutions on the performance.CAM5inallexperimentsgenerallysatisfactorilysimulatesthecloudradiativefeaturesoverEC, including the spatial distributions of the continental shortwave cloud radiative forcing (SWCF) and Stratus regimes, the responses of SWCF to the dynamic and thermodynamic ambient environment, and several relations in the environmental fields that are favorable to the Stratus formation. Meanwhile, all experiments suffer from similar biases. Models tend to underestimate the Stratus amount because of a corresponding underestimate of Stratus occurrence frequency, while the Stratus amount when present (AWP) is generally higher than that in the observation. Models also simulate similar errors in the environmental fields. The differencesbetweenlow-andhigh-resolutionexperimentsaredistinct. Anincreaseofresolutionenhancesthe SWCF in southern China, but the skill deteriorates in the Sichuan basin. Correspondingly, the Stratus amount increases in southern China from low- to high-resolution experiments, mainly because of more Stratus occurrences, which are found to be related to the better represented environmental fields in the high-resolution experiments, especially the dynamic component. Several relations in the ambient environment are also slightly improved in the high-resolution experiments. Meanwhile, the reason for the decrease of Stratus AWP within the Sichuan basin, which is mainly responsible for the decreased Stratus amounts and weaker SWCF from low- to high-resolution experiments, is also discussed.
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Vertical Structures and Physical Properties of the Cold-Season Stratus Clouds Downstream of the Tibetan Plateau: Differences between Daytime and Nighttime
Journal of Climate, 2014Co-Authors: Yi Zhang, Haoming ChenAbstract:AbstractThis study compares the daytime–nighttime (DN) differences in the occurrence frequencies and macrophysical, microphysical, and radiative vertical structures of the single-layer Stratus clouds downstream of the Tibetan Plateau (TP) during the boreal cold season (November–April) using four CloudSat products. The Stratus cloudy profiles are selected and the midtopped Stratus profiles are further classified into nimboStratus (NI) and altoStratus (AS) according to the cloud-top height and column-integrated optical depth. It is found that the entire Stratus and NI profiles tend to occur more frequently in the daytime, while the AS cloud occurs more frequently in the nighttime. Consistent with the DN differences in the occurrence frequencies, the AS tends to be much thicker with larger cloud fraction in the nighttime, while the NI becomes slightly thicker with larger cloud fraction in the daytime. An analysis of the ambient dynamic and thermodynamic fields associated with Stratus formation suggests that ...
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Dynamic and Thermodynamic Relations of Distinctive Stratus Clouds on the Lee Side of the Tibetan Plateau in the Cold Season
Journal of Climate, 2013Co-Authors: Yi Zhang, Weihua Yuan, Minghua ZhangAbstract:AbstractGiven the large discrepancies that exist in climate models for shortwave cloud forcing over eastern China (EC), the dynamic (vertical motion and horizontal circulation) and thermodynamic (stability) relations of Stratus clouds and the associated cloud radiative forcing in the cold season are examined. Unlike the Stratus clouds over the southeastern Pacific Ocean (as a representative of marine boundary Stratus), where thermodynamic forcing plays a primary role, the Stratus clouds over EC are affected by both dynamic and thermodynamic factors. The Tibetan Plateau (TP)-forced low-level large-scale lifting and high stability over EC favor the accumulation of abundant saturated moist air, which contributes to the formation of Stratus clouds. The TP slows down the westerly overflow through a frictional effect, resulting in midlevel divergence, and forces the low-level surrounding flows, resulting in convergence. Both midlevel divergence and low-level convergence sustain a rising motion and vertical wate...
Susanne Binder - One of the best experts on this subject based on the ideXlab platform.
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Reproducibility of segmentation error correction in age-related macular degeneration: Stratus versus Cirrus OCT
The British journal of ophthalmology, 2011Co-Authors: Ilse Krebs, Stefan Hagen, Eva Smretschnig, Irene Womastek, Werner Brannath, Susanne BinderAbstract:Introduction The accuracy of retinal thickness measurement in age-related macular degeneration by optical coherence tomography (OCT) is affected by threshold algorithm line errors. The reproducibility of error correction in Stratus and Cirrus OCT should be examined. Methods OCT examinations of a consecutive series of 104 patients with neovascular age-related macular degeneration included in another study were reviewed. 72 eyes exhibited failures in Stratus OCT and 32 eyes in Cirrus OCT and were included in this new study. Algorithm line failures of Stratus OCT (retinal thickness program) and Cirrus OCT (Macular Cube 512×128 program) were corrected independently twice by two ophthalmologists and two residents, respectively, using the Stratus and Cirrus OCT built-in software. Reproducibility was assessed by the interclass correlation coefficient (ICC). Results The corrected values of central retinal thickness were significantly lower than the automated measured values in Stratus OCT for all examiners (p Conclusion The reproducibility of threshold algorithm line failure correction was good overall in Stratus and Cirrus OCT and can therefore be recommended to improve retinal thickness measurement, particularly when experienced examiners perform the corrections.
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Conversion of Stratus optical coherence tomography (OCT) retinal thickness to Cirrus OCT values in age-related macular degeneration
The British journal of ophthalmology, 2011Co-Authors: Ilse Krebs, Stefan Hagen, Eva Smretschnig, Irene Womastek, Werner Brannath, Susanne BinderAbstract:Aim Spectral domain optical coherence tomography (SD OCT) is of increasing importance and is gradually replacing time domain OCT (TD OCT). Our aim was to determine a formula to convert Stratus OCT (TD OCT) to Cirrus OCT (SD OCT) retinal thickness. Methods Central retinal thickness (CRT) and retinal volume (RV) were obtained by the macular thickness program of Stratus OCT and the cube 512×128 program of Cirrus OCT in patients with exudative age-related macular degeneration (AMD). Algorithm line failures were corrected. A linear model with Stratus OCT CRT as fixed factor and Cirrus OCT CRT as dependent variable was applied to calculate the conversion formula. Results OCT examinations of 104 eyes of 104 patients were reviewed and corrected when necessary. Stratus and Cirrus OCT CRT were significantly correlated (p Conclusion Stratus OCT and Cirrus OCT use a different posterior reference line within the hyper-reflective band of the outer retina. Therefore a conversion formula is necessary to compare Stratus and Cirrus OCT CRT values, and this has been determined in our study.
Haoming Chen - One of the best experts on this subject based on the ideXlab platform.
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Simulations of Stratus Clouds over Eastern China in CAM5: Sources of Errors
Journal of Climate, 2014Co-Authors: Yi Zhang, Haoming ChenAbstract:AbstractA previous study by Zhang et al. suggested two biases of the high-resolution configured Community Atmosphere Model, version 5 (CAM5), in simulating Stratus clouds over eastern China, including an underestimation of Stratus occurrence frequency and a spurious low Stratus amount when present (AWP) value center over the Sichuan basin. In this study, the causes for these two problems are further explored.The underestimate of Stratus occurrence frequency in the model is attributed to the bias in large-scale ambient environmental fields. This is confirmed by investigating the differences between two climate counterparts. Results suggest that when the environmental fields in the climate ensemble become more realistic, the simulations of Stratus cloud radiative forcing and cloud fraction are enhanced, mainly caused by a corresponding increase in the Stratus occurrence frequency. The specific sources of the cloud changes between these two ambient climates are then investigated.The presence of a low Stratus...
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Simulations of Stratus Clouds over Eastern China in CAM5: Sensitivity to Horizontal Resolution
Journal of Climate, 2014Co-Authors: Yi Zhang, Haoming ChenAbstract:This paper evaluates the simulations of Stratus clouds over eastern China (EC) in the Community Atmosphere Model, version 5 (CAM5), with an emphasis on the impact of changing horizontal resolutions on the performance.CAM5inallexperimentsgenerallysatisfactorilysimulatesthecloudradiativefeaturesoverEC, including the spatial distributions of the continental shortwave cloud radiative forcing (SWCF) and Stratus regimes, the responses of SWCF to the dynamic and thermodynamic ambient environment, and several relations in the environmental fields that are favorable to the Stratus formation. Meanwhile, all experiments suffer from similar biases. Models tend to underestimate the Stratus amount because of a corresponding underestimate of Stratus occurrence frequency, while the Stratus amount when present (AWP) is generally higher than that in the observation. Models also simulate similar errors in the environmental fields. The differencesbetweenlow-andhigh-resolutionexperimentsaredistinct. Anincreaseofresolutionenhancesthe SWCF in southern China, but the skill deteriorates in the Sichuan basin. Correspondingly, the Stratus amount increases in southern China from low- to high-resolution experiments, mainly because of more Stratus occurrences, which are found to be related to the better represented environmental fields in the high-resolution experiments, especially the dynamic component. Several relations in the ambient environment are also slightly improved in the high-resolution experiments. Meanwhile, the reason for the decrease of Stratus AWP within the Sichuan basin, which is mainly responsible for the decreased Stratus amounts and weaker SWCF from low- to high-resolution experiments, is also discussed.
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Vertical Structures and Physical Properties of the Cold-Season Stratus Clouds Downstream of the Tibetan Plateau: Differences between Daytime and Nighttime
Journal of Climate, 2014Co-Authors: Yi Zhang, Haoming ChenAbstract:AbstractThis study compares the daytime–nighttime (DN) differences in the occurrence frequencies and macrophysical, microphysical, and radiative vertical structures of the single-layer Stratus clouds downstream of the Tibetan Plateau (TP) during the boreal cold season (November–April) using four CloudSat products. The Stratus cloudy profiles are selected and the midtopped Stratus profiles are further classified into nimboStratus (NI) and altoStratus (AS) according to the cloud-top height and column-integrated optical depth. It is found that the entire Stratus and NI profiles tend to occur more frequently in the daytime, while the AS cloud occurs more frequently in the nighttime. Consistent with the DN differences in the occurrence frequencies, the AS tends to be much thicker with larger cloud fraction in the nighttime, while the NI becomes slightly thicker with larger cloud fraction in the daytime. An analysis of the ambient dynamic and thermodynamic fields associated with Stratus formation suggests that ...
Gregory R. Ganger - One of the best experts on this subject based on the ideXlab platform.
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SoCC - Stratus: cost-aware container scheduling in the public cloud
Proceedings of the ACM Symposium on Cloud Computing, 2018Co-Authors: Andrew Chung, Jun Woo Park, Gregory R. GangerAbstract:Stratus is a new cluster scheduler specialized for orchestrating batch job execution on virtual clusters, dynamically allocated collections of virtual machine instances on public IaaS platforms. Unlike schedulers for conventional clusters, Stratus focuses primarily on dollar cost considerations, since public clouds provide effectively unlimited, highly heterogeneous resources allocated on demand. But, since resources are charged-for while allocated, Stratus aggressively packs tasks onto machines, guided by job runtime estimates, trying to make allocated resources be either mostly full (highly utilized) or empty (so they can be released to save money). Simulation experiments based on cluster workload traces from Google and TwoSigma show that Stratus reduces cost by 17-44% compared to state-of-the-art approaches to virtual cluster scheduling.
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Stratus cost aware container scheduling in the public cloud
Symposium on Cloud Computing, 2018Co-Authors: Andrew Chung, Jun Woo Park, Gregory R. GangerAbstract:Stratus is a new cluster scheduler specialized for orchestrating batch job execution on virtual clusters, dynamically allocated collections of virtual machine instances on public IaaS platforms. Unlike schedulers for conventional clusters, Stratus focuses primarily on dollar cost considerations, since public clouds provide effectively unlimited, highly heterogeneous resources allocated on demand. But, since resources are charged-for while allocated, Stratus aggressively packs tasks onto machines, guided by job runtime estimates, trying to make allocated resources be either mostly full (highly utilized) or empty (so they can be released to save money). Simulation experiments based on cluster workload traces from Google and TwoSigma show that Stratus reduces cost by 17-44% compared to state-of-the-art approaches to virtual cluster scheduling.
Ilse Krebs - One of the best experts on this subject based on the ideXlab platform.
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Reproducibility of segmentation error correction in age-related macular degeneration: Stratus versus Cirrus OCT
The British journal of ophthalmology, 2011Co-Authors: Ilse Krebs, Stefan Hagen, Eva Smretschnig, Irene Womastek, Werner Brannath, Susanne BinderAbstract:Introduction The accuracy of retinal thickness measurement in age-related macular degeneration by optical coherence tomography (OCT) is affected by threshold algorithm line errors. The reproducibility of error correction in Stratus and Cirrus OCT should be examined. Methods OCT examinations of a consecutive series of 104 patients with neovascular age-related macular degeneration included in another study were reviewed. 72 eyes exhibited failures in Stratus OCT and 32 eyes in Cirrus OCT and were included in this new study. Algorithm line failures of Stratus OCT (retinal thickness program) and Cirrus OCT (Macular Cube 512×128 program) were corrected independently twice by two ophthalmologists and two residents, respectively, using the Stratus and Cirrus OCT built-in software. Reproducibility was assessed by the interclass correlation coefficient (ICC). Results The corrected values of central retinal thickness were significantly lower than the automated measured values in Stratus OCT for all examiners (p Conclusion The reproducibility of threshold algorithm line failure correction was good overall in Stratus and Cirrus OCT and can therefore be recommended to improve retinal thickness measurement, particularly when experienced examiners perform the corrections.
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Conversion of Stratus optical coherence tomography (OCT) retinal thickness to Cirrus OCT values in age-related macular degeneration
The British journal of ophthalmology, 2011Co-Authors: Ilse Krebs, Stefan Hagen, Eva Smretschnig, Irene Womastek, Werner Brannath, Susanne BinderAbstract:Aim Spectral domain optical coherence tomography (SD OCT) is of increasing importance and is gradually replacing time domain OCT (TD OCT). Our aim was to determine a formula to convert Stratus OCT (TD OCT) to Cirrus OCT (SD OCT) retinal thickness. Methods Central retinal thickness (CRT) and retinal volume (RV) were obtained by the macular thickness program of Stratus OCT and the cube 512×128 program of Cirrus OCT in patients with exudative age-related macular degeneration (AMD). Algorithm line failures were corrected. A linear model with Stratus OCT CRT as fixed factor and Cirrus OCT CRT as dependent variable was applied to calculate the conversion formula. Results OCT examinations of 104 eyes of 104 patients were reviewed and corrected when necessary. Stratus and Cirrus OCT CRT were significantly correlated (p Conclusion Stratus OCT and Cirrus OCT use a different posterior reference line within the hyper-reflective band of the outer retina. Therefore a conversion formula is necessary to compare Stratus and Cirrus OCT CRT values, and this has been determined in our study.
