- 标题
- 摘要
- 关键词
- 实验方案
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The spectral signature of cloud spatial structure in shortwave irradiance
摘要： We found that cloud spatial structure manifests itself as spectral signature in shortwave irradiance fields – specifically in transmittance and net horizontal photon transport in the visible and near-ultraviolet wavelength range. In this paper, we demonstrate this through radiative transfer calculations with cloud imagery from a field experiment, and show that such three-dimensional effects may occur on scales up to 60 kilometers. Neglecting net horizontal photon transport leads to a transmittance bias on the order of ±12-19% even at the relatively coarse spatial resolution of 20 kilometers, and of more than ±50% for 1 kilometer. This poses a problem for radiative energy budget estimates from space because the bias for any pixel depends on its spatial context in a non-trivial way. The key for solving this problem may lie in the spectral dimension, since we found a robust correlation between the magnitude of net horizontal photon transport (H) and its spectral dependence (slope). It is scale-invariant and holds for the entire pixel population of a domain. This was at first surprising given the large degree of spatial inhomogeneity, but seems to be valid for any cloud field. We prove that the underlying physical mechanism for this phenomenon is molecular scattering in conjunction with cloud inhomogeneity. On this basis, we developed a simple parameterization through a single parameter ??, which quantifies the characteristic spectral signature of spatial heterogeneities. In a companion paper, we will show that it is accompanied by spectral radiance perturbations, which can be detected from multi-spectral imagers and may be translated into bias reductions for cloud radiative effect estimates in the future.
关键词： cloud spatial structure,molecular scattering,shortwave irradiance,spectral signature,radiative transfer,cloud radiative effect,horizontal photon transport
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Cloud Attenuation Prediction Statistics for GEO and NGSO Satellite Communication Systems Operating at Q/V Band and Above
摘要： The employment of extremely high frequency bands (like Q/V and W bands) in the next generation satellite communication system has been proposed for feeder links operation in order to satisfy the ever growing satellite users’ demands. For the feeder links’ reliable performance analysis, the total atmospheric attenuation has to be taken into account. In this paper, a methodology for the estimation of cloud attenuation induced on a satellite slant path, through time series generation of Integrated Liquid Water Content (ILWC), for GEO satellites is presented and modified to consider joint attenuation statistics of cloud attenuation for multiple slant paths and also for the cloud attenuation prediction for NGSO links (MEO and LEO cases). The models are derived from cloud attenuation time series synthesizers, based on stochastic differential equations (SDEs), that incorporate properly the spatial and temporal behavior of ILWC and the time dependence of the elevation angle for NGSO links. Numerical results for GEO, MEO and LEO satellite systems operating at Q and W band are reported. The single link cases are tested with the ITU-R. P. 840-6 model. Interesting conclusions are drawn.
关键词： Cloud attenuation,Feeder Links,diversity gain,NGSO systems,Q and W band,joint cloud attenuation statistics
更新于2025-09-04 15:30:14
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An Investigation of Optically Very Thin Ice Clouds from Ground-Based ARM Raman Lidars
摘要： Optically very thin ice clouds from the Cloud-Aerosol Lidar and Infrared Path?nder Satellite Observations (CALIPSO) and ground-based Raman lidars (RL) at the atmospheric radiation measurement (ARM) sites of the Southern Great Plains (SGP) and Tropical Western Paci?c (TWP) are analyzed. The optically very thin ice clouds, with ice cloud column optical depths below 0.01, are about 23% of the transparent ice-cloudy pro?les from the RL, compared to 4–7% from CALIPSO. The majority (66–76%) of optically very thin ice clouds from the RLs are found to be adjacent to ice clouds with ice cloud column optical depths greater than 0.01. The temporal structure of RL-observed optically very thin ice clouds indicates a clear sky–cloud continuum. Global cloudiness estimates from CALIPSO observations leveraged with high-sensitivity RL observations suggest that CALIPSO may underestimate the global cloud fraction when considering optically very thin ice clouds.
关键词： remote sensing,ice cloud detection,ice cloud optical depth,lidars
更新于2025-09-04 15:30:14
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The role of cloud contamination, aerosol layer height and aerosol model in the assessment of the OMI near-UV retrievals over the ocean
摘要： Retrievals of aerosol optical depth (AOD) at 388 nm over the ocean from the Ozone Monitoring Instrument (OMI) two-channel near-UV algorithm (OMAERUV) have been compared with independent AOD measurements. The analysis was carried out over the open ocean (OMI and MODerate-resolution Imaging Spectrometer (MODIS) AOD comparisons) and over coastal and island sites (OMI and AERONET, the AErosol RObotic NETwork). Additionally, a research version of the retrieval algorithm (using MODIS and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) information as constraints) was utilized to evaluate the sensitivity of the retrieval to different assumed aerosol properties.
关键词： MODIS,CALIOP,aerosol layer height,aerosol model,AERONET,OMI,aerosol optical depth,cloud contamination
更新于2025-09-04 15:30:14
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Improving LiDAR classification accuracy by contextual label smoothing in post-processing
摘要： We propose a contextual label-smoothing method to improve the LiDAR classification accuracy in a post-processing step. Under the framework of global graph-structured regularization, we enhance the effectiveness of label smoothing from two aspects. First, each point can collect sufficient label-relevant neighborhood information to verify its label based on an optimal graph. Second, the input label probability set is improved by probabilistic label relaxation to be more consistent with the spatial context. With this optimal graph and reliable label probability set, the final labels are computed by graph-structured regularization. We demonstrate the contextual label-smoothing approach on two separate urban airborne LiDAR datasets with complex urban scenes. Significant improvements in the classification accuracies are achieved without losing small objects (such as fa?ades and cars). The overall accuracy is increased by 7.01% on the Vienna dataset and 6.88% on the Vaihingen dataset. Moreover, most large, wrongly labeled regions are corrected by long-range interactions that are derived from the optimal graph, and misclassified regions that lack neighborhood communications in terms of correct labels are also corrected with the probabilistic label relaxation.
关键词： Neighborhood dependency,Optimal neighborhood,Point cloud,Probabilistic label relaxation
更新于2025-09-04 15:30:14
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Coupling sky images with radiative transfer models: a new method to estimate cloud optical depth
摘要： A method for retrieving cloud optical depth (τc) using a UCSD developed ground-based sky imager (USI) is presented. The radiance red–blue ratio (RRBR) method is motivated from the analysis of simulated images of various τc produced by a radiative transfer model (RTM). From these images the basic parameters affecting the radiance and red–blue ratio (RBR) of a pixel are identified as the solar zenith angle (θ0), τc, solar pixel angle/scattering angle (?s), and pixel zenith angle/view angle (?z). The effects of these parameters are described and the functions for radiance, Iλ (τc, θ0, ?s, ?z), and RBR(τc, θ0, ?s, ?z) are retrieved from the RTM results. RBR, which is commonly used for cloud detection in sky images, provides non-unique solutions for τc, where RBR increases with τc up to about τc = 1 (depending on other parameters) and then decreases. Therefore, the RRBR algorithm uses the measured I meas (?s, ?z), in addition to RBRmeas (?s, ?z), to obtain a unique solution for τc. The RRBR method is applied to images of liquid water clouds taken by a USI at the Oklahoma Atmospheric Radiation Measurement (ARM) program site over the course of 220 days and compared against measurements from a microwave radiometer (MWR) and output from the Min et al. (2003) method for overcast skies. τc values ranged from 0 to 80 with values over 80, being capped and registered as 80. A τc RMSE of 2.5 between the Min et al. (2003) method and the USI are observed. The MWR and USI have an RMSE of 2.2, which is well within the uncertainty of the MWR. The procedure developed here provides a foundation to test and develop other cloud detection algorithms.
关键词： sky imager,cloud optical depth,solar forecasting,radiative transfer model,red–blue ratio
更新于2025-09-04 15:30:14
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Preliminary assessment of two spatio-temporal forecasting technics for hourly satellite-derived irradiance in a complex meteorological context
摘要： This paper examines two spatio-temporal approaches for short-term forecasting of global horizontal irradiance using gridded satellite-derived irradiances as experimental support. The first approach is a spatio-temporal vector autoregressive (STVAR) model combined with a statistical process for optimum selection of input variables. The second is an existing operational cloud motion vector (CMV) model. An evaluation of the predictive performance of these models is presented for a case study area in the Caribbean Islands. This region is characterized by a large diversity of microclimates and land/sea contrasts, creating a challenging solar forecasting context. Using scaled persistence as a reference, we benchmark the performance of the two spatio-temporal models over an extended 220 × 220 km domain, and for three specific, climatically distinct locations within this domain. We also assess the influence of intra-day solar resource variability on model performance. Finally, we present preliminary evidence that a blend of CMV and STVAR forecasts leads to improved accuracy under all conditions.
关键词： Cloud motion vector,Spatio-temporal forecasting,Satellite-derived irradiance,Complex meteorological context
更新于2025-09-04 15:30:14
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[IEEE 2018 26th International Conference on Geoinformatics - Kunming, China (2018.6.28-2018.6.30)] 2018 26th International Conference on Geoinformatics - SPARK Processing of Computing-Intensive Classification of Remote Sensing Images: The Case on K-Means Clustering Algorithm
摘要： High performance processing of remote sensing images is an important topic in remote sensing applications. One typical type of remote sensing processing is the iterative computing algorithms such as image classification algorithms, which are often computing-intensive and time-consuming. Recent advancement of cloud computing technologies such as APACHE SPARK has shown great promise for improving the computing performance. This paper presents a MapReduce based approach for parallelizing classification algorithms of remote sensing images on the cloud computing platform. The iterative processing is transformed into iterative Map and Reduce tasks that can be executed in parallel. The K-Means clustering algorithm is experimented with the SPARK cluster deployed on the OpenStack cloud computing platform to illustrate the applicability and effectiveness of the approach.
关键词： cloud computing,classification,distributed computing,remote sensing images
更新于2025-09-04 15:30:14
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[IEEE 2018 Global Smart Industry Conference (GloSIC) - Chelyabinsk, Russia (2018.11.13-2018.11.15)] 2018 Global Smart Industry Conference (GloSIC) - Three-Dimensional Workpiece Scanning for Technological Operation Parameters Determination in Turbine Rotor Restoration
摘要： A progressive method of turbine rotor journal restoration is machining with a direct location on a bearing bottom half. In the process, the work surface form depends on the type of rotor journal previous wear. In the previous research it was assumed that the rotor journal had the form of a cylindrical surface with a polyhedral generating line. It has been established technological operation parameters determination, for example, the tool axis installation angle, significantly depends on a form of the specified generating line. However, the real surface of a rotor journal can differ from the specified noncircular cylinder. Thus, a problem of technological operation appropriate parameters determination for various rotor journal surfaces is vital. One of the known ways of obtaining exact object surface data is the formation of a point cloud by means of a 3D scanner. The scanning result is the digital double of a workpiece surface in the form of the point cloud. So, the development of the machined surface circularity deviation calculation method, based on coordinates of a point cloud and technological operation parameters, is a relevant problem. Such methodology has been developed and forecasting of the most rational parameters of technological operation to minimize the surface circularity deviation has been conducted.
关键词： digital double of surface,machining of locating surface,point cloud,3D scanning,Turbine rotor journal restoration
更新于2025-09-04 15:30:14
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[Advances in Intelligent Systems and Computing] Image Processing and Communications Challenges 10 Volume 892 (10th International Conference, IP&C’2018 Bydgoszcz, Poland, November 2018, Proceedings) || Ten Years of Image Processing and Communications
摘要： Image processing and communications have become emerging domains for researchers and societies all over the world. Both are widely implemented and become reality in everyday matters. In this article authors present an overview of the trends and reflect on aspects discussed during the Image Processing and Communications Conferences taking place in Bydgoszcz, Poland during last 10 years. The paper aims to reflect on this great event and its scientific contents.
关键词： Cloud computing,Biometrics,Applications,Image quality,Video processing,Pattern recognition,Network,Image processing,Cyber security
更新于2025-09-04 15:30:14