Time filter

Source Type

Wang J.L.,Institute of Urban Meteorology | Li S.M.,National Satellite Meteorological Center | Liu X.L.,Beijing Meteorological Information Center | Wu X.J.,National Satellite Meteorological Center
Atmospheric Research | Year: 2010

Based on the various fog remote sensing information products abstracted from the polar orbit meteorological satellite data (NOAA and FY), this paper analyzes the characteristics of the frequency and distribution that dense fogs have taken place in the Beijing district from 2001 to 2005. Among those information products, the statistical graph of the foggy days in Beijing from 2001 to 2005 by means of satellite remote-sensing reflects the frequency that dense fog has occurred in the different regions in Beijing; and the statistical graph of the foggy days of each season by satellite remote-sensing shows the characteristics of the temporal and spatial change of the fog distribution in Beijing in different seasons; the fog degree index(like pixel-level spatial measurement) by satellite remote-sensing reflects the fog frequency difference on unit area in different counties of Beijing. Meanwhile, based on the satellite remote-sensing pictures, data on the main meteorological elements that contribute to the formation of fog, geographic information, and DEM data, this paper makes an analysis in 3 areas, the traits of the fog distribution in the different regions of Beijing in different seasons; meteorological causes for temporal and spatial changes of the main fog types (advection fog, radiation fog). This paper also gave a brief introduction of the general principles of meteorological satellite remote sensing fog, fog information extraction method, as well as the process of satellite orbit selecting according to the ground visibility, data processing and product generation. © 2010 Elsevier B.V.

Xu C.,China Earthquake Administration | Shen L.,Beijing Meteorological Information Center
Environmental Earth Sciences | Year: 2016

This study compared two soft computing methods that are applied to soft computation in assessment of earthquake-triggered landslide susceptibility: the support vector machine (SVM) and artificial neural networks (ANN). As a case study, a series of landslide susceptibility maps were constructed for the affected area of the 2013 Minxian-Zhangxian, Gansu Province, China Mw 5.9 earthquake. From data available, 2330 coseismic landslides were partitioned into two subsets which were used as a training dataset and a test dataset, respectively. In addition, other 1631 points on the map were randomly selected as non-landslide samples in those areas were not influenced by the coseismic landslides. Ten conditioning factors of landslides were considered, including elevation, relative relief, slope angle, slope aspect, slope curvature, slope position, lithology, peak ground acceleration (PGA), distance from the probable seismogenic fault, and distance along the fault. Using the ANN and SVM, ten landslide susceptibility maps were produced for the study area. Cross comparisons and validations of these ten resulting maps with real coseismic landslides show that the polynomial kernel type with a high enough polynomial degree term value (e.g., 5 or 6) of the SVM technology is most appropriate for coseismic landslide susceptibility assessment, which is a challenge to the previously held notion that the SVM method with radial basis function is the most suitable. © 2016, Springer-Verlag Berlin Heidelberg.

Wang J.,Institute of Urban Meteorology | Liu X.,Beijing Meteorological Information Center | Liu J.,Support Center for Atmospheric Observing Technology | Zhao W.,Beijing Meteorological Information Center | And 4 more authors.
2011 International Conference on Electronics, Communications and Control, ICECC 2011 - Proceedings | Year: 2011

The observation automation of cloud, energy, and sky is a principal issue to solve in the modern meteorological observation field. The results of most of the research yet done show that: it is possible to achieve the observation automation of cloud, energy, and sky, since the theory and technology is basically prepared, and some of the technology is actually very mature. In the late 20th century, scientists have started to develop a kind of digital visibility automatic monitor, which has adopted advanced digital photographic technology and image recognition technology, based on the definition of visibility and fully imitating the human eye observing visibility principle. Undoubtedly, the digital visibility automatic monitor is the best instrument to replace the manual observation of visibility. Digital photography visibility automation observation instrument is made according to manual visual observation visibility's theory, more objective than traditional transmission, dispersion visibility instrument. This thesis introduced the work theory of digital photographic visibility system (for short is DPVS), compose of system, structure of hardware and software flow, in the end communication between host and outdoor cell was given. © 2011 IEEE.

Wang J.,Institute of Urban Meteorology | Liu X.,Beijing Meteorological Observation Center | Yang X.,New South Wales Office of Environment and Heritage | Lei M.,Beijing Meteorological Information Center | And 4 more authors.
Atmospheric Environment | Year: 2014

Visibility information is fundamental in aviation, navigation, land transportation, air quality and dust storm monitoring, and military activities which often require frequent and accurate real-time observation of visibility. The traditional manual observation, the primary means to obtain visibility information by human eyes, is subjective, inconsistent and costly. Instrumental observation (or traditional optical instrument) has overcome some of these limitations, but it is difficult to obtain correct visibility information in a complicated atmospheric (e.g. rainy and foggy) environment. We developed a new visibility instrument, digital photography visiometer system (DPVS), equipped with advanced digital photographic technology including high-resolution charge-coupled-device camera and computer. The new DPVS imitates the human eye observation and accurately calculates the visibility based on its definition and observational principles. We compared the results of the new DPVS with those from a forward scattering visibility instrument (FD12) and manual visibility observations in various (rainy, non-rainy, foggy) weather conditions. The comparative results show that the new DPVS, FD12, and manual observation have the same trend of change, but the observation from the new DPVS is closer to that from the manual observations in rainy days or complicated weather conditions. Our study demonstrates that the new DVPS is superior to the optical visibility instrument and can be used for automated visibility observations under all weather conditions. © 2014 Elsevier Ltd.

Wang J.-L.,Institute of Urban Meteorology | Liu X.-L.,Beijing Meteorological Observation Center | Lei M.,Beijing Meteorological Information Center | Ruan S.-X.,Institute of Urban Meteorology | And 4 more authors.
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2014

The traditional optical visibility instruments bear their respectine in observation defects. Digital photography visiometer system (DPVS) is one new type of visibility automation observation instrument, has been developed by adophing advanced digital photography technologe and imitating manual VisibiLity observation by human ege based on the definition of visibiLity visibility's theory and according to the definition of meteorological visibility. This thesis introduced the work theory of system, compose of system, structure of hardware and software flow, in the end some contrasted experiment results between DPVS and traditional optical visibility as well as manual visibility observation were given. The results show that the three ways share the same change trend with kind of differences. And in complicated weather conditions, like rainful the differences are more obvious. ©, 2014, Chinese Institute of Electronics. All right reserved.

Discover hidden collaborations