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Lin W.,Chinese Academy of Meteorological Sciences | Xu X.,Chinese Academy of Meteorological Sciences | Ma Z.,Institute of Urban Meteorology | Zhao H.,Chinese Academy of Meteorological Sciences | And 2 more authors.
Journal of Environmental Sciences | Year: 2012

SO 2 measurements made in recent years at sites in Beijing and its surrounding areas are performed to study the variations and trends of surface SO 2 at different types of sites in Northern China. The overall average concentrations of SO 2 are (16.8 ± 13.1) ppb, (14.8 ± 9.4) ppb, and (7.5 ± 4.0) ppb at China Meteorological Administration (CMA, Beijing urban area), Gucheng (GCH, relatively polluted rural area, 110 km to the southwest of Beijing urban area), and Shangdianzi (SDZ, clean background area, 100 km to the northeast of Beijing urban area), respectively. The SO 2 levels in winter (heating season) are 4-6 folds higher than those in summer. There are highly significant correlations among the daily means of SO 2 at different sites, indicating regional characteristics of SO 2 pollution. Diurnal patterns of surface SO 2 at all sites have a common feature with a daytime peak, which is probably caused by the downward mixing and/or the advection transport of SO 2-richer air over the North China Plain. The concentrations of SO 2 at CMA and GCH show highly significant downward trends (-4.4 ppb/yr for CMA and -2.4 ppb/yr for GCH), while a less significant trend (-0.3 ppb/yr) is identified in the data from SDZ, reflecting the character of SDZ as a regional atmospheric background site in North China. The SO 2 concentrations of all three sites show a significant decrease from period before to after the control measures for the 2008 Olympic Games, suggesting that the SO 2 pollution control has long-term effectiveness and benefits. In the post-Olympics period, the mean concentrations of SO 2 at CMA, GCH, and SDZ are (14.3 ± 11.0) ppb, (12.1 ± 7.7) ppb, and (7.5 ± 4.0) ppb, respectively, with reductions of 26%, 36%, and 13%, respectively, compared to the levels before. Detailed analysis shows that the differences of temperature, relative humidity, wind speed, and wind direction were not the dominant factors for the significant differences of SO2 between the pre-Olympics and post-Olympics periods. By extracting the data being more representative of local or regional characteristics, a reduction of up to 40% for SO2 in polluted areas and a reduction of 20% for regional SO2 are obtained for the effect of control measures implemented for the Olympic Games. © 2012 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.

Li N.,Nanjing University of Information Science and Technology | Wei M.,Nanjing University of Information Science and Technology | Niu B.,Wuhan Central Meteorological Observatory | Mu X.,Jiangsu Institute of Meteorological science
Meteorological Applications | Year: 2012

A new storm identification and warning technique is proposed which exclusively uses radar data as input. The new identification method assembles contiguous storm points to constitute 2D storm components and improve the vertical association of storm components to construct 3D storms, which can overcome the deficiencies existing in traditional identification methods. Based on the evolution properties and characteristic distributions, strong storms and general storms are specified to train support vector machines (SVMs) which then can be used to discriminate storms. The performance of the SVM shows that it can indicate the intensity and development of a storm, providing an important aid in severe weather warning. © 2011 Royal Meteorological Society.

Zhou J.,Key Laboratory of Meteorological Disaster | Wei M.,Key Laboratory of Meteorological Disaster | Wu T.,Wuhan Central Meteorological Observatory | Li N.,Key Laboratory of Meteorological Disaster
2011 International Conference on Remote Sensing, Environment and Transportation Engineering, RSETE 2011 - Proceedings | Year: 2011

With high temporal and spatial resolution, Doppler weather radars are important means for revealing structures and revolution of meso-micro scale weather processes. This article uses reflectivity characteristics to identify convective gale weather. 6 promising identification parameters are proposed (CR, VIL, DVIL, SWP, DCRH and SPEED), and an automated identification algorithm for convective gale is established based on fuzzy logic principles. 6 typical cases are used to obtain probability distribution characters based on the statistics of volume scan data, and then it is determined that CR, VIL, DVIL and SWP that have more concentrated probability densities are used as the input variables of the fuzzy logic technique for the identification of the convective gale. According to the statistics, these parameters can effectively identify convective gale. The algorithm identifies 150 from 174 gale wind events in 6 weather processes, with a POD probability 86.21%. © 2011 IEEE.

Xu G.-R.,Institute of Heavy Rain | Cui C.-G.,Institute of Heavy Rain | Li W.-J.,Institute of Heavy Rain | Zhang W.,Wuhan Central Meteorological Observatory | Feng G.-L.,Institute of Heavy Rain
Terrestrial, Atmospheric and Oceanic Sciences | Year: 2011

GPS technologies show many capabilities for monitoring atmospheric water vapor. This study uses GPS data from the Japan International Co-operation Agency (JICA) and Hubei GPS network to monitor precipitable water (PW) over the Qinghai-Tibet Plateau (QTP) and over the middle Yangtze River Valley (YRV). The results show that the southern QTP is wetter than the central area due to the barring effect of the Plateau on the monsoon. PW is higher in summer than other months over either the QTP or the middle YRV. The diurnal variation of PW over the QTP is more complex than that of the middle YRV with fluctuations occurring during the whole day due to the unique topography. The minimum PW over both the QTP and the middle YRV appears in the morning; however, the peak over the QTP occurs at night while the peak over the middle YRV occurs in the early afternoon. Furthermore, PW over the QTP, especially its southern and eastern edges, are positively correlated with PW over the middle YRV. This may imply that the southern and eastern Plateaus are key regions transporting atmospheric vapor to the middle YRV. Our results indicate the possibility of finding early warning signals resulting from the intensification of the QTP atmospheric vapor leading to heavy rainfall events over the middle YRV.

Lin W.L.,Chinese Academy of Meteorological Sciences | Lin W.L.,Tibet Institute of Plateau Atmospheric and Environmental science | Xu X.B.,Chinese Academy of Meteorological Sciences | Sun J.Y.,Chinese Academy of Meteorological Sciences | And 2 more authors.
Science China Earth Sciences | Year: 2011

Lorentz curve fittings are applied to frequency distributions of the concentrations of O3, CO, NOx and SO2 recorded at the Jinsha regional atmospheric background station (JSH) from June 2006 to July 2007, and the peak concentrations of these species for the different seasons are obtained. The peak concentrations are considered to be representative of different background levels for certain processes. The peak concentrations are compared with the corresponding mean (median) concentrations, and the suitability and limitations of the mean (median) values as the background levels are discussed. The mean (median) values might represent the background concentrations in the region under some circumstances, but in other cases these values often underestimate or overestimate the true background concentrations owing to the transport of pollutants and other factors. The effects of air masses transported from different regions on the pollutant background concentrations are obtained by analyzing the 72-hour backward trajectories of air masses 100 m above the ground at JSH. These trajectories are estimated using the HYSPLIT model and then clustered for the measurement period. The spatial distribution and seasonal variations of trajectories and the corresponding mean concentrations of O3, SO2, NOx and CO for different clusters are analyzed. After filtering the seasonal changes in pollutant concentrations, the relative influences of air masses from different regions are obtained. The results show that JSH can be used to obtain the atmospheric background information of different air masses originating from or passing over the Yangtze River Delta, Central South China and the Jianghan Plain. Air masses from Central China, South China, and the western Yangtze River Delta contribute significantly to O3 at JSH. Air masses from the north and northeast of JSH (i. e., the Jianghan Plain, Huang-Huai Plain and North China Plain) and the south (Central South China) contribute significantly to SO2, CO and NOx concentrations. Air masses originating from the ocean often bring clean air. Air masses originating from high altitudes over northwestern regions often have lower CO and NOx concentrations, lower relative humidity, and higher concentrations of O3 and SO2. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

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