Sun J.,Tsinghua National Laboratory for Information Sciences and Technology |
Wang Y.,Tsinghua National Laboratory for Information Sciences and Technology |
Si H.,Tsinghua National Laboratory for Information Sciences and Technology |
Mao X.,Meteorological Bureau of Shenzhen Municipality |
And 2 more authors.
IWCMC 2010 - Proceedings of the 6th International Wireless Communications and Mobile Computing Conference | Year: 2010
Understanding of urban mobility dynamics benefits both aggregate human mobility in wireless communications, and the planning and provision of urban facilities and services. Due to the high penetration of cell phones, the cellular networks provide information for urban dynamics with large spatial extent and continuous temporal coverage. In this paper, a novel approach is proposed to explore the space-time structure of urban dynamics, based on the original data collected by cellular networks in a southern city of China, recording population distribution by dividing the city into thousands of pixels. By applying principal component analysis, the intrinsic dimensionality is revealed. The structure of all the pixel population variations could be well captured by a small set of eigen pixel population variations. According to the classification of eigen pixel population variations, each pixel population variation can be decomposed into three constitutions: deterministic trends, short-lived spikes, and noise. Moreover, the most significant eigen pixel population variations are utilized in the applications of forecasting and anomaly detection. Copyright © 2010 ACM.
Yang L.,Meteorological Bureau of Shenzhen Municipality |
Yang H.,Meteorological Bureau of Shenzhen Municipality
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2012
The haze occurrence characteristics and affecting factors in Shenzhen are summarized based on statistics and meteorological data between 1953 and 2010, ground-level and 850 hPa meteorological data during haze from Shenzhen Observatory, and pollutants concentration data between 1980 and 2010 from Shenzhen Environmental Monitoring Station. Main contributing factors are selected to develop the next 1-3 day visibility prediction equation using stepwise regression procedures. The idea of haze potential prediction is then proposed based on analysis and generalization of the weather condition before haze. Typical weather condition before and during haze is analyzed for haze potential prediction. Haze forecast is further achieved through weighted classification of typical factors. Finally, based on the above analysis, haze forecast and early warning method is designed. The results shows high accuracy and reliability in this kind of comprehensive forecast method It also provides some scientific reference in establishing haze prevention and early warning system.
Nie W.,Shandong University |
Nie W.,Hong Kong Polytechnic University |
Wang T.,Shandong University |
Wang T.,Hong Kong Polytechnic University |
And 5 more authors.
Atmospheric Environment | Year: 2013
The release of large amounts of sulfur dioxide (SO2) and nitrogen oxides (NOx) from the burning of fossil fuel leads to regional air pollution phenomena such as haze and acidic deposition. Despite longstanding recognition of the severity of these problems and the numerous studies conducted in China, little is known of long-term trends in particulate sulfate and nitrate and their association with changes in precursor emissions. In this study, we analyze records covering a 14-year period (1995-2008) of PM10 composition in the subtropical city of Hong Kong, situated in the rapidly developing Pearl River Delta region of southern China. A linear regression method and a Regional Kendall test are employed for trend calculations. In contrast to the decreased levels of SO2 and NOx emissions in Hong Kong, there are increasing overall trends in ambient concentrations of PM10 sulfate and PM10 nitrate, with the most obvious rise seen during 2001-2005. The percentages of sulfate and nitrate in the PM10 mass and rainwater acidity also increased. Backward trajectories are computed to help identify the origin of large-scale air masses arriving in Hong Kong. In air masses dominated by Hong Kong urban sources and ship emissions, there was no statistically significant trend for PM10 sulfate and a small increase for PM10 nitrate; however, the evident increases in PM10 sulfate and PM10 nitrate concentrations were observed in air masses originating from eastern China and are generally consistent with changes in emissions of their precursors in eastern China. Examination of PM10 mass data recorded at a pair of upwind-urban sites also indicates that long-range transport makes a large contribution (>80%) to PM10 loadings in Hong Kong. Together with our previous study on the ozone trend, these results demonstrate the important impact exerted by long-distance sources and suggest a need to consider the impact of super-regional transport when formulating air-quality management strategy in Hong Kong in future. © 2012 Elsevier Ltd.
Mao X.,Meteorological Bureau of Shenzhen Municipality |
Xu R.,China Mobile |
Li X.,Meteorological Bureau of Shenzhen Municipality |
Wang Y.,China Mobile |
And 4 more authors.
Acta Geographica Sinica | Year: 2010
Shenzhen is the most densely populated city in China. In order to respond to emergencies, such as natural disasters, real time high resolution dynamic information of population distribution is needed. This paper analyzes the fine grid dynamic characteristics of Shenzhen population distribution, using the information of population density in respect of which the temporal resolution is an hour and the spatial resolution is a kilometer provided by the "Dynamic Monitoring System of Population Distribution Based on Mobile Stations". The mobile subscribers in Shenzhen total to 10.8259 million. The average population density is 5545 people/km 2, and the maximum density reaches 165,000 people/km 2. High density areas which have more than 50,000 people/km 2 are mainly the business centers, custom ports, railway stations, and large residential communities. The value of the maximum population density depends on the size of grid used, for example the value of 1 km 2 grid is about 18 times than the value of 1000 km 2 grid. Some 50% of the population in Shenzhen is concentrated in 10% of the city's spatial area, and 60% resides in the areas where altitudes are between 50 m to 100 m. The building density and the road density on the grid are linearly correlated with population density, that is, 1000 people are added when the building density increases by 1%, and about 2,000 people are added when the road density increases by 0.01%. The total population of a city is relatively stable during a period of time, the variation of which is commonly less than 4% and the daily variation is about 1%. Shenzhen is a typical immigration city, and the total population will decrease by 48% during the Chinese New Year because a lot of people will go back to their hometowns or traval around. This paper selects 9 typical grids to analyze the daily variation of the population and they are as follows: custom ports have a morning peak, and people going outbound crowd here at about 8 a.m.; bazaar areas have a noon peak; business centers have an evening peak with a net inflow/outflow over 20,000 people/hr; residential communities have a noon trough, and the density of population is always bigger on the weekends than on the weekdays; in the government offices and public service areas, there are fewer people on the weekends than on the weekdays and the population is decreased by 75% during the Chinese New Year; the factory area has a peak of population at about 4 a.m. because of the peak load shifting; outing area is more crowded during the holidays and weekends; in the out-of-the-way area, the daily variation of population is very little; and in the farming area, there is a morning trough of population at about 9 a.m. which corresponds to the traditional farming habits.
Chen H.,Chinese Academy of Meteorological Sciences |
Chen H.,Guangzhou Institute of Tropical and Marine Meteorology |
Wu D.,Chinese Academy of Meteorological Sciences |
Wu D.,Guangzhou Institute of Tropical and Marine Meteorology |
And 8 more authors.
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2013
In this work, we investigated the influence of various acidic gases and relative humidity on depletion of chloride on sea salt aerosols at three locations in the Pearl River Delta Region using online chemical composition data obtained by MARGA. The three locations include Nancun (NC) in Guangzhou, Xichong (XC) and Zhuzilin (ZZL) in Shenzhen. Chloride depletion reached an average of 48.0% at ZZL and 56.9% at XC, typically peaking around 14: 00. The major acidic gases were HNO2 and SO2 and the major alkaline gas was NH3 at all three stations, but their proportions differed among the stations. At XC, HNO2 was the most abundant (42%), followed by SO2 (32%). At ZZL, NH3 and SO2 accounted for 36% and 34%, respectively. At NC, SO2 dominated (58%), followed by NH3 (20%), while HNO2 only accounted for 7%. We further explored the sources of HCl, including the reactions with HNO3 and H2SO4 and the volatilization of NH4Cl. At XC and ZZL, HCl and HNO3 showed very good correlation (RXC 2=0.689, RZZL 2=0.594), suggesting that HCl was primarily from the reaction of HNO3 with NaCl. At NC in Guangzhou, the two species had a weak correlation (RNC 2=0.295), likely suggesting the presence of other chloride depletion pathways. In addition, we found that the extent of chloride loss was larger under lower relative humidity conditions.
Wei X.,Meteorological Bureau of Shenzhen Municipality |
Wei X.,Hong Kong Polytechnic University |
Liu Q.,Hong Kong Polytechnic University |
Lam K.S.,Hong Kong Polytechnic University |
Wang T.,Nanjing University
Advances in Atmospheric Sciences | Year: 2012
The relationship between the emission of ozone precursors and the chemical production of tropospheric ozone (O 3) in the Pearl River Delta Region (PRD) was studied using numerical simulation. The aim of this study was to examine the volatile organic compound (VOC)- or nitrogen oxide (NO x =NO+NO 2)-limited conditions at present and when surface temperature is increasing due to global warming, thus to make recommendations for future ozone abatement policies for the PRD region. The model used for this application is the U. S. Environmental Protection Agency's (EPA's) third-generation air-quality modeling system; it consists of the mesoscale meteorological model MM5 and the chemical transport model named Community Multi-scale Air Quality (CMAQ). A series of sensitivity tests were conducted to assess the influence of VOC and NO x variations on ozone production. Tropical cyclone was shown to be one of the important synoptic weather patterns leading to ozone pollution. The simulations were based on a tropicalcyclone-related episode that occurred during 14-16 September 2004. The results show that, in the future, the control strategy for emissions should be tightened. To reduce the current level of ozone to meet the Hong Kong Environmental Protection Department (EPD) air-quality objective (hourly average of 120 ppb), emphasis should be put on restricting the increase of NO x emissions. Furthermore, for a wide range of possible changes in precursor emissions, temperature increase will increase the ozone peak in the PRD region; the areas affected by photochemical smog are growing wider, but the locations of the ozone plume are rather invariant. © 2012 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.
Huo Y.-F.,Lanzhou University |
Huo Y.-F.,CAS Institute of Atmospheric Physics |
Duan M.-Z.,CAS Institute of Atmospheric Physics |
Jiang Z.,CAS Institute of Atmospheric Physics |
And 3 more authors.
Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis | Year: 2015
Ground-based CO2 inversion accuracy determines the understanding of CO2 source and sink. However the study about factors affecting ground-based CO2 inversion. In order to improve CO2 inversion accuracy, the effects from aerosol, spectral shift, spectral band selection, spectrometer response function type, half width and truncation error have been analyzed by using radiative transfer model. The results show that: (1) the multiple scattering of aerosol can be ignored when instrument field of view is less than 1.5° and aerosol optical depth is less than 0.5. (2) The inversion results are smaller when there are spectral offsets. The inversion errors increase nonlinear with spectral offsets. And the higher the spectral resolution, the larger the effect of spectral shift. (3) Different spectral bands have various average signal-to-noise ratio, selecting channels with appropriate signal-to-noise ratio and enhancing instrument signal-to-noise ratio can reduce the effect of instrument noise. (4) The higher the instrument resolution, the more important the degree of accuracy of instrument line function for simulated spectrum. Therefore, for hyper-spectral observation, the constancy of environmental temperature is key of acquiring high precision inversion results. (5) For over-high spectral resolution, simulated spectrum is anamorphic due to crosstalk effect. Therefore the crosstalk effect must be considered when the spectrometer resolution is advanced. © 2015, Science Press. All right reserved.
Zhang X.-L.,Meteorological Bureau of Shenzhen Municipality |
Li L.,Meteorological Bureau of Shenzhen Municipality |
Du Y.,Urban Planning and Design Institute of Shenzhen |
Jiang Y.,Meteorological Bureau of Shenzhen Municipality |
And 4 more authors.
Journal of Tropical Meteorology | Year: 2011
By means of the regional boundary layer model (RBLM), a study on the influences of the urban planning and construction on the summer urban heat island (UHI) in the metropolis of Shenzhen is performed. In the study, the current summer UHI distribution, the influences of the increasing high-density construction and the energy consumption on the summer air temperature distribution, and the influences of the urban ventilation corridor on the summer air temperature distribution are numerically analyzed. Some conclusions are drawn in the light of the study: (1) The summer UHI is more obvious in day time than that in night time in the summer of Shenzhen, and the maximum values of UHI intensity in the day time appear in the areas with high-density construction, which are located in Nanshan, Futian and Luohu and western Bao'an districts. (2) The increase of construction density and energy consumption in the urban area will lead to the increase of temperature near the ground, and the increase of temperature at nighttime is more obvious than that at daytime. (3) The ventilation corridor can effectively reduce the UHI intensity and can be taken as a method to eliminate the negative climatic effect caused by the increase of high-density construction and energy consumption in the future.