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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. Source

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. Source

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. Source

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. Source

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. Source

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