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Hao T.Y.,Tianjin Environmental Meteorological Center | Chen S.C.,Tianjin Meteorological Observation Center | Han S.Q.,Tianjin Institute of Meteorological Sciences | Shan X.L.,Tianjin Binhai New Area Meteorological Bureau | Meng L.H.,Tianjin Institute of Meteorological Sciences
IOP Conference Series: Earth and Environmental Science | Year: 2017

Using trend coefficient method, vector analysis method, and monitored meteorological data across China, climatic characteristics and spatial pattern of fogs in China were investigated. The results show that most fogs occur in southeastern China. Thin fogs usually occur in fog-rare regions and dense fogs take place in fog-prone regions. The number of annual fog days in most regions of China exhibits a decreasing trend from 1980 to 2010. It also found that the regions with more fog days correspond to the lower concentration degree of fogs, and vice versa. In terms of the national scale, the concentration periods of fogs are mainly in November, December, and January in China. We further classified the occurrence frequencies of fogs into five spatial distribution patterns over a single year according to the spatial distribution characteristics of fogs occurrence frequencies of 36 dekads, namely, a whole year can be correspondingly divided into five phases. Based on this, multi-year average fog-prone regions in the five phases are obtained. Our results also identify the high incidence periods of fogs in different fog-prone regions. © Published under licence by IOP Publishing Ltd.

Sun Z.,Australian Bureau of Meteorology | Li J.,Environment Canada | He Y.,Nanjing University of Information Science and Technology | Li J.,CAS Institute of Atmospheric Physics | And 2 more authors.
Quarterly Journal of the Royal Meteorological Society | Year: 2016

An issue in the determination of the direct component of solar radiation involving the circumsolar contribution in numerical weather prediction (NWP) and climate models is discussed. The direct solar radiation has multiple definitions in different applications, but this ambiguity has not always been clearly identified and has therefore sometimes caused confusion. The confusion arises from a fact that the photons that are scattered into the direct solar beam path by atmospheric particles are no different from the non-scattered photons travelling in the same direction. Therefore there is a question whether these scattered photons should be included in the direct flux calculation or whether they should be excluded. Different definitions of the direct solar radiation in a wide range of applications have been discussed by Blanc et al. (2014). We further discuss it in terms of its relation to NWP and climate models. The short-wave radiation schemes used in NWP and climate models can be classified into two groups: those that calculate the direct solar radiation without including scattering contributions and those which include the scattering contribution in terms of the delta-Eddington approximation. We assess the two treatments by comparing modelled direct solar radiation with observations. It is found that the use of delta-Eddington scaling results in positive errors in the direct solar flux at the surface, while neglecting the delta-scaling leads to negative errors. The important result is that the positive error from using the delta-Eddington scaling is at least 1 order of magnitude larger than the absolute negative error due to neglecting it. In order to include properly the scattering contribution in the direct flux calculation, a simple parametrization for dust aerosol is developed which can be used to consider the scattering contribution due to the particular case of dust aerosol to the direct solar radiation within the circumsolar region. © 2016 Royal Meteorological Society

Sha J.,Nankai University | Li Z.,Nankai University | Swaney D.P.,Cornell University | Hong B.,Cornell University | And 2 more authors.
Water Resources Management | Year: 2014

Excessive nitrogen loads and subsequent eutrophication risk have led to a series of critical water quality problems in Chinese watersheds. To address this issue, a modeling approach is useful for quantifying nitrogen sources, assessing source apportionment, and guiding management responses. In this study, we modeled the main hydrochemical processes of the Lian River watershed located in the south of China using the Regional Nutrient Management (ReNuMa) model, a model derived from the Generalized Watershed Loading Function (GWLF) model and incorporating Net Anthropogenic Nitrogen Inputs (NANI) to estimate runoff nitrogen concentrations. An informal Bayesian method, the Generalized Likelihood Uncertainty Estimation (GLUE) procedure, was applied for model calibration and uncertainty analysis. The resulting modeled monthly total nitrogen fluxes have high Nash-Sutcliff coefficients (>0.85) for the calibration (2005-2009) and verification (2003, 2004 and 2010) periods, representing an acceptable goodness-of-fit. The model outputs were further processed using multivariate statistical analysis to determine latent rules of nitrogen source apportionment under different circumstances, including different water regimes, seasonal patterns, and loading levels. The main nitrogen contributions in different natural and management-driven conditions have been identified, and appear to be significant for supporting decision-making priorities. We find that the ReNuMa model, with its Bayesian procedure and the linkage of subsequent multivariate statistical analysis, represents a useful approach with applicability within China and a great potential to be extended elsewhere. © Springer Science+Business Media Dordrecht 2014.

Gu J.,Tianjin Institute of Urban Construction | Gu J.,Nankai University | Bai Z.,Nankai University | Li W.,Nankai University | And 5 more authors.
Particuology | Year: 2011

PM2.5 samples for 24 h were collected during winter in Tianjin, China. The ambient mass concentration and chemical composition of the PM 2.5 were determined. Ionic species were analyzed by ion chromatography, while carbonaceous species were determined with the IMPROVE thermal optical reflectance (TOR) method, and inorganic elements were measured by inductively coupled plasma-atomic emission spectrometer. The daily PM 2.5 mass concentrations ranged from 48.2 to 319.2 μg/m3 with an arithmetic average of 144.6 μg/m3. The elevated PM 2.5 in winter was mostly attributed to combustion sources such as vehicle exhaust, heating, cooking and industrial emissions, low wind speeds and high relative humidity (RH), which were favorable for pollutant accumulation and formation of secondary pollutants. By chemical mass balance, it was estimated that about 89.1% of the PM2.5 mass concentrations were explained by carbonaceous species, secondary particles, crustal matters, sea salt and trace elements. Organic material was the largest contributor, accounting for about 32.7% of the total PM2.5 mass concentrations. SO4 2-, NO3 -, Cl- and NH 4 + were four major ions, accounting for 16.6%, 11.5%, 4.7% and 6.0%, respectively, of the total mass of PM2.5. © 2011 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Zhao P.S.,Institute of Urban Meteorology | Dong F.,Institute of Urban Meteorology | He D.,Institute of Urban Meteorology | Zhao X.J.,Institute of Urban Meteorology | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2013

In order to study the temporal and spatial variations of PM2.5 and its chemical compositions in the region of Beijing, Tianjin, and Hebei (BTH), PM2.5 samples were collected at four urban sites in Beijing (BJ), Tianjin (TJ), Shijiazhuang (SJZ), and Chengde (CD), and also one site at Shangdianzi (SDZ) regional background station over four seasons from 2009 to 2010. The samples were weighted for mass concentrations and analyzed in the laboratory for chemical profiles of 19 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, Sr, Ti, V, and Zn), eight water-soluble inorganic ions (Na+, NH4 +, K+, Mg 2+, Ca2+, Cl-, NO3 -, and SO4 2-), and carbon fractions (OC and EC). The concentrations of PM2.5 and its major chemical species were season dependent and showed spatially similar characteristics in the plain area of BTH. The average annual concentrations of PM2.5 were 71.8-191.2 μg m-3 at the five sites, with more than 90% of sampling days exceeding 50μgm-3 at BJ, TJ, and SJZ. PM2.5 pollution was most serious at SJZ, and the annual concentrations of PM2.5, secondary inorganic ions, OC, EC, and most crustal elements were all highest. Due to stronger photochemical oxidation, the sum of concentrations of secondary inorganic ions (NH4 +, NO3 -, and SO4 2-) was highest in the summer at SDZ, BJ, TJ, and CD. Analysis of electric charges of water-soluble inorganic ions indicated the existence of nitric acid or hydrochloric acid in PM2.5. For all five sites, the concentrations of OC, EC and also secondary organic carbon (SOC) in the spring and summer were lower than those in the autumn and winter. SOC had more percentages of increase than primary organic carbon (POC) during the winter. The sums of crustal elements (Al, Ca, Fe, Mg, Ti, Ba, and Sr) were higher in the spring and autumn owing to more days with blowing or floating dust. The concentrations of heavy metals were at higher levels in the BTH area by comparison with other studies. In Shijiazhuang and Chengde, the PM2.5 pollution was dominated by coal combustion. Motor vehicle exhausts and cos a al combustion emissions both played important roles in Tianjin PM2.5 pollution. However, motor vehicle exhausts had played a more important role in Beijing owing to the reduction of coal consumption and sharp increase of cars in recent years. At SDZ, regional transportation of air pollutants from southern urban areas was significant. © Author(s) 2013.

Zhao P.,Institute of Urban Meteorology | Dong F.,Institute of Urban Meteorology | Yang Y.,Institute of Urban Meteorology | He D.,Institute of Urban Meteorology | And 4 more authors.
Atmospheric Environment | Year: 2013

More than 400 PM2.5 samples were collected at four urban sites in Beijing (BJ), Tianjin (TJ), Shijiazhuang (SJZ), and Chengde (CD), and also one site in Shangdianzi (SDZ), which was used as a regional background station, over four seasons from 2009 to 2010. The organic carbon (OC) and elemental carbon (EC) in each sample were analyzed. The average annual concentrations were 71.8-191.2 μg m-3 for PM2.5, 10.8-26.4 μg m-3 for OC, and 3.9-9.7 μg m-3 for EC at the five sites. OC and EC concentrations were lower in the spring and summer and much higher in the autumn and winter, mainly due to aerosol emissions from additional fuel combustion for heating. OC/EC ratios were lowest in the summer and highest in the winter at SDZ, BJ, TJ, and SJZ. These seasonal trends indicate that the characteristics of carbonaceous aerosol pollution were spatially similar and season-dependent in the plain area of Beijing, Tianjin, and Hebei (BTH). An EC tracer method was used to calculate the concentrations for secondary organic carbon (SOC); SOC concentrations were also higher in the autumn and winter and lowest during the summer at all five sites. A stable atmosphere and low temperatures, which were more frequent during the winter and autumn, facilitated the accumulation of air pollutants and accelerated the condensation or adsorption of volatile organic compounds in the BTH area. Over the past ten years (1999-2009), Beijing had observed a decrease in the EC concentrations during every season and a remarkable reduction in aerosol emissions from coal combustion for heating. © 2013 Elsevier Ltd.

Han S.,Tianjin Institute of Meteorological Sciences | Bian H.,Tianjin Institute of Meteorological Sciences | Zhang Y.,Tianjin Institute of Meteorological Sciences | Wu J.,Nankai University | And 5 more authors.
Aerosol and Air Quality Research | Year: 2012

Meteorological and aerosol data were measured at the atmospheric boundary layer observation station in Tianjin, China, and were analyzed to study the effects of aerosol mass, composition, and size distributions on visibility and short-wave radiation flux. The results show that fine particles played important roles in controlling visibility in Tianjin. The major contributors to light extinction coefficients included sulfate (28.7%), particulate organic matter (27.6%), elemental carbon (19.2%), and nitrate (6.1%). In addition to the measurement of aerosol composition, the size distribution of aerosol number concentrations were also measured and classified between haze days and non-haze days during spring. The extinction characteristics of ambient aerosol in haze days and non-haze days were calculated using Mie theory model. The average extinction coefficient and scattering coefficient of atmospheric aerosols were 0.253 1/km and 0.213 1/km in non-haze days, while 0.767 1/km and 0.665 1/km in haze days. A radiation transmission model LOWTRAN7 is also applied in this study. The model calculated radiant flux densities in haze days and non-haze days, which showed a fairly agreement with the observation results, showing that the heavy aerosol loadings in Tianjin had significantly impact on atmospheric visibility and radiation fluxes. © Taiwan Association for Aerosol Research.

Quan J.,Beijing Weather Modification Office | Quan J.,Institute of Urban Meteorology | Gao Y.,Beijing Weather Modification Office | Zhang Q.,Beijing Weather Modification Office | And 7 more authors.
Particuology | Year: 2013

A field experiment was conducted in Tianjin, China from September 9-30, 2010, focused on the evolution of Planetary Boundary Layer (PBL) and its impact on surface air pollutants. The experiment used three remote sensing instruments, wind profile radar (WPR), microwave radiometer (MWR) and micro-pulse lidar (MPL), to detect the vertical profiles of winds, temperature, and aerosol backscattering coefficient and to measure the vertical profiles of surface pollutants (aerosol, CO, SO2, NOx), and also collected sonic anemometers data from a 255-m meteorological tower. Based on these measurements, the evolution of the PBL was estimated. The averaged PBL height was about 1000-1300 m during noon/afternoon-time, and 200-300 m during night-time. The PBL height and the aerosol concentrations were anti-correlated during clear and haze conditions. The averaged maximum PBL heights were 1.08 and 1.70 km while the averaged aerosol concentrations were 52 and 17 μg/m 3 under haze and clear sky conditions, respectively. The influence of aerosols and clouds on solar radiation was observed based on sonic anemometers data collected from the 255-m meteorological tower. The heat flux was found significantly decreased by haze (heavy pollution) or cloud, which tended to depress the development of PBL, while the repressed structure of PBL further weakened the diffusion of pollutants, leading to heavy pollution. This possible positive feedback cycle (more aerosols → lower PBL height → more aerosols) would induce an acceleration process for heavy ground pollution in megacities. © 2012 2012 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Han S.-Q.,Tianjin Institute of Meteorological Sciences | Wu J.-H.,Nankai University | Zhang Y.-F.,Nankai University | Cai Z.-Y.,Tianjin Institute of Meteorological Sciences | And 5 more authors.
Atmospheric Environment | Year: 2014

Several heavy haze and fog episodes occurred in northern China in January of 2013. Data were collected and used to analyze the characteristics and mechanisms of formation of the haze-fog (HF) episode that occurred from January 10 to 12. The minimum hourly visibility was 112 m, as recorded on 12 January. The concentrations of particulate and gaseous pollutants increased continuously during this HF period. The concentration of PM2.5 increased faster than that of SO2 and NOx, and the rate of accumulation was greater at the beginning of the HF process than at other times. The average concentration of PM2.5, PM10, NOx, and SO2 on the HF days was 3.9, 3.6, 2.5, and 2.1 times higher than the values in the non-haze days. The scattering and absorption coefficients σsp and σap on the HF days were 4.0 and 4.3 times higher than the values in the non-HF days. The highest black carbon (BC) concentration was about 10 times higher than on the non-HF days. The concentrations of total carbon (TC), organic carbon (OC), and elemental carbon (EC) all increased, and the speed of the increase in OC was quicker than that of the EC. An increase in secondary inorganic pollutants (SO4 2-, NO3 -) in PM2.5 was also observed. The concentrations of SO4 2- and NO3 - on the HF days were 4 and 2 times those of the non-HF days. The increase in relative humidity on the HF days favored the formation of sulfate and nitrate during HF episode. Unfavorable meteorological conditions were the external cause of this HF episode. The southwest wind transported the pollutants from areas to the south of the study regions at the beginning of the HF episode. After the HF took shape, a strong descending air mass located in the high layer severely limited pollutant diffusion in the vertical direction. The strong temperature inversion and the weak horizontal wind limited the horizontal and vertical dispersion of pollutants. The high layer transport of the pollutants during the early period and the late accumulation of pollutants and the secondary formation of aerosols were important mechanisms for causing the formation of this HF episode. © 2014 Elsevier Ltd.

PubMed | Tianjin Institute of Meteorological Sciences and Nankai University
Type: | Journal: Environmental pollution (Barking, Essex : 1987) | Year: 2016

To investigate the size distributions of chemical compositions and sources of particulate matter (PM) at ground level and from the urban canopy, a study was conducted on a 255m meteorological tower in Tianjin from December 2013 to January 2014. Thirteen sets of 8 size-segregated particles were collected with cascade impactor at 10m and 220m. Twelve components of particles, including water-soluble inorganic ions and carbonaceous species, were analyzed and used to apportion the sources of PM with positive matrix factorization. Our results indicated that the concentrations, size distributions of chemical compositions and sources of PM at the urban canopy were affected by regional transport due to a stable layer approximately 200m and higher wind speed at 220m. The concentrations of PM, Cl

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