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Wang M.-T.,Nanjing University of Information Science and Technology | Zhu B.,Nanjing University of Information Science and Technology | Wang H.-L.,Nanjing University of Information Science and Technology | Xue G.-Q.,Nanjing University of Information Science and Technology | And 3 more authors.
Huanjing Kexue/Environmental Science | Year: 2015

To investigate the pollution characteristics of water soluble ions in fine atmospheric particles in Yangtze River Delta during the haze period from 18th to 24th Jan 2013, a joint sampling campaign using Andersen sampler was conducted at five cities (including Nanjing, Suzhou, Hangzhou, Lin'an and Ningbo). The analysis of size distribution of these ionic species coupled with the local meteorological conditions may shed some insightful light on the haze formation mechanism in this region. The result has shown: firstly, during the observation period, when Yangtze River Delta located at high pressure or in the front of high pressure, and has a large pressure gradient, the lower atmosphere has a significant airflow divergence in favor of pollutant dispersion; while located in weak low pressure and weak high pressure, the equalizing pressure field is not favorable for pollutant dispersion, especially accompanied with lower atmosphere convergence airflow. Secondly, during the hazy period, the concentration of fine particles and total water-soluble inorganic ions (TWSS) has increased dramatically; the increasing proportions of TWSS in fine particles are: Hangzhou 0.9%, Lin'an 4.2%, Nanjing 8.1%. The particle size of secondary ions of SO42-, NO3-, NH4+ complies fine mode (particle size<2.1 μm), whose peaks migrates from 0.43-0.65 μm to 0.65-1.1 μm during the observation period, the peak of particle size of Ca2+, Mg2+ appears at 4.7-5.8 μm, while the ions of Na+, Cl-, K+ show a bimodal distribution. Moreover, secondary inorganic ions play a significant role in the formation of haze pollution, where the concentrations of secondary inorganic ions of NH4+, SO42- and NO3- have higher increasing rates; their relative proportions of increasing from each monitoring points are: Hangzhou 3%, Lin'an 55% and Nanjing 64.9%. Finally, SO42- has the highest mass contribution to SNA, up to 45%; also, the NO3-/SO42- ratios in each monitoring points are always higher than a fair 0.5, which could indicate the significant contribution of mobile source towards this particle pollution. ©, 2015, Science Press. All right reserved. Source

Zhang Z.,CAS Lanzhou Cold and Arid Regions Environmental and Engineering Research Institute | Zhang Z.,Nanjing University | Jiang H.,Nanjing University | Jiang H.,Zhejiang Agriculture And forestry University | And 4 more authors.
Terrestrial, Atmospheric and Oceanic Sciences | Year: 2013

As the atmospheric carbon dioxide (CO2) increases substantially, the spatial distribution of atmospheric CO2 should be considered when estimating the effects of CO2 on the carbon and water cycle coupling of terrestrial ecosystems. To evaluate this effect on future ecohydrological processes, the spatial-temporal patterns of CO2 were established over 1951 - 2099 according to the IPCC emission scenarios SRES A2 and SRES B1. Thereafter, water use efficiency (WUE) was used (i.e., Net Primary Production/Evaportranspiration) as an indicator to quantify the effects of climate change and uneven CO2 fertilization in China. We carried out several simulated experiments to estimate WUE under different future scenarios using a land process model (Integrated Biosphere Simulator, IBIS). Results indicated that the geographical distributions of averaged WUE have considerable differences under a heterogeneous atmospheric CO2 condition. Under the SRES A2 scenario, WUE decreased slightly with a 5% value in most areas of the southeastern and northwestern China during the 2050s, while decreasing by approximately 15% in southeastern China during the 2090s. During the period of the 2050s under SRES B1 scenario, the change rate of WUE was similar with that under SRES A2 scenario, but the WUE has a more moderate decreasing trend than that under the SRES A2 scenario. In all, the ecosystems in median and low latitude areas had a weakened effect on resisting extreme climate event such as drought. Conversely, the vegetation in a boreal forest had an enhanced buffering capability to tolerate drought events. Source

Zhang Z.,Nanjing University | Jiang H.,Nanjing University | Jiang H.,Zhejiang Agriculture And forestry University | Liu J.,U.S. Geological Survey | And 6 more authors.
Proceedings - 2011 19th International Conference on Geoinformatics, Geoinformatics 2011 | Year: 2011

The climate change has significantly affected the carbon cycling in Yangtze River Basin. To better understand the alternation pattern for the relationship between carbon cycling and climate change, the net primary production (NPP) were simulated in the study area from 1956 to 2006 by using the Integrated Biosphere Simulator (IBIS). The results showed that the average annual NPP per square meter was about 0.518 kg C in Yangtze River Basin. The high NPP levels were mainly distributed in the southeast area of Sichuan, and the highest value reached 1.05 kg C/m2. The NPP increased based on the simulated temporal trends. The spatiotemporal variability of the NPP in the vegetation types was obvious, and it was depended on the climate and soil condition. We found the drought climate was one of critical factor that impacts the alterations of the NPP in the area by the simulation. © 2011 IEEE. Source

Yang J.,Nanjing University | Liu H.,Nanjing University | Liu H.,Jiangsu Collaborative Innovation Center for Climate Change | Sun J.,Nanjing University | And 4 more authors.
Journal of Applied Meteorology and Climatology | Year: 2015

A forest canopy model is developed and coupled into the Regional Boundary Layer Model (RBLM) to fully consider the vertical structure of tree morphology. Instead of a slab surface model formerly used to represent trees in RBLM, the new version allows refinement of the radiation budgets as well as sensible and latent heat fluxes and, hence, more precise simulation of the thermal impacts of tree plantings on urban meteorological behavior. By applying this new version of RBLM, sensitivity tests are conducted to explore the potential impacts of different greenery scenarios on the thermal environment in an eastern Chinese city, Suzhou, during hot summer days. Greenings, both tree planting and grass surfacing, are beneficial in cooling the ambient air temperature. In general, tree planting is more beneficial than grass surfacing with the same coverage. In terms of surface energy balance, with tree coverage increasing from0%to 20%, and then to 40%, the average surface net radiation fluxes at noon (1200 LST) are 591, 512, and 421Wm-2, respectively. Correspondingly, the Bowen ratio is reduced from 8.78 to 1.20 and then to 0.43 as result of the redistribution of solar energy absorbed at the ground. The cooling effect of trees is more significant at noontime and can remarkably lower the daily maximum air temperature in urban areas. The cooling effect of urban greenery increases with its coverage. Using the study results, a tree coverage of around 40% may be a feasible and optimized urban greenery scheme. © 2015 American Meteorological Society. Source

Zhang N.,Nanjing University | Zhu L.,Suzhou Meteorological Bureau | Zhu Y.,Suzhou Meteorological Bureau
Advances in Atmospheric Sciences | Year: 2011

A strong urban heat island (UHI) appeared in a hot weather episode in Suzhou City during the period from 25 July to 1 August 2007. This paper analyzes the urban heat island characteristics of Suzhou City under this hot weather episode. Both meteorological station observations and MODIS satellite observations show a strong urban heat island in this area. The maximum UHI intensity in this hot weather episode is 2. 2°C, which is much greater than the summer average of 1. 0°C in this year and the 37-year (from 1970 to 2006) average of 0. 35°C. The Weather Research and Forecasting (WRF) model simulation results demonstrate that the rapid urbanization processes in this area will enhance the UHI in intensity, horizontal distribution, and vertical extension. The UHI spatial distribution expands as the urban size increases. The vertical extension of UHI in the afternoon increases about 50 m higher under the year 2006 urban land cover than that under the 1986 urban land cover. The conversion from rural land use to urban land type also strengthens the local lake-land breeze circulations in this area and modifies the vertical wind speed field. © 2011 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg. Source

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