The Weather Research and Forecasting/Chemistry model （WRF-Chem） was updated by including pho- toexeited nitrogen dioxide （NO2） molecules, heterogeneous reactions on aerosol surfaces, and direct emissions of nitrou...The Weather Research and Forecasting/Chemistry model （WRF-Chem） was updated by including pho- toexeited nitrogen dioxide （NO2） molecules, heterogeneous reactions on aerosol surfaces, and direct emissions of nitrous acid （HONO） in the Carbon-Bond Mechanism Z （CBM-Z）. Five simulations were conducted to assess the effects of each new component and the three additional HONO sources on concentrations of major chemical components. We calculated percentage changes of major aerosol components and concentration ratios of gas NOy （NOyg） to NOy and particulate nitrates （NO3-） to NOy due to the three additional HONO sources in the North China Plain in August of 2007. Our results indicate that when the three additional HONO sources are included, WRF-Chem can reasonably reproduce the HONO observations. Heterogeneous reactions on aerosol surfaces are a key contributor to concentrations of HONO, nitrates （NO3-）, ammonium （NH＋）, and PM2.5 （concentration of particulate matter of ≤2.5 um in the ambient air） across the North China Plain. The three additional HONO sources produced a -5% -20% increase in monthly mean daytime concentration ratios of NO3-/NOy, a -15%- 52% increase in maximum hourly mean concentration ratios of NO3-/NOy, and a -10% -50% increase in monthly mean concentrations of NOx and NH＋ across large areas of the North China Plain. For the Bohai Bay, the largest hourly increases of NO3- exceeded 90%, of NH＋ exceeded 80%, and of PM2.5 exceeded 40%, due to the three additional HONO sources. This implies that the three additional HONO sources can aggravate regional air pollution, further impair visibility, and enhance the incidence of haze in some industrialized regions with high emissions of NOx and particulate matter under favorable meteorological conditions.展开更多
Two parameterization schemes for vertical eddy diffusivity were utilized to investigate their impacts on both the daily and monthly mean concentrations of ozone and NOy, which are the major fractions of the sum of all...Two parameterization schemes for vertical eddy diffusivity were utilized to investigate their impacts on both the daily and monthly mean concentrations of ozone and NOy, which are the major fractions of the sum of all reactive nitrogen species, i.e., NOy=NO＋NO2＋HNO3＋PAN. Simulations indicate that great changes in the vertical diffusivity usually occur within the planetary boundary layer （PBL）. Daily and monthly mean concentrations of NOy are much more sensitive to changes in the vertical diffusivity than those of ozone and ozone and NOy levels only at or in （relatively） clean sites and areas, where long-range transport plays a crucial role, display roughly equivalent sensitivity. The results strongly suggest that a widely-accepted parameterization scheme be selected and the refinement of the model＇s vertical resolution in the PBL be required, even for regional and long-term studies, and ozone only being examined in an effort to judge the model＇s performance be unreliable, and NOy be included for model evaluations.展开更多
The spatial and temporal variations of the vegetation carbon flux in China from 1901 to 2005 were studied using the vegetation net primary production(NPP)values from seven Earth-system models.In addition,the temporal ...The spatial and temporal variations of the vegetation carbon flux in China from 1901 to 2005 were studied using the vegetation net primary production(NPP)values from seven Earth-system models.In addition,the temporal and spatial changes in the nitrogen deposition flux in China were studied using the NHx and NOy fluxes from 1901 to 2005.The relationship between changes in the carbon flux,nitrogen flux and climate was analyzed.The results show that(1)over the past 100 years,NPP in China has shown an upward trend.The average trend coefficient is 0.88 and the NPP distribution trend is generally low in the north and high in the south,with a gradual increase from the northwest to the southeast.Temperature,precipitation and radiation are all conducive to plant growth in the direction of the gradient.The correlation coefficients between the ensemble model mean NPP and temperature,precipitation,longwave radiation and shortwave radiation are 0.88,0.73,0.91 and 0.67,respectively.(2)In the past 100 years,the NHx and NOy fluxes in China have shown an upward trend,with trend coefficients of 0.98 and 0.98,respectively,which pass the 99.9%confidence level of the t-test.NHx and NOy fluxes are also generally low in the north and high in the south,with a gradual increase from the northwest to the southeast in a step-like pattern.(3)The spatial distribution of the correlation coefficients between the NHx and NOy fluxes and air temperature is similar,with only slight differences in values.The spatial distribution of the correlation coefficients between the NHx and NOy fluxes and precipitation is similar in overall pattern,but the pattern is relatively complicated,with a positive-negative-positive-negative-positive pattern occurring across the monsoon region from north to south,and a negative-positive-negative-positive pattern occurring beyond the monsoon region from east to west.(4)The spatial distribution of the correlation coefficients between the NHx and NOy fluxes and NPP shows a generally consistent pattern,but the pattern is re展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 41175105 and 40905055)the Key Project of Chinese Academy of Sciences (Grant No. kzcx1-yw-06-04)
文摘The Weather Research and Forecasting/Chemistry model （WRF-Chem） was updated by including pho- toexeited nitrogen dioxide （NO2） molecules, heterogeneous reactions on aerosol surfaces, and direct emissions of nitrous acid （HONO） in the Carbon-Bond Mechanism Z （CBM-Z）. Five simulations were conducted to assess the effects of each new component and the three additional HONO sources on concentrations of major chemical components. We calculated percentage changes of major aerosol components and concentration ratios of gas NOy （NOyg） to NOy and particulate nitrates （NO3-） to NOy due to the three additional HONO sources in the North China Plain in August of 2007. Our results indicate that when the three additional HONO sources are included, WRF-Chem can reasonably reproduce the HONO observations. Heterogeneous reactions on aerosol surfaces are a key contributor to concentrations of HONO, nitrates （NO3-）, ammonium （NH＋）, and PM2.5 （concentration of particulate matter of ≤2.5 um in the ambient air） across the North China Plain. The three additional HONO sources produced a -5% -20% increase in monthly mean daytime concentration ratios of NO3-/NOy, a -15%- 52% increase in maximum hourly mean concentration ratios of NO3-/NOy, and a -10% -50% increase in monthly mean concentrations of NOx and NH＋ across large areas of the North China Plain. For the Bohai Bay, the largest hourly increases of NO3- exceeded 90%, of NH＋ exceeded 80%, and of PM2.5 exceeded 40%, due to the three additional HONO sources. This implies that the three additional HONO sources can aggravate regional air pollution, further impair visibility, and enhance the incidence of haze in some industrialized regions with high emissions of NOx and particulate matter under favorable meteorological conditions.
基金the National Natural Science Foundation of China （Grant No. 40575068） the National Key Project of Basic Research of China （Grant No. 2005CB422205） the Knowledge Innovation Project of Chinese Academy of Sciences （Grant No. KZCX2-YW-205）.
文摘Two parameterization schemes for vertical eddy diffusivity were utilized to investigate their impacts on both the daily and monthly mean concentrations of ozone and NOy, which are the major fractions of the sum of all reactive nitrogen species, i.e., NOy=NO＋NO2＋HNO3＋PAN. Simulations indicate that great changes in the vertical diffusivity usually occur within the planetary boundary layer （PBL）. Daily and monthly mean concentrations of NOy are much more sensitive to changes in the vertical diffusivity than those of ozone and ozone and NOy levels only at or in （relatively） clean sites and areas, where long-range transport plays a crucial role, display roughly equivalent sensitivity. The results strongly suggest that a widely-accepted parameterization scheme be selected and the refinement of the model＇s vertical resolution in the PBL be required, even for regional and long-term studies, and ozone only being examined in an effort to judge the model＇s performance be unreliable, and NOy be included for model evaluations.
基金supported by the National Natural Science Foundation of China(Grant Nos.41630532&41575093)the National Key Research and Development Program of China(Grant Nos.2016YFA0602501&2018YFA0606004).
文摘The spatial and temporal variations of the vegetation carbon flux in China from 1901 to 2005 were studied using the vegetation net primary production(NPP)values from seven Earth-system models.In addition,the temporal and spatial changes in the nitrogen deposition flux in China were studied using the NHx and NOy fluxes from 1901 to 2005.The relationship between changes in the carbon flux,nitrogen flux and climate was analyzed.The results show that(1)over the past 100 years,NPP in China has shown an upward trend.The average trend coefficient is 0.88 and the NPP distribution trend is generally low in the north and high in the south,with a gradual increase from the northwest to the southeast.Temperature,precipitation and radiation are all conducive to plant growth in the direction of the gradient.The correlation coefficients between the ensemble model mean NPP and temperature,precipitation,longwave radiation and shortwave radiation are 0.88,0.73,0.91 and 0.67,respectively.(2)In the past 100 years,the NHx and NOy fluxes in China have shown an upward trend,with trend coefficients of 0.98 and 0.98,respectively,which pass the 99.9%confidence level of the t-test.NHx and NOy fluxes are also generally low in the north and high in the south,with a gradual increase from the northwest to the southeast in a step-like pattern.(3)The spatial distribution of the correlation coefficients between the NHx and NOy fluxes and air temperature is similar,with only slight differences in values.The spatial distribution of the correlation coefficients between the NHx and NOy fluxes and precipitation is similar in overall pattern,but the pattern is relatively complicated,with a positive-negative-positive-negative-positive pattern occurring across the monsoon region from north to south,and a negative-positive-negative-positive pattern occurring beyond the monsoon region from east to west.(4)The spatial distribution of the correlation coefficients between the NHx and NOy fluxes and NPP shows a generally consistent pattern,but the pattern is re
