Vertical distributions of aerosol optical properties based on aircraft measurements over the Loess Plateau were measured for the first time during a summertime aircraft campaign, 2013 in Shanxi, China. Data from four flights were analyzed. The vertical distributions of aerosol optical properties including aerosol scattering coefficients(σsc), absorption coefficients(σab),Angstr?m exponent(α), single scattering albedo(ω), backscattering ratio(βsc), aerosol mass scattering proficiency(Q sc) and aerosol surface scattering proficiency(Q sc′) were obtained. The mean statistical values of σsc were 77.45 Mm-1(at 450 nm), 50.72 Mm-1(at 550 nm), and32.02 Mm-1(at 700 nm). The mean value of σab was 7.62 Mm-1(at 550 nm). The mean values ofα, βsc and ω were 1.93, 0.15, and 0.91, respectively. Aerosol concentration decreased with altitude. Most effective diameters(ED) of aerosols were less than 0.8 μm. The vertical profiles of σsc,, α, βsc, Q sc and Q sc′ showed that the aerosol scattering properties at lower levels contributed the most to the total aerosol radiative forcing. Both α and βsc had relatively large values, suggesting that most aerosols in the observational region were small particles. The mean values of σsc, α, βsc, Q sc, Q sc′, σab and ω at different height ranges showed that most of the parameters decreased with altitude. The forty-eight hour backward trajectories of air masses during the observation days indicated that the majority of aerosols in the lower level contributed the most to the total aerosol loading, and most of these particles originated from local or regional pollution emissions.
Size-resolved aerosols were continuously collected by a Nano Sampler for 13 days at an urban site in Beijing during winter 2012 to measure the chemical composition of ambient aerosol particles. Data collected by the Nano Sampler and an ACSM(Aerodyne Aerosol Chemical Speciation Monitor) were compared. Between the data sets,similar trends and strong correlations were observed,demonstrating the validity of the Nano Sampler. PM10 and PM2.5concentrations during the measurement were 150.5 ± 96.0 μg/m3(mean ± standard variation)and 106.9 ± 71.6 μg/m3,respectively. The PM2.5/PM10 ratio was 0.70 ± 0.10,indicating that PM2.5dominated PM10. The aerosol size distributions showed that three size bins of 0.5–1,1–2.5 and 2.5–10 μm contributed 21.8%,23.3% and 26.0% to the total mass concentration(TMC),respectively. OM(organic matter) and SIA(secondary ionic aerosol,mainly SO42-,NO3-and NH4+) were major components of PM2.5. Secondary compounds(SIA and secondary organic carbon) accounted for half of TMC(about 49.8%) in PM2.5,and suggested that secondary aerosols significantly contributed to the serious particulate matter pollution observed in winter. Coal burning,biomass combustion,vehicle emissions and SIA were found to be the main sources of PM2.5. Mass concentrations of water-soluble ions and undetected materials,as well as their fractions in TMC,strikingly increased with deteriorating particle pollution conditions,while OM and EC(elemental carbon) exhibited different variations,with mass concentrations slightly increasing but fractions in TMC decreasing.
Kang SunYu QuQiong WuTingting HanJianwei GuJingjing ZhaoYele SunQi JiangZiqi GaoMin HuYuanhang ZhangKeding LuStephan NordmannYafang ChengLi HouHui GeMasami FuruuchiMitsuhiko HataXingang Liu
Simulated regional precipitation,especially extreme precipitation events,and the regional hydrologic budgets over the western North Pacific region during the period from May to June 2008 were investigated with the high-resolution(4-km grid spacing)Weather Research and Forecast(WRF v3.2.1)model with explicit cloud microphysics.The model initial and boundary conditions were derived from the National Centers for Environmental Prediction/Department of Energy(NCEP/DOE)Reanalysis 2 data.The model precipitation results were evaluated against the Tropical Rainfall Measuring Mission(TRMM)Multisatellite Precipitation Analysis 3B42 product.The results show that the WRF simulations can reasonably reproduce the spatial distributions of daily mean precipitation and rainy days.However,the simulated frequency distributions of rainy days showed an overestimation of light precipitation,an underestimation of moderate to heavy precipitation,but a good representation of extreme precipitation.The downscaling approach was able to add value to the very heavy precipitation over the ocean since the convective processes are resolved by the high-resolution cloud-resolving model.Moreover,the water vapor budget analysis indicates that heavy precipitation is contributed mostly by the stronger moisture convergence;whereas,in less convective periods,the precipitation is more influenced by the surface evaporation.The simulated water vapor budgets imply the importance in the tropical monsoon region of cloud microphysics that afects the precipitation,atmospheric latent heating and,subsequently,the large-scale circulation.
A field campaign on air quality was carried out in Shanghai in winter of 2012. The concentrations of NO, NO2, NOx, SO2, CO, and PM2.5increased during haze formation. The average masses of SO42-, NO3-and NH4+were 10.3, 11.7 and 6.7 μg/m3 during the haze episodes, which exceeded the average(9.2, 7.9, and 3.4 μg/m3) of these components in the non-haze days. The mean values for the aerosol scattering coefficient(b sp), aerosol absorption coefficient(b ap) and single scattering albedo(SSA) were 288.7, 27.7 and0.91 Mm-1, respectively. A bi-peak distribution was observed for the mass concentrations of CO, NO, NO2, and NOx. More sulfate was produced during daytime than that in the evening due to photochemical reactions. The mass concentration of NH4+achieved a small peak at noontime. NO3-showed lower concentrations in the afternoon and higher concentrations in the early morning. There were obvious bi-peak diurnal patterns for b sp and b ap as well as SSA. b sp and b ap showed a positive correlation with PM2.5mass concentration.(NH4)2SO4, NH4NO3, organic mass, elemental carbon and coarse mass accounted for 21.7%, 19.3%, 31.0%, 9.3% and 12.3% of the total extinction coefficient during non-haze days, and 25.6%, 24.3%, 30.1%, 8.1% and 8.2% during hazy days. Organic matter was the largest contributor to light extinction. The contribution proportions of ammonium sulfate and ammonium nitrate to light extinction were significantly higher during the hazy time than during the non-haze days.
