Atmospheric & Oceanic Science
Permanent URI for this communityhttp://hdl.handle.net/1903/2264
Formerly known as the Department of Meteorology.
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Item Emissions, Transport, and Evolution of Atmospheric Pollutants from China: An Observational Study(2008-11-20) Li, Can; Dickerson, Russell R.; Li, Zhanqing; Atmospheric and Oceanic Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)China's air pollution issue, a byproduct of recent phenomenal economic growth, has received increasing attention in light of its local and large-scale impacts. I investigated the emissions, transport, and evolution of pollutants from China using measurements near some source regions in northern China in 2005. Surface pollution near Beijing in March was overall heavy but changed dramatically, as passing mid-latitude cyclones led to fast transitions between polluted prefrontal and clean postfrontal conditions. Large differences found between measurements and inventories suggest substantial uncertainties in emission estimates. Small, coal-fired boilers are shown unlikely to be the major source of inventory error; experiments measuring traffic emissions are called for. Ground-level aerosols absorb light and are from both wind-blown dust and anthropogenic emissions. Their effects on climate are to be further studied. Pollutants at higher altitudes are more likely to have large-scale impact than pollutants that remain near the surface. The aircraft campaign in April was among the first efforts to measure the vertical distribution of pollutants over inland China. The largest pollutant levels observed in the free troposphere during the campaign were related to dry convective lofting over an industrial region. This differs from earlier experiments over the Pacific, which recognized the warm conveyor belt (WCB) as the main lofting mechanism. Dry convection over the continent may be followed by WCB lifting as the systems move out over the ocean. Their relative roles are yet to be determined. Analyses of meteorological and satellite cloud data reveal the importance of in-cloud processing in oxidizing SO2 transported behind cold fronts. Through integration of satellite sensors, in-situ measurements, trajectory and chemical transport models, I tracked a pollution plume as it traveled away from source region. The decay of SO2 in the plume over three days was quantified, suggesting an SO2 lifetime of 1-4 d. Formation of sulfate and loss of dust together changed the aerosol loading of the plume. This analysis showcases the potential for employing satellites to trace transport events and pollutant evolution, and highlights the main uncertainties in quantitative application of satellite data.Item Aircraft Observations of Dust and Pollutants over NE China: Insight into the Meteorological Mechanisms of Long-Range Transport(2006) Dickerson, Russell; Li, Can; Li, Zhanqing; Marufu, Lackson; Stehr, Jeffrey; Chen, H.; Wang, P; Xia, X.; Ban, X.; Gong, F.; Yaun, J.; Yang, J.Substantial concentrations of trace gases and aerosols are lofted and carried from Asia over the Pacific producing an inter-hemispheric impact on atmospheric chemistry and climate. The meteorological mechanism leading to this large-scale transport of dust and pollutants remains a major uncertainty in quantifying the global effects of emissions from the developing world. Models and downwind measurements have identified isentropic advection associated with wave cyclones (warm conveyor belt circulation) as an important mechanism. We present data from a case study conducted over Shenyang in NE China as part of EAST-AIRE in April 2005 in which upstream convection, rather than WCB lofting appears to dominate. Observations from instrumented aircraft flights, back trajectories, and satellite images of clouds (GOES) and aerosols (MODIS) are analyzed. In this heavily industrialized and populated region, the warm-sector PBL air ahead of a cold front was highly polluted. In the free troposphere, between ~1000 and 4000 m altitude, concentrations of trace gases and aerosols were lower, but well above background; we measured ~70 ppb O3, ~300 ppb CO, ~2 ppb SO2, and ~ 8x10-5 m-1 aerosol scattering. These observations show that dry (non-precipitating) convection can be an important mechanism for converting local air pollution problems into regional or global atmospheric chemistry problems. Climatological data indicate that spring (MAM) precipitation over NE China is low, about 90 mm compared to 290 mm over the NE US. Cloud cover, however, is similar with cumulus clouds reported about 7% of the time over NE China and about 9% of the time over the NE US suggesting that lofting in dry convective events may be common over NE Asia. Evaluation of models’ convective schemes and further observations near the source regions are called for.