Atmospheric & Oceanic Science Research Works
Permanent URI for this collectionhttp://hdl.handle.net/1903/1596
Formerly known as the Department of Meteorology.
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Item The Urban–Rural Heterogeneity of Air Pollution in 35 Metropolitan Regions across China(MDPI, 2020-07-19) Han, Wenchao; Li, Zhanqing; Guo, Jianping; Su, Tianning; Chen, Tianmeng; Wei, Jing; Cribb, MaureenUrbanization and air pollution are major anthropogenic impacts on Earth’s environment, weather, and climate. Each has been studied extensively, but their interactions have not. Urbanization leads to a dramatic variation in the spatial distribution of air pollution (fine particles) by altering surface properties and boundary-layer micrometeorology, but it remains unclear, especially between the centers and suburbs of metropolitan regions. Here, we investigated the spatial variation, or inhomogeneity, of air quality in urban and rural areas of 35 major metropolitan regions across China using four different long-term observational datasets from both ground-based and space-borne observations during the period 2001–2015. In general, air pollution in summer in urban areas is more serious than in rural areas. However, it is more homogeneously polluted, and also more severely polluted in winter than that in summer. Four factors are found to play roles in the spatial inhomogeneity of air pollution between urban and rural areas and their seasonal differences: (1) the urban–rural difference in emissions in summer is slightly larger than in winter; (2) urban structures have a more obvious association with the spatial distribution of aerosols in summer; (3) the wind speed, topography, and different reductions in the planetary boundary layer height from clean to polluted conditions have different effects on the density of pollutants in different seasons; and (4) relative humidity can play an important role in affecting the spatial inhomogeneity of air pollution despite the large uncertainties.Item The Sensitivity of Modeled Ozone to the Temporal Distribution of Point, Area, and Mobile Emissions in the Eastern US(Elsevier, 2009) Castellanos, Patricia; Ehrman, Sheryl H.; Stehr, Jeffrey W.; Dickerson, Russell R.Ozone remains one of the most recalcitrant air pollution problems in the US. Hourly emissions fields used in air quality models (AQMs) generally show less temporal variability than corresponding measurements. In order to understand how the daily cycle of estimated emissions affects modeled ozone, we analyzed the effects of altering all anthropogenic emissions’ temporal distributions by source group 2 on 2002 summer-long simulations of ozone using the Community Multi-Scale Air Quality Model (CMAQ) v4.5 and the carbon bond IV (CBIV) chemical mechanism with a 12 km grid. We find that when mobile source emissions were made constant over the course of a day, 8-hour maximum ozone predictions changed by ±7 parts per billion by volume (ppbv) in urban areas on days when ozone concentrations greater than 80 ppbv were simulated in the base case. Increasing the temporal variation of point sources resulted in ozone changes of +6 and –6 ppbv, but only for small areas near sources. Changing the daily cycle of mobile source emissions produces substantial changes in simulated ozone, especially in urban areas at night; implications for abatement strategy are discussed.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.