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Impacts of emissions changes from four potential U.S. CO2 emission reduction policies on 2050 air quality are analyzed using the community multiscale air quality model (CMAQ). Future meteorology was downscaled from the Goddard Institute for Space Studies (GISS) ModelE General Circulation Model (GCM) to the regional scale using the Weather Research Forecasting (WRF) model. We use emissions growth factors from the EPAUS9r MARKAL model to project emissions inventories for two climate tax scenarios, a combined transportation and energy scenario, a biomass energy scenario and a reference case. Implementation of a relatively aggressive carbon tax leads to improved PM2.5 air quality compared to the reference case as incentives increase for facilities to install flue-gas desulfurization (FGD) and carbon capture and sequestration (CCS) technologies. However, less capital is available to install NOX reduction technologies, resulting in an O3 increase. A policy aimed at reducing CO2 from the transportation sector and electricity production sectors leads to reduced emissions of mobile source NOX, thus reducing O3. Over most of the U.S., this scenario leads to reduced PM2.5 concentrations. However, increased primary PM2.5 emissions associated with fuel switching in the residential and industrial sectors leads to increased organic matter (OM) and PM2.5 in some cities. [ABSTRACT FROM AUTHOR]

Heat-related mortality in US cities is expected to more than double by the mid-to-late 21st century. Rising heat exposure in cities is projected to result from: 1) climate forcings from changing global atmospheric composition; and 2) local land surface characteristics responsible for the urban heat island effect. The extent to which heat management strategies designed to lessen the urban heat island effect could offset future heat-related mortality remains unexplored in the literature. Using coupled global and regional climate models with a human health effects model, we estimate changes in the number of heat-related deaths in 2050 resulting from modifications to vegetative cover and surface albedo across three climatically and demographically diverse US metropolitan areas: Atlanta, Georgia, Philadelphia, Pennsylvania, and Phoenix, Arizona. Employing separate health impact functions for average warm season and heat wave conditions in 2050, we find combinations of vegetation and albedo enhancement to offset projected increases in heat-related mortality by 40 to 99% across the three metropolitan regions. These results demonstrate the potential for extensive land surface changes in cities to provide adaptive benefits to urban populations at risk for rising heat exposure with climate change. [ABSTRACT FROM AUTHOR]

Air quality impacts of volatile organic compound (VOC) and nitrogen oxide (NOx) emissions from major sources over the northwestern United States are simulated. The comprehensive nested modeling system comprises three models: Community Multiscale Air Quality (CMAQ), Weather Research and Forecasting (WRF), and Sparse Matrix Operator Kernel Emissions (SMOKE). In addition, the decoupled direct method in three dimensions (DDM-3D) is used to determine the sensitivities of pollutant concentrations to changes in precursor emissions during a severe smog episode in July of 2006. The average simulated 8-hr daily maximum O3concentration is 48.9 ppb, with 1-hr O3maxima up to 106 ppb (40 km southeast of Seattle). The average simulated PM2.5(particulate matter with an aerodynamic diameter <2.5 μm) concentration at the measurement sites is 9.06 μg m−3, which is in good agreement with the observed concentration (8.06 μg m−3). In urban areas (i.e., Seattle, Vancouver, etc.), the model predicts that, on average, a reduction of NOxemissions is simulated to lead to an increase in average 8-hr daily maximum O3concentrations, and will be most prominent in Seattle (where the greatest sensitivity is −0.2 ppb per % change of mobile sources). On the other hand, decreasing NOxemissions is simulated to decrease the 8-hr maximum O3concentrations in remote and forested areas. Decreased NOxemissions are simulated to slightly increase PM2.5in major urban areas. In urban areas, a decrease in VOC emissions will result in a decrease of 8-hr maximum O3concentrations. The impact of decreased VOC emissions from biogenic, mobile, nonroad, and area sources on average 8-hr daily maximum O3concentrations is up to 0.05 ppb decrease per % of emission change, each. Decreased emissions of VOCs decrease average PM2.5concentrations in the entire modeling domain. In major cities, PM2.5concentrations are more sensitive to emissions of VOCs from biogenic sources than other sources of VOCs. These results can be used to interpret the effectiveness of VOC or NOxcontrols over pollutant concentrations, especially for localities that may exceed National Ambient Air Quality Standards (NAAQS). [ABSTRACT FROM AUTHOR]

A recently developed aerosol retrieval algorithm based on O4 slant column densities (SCDs) measured at a visible wavelength (476 nm) was utilized to derive aerosol information (e.g., aerosol optical depth (AOD) and vertical distributions of aerosol extinction coefficients (AECs)) in the lower troposphere during a severe Asian dust period. The MAX-DOAS measurements were carried out at Gwangju, Korea for nearly three months from February through May 2008. Comparison with AOD and surface PM10, measured by collocated sunphotometer and beta gauge sampler, were made to validate the retrieved AODs and AECs in the atmospheric layer surface to 1 km height above ground. On the Asian dust days, temporal variations of the AODs retrieved fromMAX-DOAS measurements show similar patterns, but with reduced magnitudes, to those measured by sunphotometer whereas similar AOD magnitude and temporal variation was observed between MAX-DOAS and sunphotometer measurements during the non-episodic days. Smaller correlation was observed between the surface PM10 and AECs at 0.5 km during the Asian dust period compared to the correlation obtained for the non episodic days. This study demonstrates the ability ofMAX-DOAS as a remote sensing technique for surface aerosol measurements under conditions of homogeneously distributed pollution in the planetary boundary layer. However, for the measurement of significantly enhanced aerosol loads with heterogeneous vertical distribution (e.g., Asian dust), measured AODs and AECs are underestimated at altitudes above 1 km due to decreased sensitivity of MAX-DOAS measurements at high altitudes. [ABSTRACT FROM AUTHOR]