With harmful ozone concentrations tied to meteorological conditions, EPA investigates the U.S. air quality implications of a changing climate. Consequently, the 03 NAAQS are most often exceeded during summertime hot spells in places with large natural or anthropogenic precursor emissions (e.g., cities and suburban areas). Table 2 The average maximum or minimum temperature and/or changes in their spatial distribution and duration, leading to a change in reaction rate coefficients and the solubility of gases in cloud water solution;The frequency and pattern of cloud cover, leading to a change in reaction rates and rates of conversion of S02to acid deposition;The frequency and intensity of stagnation episodes or a change in the mixing layer, leading to more or less mixing of polluted air with background air;Background boundary layer concentrations of water vapor, hydrocarbons, NOx, and 03, leading to more or less dilution of polluted air in the boundary layer and altering the chemical transformation rates;

[1] The WRF-Chem model, with the added capability of diagnosing the direct radiative forcing of individual aerosol species, is used to characterize the spatial and seasonal distribution of speciated aerosol direct radiative forcing over California. Overall, the simulation in 2005 is able to reproduce the observed spatial and seasonal distribution of total PM 2.5 mass concentration and the relative contribution from individual aerosol species. On statewide average over California, all aerosol species reduce the surface net radiation fluxes, with a total by about 1.5 W m À2 (winter minimum) to 3 W m À2 (summer maximum). Elemental carbon (EC) is the largest contributor in summer (À1.1 W m À2 and 35%), and sulfate is the largest in winter (À0.45 W m À2 and~30%). In the atmosphere, total aerosol introduces a warming effect of about 0.5 W m À2 (winter minimum) to 2 W m À2 (summer maximum). EC and dust contribute about 75 À 95% and 1 À 10% of the total warming through the seasons, respectively. At the top of the atmosphere (TOA), the overall total aerosol direct radiative effect is cooling of À1.0 W m À2 through the seasons, with sulfate as the biggest contributor of À0.4 W m À2 (winter minimum) to À0.7 W m À2(summer maximum). EC produces a TOA warming of up to about 0.7 W m À2 , whereas all other aerosol species produce a TOA cooling. The diagnostic method implemented in WRF-Chem can be applied to other regions to understand the roles of different aerosols in the direct radiative forcing and regional climate.Citation: Zhao, C., L. Ruby Leung, R. Easter, J. Hand, and J. Avise (2013), Characterization of speciated aerosol direct radiative forcing over California,

Abstract. Air pollution is of concern in many parts of California and is impacted by both local emissions and also by pollution inflow from the North Pacific Ocean. In this study, we use the regional chemical transport model WRF-Chem V3.2 together with the global Model for OZone and Related Chemical Tracers to examine the CO budget over California. We include model CO tracers for different emission sources in the models, which allow estimation of the relative importance of local sources versus pollution inflow on the distribution of CO at the surface and in the free troposphere. The focus of our study is on the 15 June-15 July 2008 time period, which coincides with the aircraft deployment of the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) mission over California. Model simulations are evaluated using these aircraft observations as well as satellite retrievals and surface observations of CO.Evaluation results show that the model overall predicts the observed CO fields well, but points towards an underestimate of CO from the fires in Northern California, which had a strong influence during the study period, and towards a slight overestimate of CO from pollution inflow and local anthropogenic sources. The analysis of the CO budget over California reveals that inflow of CO explains on average 99 ± 11 ppbV of surface CO during the study period, compared to 61 ± 95 ppbV for local anthropogenic direct emissions of CO and 84 ± 194 ppbV for fires. In the free Correspondence to: G. G. Pfister (pfister@ucar.edu) troposphere, the average CO contributions are estimated as 96 ± 7 ppbV for CO inflow, 8 ± 9 ppbV for CO from local anthropogenic sources and 18 ± 13 ppbV for CO from fires. Accounting for the low bias in the CO fire emission inventory, the fire impact during the study period might have been up to a factor 4 higher than the given estimates.

Abstract. The impact that changes in future climate, anthropogenic US emissions, background tropospheric composition, and land-use have on summertime regional US ozone and PM 2.5 concentrations is examined through a matrix of downscaled regional air quality simulations, where each set of simulations was conducted for five months of July climatology, using the Community Multi-scale Air Quality (CMAQ) model. Projected regional scale changes in meteorology due to climate change under the Intergovernmental Panel on Climate Change (IPCC) A2 scenario are derived through the downscaling of Parallel Climate Model (PCM) output with the MM5 meteorological model. Future chemical boundary conditions are obtained through downscaling of MOZART-2 (Model for Ozone and Related Chemical Tracers, version 2.4) global chemical model simulations based on the IPCC Special Report on Emissions Scenarios (SRES) A2 emissions scenario. Projected changes in US anthropogenic emissions are estimated using the EPA Economic Growth Analysis System (EGAS), and changes in land-use are projected using data from the Community Land Model (CLM) and the Spatially Explicit Regional Growth Model (SER-GOM). For July conditions, changes in chemical boundary conditions are found to have the largest impact (+5 ppbv) on average daily maximum 8-h (DM8H) ozone. Changes in US anthropogenic emissions are projected to increase average DM8H ozone by +3 ppbv. Land-use changes are projected to have a significant influence on regional air quality due to the impact these changes have on biogenic hydrocarbon emissions. When climate changes and land-use changes are conCorrespondence to: B. Lamb (blamb@wsu.edu) sidered simultaneously, the average DM8H ozone decreases due to a reduction in biogenic VOC emissions (−2.6 ppbv). Changes in average 24-h (A24-h) PM 2.5 concentrations are dominated by projected changes in anthropogenic emissions (+3 µg m −3 ), while changes in chemical boundary conditions have a negligible effect. On average, climate change reduces A24-h PM 2.5 concentrations by −0.9 µg m −3 , but this reduction is more than tripled in the Southeastern US due to increased precipitation and wet deposition.

C limate change is likely to have serious and long-term consequences for public health. Among these are illness and mortality related to heat and worsening air quality In this study we examined the historical relationship between age-and cause-specific mortality rates and heat events at the 99 th percentile of humidex values in the greater Seattle area (King, Pierce and Snohomish counties), Spokane County, the Tri-Cities (Benton and Franklin counties) and Yakima County from 1980 through 2006; the relative risk of mortality during heat events compared with more temperate periods were then applied to population and climate projections for Washington State to calculate number of deaths above the baseline expected to occur during projected heat events in 2025, 2045 and 2085. We also estimated excess deaths due to ground-level ozone concentrations for mid century (2045)(2046)(2047)(2048)(2049)(2050)(2051)(2052)(2053)(2054) in King and Spokane counties. Estimates were based on current (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) ozone measurements and mid-21 st century ozone projections, using estimates from the scientific literature to determine the effect of ozone on overall and cardiopulmonary mortality. For the historical heat analysis, relative risks derived for the greater Seattle area showed a significant dose-response relationship between duration of the heat event and the daily mortality rate for non-traumatic deaths for persons aged 45 and above, typically peaking at four days of exposure to humidex values above the 99 th percentile. Three different warming scenarios were considered, including high, low and moderate estimates. In the greater Seattle area, the largest number of excess deaths in all years and scenarios was predicted for persons aged 65 and above. Under the middle scenario, this age group is expected to have 96 excess deaths in 2025, 148 excess deaths in 2045 and 266 excess deaths in 2085 from all non-traumatic causes. Daily maximum 8 hour ozone concentrations are forecasted to be 16-28% higher in the mid 21 st century [1997][1998][1999][2000][2001][2002][2003][2004][2005][2006]. We estimated that the total non-traumatic ozone mortality rate by mid-century for King County would increase from baseline (0.026 per 100,000; 95% confidence interval 0.013-0.038) to 0.033 (0.017-0.049). For the same health outcome in Spokane County, the baseline period rate was 0.058 (0.030-0.085) and increased to 0.068 (0.035 -0.100) by mid-century. The cardiopulmonary death rate per 100,000 due to ozone was estimated to increase from 0.011 (0.005-0.017) to 0.015 (0.007-0.022) in King County, and from 0.027 (0.013-0.042) to 0.032 (0.015-0.049) in Spokane County. Public health interventions aimed at protecting Washington's population from excessive heat and increased ozone concentrations will become increasingly important for preventing deaths, especially among older adults. Furthermore, heat and air quality related illnesses that do not result in death, but are serious nevertheless, may be r...

[1] The Air Indicator Report for Public Access and Community Tracking (AIRPACT) real-time numerical air quality forecast system operates daily in the Pacific Northwest region to predict hourly ozone, PM 2.5 and related precursor and pollutant species. In an update to the existing AIRPACT forecast system, the MM5/SMOKE/CMAQ Eulerian modeling system replaces the MM5/CALMET/CALGRID model framework. The new system, AIRPACT-3, has a larger domain that encompasses Washington, Oregon, Idaho, and bordering areas. The system includes a highly dynamic emission processing subsystem which incorporates anthropogenic and biogenic emissions, as well as real-time wildfire emission estimates, and a dynamic dairy ammonia emissions module. As an initial evaluation of the system, forecast results were compared against measurement data for the August-November 2004 period. Analyses showed that the system is skillful in predicting episodic ozone conditions (8-h daily maxima) above 50 ppbv, but systematically over-predicts levels less than 40 ppbv. For fine particulate matter, PM 2.5 , the system captures the concentration differences between urban and rural regions, and captures qualitatively the speciated distribution of fine PM 2.5 component concentrations. A separate emission sensitivity study shows the system can adequately simulate the PM pollution impacts from fire events; however, the new dairy ammonia emission module has lesser impact on the overall PM 2.5 forecast performance.

a b s t r a c t A regional modeling system was applied with inputs from global climate and chemistry models to quantify the effects of global change on future biogenic emissions and their impacts on ozone and biogenic secondary organic aerosols (BSOA) in the US. Biogenic emissions in the future are influenced by projected changes in global and regional climates and by variations in future land use and land cover (LULC). The modeling system was applied for five summer months for the present-day case (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999), Case 1) and three future cases covering 2045-2054. Individual future cases were: present-day LULC (Case 2); projected-future LULC (Case 3); and future LULC with designated regions of tree planting for carbon sequestration (Case 4). Results showed changing future meteorology with present-day LULC (Case 2) increased average isoprene and monoterpene emission rates by 26% and 20% due to higher temperature and solar insolation. However when LULC was changed together with climate (Case 3), predicted isoprene and monoterpene emissions decreased by 52% and 31%, respectively, due primarily to projected cropland expansion. The reduction was less, at 31% and 14% respectively, when future LULC changes were accompanied by regions of tree planting (Case 4). Despite the large decrease in biogenic emission, future average daily maximum 8-h (DM8H) ozone was found to increase between þ8 ppbv and þ10 ppbv due to high future anthropogenic emissions and global chemistry conditions. Among the future cases, changing LULC resulted in spatially varying future ozone differences of À5 ppbv to þ5 ppbv when compared with present-day case. Future BSOA changed directly with the estimated monoterpene emissions. BSOA increased by 8% with current LULC (Case 2) but decreased by 45%-28% due to future LULC changes. Overall, the results demonstrated that on a regional basis, changes in LULC can offset temperature driven increases in biogenic emissions, and, thus, LULC projection is an important factor to consider in the study of future regional air quality.

Abstract.A comprehensive numerical modeling framework was developed to estimate the effects of collective global changes upon ozone pollution in the US in 2050. The framework consists of the global climate and chemistry models, PCM (Parallel Climate Model) and MOZART-2 (Model for Ozone and Related Chemical Tracers v.2), coupled with regional meteorology and chemistry models, MM5 (Mesoscale Meteorological model) and CMAQ (Community Multi-scale Air Quality model). The modeling system was applied for two 10-year simulations: 1990-1999 as a present-day base case and 2045-2054 as a future case. For the current decade, the daily maximum 8-h moving average (DM8H) ozone mixing ratio distributions for spring, summer and fall showed good agreement with observations. The future case simulation followed the Intergovernmental Panel on Climate Change (IPCC) A2 scenario together with business-as-usual US emission projections and projected alterations in land use, land cover (LULC) due to urban expansion and changes in vegetation. For these projections, US anthropogenic NO x (NO+NO 2 ) and VOC (volatile organic carbon) emissions increased by approximately 6% and 50%, respectively, while biogenic VOC emissions decreased, in spite of warmer temperatures, due to decreases in forested lands and expansion of croplands, grasslands and urban areas. A stochastic model for wildfire emissions was applied that projected 25% higher VOC emissions in the future. For the global and US Correspondence to: B. Lamb (blamb@wsu.edu) emission projection used here, regional ozone pollution becomes worse in the 2045-2054 period for all months. Annually, the mean DM8H ozone was projected to increase by 9.6 ppbv (22%). The changes were higher in the spring and winter (25%) and smaller in the summer (17%). The area affected by elevated ozone within the US continent was projected to increase; areas with levels exceeding the 75 ppbv ozone standard at least once a year increased by 38%. In addition, the length of the ozone season was projected to increase with more pollution episodes in the spring and fall. For selected urban areas, the system projected a higher number of pollution events per year and these events had more consecutive days when DM8H ozone exceed 75 ppbv.