Climate impact on airborne particulate matter concentrations in California using seven year analysis periods

Abstract

Abstract. The effect of global climate change on the annual average concentration of fine particulate matter (PM 2.5 ) in California was studied using a climate-air quality modeling system composed of global through regional models. Output from the NCAR/DOE Parallel Climate Model (PCM) generated under the "business as usual" global emissions scenario was downscaled using the Weather Research and Forecasting (WRF) model followed by air quality simulations using the UCD/CIT airshed model. The system represents major atmospheric processes acting on gas and particle phase species including meteorological effects on emissions, advection, dispersion, chemical reaction rates, gas-particle conversion, and dry/wet deposition. The air quality simulations were carried out for the entire state of California with a resolution of 8-km for the years 2000-2006 (present climate with present emissions) and 2047-2053 (future climate with present emissions). Each of these 7-year analysis periods was analyzed using a total of 1008 simulated days to span a climatologically relevant time period with a practical computational burden. The 7-year windows were chosen to properly account for annual variability with the added benefit that the air quality predictions under the present climate could be compared to actual measurements. The climate-air quality modeling system successfully predicted the spatial pattern of present climate PM 2.5 concentrations in California but the absolute magnitude of the annual average PM 2.5 concentrations were under-predicted by ∼4-39% in the major air basins. The majority of this under-prediction was caused by excess ventilation predicted by PCM-WRF that should be present to the same degree in the current and future time periods so that the net bias introduced into the comparison is minimized.Correspondence to: M. J. Kleeman (mjkleeman@ucdavis.edu) Surface temperature, relative humidity (RH), rain rate, and wind speed were predicted to increase in the future climate while the ultra violet (UV) radiation was predicted to decrease in major urban areas in the San Joaquin Valley (SJV) and South Coast Air Basin (SoCAB). These changes lead to a predicted decrease in PM 2.5 mass concentrations of ∼0.3-0.7 µg m −3 in the southern portion of the SJV and ∼0.3-1.1 µg m −3 along coastal regions of California including the heavily populated San Francisco Bay Area and the SoCAB surrounding Los Angeles. Annual average PM 2.5 concentrations were predicted to increase at certain locations within the SJV and the Sacramento Valley (SV) due to the effects of climate change, but a corresponding analysis of the annual variability showed that these predictions are not statistically significant (i.e. the choice of a different 7-year period could produce a different outcome for these regions). Overall, virtually no region in California outside of coastal + central Los Angeles, and a small region around the port of Oakland in the San Francisco Bay Area experienced a statistically significant change in annual average PM 2.5 concentra...

Water uptake by organic aerosol and its influence on gas/particle partitioning of secondary organic aerosol in the United States

“…Modules used to represent various processes in the model are described elsewhere: transport (Kleeman and Cass, 2001;Hu et al, 2010), gas-phase chemical mechanism (Carter and Heo, 2013), inorganic aerosol thermodynamics (Nenes et al, 1998) and deposition (Kleeman et al, 1997;Mahmud et al, 2010). Here, we only describe updates made to the UCD/CIT model.…”

Sources and contents of air pollution affecting term low birth weight in Los Angeles County, California, 2001–2008

“…Meteorological inputs were prepared using the Weather Research and Forecast (WRF) model version 3.1 (Skamarock et al, 2008). Published papers describe the bulk advection and turbulent diffusion algorithm (Kleeman and Cass, 2001), the dry deposition approach (Kleeman et al, 1997), the vertical advection scheme (Hu et al, 2010), and the wet deposition scheme (Mahmud et al, 2010) used in the model. Every source with a unique emissions inventory code (EIC) in the emissions database was tracked separately through model simulations.…”

Dynamic evaluation of a multi-year model simulation of particulate matter concentrations over Europe

“…So far, most of the PM studies have focused on the United States and, to a lesser extent, Europe (e.g., Racherla and Adams, 2006;Dawson et al, 2007Dawson et al, , 2009Zhang et al, 2008;Avise et al, 2009;Pye et al, 2009;Tagaris et al, 2009;Mahmud et al, 2010;Singh and Palazoglu, 2012;Tai et al, 2010Tai et al, , 2012Kelly et al, 2012), but simulations have typically been limited to a year or several months. The individual effects of various meteorological variables have been examined for the United States by perturbing each meteorological variable separately.…”

“…The results suggest that the strongest effects of changes in meteorology on PM 2.5 concentrations are the effects of temperature, wind speed, absolute humidity, mixing height, and precipitation. According to these studies (Dawson et al, 2007;Mahmud et al, 2010;Galindo et al, 2011), temperature tends to increase average sulfate concentrations and decrease average nitrate and organic concentrations, leading to an overall decrease in PM 2.5 concentrations. Increasing absolute humidity increases nitrate aerosol, which leads to increased PM 2.5 concentrations.…”