Regional-scale transport of air pollutants: impacts of Southern California emissions on Phoenix ground-level ozone concentrations

Abstract

In this study, WRF-Chem is utilized at high resolution (1.333 km grid spacing for the innermost domain) to investigate impacts of southern California anthropogenic emissions (SoCal) on Phoenix ground-level ozone concentrations ([O 3 ]) for a pair of recent exceedance episodes. First, WRF-Chem control simulations, based on the US Environmental Protection Agency (EPA) 2005 National Emissions Inventories (NEI05), are conducted to evaluate model performance. Compared with surface observations of hourly ozone, CO, NO X , and wind fields, the control simulations reproduce observed variability well. Simulated [O 3 ] are comparable with the previous studies in this region. Next, the relative contribution of SoCal and Arizona local anthropogenic emissions (AZ) to ozone exceedances within the Phoenix metropolitan area is investigated via a trio of sensitivity simulations: (1) SoCal emissions are excluded, with all other emissions as in Control; (2) AZ emissions are excluded with all other emissions as in Control; and (3) SoCal and AZ emissions are excluded (i.e., all anthropogenic emissions are eliminated) to account only for Biogenic emissions and lateral boundary inflow (BILB). Based on the USEPA NEI05, results for the selected events indicate the impacts of AZ emissions are dominant on daily maximum 8 h average (DMA8) [O 3 ] in Phoenix. SoCal contributions to DMA8 [O 3 ] for the Phoenix metropolitan area range from a few ppbv to over 30 ppbv (10-30 % relative to Control experiments). [O 3 ] from SoCal and AZ emissions exhibit the expected diurnal characteristics that are determined by physical and photochemical processes, while BILB contributions to DMA8 [O 3 ] in Phoenix also play a key role.Finally, ozone transport processes and pathways within the lower troposphere are investigated. During daytime, pollutants (mainly ozone) near the Southern California coasts are pumped into the planetary boundary-layer over the Southern California desert through the mountain chimney and pass channel effects, aiding eastward transport along the desert air basins in southern California and finally, northeastward along the lower Gila River basin in Arizona, thereby affecting Phoenix air quality during subsequent days. This study indicates that local emission controls in Phoenix need to be augmented with regional emission reductions to attain the federal ozone standard, especially if a more stringent standard is adopted in the future.

Impacts of agricultural irrigation on ozone concentrations in the Central Valley of California and in the contiguous United States based on WRF-Chem simulations

“…Misenis and Zhang (2010) show that WRF-Chem simulations at 4 km are superior to simulations at 12 km in Houston. Li et al (2015) indicate that model results at 1.33 km resolution are better than at 4 km resolution in simulating air quality in Phoenix and Los…”

“…Because it has been widely and successfully used in this region (e.g., Joe et al, 2014, Li et al 2015, we chose WRF-Chem (version 3.6.1) as the chemicaltransport model. In WRF-Chem, the Weather Research and Forecasting (WRF) model (Skamarock et al, 2008) is employed to resolve atmospheric physics and dynamical processes, while the coupled chemistry (Chem) model is used to simulate chemical processes such as gaseous and aqueous chemical reactions, dispersion, and deposition.…”

Climate change and growing megacities: hazards and vulnerability

“…The main hazards associated with pollutants in urban areas also arise from high concentrations of contaminants from industry, transport and agriculture, as well as particulates arising from natural sources (e.g. wind-blown sand or noxious gases from lakes) (Jacobson, 2012;Li et al 2015Li et al , 2016a, and may cause serious health implications (Pope and Dockery, 2006).…”

“…This is why cities are also becoming more vulnerable to hazards produced by other megacities located upwind and by upwind environmental dangers, such as smoke from burning and pollutants from shipping (e.g. Cheng and Chan, 2012;Lin et al, 2014;Li et al, 2015;Zhang et al, 2011). As cities and clusters of cities, or conurbations, expand, their energy use (Madlener and Sunak, 2011) and pollution emissions increase (Akimoto, 2003).…”

Perfiles verticales de ozono y del coeficiente de extinción: contribución al diagnóstico de la calidad del aire en Segovia

“…A escala regional la orografía puede desempeñar un papel importante. Por ejemplo, los contaminantes emitidos a la baja atmósfera desde el sur de California son canalizados hacia el este por las montañas e impactan en Phoenix donde alteran la calidad de su aire, lo que determina que sean necesarias reducciones regionales de las emisiones si se desean alcanzar ciertos niveles de calidad (Li et al, 2015b).…”