Achieving accurate simulations of urban impacts on ozone at high resolution

Abstract

The effects of urbanization on ozone levels have been widely investigated over cities primarily located in temperate and/or humid regions. In this study, nested WRF-Chem simulations with a finest grid resolution of 1 km are conducted to investigate ozone concentrations [O 3 ] due to urbanization within cities in arid/semi-arid environments. First, a method based on a shape preserving Monotonic Cubic Interpolation (MCI) is developed and used to downscale anthropogenic emissions from the 4 km resolution 2005 National Emissions Inventory (NEI05) to the finest model resolution of 1 km. Using the rapidly expanding Phoenix metropolitan region as the area of focus, we demonstrate the proposed MCI method achieves ozone simulation results with appreciably improved correspondence to observations relative to the default interpolation method of the WRF-Chem system. Next, two additional sets of experiments are conducted, with the recommended MCI approach, to examine impacts of urbanization on ozone production: (1) the urban land cover is included (i.e., urbanization experiments) and, (2) the urban land cover is replaced with the region's native shrubland. Impacts due to the presence of the built environment on [O 3 ] are highly heterogeneous across the metropolitan area. Increased near surface [O 3 ] due to urbanization of 10-20 ppb is predominantly a nighttime phenomenon while simulated impacts during daytime are negligible. Urbanization narrows the daily [O 3 ] range (by virtue of increasing nighttime minima), an impact largely due to the region's urban heat island. Our results demonstrate the importance of the MCI method for accurate representation of the diurnal profile of ozone, and highlight its utility for high-resolution air quality simulations for urban areas.

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

“…Chemical transport models (CTMs) are increasingly common in simulating atmospheric chemical and transport processes at regional/continental/global scales because of the detailed physical and chemical processes which they are capable of simulating. For example, using a CTM (GFDL AM3), Lin et al (2012) found that Asian O 3 pollutants can affect surface [O 3 ] in the western US, contributing up to 8-15 ppbv to the DMA8; and that Asian pollution increases the DMA8 O 3 exceedance days by 53 % in the southwestern US. Huang et al (2013) combining model simulations at 12 km resolution (WRF/STEM), remote-sensing, and ground-based observations, have studied the effect of Southern California anthropogenic emissions (SoCal) on ozone pollution in southwestern US mountain states.…”

“…We chose WRF-Chem (version 3.5.1) as the CTM since it has been successfully used in this region (Chen et al, 2013;Li et al, 2014;Zhao et al, 2012). 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.…”

“…To overcome this issue, we have used Monotonic Cubic Interpolation to downscale the 4 km resolution NEI05 data to a 1.333 km resolution grid (the finest model grid spacing of our WRF-Chem simulations). Details on the NEI05 downscaling method and improved simulation performance are discussed separately (Li et al, 2014).…”

Impact of future urbanization on a hot summer: a case study of Israel

“…Although the most direct evidence of urbanization, characterized as the urban heat island (UHI) effect, is manifest as higher urban temperatures relative to rural (or undeveloped) areas (Arnfield 2003;Brazel et al 2000;Oke 1973), the effect of cities is more widespread. In addition to their direct alteration of local and regional climates, urban areas increase energy consumption (Salamanca et al 2014), negatively impact human comfort and raise heat stress within already hot environments (Hondula et al 2014;Yang et al 2014), can promote air quality degradation (Georgescu 2015;Li et al 2014), and have profound impacts on indoor thermal environments (Sailor 2014;Taleghani et al 2014). …”

Outdoor thermal comfort by different heat mitigation strategies- A review

“…The most direct effect of UHI is lower thermal comfort of people in urban spaces, where there is no access to air conditioning systems [7][8][9][10][11]. UHI indirectly increases energy consumption for cooling [12,13], reduces the air quality in cities [14][15][16][17][18], and threats the ecosystem by warmer water flowing from the cities [19,20].…”