Summer ozone concentrations in the vicinity of the Great Salt Lake

John Horel,Ansley Long,Alexander Jacques,John Sohl,Randal Martin,Brian Blaylock,Seth Arens,Erik Crosman

doi:10.1002/asl.680

Abstract

AbstractResidents near the Great Salt Lake in northern Utah, USA have been exposed to ozone levels during recent summers exceeding the current United States National Ambient Air Quality Standard. Accurately forecasting those exceedances has been difficult as a result of the complex meteorological and photochemical processes fostering them. To help improve such forecasts, a low‐cost field study was conducted during summer 2015 to provide comprehensive observations of boundary‐layer ozone concentrations in the context of the prevailing meteorological conditions. A network of surface ozone sensors was supplemented by sensors mounted on vehicles, a public transit light‐rail car, news helicopter, tethered sonde, and unmanned aerial vehicle. The temporal and spatial evolution of boundary‐layer ozone concentrations were compared with the prevailing regional and local meteorological conditions on the basis of gridded operational analyses, surface weather stations, and additional sensors deployed for the field study. High ozone concentrations during June 2015 resulted primarily from local processes while smoke transported from distant wildfires contributed to elevated ozone concentrations during August. The Great Salt Lake influenced ozone concentrations along the Wasatch Front through several mechanisms, most importantly its impact on local wind circulations. The highest ozone concentrations were often found in a narrow zone between the Great Salt Lake and the urban regions to its south and east. Observations from multiple fixed site and mobile platforms during 18–19 August illustrate the complex variations in ozone concentrations as a function of elevation at the surface as well as vertically through the deep boundary layer.

Highlights

Air quality in northern Utah, USA has improved over the past two decades (Simon et al, 2014; Whiteman et al, 2014)
We provide here an overview of the GSLSO3S with initial findings to highlight the complex spatial and temporal fluctuations in ozone commonplace during the summer along the Wasatch Front in the context of the prevailing meteorological conditions
The outcomes of this study exceeded the original goals identified at the outset of the project due to: (1) the unique mix of season-long monitoring of ozone, other pollutants, and surface and boundary layer meteorological conditions; (2) opportunistic observations from sensors onboard diverse mobile platforms; and (3) reliance on real-time communications to help position sensors and evaluate the data collected as the season progressed

Summary

Introduction

Air quality in northern Utah, USA has improved over the past two decades (Simon et al, 2014; Whiteman et al, 2014). While particulates tend to be trapped in low-lying areas of the Wasatch Front during winter, deep boundary layers during summer afternoons combined with local and regional transport of ozone and its precursors can lead to high ozone concentrations both in the valleys and nearby mountains. As a step towards complying with those standards and to address the challenges to forecast ozone levels along the Wasatch Front, the DAQ supported a low-cost field project referred to as the 2015 Great Salt Lake Summer Ozone Study (GSLSO3S). The meteorological conditions favoring elevated ozone concentrations along the Wasatch Front are known (high pressure, light winds, and high temperatures) and the influence on air quality of thermally driven circulations arising from the GSL and nearby mountains is recognized (Doran et al, 2002; Zumpfe and Horel, 2007). We present here a brief introduction illustrating how the Wasatch Front is a natural laboratory to understand the diverse factors affecting ozone production, transport, and destruction in metropolitan areas embedded within complex terrain

The 2015 Great Salt Lake summer ozone study

Initial findings

Summary