DAQ-2024-004527

1

Impacts of the Great Salt Lake on Summer Ozone Concentrations Along the Wasatch Front

Principal Investigator: Professor John Horel
[phone]
[e-mail]
Department of Atmospheric Sciences, University of Utah
135 S 1460 E, Rm 819
Salt Lake City, UT 84112-0110

Project Period: 1 July 2021- 31 December 2022

Report Submitted: 24 March 2023

Aerial view of the wetlands at the southern end of Farmington Bay

N
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Executive Summary

We examined the meteorological factors contributing to elevated ozone concentrations along
the southeastern margins of the Great Salt Lake that may serve as a source region for high
ozone concentrations along the Wasatch Front. Multiple factors were hypothesized to
contribute to elevated ozone in the Farmington Bay region: (1) ozone precursors from the
urban corridor (NOx and VOCs) and local biogenic precursors near freshwater ponds are
transported by the nocturnal land breeze over the playa surfaces; (2) actinic fluxes are elevated
due to the high albedo over exposed playa surfaces; (3) initial development of the lake breeze
concentrates precursors and ozone within the relatively shallow stable lake boundary layer; and
(4) the lake breeze then transports ozone into the nearby urban regions later in the afterno on.

This study tied directly to the overarching goals of the Science for Solutions program to improve
understanding of summertime ozone pollution along the Wasatch Front. The primary foci for
this study were Priority I- Source Contributions to Summer-Time Ozone and Priority V- Air
Exchange Processes and Pollutants Mass Transport. We examined summer ozone exceedances
exacerbated by emission sources and processes near the Farmington Bay region and how air
mass exchanges affect the transport of ozone and its precursors.

Our hypotheses were addressed using existing observations in Salt Lake and Davis counties
during the 2015-2022 summers. Additional sensors were deployed during summer 2022 to fill
gaps in critical locations that have not been sampled adequately before. The core task for this
project was to evaluate from ozone observations and meteorological observations the timing of
buildup in ozone in the southern Farmington Bay region and subsequent transport into Davis
and Salt Lake counties.

Summer 2017 had the highest ozone concentrations across Davis and Salt Lake counties during
the 2015-2022 period. The number of ozone exceedance events during summer 2021 were
nearly as high as those during 2017 in part as a result of nearby and distant wildfires. The
number of exceedances at stations in Davis and Salt Lake counties during summer 2022 were
near the median of such events during the 2015-2022 period with limited impacts from
wildfires.

The diurnal evolution of high ozone events in the Farmington Bay region during summer 2022
have many features in common: high ozone titration overnight followed by very rapid increases
during morning hours; and generally quiescent synoptic meteorological conditions such that
local thermally-forced circulations dominate. Down-valley flows overnight extend through
metropolitan Salt Lake County and often extend across the wetlands south of Farmington Bay.
Downslope flows through the less-urbanized Weber and Davis population centers extend
southwestward and westward respectively into Farmington Bay. Flows reverse to up-valley
through the Salt Lake Valley and eastward in Weber and Davis counties during late
morning/early afternoon coinciding with maximum ozone increases. Lake breezes often
develop from Gilbert Bay and then extend eastward across the Salt Lake Airport region and
southeastward into the Salt Lake Valley.
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Enhanced actinic fluxes due to increased albedo of exposed playa surfaces in the Farmington
Bay region do not appear to be related to enhanced increases in ozone concentrations.
Characteristics of the playa surfaces (wetness, soil type, etc.) affect total shortwave and
ultraviolet radiation albedo. Playa surfaces have substantively lower albedo after rainstorms.
There is no strong connection between the times when higher peak ozone concentrations were
observed and when playa surfaces were dry with higher surface albedos during the summer of
2022. Since our site on the playa was furthest from major point and mobile sources of NOx and
VOC emissions, it is not surprising that ozone concentrations there tended to be lower even
though the underlying surface was more reflective in that region.

We intend to continue examining the data collected as part of this study. Provisional data and
figures are available via the link: https://home.chpc.utah.edu/~u1375211/o3_2022/.
The data and results from this study should be of great utility for future studies of summer
ozone along the Wasatch Front. We have demonstrated the utility of the data available from
the operational Terminal Doppler Weather Radar and research deployments of surface based
remote sensors (sodars, ceilometers) to examine the impacts of complex boundary layer flows
on transport of chemical species affecting ozone along the Wasatch Front.

Future field programs intended to inform State Implementation Plans required for ozone
exceedances along the Wasatch Front should recognize the need to monitor conditions both
continuously throughout the summer season and during intensive field periods that take
advantage of a range of instrumentation. The interplay between emission sources and
photochemical production and destruction of ozone is modulated extensively by a rich mix of
boundary layer processes spanning a wide range of temporal and spatial scales. Considerable
in-situ and remote observational assets are available that can be used to understand the
coupling between atmospheric conditions and chemical processes and to initialize and validate
models used to test strategies required for State Implementation Plans.
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Background and Significance

The Wasatch Front experiences exceedances of the National Ambient Air Quality Standard
(NAAQS) for ozone during summer due to a complex mix of local and remote photochemical
processes. The 2015 Great Salt Lake Summer Ozone Study that was supported by the Division of
Air Quality was a small, yet the most comprehensive, field campaign to understand ozone
concentrations in the vicinity of the Great Salt Lake (Horel et al. 2016a, b). The 2015 Summer
Ozone Study identified that the Farmington Bay region was potentially a source region for high
ozone concentrations in Davis and Salt Lake counties but did not fully explain why that may be
the case. Figure 1 summarizes the variations in ozone concentrations during 16-30 June 2015
when ozone concentrations were high around the Great Salt Lake and along the Wasatch Front
(Long 2016). Nighttime land breezes carry low ozone concentrations towards the lake while
afternoon lake breezes transport much higher ozone concentrations towards the urban
corridor. The concentrations during the afternoon at Bountiful (QBV), SaltAir (QSA), and the
temporary site O3SO2 were consistently some of the highest during the field campaign. Ozone
concentrations in those areas built up rapidly in the late morning. Based on observational data
and modeling, Blaylock et al. (2017a) provided a detailed examination of how a lake breeze
front contributes to transport of high concentrations of ozone from the Farm ington Bay region
southward throughout the Salt Lake Valley.

We hypothesized that multiple factors contribute to elevated ozone in the southern Farmington
Bay region: (1) ozone precursors from the urban corridor (NOx and VOCs) and local biogenic
precursors near freshwater ponds are transported by the nocturnal land breeze over the playa
surfaces; (2) actinic fluxes are elevated due to the high albedo over exposed playa surfaces; (3)
initial development of the lake breeze concentrates precursors and ozone within the relatively
shallow stable lake boundary layer; and (4) the lake breeze then transports ozone into the
nearby urban regions later in the afternoon. VOC precursor emission sources likely include the
refineries nearby in North Salt Lake.

Figure 2 summarizes NOX and VOC emissions for Davis and Salt Lake counties from the
Northern Wasatch Front 2017 Summertime Emissions Inventory estimated for 5 July 2017, a
weekday with high ozone concentrations and record high temperatures over 40 oC
(https://home.chpc.utah.edu/~u0864163/OZONE_public/NWF-SMOKE-Summary-Report.html).
Vehicles and solvents are the leading sources for NOX and VOCs, respectively, in both count ies
with substantively higher emissions from Salt Lake than Davis. The emissions inventory was
derived without considering chemical interactions or meteorological impacts. For context for
our later results, Figure 3 illustrates the interplay between emissions, chemical reactions, and
meteorology at Bountiful (QBV), Davis County on 5 July 2017. Relatively weak easterly winds
after midnight transported moderate levels of background ozone downslope that underwent
titration with the lowest concentrations observed at sunrise. Concentrations peaked during this
hot afternoon when winds were directed from the Farmington Bay region towards Bountiful.
Strong easterly downslope winds that evening brought relatively high background ozone
concentrations downward into the metropolitan area.

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Figure 1. (a and c) Daytime (8 AM – 8 PM) ozone wind roses for 16-30 June 2015. The length
of each of the 16 cardinal direction colored wedges represents the percentage of time the
ozone concentrations fall within each colored range when the wind is blowing from that
direction. (b and d) Nighttime (8PM-8AM) ozone wind roses. From Long (2016)
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The remainder of this report is subdivided into sections beginning with examination of summer
ozone concentrations in the Farmington Bay region during 2015-2020 and followed by more in-
depth analysis of the conditions during summer 2021 and 2022. That includes representative
case studies during both summers, description of data assets deployed during summer 2022,
and results pertaining to the hypotheses on the role of thermally-driven circulations and
reflective underlying surfaces. Data Management for the information collected from th e study
follows.

Figure 3. Evolution of hourly ozone concentrations at Bountiful on 5 July 2017.

Figure 2. NOx and VOC emissions inventory for Davis (DV) and Salt Lake (SL) Counties from the
Northern Wasatch Front 2017 Summertime Emissions Inventory.
0
5
10
15
20
25
30
35
40
45
Road
Mobile
Solvents Point (not
EGU)
NonRoad
Mobile
Other
NonPoint
Rail Airports
Em
i
s
s
i
o
n
s

(
T
o
n
n
s

d
a
y
-1)
DV NOX DV VOC SL NOX SL VOC
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The personnel participating in this study are as follows:

Personnel Level Responsibilities
John Horel PI Project management
and data analysis
Sebastian Hoch CoI Deployment of sensors
on Farmington Bay
playa
Alexander Jacques Staff Data acquisition and
analysis
Colin Johnson Staff Management of field
equipment and analysis
Aaron McCutchan Graduate Student Analysis of TDWR radar
imagery
Nicholas Buckley Undergraduate Assist installation of
field equipment
Nadine Gabriel Undergraduate Examine ozone 2015-
2020
Ashlynn Searer Undergraduate Analyze 2021 ozone
Samuel Jurado Undergraduate Analyze ozone
Alejandra Garcia Undergraduate Analyze 2022 ozone

1. Ozone Concentrations during 2015-2020 Summer Seasons

a) Background
To provide a baseline for understanding ozone concentrations during the 2021 and 2022
summer seasons, the previous six summer seasons (2015-2020) were examined to identify
periods of high ozone concentrations for several sites near the Farmington Bay region and in
the northern portion of Salt Lake County. Data acquisition and methodologies described in this
section were then also applied to ozone concentration data collected during the 2021 and 2022
summer seasons.
b) Data and Methodology
Ozone concentration observations were acquired through observation data API Services made
available from Synoptic Data PBC. For the 2015-2020 summer seasons, provisional observations
from Utah Division of Air Quality sites located in Bountiful (site QBV) and Hawthorne
Elementary School in Salt Lake City (site QHW) were accessed, as well as data from a Federal
Equivalent Method (FEM) 2B Technologies 205 Ozone Monitor located on the University of
Utah campus near the entrance of Red Butte Canyon (site MTMET). Starting with the 2018
summer season, observations from a new Utah Division of Air Quality site located in Rose Park
(site QRP) were also added to this analysis, as Rose Park is often impacted by the thermally-
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driven flows common to the region. Concentrations for each summer season were acquired for
the time period of 1 June to 15 September in order to capture potential late summer season
ozone exceedance episodes.
For each location and year, the ozone concentration dataset was reviewed, and any instances
of clearly erroneous data were removed. The time series data from MTMET were transformed
into hourly averaged time series to better align with the hourly averages produced by the Utah
DAQ sites, as the nominal data reporting frequency of MTMET was every 5 minutes. An 8-hour
averaged time series was then constructed from each hourly time series to align with the
NAAQS for ozone.
Both the 1-hour and 8-hour time series per station per year were run through a series of
statistical algorithms. For each calendar day, several ozone concentration percentiles (0, 25, 50,
75, 90, 100) were computed. Additionally, calendar days were logged if a particular site reached
a maximum ozone concentration greater than several different thresholds (55, 60, 65, 70, 85,
and 105 ppbv) to summarize occurrences of high ozone concentrations.
c) Results and Implications
Tables 1 and 2 provide the percentage of summer days sampled each year where the four sites
eclipsed thresholds of ozone for 8-hour and 1-hour averages respectively. In summary, a
median 11-15% of summer days each year surpassed the current 8 -hour average NAAQS
standard of greater than 70 ppbv. This translates to about 10-14 days each summer season
(June-July-August). However, there can be large variability from season to season, as the
summer of 2017 had over 20% of days surpassing the NAAQS standard for ozone at all four
sites.
Any lowering of the current NAAQS standard from 70 to 65 or 60 ppbv would result in
significant increases of occurrences where such new standards would be surpassed. The
median percentage of days in violation of the standard increases to over 20% if the standard
was 65 ppbv based on past data and would increase to well over one-third of the summer
season if lowered to 60 ppbv. This scenario is illustrated in Figure 4 which shows the daily
maximum 8-hour average ozone concentration for Bountiful (QBV) during the summer of 2020,
where there are several instances falling short of the current NAAQS standard (70 pbbv -
orange dashed line) but surpassing 60 or 65 ppbv.
Statistical occurrences were also computed using 1-hour averages in order to better understand
high ozone event occurrences that might not be adequately captured by the current NAAQS
standard of 8-hour averages, particularly given the large diurnal variability of ozone in this
region due to urban titration that typically occurs overnight. Table 2 provides a similar summary
to Table 1 but instead for hourly averages. In particular, it is noticeable that hourly ozone
concentrations surpass 70 ppbv for 20-32% of days during the summer, which implies that even
if the current NAAQS standard on an 8-hour average isn’t reached, there are still several hours
per day where the ozone concentrations reach a threshold of “unhealthy for sensitive groups”
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during a median 18-30 days each summer. As with the results in Table 1, there can be large
variability from year to year, as the summer of 2017 shows that over half of the season had
days with hourly ozone concentrations reaching 70 ppbv for sites QHW and MTMET, and had
12-20% of days reaching maximum hourly ozone concentrations into the “unhealthy for all”
category (larger than 85 ppbv).
Table 1: Percentage of days (relative to the days sampled) per site per summer season where
the daily maximum 8-hour ozone concentration surpassed the thresholds shown, with
median percentages per site calculated from the yearly totals.
Site QBV Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2015 99 42.4 28.3 13.1 0.0
2016 106 34.9 14.2 7.5 0.0
2017 106 65.1 37.7 22.6 0.0
2018 106 58.5 33.0 13.2 0.9
2019 106 34.9 13.2 4.7 0.0
2020 106 34.0 17.0 11.3 0.0
Median 106 37.3 21.7 11.8 0.0

Site QHW Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2015 106 47.2 30.2 20.8 0.0
2016 101 29.7 16.8 10.9 0.0
2017 106 60.4 42.5 21.7 0.0
2018 104 51.0 26.9 11.5 1.0
2019 106 40.6 23.6 8.5 0.0
2020 103 35.9 21.4 12.6 0.0
Median 105 44.3 25.2 11.9 0.0

Site QRP Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2018 105 33.3 16.2 12.4 1.0
2019 106 60.4 40.6 22.6 0.9
2020 81 48.1 23.5 8.6 0.0
Median 105 37.1 18.1 12.4 1.0

Site
MTMET
Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2015 102 35.3 23.5 12.7 0.0
2016 106 23.6 14.2 6.6 0.0
2017 99 67.7 48.5 27.3 0.0
2018 79 81.0 55.7 32.9 1.3
2020 95 45.3 27.4 15.8 1.1
Median 99 43.4 26.3 15.2 0.0

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Table 2: Percentage of days (relative to the days sampled) per site per summer season where
the daily maximum 1-hour ozone concentration surpassed the thresholds shown, with
median percentages per site calculated from the yearly totals.

Site QBV Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2015 99 59.6 46.5 34.3 11.1
2016 106 50.0 34.0 21.7 3.8
2017 106 84.0 67.0 44.3 12.3
2018 106 71.7 62.3 40.6 5.7
2019 106 50.0 37.7 23.6 2.8
2020 106 52.8 35.8 25.5 6.6
Median 106 54.2 40.6 28.8 6.1

Site QHW Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2015 106 65.1 53.8 32.1 11.3
2016 101 48.5 31.7 19.8 5.9
2017 106 77.4 67.9 52.8 15.1
2018 104 68.3 53.8 37.5 4.8
2019 106 62.3 41.5 26.4 1.9
2020 103 51.5 36.9 24.3 5.8
Median 105 64.3 47.6 29.5 5.7

Site QRP Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2018 105 72.4 57.1 44.8 8.6
2019 106 52.8 34.0 17.9 2.8
2020 81 61.7 44.4 25.9 9.9
Median 105 53.3 34.3 20.0 7.6

Site MTMET Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
2015 102 63.7 44.1 29.4 7.8
2016 106 44.3 32.1 17.9 2.8
2017 99 82.8 69.7 57.6 19.2
2018 79 87.3 79.7 65.8 15.2
2020 95 58.9 50.5 32.6 9.5
Median 99 65.7 48.5 31.3 9.1

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Figure 4: Daily maximum 8-hour average ozone concentrations (blue circles) for Bountiful
(site QBV) calculated from 1 June - 15 September 2020. Dashed lines represent current
NAAQS thresholds for moderate (>55 ppbv - yellow), unhealthy for sensitive groups (>70 -
orange), unhealthy for all (>85 - red), and very unhealthy (>106 - magenta).

2. Results: Ozone Concentrations during 2021-2022 Summer Seasons

a) Introduction
The summer seasons of 2021 and 2022 were analyzed in more detail to (a) compare aggregate
statistics with those provided for 2015-2020, (b) assess the evolution of specific high ozone case
events in the Farmington Bay region with respect to meteorological conditions, and (c)
delineate high ozone events where local and regional wildfire activity were present. Due to
remaining concerns with coronavirus exposure, equipment deployment during summer 2021
was limited to placement of additional remote sensing and air quality equipment at existing
sites. Considerable research equipment was deployed during summer 2022 for additional
measurements of ozone concentrations and planetary boundary layer conditions.
b) Summer 2021 and 2022 Ozone Summary
The same data collection resources, averaging techniques, and occurrence tabulation
methodologies used for the results in Section 2 were executed on data from the same sites for
the two most recent summers. Table 3 depicts the percentage of days (1 June – 15 September)
where 8-hour and 1-hour ozone concentrations eclipsed moderate, unhealthy for sensitive
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groups, and unhealthy for all thresholds. The summer of 2021 produced more days with higher
ozone concentrations compared to the median statistics from 2015-2020.
Table 3: Percentage of days (relative to the days sampled) from 1 June – 15 September 2021
where the daily maximum 8-hour and 1-hour ozone concentrations surpassed the thresholds
shown, with median percentages per site calculated from the yearly totals.
8-Hour Average Ozone 2021
Site ID Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
QBV 106 67.9 47.2 22.6 0.9
QHW 106 67.9 46.2 21.7 1.9
QRP 106 60.4 40.6 22.6 0.9
MTMET 106 72.6 50.9 25.5 0.0

1-Hour Average Ozone 2021
Site ID Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
QBV 106 77.4 66.0 48.1 8.5
QHW 106 81.1 63.2 43.4 8.5
QRP 106 75.5 64.2 42.5 8.5
MTMET 106 84.0 67.0 53.8 10.4

Table 4 provides a similar summary for summer 2022. Statistically, the percentages of high
ozone occurrence days for summer 2022 were closer to the median percentages shown above
for 2015-2020. For example, site QBV recorded an 8-hour average concentration above 70 ppbv
on 11.9% of assessed days during the 2022 study period (2015 -2020 median was 11.8%).
Table 4: Percentage of days (relative to the days sampled) from 1 June – 15 September 2022
where the daily maximum 8-hour and 1-hour ozone concentrations surpassed the thresholds
shown, with median percentages per site calculated from the yearly totals.
8-Hour Average Ozone 2022
Site ID Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
QBV 92 59.8 33.7 12.0 0.0
QHW 77 49.4 27.3 6.5 0.0
QRP 92 42.4 20.7 7.6 0.0
MTMET 92 30.4 12.0 4.3 0.0

1-Hour Average Ozone 2022
Site ID Days
Sampled
% ≥60 ppbv % ≥65 ppbv % ≥70 ppbv % ≥85 ppbv
QBV 92 78.3 58.7 38.0 5.4
QHW 77 66.2 55.8 40.3 6.5
QRP 92 65.2 45.7 32.6 6.5
MTMET 92 65.2 48.9 31.5 3.3

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Figure 5 illustrates the influence of local and regional wildfires upon ozone concentrations
based on simultaneous measurements of ozone, PM2.5 and biomass black carbon
concentrations at the MTMET site during both summers. As will be shown in Section 4, the
impact of wildfires was much greater during the second half of summer 2021. Reviewing those
data with respect to the ozone concentrations recorded at site MTMET, it was found that 61%
of the days where the 8-hour average ozone concentration exceeded 65 ppbv also recorded
PM2.5 and black carbon concentration values that indicated the presence of wildfire smoke.
Initial multi-day smoke episodes were detected from 10-16 July and 24-26 July, though all days
with higher ozone concentrations during August and September 2021 occurred during the
presence of wildfire smoke in the greater Wasatch Front region. A case study of the impacts of
wildfire smoke on ozone concentration during August 6-8 2021 will be presented in Section 4.
Compared to conditions during summer 2021, summer 2022 ozone concentrations were not
heavily influenced by local and regional wildfire smoke. The only period where smoke appeared
to have a larger influence on ozone concentrations in 2022 was from 7 -12 September.

Figure 5. MTMET observations of 8h daily maximum O3 (green dots), PM2.5 (purple line), and
biomass black carbon (red line) during summer 2021 (top) and summer 2022 (bottom) .

During summer 2022, ozone concentrations were collected and analyzed in greater detail from
10-12 permanent and field campaign sites in our region of interest. Figure 6 depicts, on a daily
basis, how many of those reporting sites surpassed 8-hour and 1-hour average ozone
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concentration thresholds for moderate (yellow), unhealthy for sensitive groups (orange), and
unhealthy for all (red) categories.

Figure 6: Count of reporting stations per day from 15 June - 15 September 2022 that
exceeded maximum 8-hour (top) and 1-hour (bottom) average ozone concentrations for the
thresholds defined in the legend below the graph.

Figure 6 highlights the multi-day episodic nature of these higher ozone occurrences during
summer 2022. The first third of the study period (15 June – 15 July) only had two days with at
least one site exceeding an 8-hour average of 70 ppbv. Meteorologically, much of this period
was dominated with an unusually active weather pattern, with several periods of disturbances,
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frontal passages, and strong synoptic flows influencing the region. This resulted in the majority
of days only achieving maximum concentrations that were similar in magnitude to general
“background” levels of ozone, which tend to be lower earlier in the summer. After mid-July the
overall synoptic weather pattern shifted to a pattern more typical of mid -summer months, with
summer monsoon influences taking hold later in the summer. Higher ozone days were seen
more frequently in late July, a few shorter periods in August, and then an extended period in
late August and early September.
Figure 7 provides a summary of ozone exceedances above selected thresholds for the entire
period 2015-2022 in the Davis and Salt Lake County areas. The more “typical” conditions during
summer 2022 are evident in contrast to the higher ozone concentrations in summer 2021 and
2017.

Figure 7: Percentage of summer days from 2015-2022 that exceeded maximum 8-hour
average ozone concentrations for the thresholds defined in the legend below the graphs.

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3. Summer 2022 Data Resources

In order to examine the meteorological conditions in the vicinity of Farmington Bay, we rel y on
the extensive networks of automated sensors that are available in the region (top panel of
Figure 8). Data from these stations are available from Synoptic Data PBC or graphical displays
from https://mesowest.utah.edu/. In addition, the twice-daily NWS rawinsonde launches
provide critical temperature, moisture, and wind profiles through the boundary layer.
Rawinsonde data and images are available from the University of Wyoming:
https://weather.uwyo.edu/upperair/sounding.html.

Surface-based field instrumentation packages were deployed at selected locations during
summer 2022 to augment DAQ and existing University of Utah sensor locations (bottom pa nel of
Figure 8). As shown in the bottom panel of Figure 8, existing sites deployed by the University of
Utah include those on campus (WBB and MTMET), at the Salt Lake landfill (USDR1), and at the
entrance to the Antelope Island causeway (UUSYR). These were supplemented during summer
2022 by sensors located from south to north at UFD15/USDR5, USDR4, and UUPYA that were
installed during the first part of June 2022. Sensors remain deployed during 2023 with the
exception of the sodar at USDR5 and ozone sensor at UUPYA. These sites helped fill critical needs
to sample meteorological conditions and ozone concentrations on the playa surfaces of
Farmington Bay and adjacent wetlands. Table 5 summarizes site location information for stations
referenced in this report. Table 6 provides a summary of measurement parameters collected at
each station.

17

Figure 8. Top: Ongoing meteorological observing sites. Bottom: Existing
DAQ and university sites and additional sensors deployed at locations for
this study.

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Table 5: Summer 2022 Ozone Station Deployment Information Table
2022 Ozone Instrumentation - University of Utah Mesonet (UUNET)
Station ID -
Name Latitude Longitude Elevati
on (ft)
Deployment
Start
Deployment
End Site Description
WBB – UU
William
Browning
Building
40.766230 -111.84755 4728 1997-01-01
T00:00:00Z ongoing Urban, rooftop
MTMET – UU
Mountain
Meteorology
Lab
40.766573 -111.82821 4993 2012-04-26
T00:00:00Z ongoing
urban fringe, near
grasslands,
downslope from
canyon
USDR1 – UU
MiniSodar1 40.748950 -112.03392 5177 2013-07-23
T00:00:00Z ongoing
Industrial,
grassland, 200ft
slope to the west
UUSYR –
Syracuse 41.088470 -112.11880 4216 2017-03-17
T19:46:00Z ongoing urban fringe,
grassland, remote
USDR4 – UU
MiniSodar4 40.902080 -111.93253 4213 2022-06-07
T23:10:00Z
Sodar:
ongoing
Ozone:
removed
2022-09-15
Industrial,
grasslands,
located at water
treatment facility
UUPYA – UU
Playa
Research
41.030280 -112.11750 4987 2022-06-09
T02:13:00Z
Station:
ongoing
Ozone:
removed
2022-09-12
Playa, evaporated
lake bed,
dirt/dust
UFD15 – UU
2022 Ozone
Trailer
40.832010 -111.98509 4216 2022-06-15
T18:15:00Z 2022-09-12
Grassland,
intermittent
wetland, older
playa
USDR5 – UU
MiniSodar5 40.830855 -111.98339 4223 2022-06-23
T18:45:00Z 2022-09-12
Grassland,
intermittent
wetland, older
playa

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Table 6: Summer 2022 Ozone Station Measurement Parameters. Winds include wind speed and
direction, Temp and RH include air temperature and relative humidity, pressure is local station
pressure, and precipitation measured via tipping bucket rain gauge and/or weight based all-
weather precipitation gauges filled with an antifreeze solution.
2022 Ozone Instrumentation - University of Utah MesoNet (UUNET)
Station Name Air Quality Boundary Layer Meteorological Radiation
WBB – UU William
Browning Building - - Wind, Temp, RH,
Pressure, Precipitation
Shortwave:
IN
MTMET – UU
Mountain
Meteorology Lab
Ozone, PM2.5,
Black Carbon Ceilometer Wind, Temp, RH,
Pressure, Precipitation
Shortwave:
IN
USDR1 – UU
MiniSodar1 - Sodar - -
UUSYR – Syracuse - Ceilometer Wind, Temp, Pressure -
USDR4 – UU
MiniSodar4 Ozone Sodar - -
UUPYA – UU Playa
Research Ozone - Wind, Temp, RH,
Pressure, Precipitation
Shortwave:
IN & OUT
UV: IN &
OUT
Longwave:
IN & OUT
UFD15 – UU 2022
Ozone Trailer Ozone - Wind, Temp, RH,
Pressure
Shortwave:
IN & OUT
UV: IN &
OUT
USDR5 – UU
MiniSodar5 - Sodar - -

20

UFD15 and USDR5 Sites
The trailer UFD15 was installed on a playa
surface within the wetlands of the Rudy
Duck Hunting Club (Figure 9). Surface
meteorological weather sensors and a 2B
205 ozone concentration sensor were
mounted on the trailer. Upward and
downward pairs of Apogee shortwave
and ultraviolet radiation sensors
extended out over the reflective playa
surface to provide quantitative
assessment of surface shortwave and
ultraviolet albedo. An Atmospheric
Science Corporation (ASC) Mini-Sodar
unit (USDR5), capable of sensing
boundary layer winds in the lowest few
hundred meters of the atmosphere, was
located ~100 m from the trailer. Figure 10
illustrates a typical wind reversal at this
site between 15-16 UTC (9-10 MDT) on 9
August 2022 from early morning offshore
to late morning onshore flow.

Figure 9. Weather, radiation, and ozone sensors
deployed with up/down pairs of radiation sensors
viewing a playa surface within the wetlands of
Farmington Bay. Sodar, USDR5, was located
nearby. Undergraduates Alejandra Garcia, Sam
Jurado (foreground), undergraduate Nicholas
Buckley (left), staff Colin Johnson and graduate
student Aaron McCutchan (background).

Figure 10. Boundary layer winds at USDR5 during the morning and
afternoon of 9 August 2022 illustrating the wind reversal between 15 -16
UTC from southerly (offshore) winds in the morning to northwesterly
(onshore) winds in the afternoon.
21

USDR4 Site
Another ASC Mini-Sodar unit and 2B 205 ozone
concentration sensor were placed at site USDR4 at
the South Davis Water Treatment Plant immediately
adjacent to Farmington Bay wetlands (Figure 11).
This site was chosen to be close to the QBV DAQ site
in order to evaluate typical conditions downwind of
QBV during night and early morning hours and
upwind of QBV during much of the day. Another
aspect of this site is the likely local VOC emission
resulting from water treatment processes (Byliński
et al. 2019).
UUPYA and UUSYR Sites

Figure 12. Location (star) of UUPYA site on the Farmington Bay playa.

In coordination with a NSF-funded research
project focused on dust production from playa
surfaces, extensive instrumentation was installed
on a 10m tower at the UUPYA site. To support
this project, a 2B 205 ozone sensor and upward
and downward pairs of Apogee shortwave and
ultraviolet radiation sensors were added. The
radiation sensors provide surface shortwave and
ultraviolet albedo representative of the highly
reflective playa surfaces in Farmington Bay. In
addition, a CL31 ceilometer was deployed at an
existing University of Utah site in Syracuse
(UUSYR) to be able to evaluate aerosol
concentrations near the UUPYA site.

Figure 11. ASC mini-sodar located at
USDR4. Similar sodars were in
operation at USDR1 and USDR5.

Figure 13. UUPYA tower on the
Farmington Bay playa. Ozone and
extensive meteorological sensors mounted
on the tower.
22

Terminal Doppler Weather Radar (TDWR)
Examination of boundary layer winds above Farmington Bay during summer 2022 is greatly
aided by the TDWR radar installed directly north of the Salt Lake International Airport . The
TDWR is used to detect hazardous low-level wind shear that affect plane landings and takeoffs.
Data from the C-Band single-pol radar are accessible from cloud providers as part of the NOAA
Open Data Program for the period from Aug 2020 to the present at volume scan intervals of 3 –
6 min and 150 m range resolution. Figure 13 illustrates the result of software developed by M.S.
student Aaron McCutchan to monitor vertical wind profiles near the radar. Radial winds from
scans at multiple elevation angles are available as shown in Figure 24.
CL-31 Ceilometers
CL-31 ceilometers that provide estimates of aerosol backscatter were deployed during the
summer 2022 on the valley floor (USDR1), University of Utah campus on the east bench
(MTMET), and near the Farmington Bay playa (UUSYR). In addition, aerosol backscatter data
remains to be processed from the DAQ Hawthorne site (QHV). Daily time series of aerosol
backscatter as a function of elevation are available at
https://meso1.chpc.utah.edu/ceilometer/. For example, Figure 14 shows aerosol backscatter

Figure 13. Wind speed (shading, m s-1) and horizontal vector wind (wind barbs in m s-1)
during 6 UTC 3 Sep - 6 UTC 4 Sep 2022 in the lowest 1000 m from the TDWR north of the Salt
Lake City Airport.
23

from near the Farmington Bay playa (UUPYA) and southwest of the Salt Lake International
Airport (USDR1) on 3 Sep 2022. The boundary layer depth is estimated to remain lower
throughout the day at UUPYA compared to that evident south of Farmington Bay at USDR1.
Note also the higher aerosol backscatter at UUPYA between 8-10 MDT compared to that at
USDR1.

Figure 14. Aerosol backscatter from ceilometers at UUSYR (top) and USDR1 (bottom) on 3
Sep 2022.

24

Mobile Observations: KSL
Helicopter and TRAX/E-BUS
PM2.5 and ozone concentrations
through the boundary layer are
available when having the sensors
onboard do not affect KSL
helicopter operations (Crosman et
al. 2017). During summer 2022,
one or more flights are available on
36 days (Figure 15). For example,
two flights (near noon and 6 PM
local time ) were available on 3
Sept 2022 (Figure 15). Displays of
the KSL helicopter data are
available from https://utahaq.chpc.
utah.edu/. Additional mobile
observations of PM2.5 and ozone
concentrations from sensors
onboard three light rail cars and 1
E-BUS are also available during
summer 2022 from the same link.
High Resolution Rapid Refresh
(HRRR) Analyses
We have available extensive
capabilities to efficiently access and
evaluate the analyses from the
HRRR operational model (Blaylock
et al. 2017b, 2018; Blaylock and
Horel 2020; Gowan et al. 2022).
Gowan et al. (2022) describe how
the HRRR model output can be
efficiently accessed at no cost now
from the Amazon Web Services (AWS) Open Data program. HRRR model output is archived for
both near-surface fields and for 3-dimensional fields both at pressure levels and in terrain
following coordinates. As will be shown later, the HRRR operational model produces smoke
products that capture the dominant features of large -scale smoke plumes. Beginning with the
release of HRRRv4 in December 2020, the operational HRRR model has included a smoke tracer
(primary PM2.5) and parameterizations of plume rise (Freitas et al. 2010) and satellite-derived
fire radiative2 power (Ahmadov et al. 2017). Ye et al. (2021) summarize exhaustively the
strengths and weaknesses of the HRRR approach to simulating smoke development and

Figure 15. Vertical profiles of ozone concentrations
(green lines) were available aloft from a sensor
onboard the KSL traffic helicopter on 36 days during
summer 2022.
25

transport in comparison to research
models for the 2019 Williams, WA fire.
Fotini et al. (2021) found that the HRRR
model captured well the spread of dense
smoke from California’s 2018 Camp Fire
during the early stages of the fire but
later underestimated smoke
concentrations due to underestimated
satellite-derived fire radiative power.

The HRRR smoke-related products
available at hourly temporal and 3-km
spatial resolution across the contiguous
U.S. during the summer seasons from
2021 to the present are:
• Near-surface (8 m) Smoke Mass
Density (kg m-3)
• Total Column-Integrated Mass
Density kg m-2)
• Fire Radiative Power (MW)
The lack of substantial wildfire impacts
on ozone concentrations during summer
2022 reduced our reliance on HRRR
analyses. We have relied on quick look
displays to help evaluate flow features in
the Farmington Bay region. For example,
Figure 16 illustrates the down-valley to
up-valley 10 m wind reversal between
1700 and 2000 UTC 3 Sep 2022 in the
Salt Lake Valley from the HRRR.

Figure 16. HRRR 10 m vector wind analyses (m s-1)
at 1700 and 2000 UTC 3 Sep 2022.
26

4. Results: Impacts of Wildfire Smoke on Ozone
Concentrations

While the impact of wildfires on ozone production
has been recognized for decades (Jaffe and Widge
2012), there is an increasing body of literature on
the complex impacts of wildfires on ozone
concentrations in urban areas. For example,
Ninneman and Jaffe (2021) highlight that P(O3) on
smoky days is largely driven by local
photochemistry. They further postulate that a
combination of anthropogenic VOC and NOx
reductions would be more effective to decrease
O3 on smoke-free days while NOx reductions
alone would be more effective on smoky days due
to the high VOC levels present in smoke plumes.
Wang et al. (2021) illustrate that vertical mixing
and advection were major drivers of changes in
surface ozone associated with wildfires in the
southeastern U.S. Gao et al. (2020) describe more
generally how aerosols weaken ozone
photochemical production not only at the surface
but also within the lower boundary layer leading
to vertical ozone gradients that may result in
higher amounts of ozone that can be later
entrained back down towards the surface.

The impacts of wildfire smoke on ozone
concentration are strikingly evident during the 5-7
Aug 2021 period in Davis and Salt Lake Counties.
Figure 17 highlights the arrival of the dense smoke
plume from the California Dixie Fire on 6 Aug 2021
on the basis of a MODIS satellite image during the
afternoon and the operational High Resolution
Rapid Refresh (HRRR) vertically-integrated smoke analysis at 16 UTC (10 MDT). Camera imagery
confirms the rapid progression of the dense smoke plume across the Wasatch Front from 9 -11
AM (not shown). As shown in Figure 18, the diurnal variations in Bountiful DAQ ozone (QBV)
and PM2.5 concentrations on the day before (5 Aug) are fairly typical for the summer with
moderate ozone and PM2.5 concentrations in the afternoon. As the smoke plume crossed Davis
County, PM2.5 at QBV spiked at 10 AM 6 Aug and P(O3) flattened during the rest of the morning
when the largest increases typically occur. As smoke continued to blanket the Wasatch Front on
7 Aug, PM2.5 concentrations remained elevated, ozone nocturnal titration was reduced, and
ozone concentrations increased during the afternoon.

Figure 17. Dense smoke from the Dixie
Fire on 6 Aug 2021 from: top- MODIS
during the afternoon and bottom: HRRR
vertically integrated smoke analysis at
16 UTC.
27

The suite of instrumentation near the
mouth of Red Butte Canyon (MTMET)
helps to illustrate in greater detail some
of the processes underway during this
period (Figure 19). As the smoke plume
crossed the Wasatch Front, PM2.5 and
biomass black carbon concentrations
spiked with incoming solar radiation
reduced throughout the rest of the day
leading to reduced P(O3). Reduced
nighttime destruction of ozone arising
from higher background ozone
concentrations due to the Dixie Fire
plume contributed to higher ozone
concentrations on 7 Aug.

The interaction of the local
meteorology on ozone concentrations
during the entire 3-day period is
illustrated in Figure 20. Note the
transport of higher ozone
concentrations from the Farmington
Bay region into Davis County (QBV)
due to the afternoon lake breeze and
the nocturnal transport of low-
moderate background concentrations
from downslope winds at both QBV
and MTMET.

Table 7 focuses on the 30 min when
the smoke plume crossed MTMET
and illustrates the obvious flattening
of P(O3) as a result of the smoke
shading. (Note: the values of PM2.5 >
150 μg m-3 from the Met-One sensor
at MTMET are likely an overestimate
by as much as a factor of 2, a
common deficiency for optical PM
sensors, Delp and Singer 2020.)

Figure 19. Ozone (top), incoming solar radiation
(middle), and PM2.5(bottom) at MTMET from 5-7 Aug
2021.

Figure 18. Ozone (top) and PM2.5 (bottom) at
Bountiful DAQ from 5-7 Aug 2021.
28

Figures 17-20 and Table 7 illustrate the complex
mix of meteorological and photochemical
processes affecting ozone production along the
Wasatch Front. Not surprisingly, the peak smoke
concentration evident in Figure 21 at midnight 16
August 2021 in the Salt Lake Valley due to smoke
drainage from the nearby Parley’s Canyon fire was
not captured at all by the HRRR near-surface or
total column-integrated metrics (not shown). Both
of those products simply depicted widespread
light concentrations of smoke across Utah at that
time. However, distinctive local smoke plumes
present earlier that afternoon were evident in the
HRRR analyses. Hence, establishing the extent to
which the HRRR analyses are useful for local and
remote sources of smoke needs to be assessed in
greater detail than we have to date.

Figure 21. Ozone (left) and PM2.5 (right) at Hawthorne DAQ from 14-16 Aug 2021. The
Parley’s Canyon fire started during the afternoon of the 14th.
Table 7. Change in conditions between
9:45-10:15 MDT 6 Aug 2021 as the smoke
plume crossed MTMET in the Salt Lake
Valley
Time
(MDT)
Solar
(W m-
2)
PM2.5
(μg m-
3)
BLK C
(μg m-
3)
Ozone
(ppb)
9:45 533 9 0.1 42
9:50 550 9 0.0 41
9:55 427 132 .55 42
10:00 402 322 7.6 41
10:05 408 328 12.8 39
10:10 419 324 13.94 37
10:15 425 291 13.04 36

Figure 20. Ozone concentrations as a
function of wind direction for the 3-day
period 5-7 Aug 2021 at QBV (top) and
MTMET (bottom).
29

5. Results: High Ozone
Concentration Case
Studies
Figure 22 highlights the
increase in ozone
concentrations during the
five days with highest peak
ozone concentrations at each
of the sites near Farmington
Bay. While all four sites have
substantive ozone titration
prior to sunrise, the lowest
ozone concentrations at
sunrise are at USDR4 and
highest are at the Bountiful
DAQ site (QBV). The former
may result from the
abundance of VOCs
immediately upstream from
the Davis water treatment
facility and the latter may be
due to downslope transport
of background ozone
concentrations. High ozone
production rates, P(O3), are
evident during all of these
mornings with slight
differences as to when the
peak concentrations occur.
As a general rule, peak
concentrations are observed
roughly an hour later at QBV
than at the other sites, which
could result in part from the
hourly time averaging for
QBV.

The upper panel of Figure 23
overlays the ozone
concentrations at 5 sites in
northern Salt Lake and Davis
Counties on 9 Aug 2022, a
day with some of the highest
ozone concentrations observed during the summer (Figure 22). On this day, northern Utah was

Figure 22. Ozone concentrations during the 5 days with the
highest maximum O3 concentration at: (a) UUPYA; (b) USDR4;
(c) UFD15 and (d) QBV.
30

on the western edge of an upper level ridge that suppressed monsoon moisture from reaching
the area. Afternoon temperatures were very high reaching 37.2oC at the Salt Lake City Airport
(KSLC) and surface winds were driven by local thermally-driven flows due to terrain and Lake.
The lower panels illustrate the availability of ozone observations from mobile light rail cars as
well as the available fixed sites at 6 MDT (left panel) and 22 MDT (right panel) respectively.
Morning concentrations on and near Farmington Bay tend to be lower than those in the urban
Salt Lake Valley. The ozone production rate is high at all locations, but peak concentrations tend
to be lower over the playa and in the wetland regions (UUPYA, UFD15, USDR4, QIP) relative to
the higher peak at Bountiful (QBV).

The onset of lake breeze flows during 3 Sept 2022 are shown in Figure 24. At 11 MDT (17 UTC),
southerly down valley near-surface flows and low ozone concentrations are evident before the
development of the lake breeze originating over Gilbert Bay. Wind confluence over the

Figure 23. Top: Evolution of ozone concentrations on 9 Aug 2022 at 6 sites in northern Salt
Lake and Davis Counties. Bottom left: Wind speed (m s-1) and direction and ozone at 12 UTC
(6 MDT). Bottom right: As in the left panel except for 22 UTC (16 MDT). Full barbs denote 2
m s-1.
31

southern playa surfaces and wetlands of Farmington Bay is evident in the radial winds from the
TDWR radar at this time with northerly winds in the north and southerly flow in the south. Such
flow would tend to concentrate precursor chemicals in this region and possibly lead to
enhanced ozone production rates. Three hours later (14 MDT), northwesterly flows from
Gilbert Bay impinge on the northern end of the Salt Lake Valley and northerly flows extend
across the Salt Lake City Airport from Farmington Bay. The large arrows in Figure 24 help to
illustrate the radial wind directions that define the critical flow features during this period.

Figure 24. Top left: Ozone concentrations and wind at 17 UTC (11 MDT) 3 Sep 2022. Top
right: Radial wind speeds from the TDWR at 0.5o scan angle at 17 UTC. Lower left: As in the
top left except for 20 UTC (14 MDT). Lower right: As in the top right except for 20 UTC.
32

6. Results: Impacts of Surface Reflectance on Ozone Production

Based on the needs expressed by DAQ modelers, we purchased and installed two pairs of UV-A
radiation sensors (300-400 nm) from Apogee Instruments: at the playa (UUPYA) and wetland
playa (UFD15) sites. Underestimates of ozone production identified in recent DAQ simulations
were thought to possibly result from underestimating the albedo of high-intensity UV-A
radiation. As expected, the UUPYA had higher UV-A albedo due to increased reflectance from
the exposed soil surface (see Figure 25). The soil type at UFD15 had higher amounts of clay
leading to lower albedo during the summer than at UUPYA.

Notable in Figure 25 is the extent to which albedo estimates for UV or total shortwave exhibit
similar trends over the summer. Hence, since total shortwave albedo is more commonly
observed, it may be less critical to deploy additional sensors to measure UV albedo. However,
additional work should be done to assess the extent to which the reduce d UV albedo relative to
shortwave albedo is independent of soil type.

Also evident in Figure 25 is the anticipated high sensitivity of albedo to surface wetness and soil
type of playa surfaces (Craft and Horel 2019). The camera and MODIS imagery in Figure 25 for
conditions before and after measurable precipitation provide the context for the sharp drop in
albedo at UUPYA between 11 and 17 July 2020. The smaller drop in albedo at UFD15 likely
results from the originally darker surface due to the higher clay content of the soil.

33

Figure 25. Shortwave (Total) and ultraviolet (UV) albedo at UUPYA
(top) and UFD15 (bottom). Middle frames: Camera and MODIS
images before and after mid-July rain event.
34

7. Recommendations

The data and results from this study should be of great utility for planning future studies of
summer ozone along the Wasatch Front. We have demonstrated the utility of the image
processing required to utilize the images from the operational Terminal Doppler Weather Radar
and research deployments of surface based remote sensors (sodars, ceilometers) to examine
the impacts of complex boundary layer flows on transport of chemical species affecting ozone
along the Wasatch Front.

Future field programs intended to inform State Imp lementation Plans required for ozone
exceedances along the Wasatch Front should recognize the need to monitor conditions
continuously throughout the summer season, and also during intensive field periods that take
advantage of a range of instrumentation. The interplay between emission sources and
photochemical production and destruction of ozone is modulated extensively by a rich mix of
boundary layer processes spanning a wide range of temporal and spatial scales. Considerable
in-situ and remote observational assets are available that can be used to understand the
coupling between atmospheric conditions and chemical processes and to initialize and validate
models used to test strategies required for State Implementation Plans.

8. Data Management

Extensive amounts of publicly-accessible provisional data, quality-controlled data, and figures
generated as part of this project are available via:
https://home.chpc.utah.edu/~u1375211/o3_2022/. Our archive will be maintained and
developed further over the next several years as we intend to continue analyzing data resulting
from this project. For example, comma-delimited files for each sodar are available now at 15
minute time resolution here:
https://home.chpc.utah.edu/~u1375211/o3_2022/data/sodar_data/_Processed/2022_Process
ed/. Images are available to assess sodar data quality as well:
https://home.chpc.utah.edu/~u1426024/SODAR/

35

References

Ahmadov, R., and Coauthors, 2017: Using VIIRS fire radiative power data to simulate biomass
burning emissions, plume rise and smoke transport in a real-time air quality modeling
system. 2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS),
2806–2808.
Blaylock, B., J. Horel, E. Crosman, 2017a: Impact of Lake Breezes on Summer Ozone
Concentrations in the Salt Lake Valley. J. Appl. Meteor. Clim.56, 353-370.
http://journals.ametsoc.org/doi/abs/10.1175/JAMC-D-16-0216.1
Blaylock, B., J. Horel, S. Liston, 2017b: Cloud archiving and data mining of High Resolution Rapid
Refresh Model Output. Computers and Geosciences, 109, 43-50.
doi.org/10.1016/j.cageo.2017.08.005
Blaylock, B., J. Horel, C. Galli, 2018: High-Resolution Rapid Refresh Model Data Analytics Derived
on the Open Science Grid to Assist Wildfire Weather Assessment. Journal of
Atmospheric and Oceanic Technology, 35, 2213-2227.
https://journals.ametsoc.org/doi/abs/10.1175/JTECH-D-18-0073.1
Blaylock, B., J. Horel, 2020: Comparison of Lightning Forecasts from the High -Resolution Rapid
Refresh Model to Geostationary Lightning Mapper Observations. Wea. Forecasting. 35,
401-416. https://journals.ametsoc.org/doi/abs/10.1175/WAF-D-19-0141.1
Byliński, H., J. Gębicki, and J. Namieśnik1, 2019: Evaluation of Health Hazard Due to Emission of
Volatile Organic Compounds from Various Processing Units of Wastewater Treatment
Plant. Int J Environ Res Public Health. 2019 May; 16(10): 1712. doi:
10.3390/ijerph16101712
Craft, K., J. Horel, 2019: Variations in surface albedo arising from flooding and dessication cycles
on the Bonneville Salt Flats, Utah. J. Appl. Meteor. Clim., 58. 773 -785.
https://journals.ametsoc.org/doi/ full/10.1175/JAMC-D-18-0219.1
Crosman, E., A. Jacques, J. Horel, 2017: A Novel Approach for Monitoring Vertical Profiles of
Boundary-Layer Pollutants: Utilizing Routine News Helicopter Flights. Atmospheric
Pollution Research. 8, 828-835. http://dx.doi.org/10.1016/j.apr.2017.01.013
Delp, W, and B. Singer, 2020: Wildfire Smoke Adjustment Factors for Low-Cost and Professional
PM2.5 Monitors with Optical Sensors. Sensors, 20, 3683; doi:10.3390/s20133683
Fotini, K. and coauthors, 2022: High-resolution smoke forecasting for the 2018 Camp Fire in
California. Bull. Amer. Met. Soc. In Press. DOI: https://doi.org/10.1175/BAMS-D-20-
0329.1
Freitas, S. R., K. M. Longo, J. Trentmann, and D. Latham, 2010: Technical Note: Sensitivity of 1-D
smoke plume rise models to the inclusion of environmental wind drag. Atmospheric
Chemistry and Physics, 10 (2), 585–594, doi:https://doi.org/10.5194/acp-10-585-2010,
https://acp.copernicus.org/articles/10/585/2010/
Gao, J. Y. Li, B. Zhu, B. Hu, L. Wang, and F. Bao, 2020: What have we missed when studying the
impact of aerosols on surface ozone via changing photolysis rates? Atmos. Chem. Phys.,
20, 10831–10844, 2020. https://doi.org/10.5194/acp-20-10831-2020
36

Gowan, T. A., J. Horel, A. Jacques, 2022: Using cloud computing to analyze model output
archived in ZARR format. Journal of Atmospheric and Oceanic Technology. DOI:
10.1175/JTECH-D-21-0106.1
Horel, J., E. Crosman, R. Martin, J. Sohl, S. Arens, 2016a: 2015 Great Salt Lake Summer Ozone
Study. Final Report to the Utah Division of Air Quality. 38 pp.
Horel, J., E. Crosman, A. Jacques, B. Blaylock, S. Arens, A. Long, J. Sohl, R. Martin, 2016b:
Influence of the Great Salt Lake on summer air quality over nearby urban areas.
Atmospheric Science Letters, 17, 480-486. doi: 10.1002/asl.680
Jaffe, D.A., and Wigder, N.L., 2012. Ozone production from wildfires: A critical review.
Atmospheric Environment 51, 1–10, doi:10.1016/j.atmosenv.2011.11.063.
Long, A., 2016: Analysis of summer ozone concentration in the salt lake valley . M.S. thesis.
University of Utah. 83pp
Ninneman M., D. Jaffe, 2021: The impact of wildfire smoke on ozone production in an urban
area: Insights from field observations and photochemical box modeling, Atmospheric
Environment 267 (2021) 118764. https://doi.org/10.1016/j.atmosenv.2021.118764
Searer, A., N. Gabriel, John Horel, 2022: Impact of Lake Breezes on Ozone Concentrations Near
The Great Salt Lake from 2015-2020. 2022 AMS Student Conference.
https://ams.confex.com/ams/102ANNUAL/meetingapp.cgi/Paper/397748
Wang, B., Kuang, S., Pfister, G. G., Pour-Biazar, A., Buchholz, R. R., Langford, A. O., &
Newchurch, M. J. (2021). Impact of the 2016 Southeastern US Wildfires on the vertical
distribution of ozone and aerosol at Huntsville, Alabama. Journal of Geophysical
Research: Atmospheres, 126, e2021JD034796. https://doi.org/10.1029/2021JD034796
Ye, X., and coauthors, 2021: Evaluation and intercomparison of wildfire smoke forecasts from
multiple modeling systems for the 2019 Williams Flats fire. Atmos. Chem. Phys., 21,
14427–14469, 2021 https://doi.org/10.5194/acp-21-14427-2021