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TO: Texas Air Research Center

FROM: David Allen (PI; [email protected]), Elena McDonald-

Buller (co-PI; [email protected]), and Gary McGaughey

University of Texas at Austin, Center for Energy and

Environmental Resources, Austin, Texas 78758

SUBJECT: Final Report

PROJECT NUMBER: 413UTA0148A

PROJECT TITLE: Emissions inventory evaluations using DISCOVER-

AQ aircraft data

PROJECT PERIOD: September 2013 – July 15, 2015

DATE: June 30, 2015

Introduction and Datasets

The first and second Texas Air Quality Studies documented significant reductions in ambient concentrations of ozone precursors in the Houston-Galveston-Brazoria (HGB) region; however, the studies also revealed significant uncertainties in emission estimates, especially those associated with industrial sources in the Houston Ship Channel (HSC). This project used data collected during September 2013 as part of the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) field campaign to characterize the magnitude and spatial variability in concentrations of selected gas-phase species likely associated, in part, with emissions from HSC industrial sources. One of the primary instrument clusters deployed during DISCOVER-AQ was onboard a NASA P-3 aircraft; measurements included meteorological variables (e.g., temperature, humidity, winds), trace gases such as most reactive nitrogen species, CO, and SO2, as well as various hydrocarbon species (more information at http://www-air.larc.nasa.gov/missions/discover-aq/discover-aq.html).

NASA P-3 Measurements

NASA P-3 flights were performed in Houston on a total on nine days during September 2013 as summarized in Attachment 1. A representative flight track (repeated three times throughout the day on September 25, 2013) is shown in Figure 1. Spirals at eight different locations along the flight track were typically flown between the near-surface and 3.5-4 km above the ground surface (AGL). Each flight circuit included a low altitude, east-west transect of the HSC followed by an upward spiral in the vicinity of Moody Tower over urban Houston. The flights also called for a downward spiral at Channelview (located immediately north of the HSC) followed by a southward low-level leg, a touch-and-go at La Porte Airport, and an upward spiral at Deer Park (immediately south of the HSC). Our analyses focus on measurements collected within four distinct regions within or adjacent to the HSC: the east-west HSC transects (25 in total) and the spiral patterns flown over Channelview (22), Deer Park (22), and Moody Tower (26). The one-second aircraft locations across the nine flight days collected within each of these four regions (as defined for analysis) are shown in Figure 2.

Figure 1. NASA P-3 flight track on September 25, 2013.

Figure 2. One-second P-3 locations (across all nine P-3 flight days during September 2013) grouped into four HSC (or nearby) regions for analysis: the spiral patterns flown over (1) Moody Tower (light blue), (2) Channelview (bright green), and (3) Deer Park (dark blue) as well as the (4) east-west HSC Transects (red).

Attachment 2 presents a summary of the NOAA P-3 datasets that were retrieved and analyzed in support of our work. All retrieved datasets provide measurements at one-second time resolution. The measurements include:

Geographic: altitude, latitude, longitude

Meteorological: mixing ratio, relative humidity, static temperature, potential temperature, wind speed, wind direction

Trace gases: Carbon Dioxide (CO2), *Carbon Monoxide (CO), *Ozone (O3), *Total Reactive Nitrogen (NOy), *Nitrogen Oxide (NO), *Nitrogen Dioxide (NO2), *Sulfur Dioxide (SO2)

Biogenic VOCs: Monoterpenes, Isoprene and its oxidation products MVK_MACR_Crotonaldehyde

Oxygenated VOCs: *acetaldehyde, MEK_butanal, aceticacid_glycoaldehyde, acetone_propanal

Aromatics: *benzene, *toluene, *C8-alkylbenzenes, *C9-alkylbenzenes

Alkenes: *propene (ethylene was not measured)

Other: acetonitrile, formaldehyde

The current study analyzes the P-3 gas phase measurements for a representative subset of species (identified by asterisks above) that are typically associated with HSC industrial source emissions. The investigated species for our work included trace gases associated with combustion (CO, NO, NO2, SO2) in addition to total reactive nitrogen (NOy). Previous field studies have shown substantial emissions of Highly Reactive Volatile Organic Compounds (HRVOCs such as ethylene and propene) from industrial facilities in Houston and surrounding areas (e.g., Washenfelder, et al., 2010; Kim et al, 2011); ethylene was not measured by the P-3 but propene was included for our study. Other analyzed VOCs potentially associated with HSC industrial processes were benzene, toluene, and C8/C9-alkylbenzenes. Finally, in addition to ozone, an oxygenated VOC (acetaldehyde) was included for analysis. Formaldehyde, which may be a primary and/or secondary pollutant associated with HSC industrial emissions, is being intensively investigated in a separate concurrent study to our work (Air Quality Research Program (AQRP) project entitled “Analysis of Airborne Formaldehyde Data Over Houston Texas Acquired During the 2013 DISCOVER-AQ and SEAC4RS Campaigns”; Alan Fried, University of Colorado, more information at http://aqrp.ceer.utexas.edu/aprojectsFY14-15.cfm).

Meteorological Measurements

Measurements from multiple data platforms were utilized to estimate wind speed, wind direction, and boundary layer heights. The P-3 one-second measurements include wind speed and wind direction as well as temperature and specific humidity. The P-3 wind observations are continuously available for the east-west HSC Transects (ref. Figure 2) but are not valid when the aircraft is flying spiral patterns; however, the temperature and humidity measurements obtained within the spirals were sometimes useful for estimating boundary layer heights. Additional sources of wind observations (5-minute averages) were the Deer Park and Channelview Continuous Ambient Monitoring Stations (CAMS) and the observation station located atop University of Houston’s Moody Tower (70 m AGL). Estimates of wind speed and wind direction throughout the lower atmosphere were provided by data collected by the La Porte Radar Wind Profiler (RWP). The La Porte RWP was operational in support of DISCOVER-AQ throughout September 2013 and measurements at this location are typically (but not always) representative of meteorological conditions throughout the HSC region. Recently, hourly estimates of mixing heights have been made available (Daniel Alrick, personal communication). The locations of the aforementioned ground-based meteorological stations are provided in Figure 1.

For the purposes of our study, it was important to analyze wind observations to approximate a predominant wind direction within portions of the mixed layer for the sampling periods and locations of interest. This was accomplished by plotting the aforementioned wind direction measurements encompassing the time period of P-3 HSC data collection (generally 8:00-4:00 CST) for each of the nine flight days. Figure 3 presents an example scatter plot showing the wind directions measured at the various platforms on September 26, 2013. The time periods of data collection within the spirals (“Moody Spiral”, plotted in red; “HSC Spirals”, plotted in grey) are shown as well as the P-3 measured wind directions during the two HSC Transects (plotted in light blue) spanning 11:31:30-11:35:10 CST and 14:00:56-14:04:36 CST. The wind directions between the surface and 1.5 km AGL were relatively consistent across the monitoring locations on this day; for example, directions were 120-160 degrees (corresponding to winds blowing from the southeast and south-southeast) and 110-155 degrees (primarily east-southeast and southeast) during the time periods of the first and second HSC Transects, respectively. Note that the La Porte wind directions at 1.5-2.0 km AGL have a more westerly component compared to the other observations.

Wind direction scatter plots similar to Figure 3 are provided as Attachment 3 for each of the nine flight days. Compared to September 26, 2013, some days were more difficult to characterize because of relatively large spatial (both horizontal and vertical) variability in wind directions throughout the HSC region (e.g., ref. scatter plot graphic for September 25, 2013 in Attachment 3). Large variability might occur, for example, on days with relatively light wind speeds and/or days that had high wind shear (i.e., large changes in wind direction with respect to height AGL) associated with large-scale atmospheric circulation features and/or highly important local phenomena such as the land-sea breeze. When wind directions were analyzed in support of an overall survey of results across many flight days, every attempt was made to incorporate as many sampling periods as possible that had generally appropriate wind flow even if the analyzed prevailing wind direction was not ideal but somewhat variable in space and/or time.

Figure 3. Scatter plot of selected wind direction data on September 26, 2013. The measurement platforms are the La Porte RWP station (“LP” averaged over 4 depths AGL), the east-to-west HSC Transects flown at ~350 m AGL three times a day (shown in light blue), Moody Tower (70 m AGL), and the Deer Park and Channelview CAMS (ground sites). Refer to text for additional discussion of the results shown in Figure 3.

Objectives

This project consists of three major tasks:

(1) For P-3 flight periods, characterize mixing heights and wind directions throughout the HSC region to quantify the spatial variation of concentrations of key pollutants during DISCOVER-AQ;

(2) Analyze P-3 data at specific upwind and downwind locations for representative sampling periods throughout DISCOVER-AQ to calculate concentration enhancements of key pollutants potentially associated with HSC emissions;

(3) Obtain and analyze photochemical modeling developed specifically for the DISCOVER-AQ period and conduct comparisons with P-3 observations.

Results

Average and percentile low-level concentrations

This section presents an overview of low-level concentrations measured within each of the four geographic regions of interest (ref. Figure 2) across the nine P-3 flight days. An analysis of temperature, humidity, and NOy data collected within the HSC/Moody spirals in addition to a review of available hourly estimates of boundary layer heights provided by the La Porte RWP indicates that mixing heights were typically greater than 1 km AGL during the sampling periods of interest. Within the four HSC analysis regions (i.e., HSC Transects; Moody Tower, Channelview, and Deer Park spirals; ref. Figure 2), the P-3 aircraft flew as low as 250m AGL; therefore, for the purposes of summarizing representative boundary layer concentrations, the P-3 measurements collected between 250m and 1km AGL across all flights were utilized. Table 1 presents the average concentrations grouped by region and selected pollutant species. Statistical metrics (minimum/average/maximum/95thpercentile concentrations) were calculated and presented graphically in Figure 4.

Table 1. Average concentrations (ppbv) for selected pollutant species using all available 250-1000m AGL DISCOVER-AQ one-second P-3 measurements within each of the four HSC analysis regions (ref. Figure 2).

Species**

HSC Transects

Moody Tower

Spirals

Channelview

Spirals

Deer Park

Spirals

C8/C9-alkylbenzenes

0.30

0.06

0.08

0.08

Toluene

0.32

0.07

0.09

0.10

Benzene

0.39

0.08

0.14

0.12

Propene

0.89

0.20

0.32

0.31

NO

1.61

0.27

0.36

0.42

Acetaldehyde

1.65

0.64

0.71

0.72

SO2

2.56

0.61

0.54

0.75

NO2

4.57

0.79

1.11

1.19

NOy

9.42

2.68

3.03

3.20

CO

149.84

106.88

111.64

110.85

Ozone

57.49

59.02

59.73

58.80

**All concentrations shown in Table 1 are in units of ppbv.

12

Figure 4. The minimum/median/maximum (indicated by the green boxes), average (plotted using a diamond symbol) and 95th percentile (upper whisker) one-second concentrations for selected gas phase species across all DISCOVER-AQ P-3 flight days within the four HSC analysis regions: (a) HSC Transects, (b) Moody Tower Spirals, (c) Channelview Spirals and (d) Deer Park Spirals.

Because the P-3 sampled each of the four HSC regions multiple times on each of the nine flight days, the sampling within each region for a given day as well as between days was likely often characterized by different meteorological, atmospheric chemical, and (potentially) emissions conditions affecting, for example, both local and long-range transport. As shown in Table 1 and Figure 4, SO2, NO2, and NOy were typically measured at greater absolute concentrations than VOCs (with the exception of acetaldehyde). For example, the 95th percentile concentrations for toluene (propene) range between 0.33 (0.71) ppbv at Moody Tower and 1.05 (2.54) ppbv for HSC Transects. Acetaldehyde concentrations vary between 1.84 ppbv (Moody Tower) and 4.13 ppbv (HSC Transects). The 95th percentile SO2/NO2/NOy concentrations range from a minimum of 2.41 ppbv for SO2 (Channelview) to 26.10 for NOy (HSC Transects).

In contrast to the spirals where sampling was conducted over a relatively localized region and throughout a substantial portion of the mixed layer, the HSC Transects were flown at a relatively low and static level (~300 m AGL) along the full extent of the HSC. During these transects, the P-3 likely intercepted multiple plumes associated with emissions from surrounding ship channel sources regardless of the prevailing (e.g., transport) conditions in the lower atmosphere. As shown in Table 1 and Figure 4, the concentrations for any given statistical metric are greatest within the HSC Transects for all compound species except ozone. Differences could be substantial; for example, the median NOy concentration in the HSC Transects is 6.9 ppbv compared to values of ~1.3 ppbv within each of the three spirals.

The statistical results in Figure 4 indicate that the measurements for a number of species are not normally distributed but show evidence of a skewed distribution towards higher concentrations. This is especially true within the spiral regions; note, for example, that the median Deer Park NO2 concentration is only 0.10 ppbv compared to an average concentration of 1.19 ppbv. A skewed distribution may arise, in part, from the sampling of individual emissions plumes with relatively high concentrations that are distinct from the surrounding atmosphere. Such sampling would be expected given the close proximity to numerous HSC emissions sources; evidence of individual plumes is provided in subsequent sections of this report.

Maximum low-level concentrations

In order to provide information on the most extreme concentrations measured by the P-3, the one-second maximum values across all flight days are presented in Table 2 grouped by HSC region and pollutant species. The times and dates of maximum values (color-coded in Table 2) are often similar among multiple species; a review of the time series of concentration measurements suggests that the P-3 was flying through regions of locally-elevated concentrations suggesting one or more distinct plumes likely emanating from sources within one or more nearby industrial facilities to the P-3 flight track.

Table 2. Maximum one-second concentrations of selected gas phase species within the HSC analysis regions. The measurement times are included and the overall maximum values are bolded. Color-coding is used to indicate when three or more species within a given region had maximum values at similar dates and times.

Species

Maximum One-Second Concentrations (ppbv)

Moody Tower

HSC Transects

Deer Park

Channelview

Ozone

104.14

110.90

132.28

111.77

(m/dd; hh:mm:ss)

9/25; 14:02:29

9/25; 11:35:17

9/25; 15:20:05

9/25; 15:07:30

NO

13.48

38.59

27.88

15.93

(m/dd; hh:mm:ss)

9/13; 8:50:00

9/4; 15:19:07

9/25; 10:23:38

9/4; 10:33:34

NO2

18.87

39.91

55.99

32.72

(m/dd; hh:mm:ss)

9/11; 8:50:46

9/4; 15:19:07

9/25; 10:20:34

9/26; 15:18:39

NOy

37.69

85.75

76.74

46.59

(m/dd; hh:mm:ss)

9/13; 8:50:00

9/4; 15:19:07

9/25; 10:21:03

9/26; 15:18:39

SO2

27.41

140.90

101.03

20.89

(m/dd; hh:mm:ss)

9/12; 14:25:10

9/4; 15:21:58

9/13; 10:07:47

9/4; 10:33:29

CO

419.30

696.89

605.89

408.55

(m/dd; hh:mm:ss)

9/25; 8:53:15

9/4; 15:19:09

9/25; 10:21:04

9/25; 10:14:32

Benzene

1.59

11.93

5.00

7.56

(m/dd; hh:mm:ss)

9/11; 8:51:56

9/6; 10:56:27

9/25; 10:21:03

9/25; 12:44:23

Propene

3.73

29.70

9.67

9.26

(m/dd; hh:mm:ss)

9/11; 8:51:02

9/13; 13:42:47

9/26; 15:24:32

9/12; 15:38:33

Toluene

1.88

13.50

3.96

15.54

(m/dd; hh:mm:ss)

9/11; 8:50:46

9/4; 12:11:34

9/25; 10:21:10

9/4; 10:30:46

C8/C9-Alkylbenzenes

1.30

5.35

3.86

4.11

(m/dd; hh:mm:ss)

9/11; 8:50:55

9/26; 11:35:01

9/25; 10:21:00

9/4; 10:33:30

Over the past decade, HRVOCs such as ethene and propene have been intensively investigated in Houston due to their role in ozone formation. Within the HSC Transects, which have the highest concentrations, there were 4834 valid propene one-second measurements sampled by the P-3 across the nine DISCOVER-AQ flight days; the 95th percentile and 99th percentile concentrations are 2.54 ppbv and 4.18 ppbv with only 29 of the 4834 one-second measurements greater than 5 ppbv.

Figure 5 presents a time series of selected pollutant concentrations for the early afternoon HSC Transect on September 13, 2013 (ref. Table 2). The overall maximum DISCOVER-AQ propene concentration of 29.70 ppbv was measured within the eastern portion of the HSC in a narrow and well-defined plume. A co-located peak in acetaldehyde suggests potential secondary formation of acetaldehyde from the oxidation of propene. A plume of NOy (and other species associated with combustion sources; not shown in Figure 5) was intercepted immediately prior to the propene plume. Multiple plumes of NOy and, to a lesser extent SO2, were sampled along the HSC region (ref. Figure 5) in contrast to the lack of any additional regions of elevated propene (or acetaldehyde) concentrations.

Figure 5. Time series of selected species concentrations (ppbv) measured during the HSC Transect from 13:41:54-13:45:26 CST on September 13, 2013.

The maximum concentrations in Table 2 indicate that a number of species had very high concentrations during the Deer Park spiral flown on the morning of September 25, 2013. The vertical profile of water vapor mixing ratios (ref. Figure 6) suggests multiple distinct atmospheric layers (characterized by different atmospheric moisture values): 0.0-0.2km, 0.2-0.7km, a dry layer at ~0.7-1.2km, and an elevated relatively moister air mass within 1.2-1.5km AGL. (The data shown in Figure 6 collected between the surface and 300m were from a low-level missed approach at La Porte airport flown prior to entering the Deer Park vertical spiral pattern.) A review of wind data (e.g., ref. Attachment 3) indicates very light wind speeds and a generally northwesterly direction throughout the lower atmosphere; the nearly calm winds suggest stable atmospheric conditions that would not be conducive to vigorous vertical mixing. The light northwesterly flow places the Deer Park location immediately downwind of portions of the HSC.

Figure 6. Water vapor mixing ratio (g/kg) measured by the P-3 during 10:18:11-10:24:24 CST on September 25, 2013 (collected within the morning Deer Park spiral pattern).

Vertical concentration profiles for selected pollutant species (ref. Figure 7) indicate a good correspondence of relative changes with respect to height AGL between mixing ratio values and concentrations. For example, NOy, SO2, propene, and benzene are all characterized by relatively high near-surface concentrations, near-zero concentrations within the 700m-1.1km (relatively dry) layer, and a region of relatively higher concentrations at 1.2-1.4km AGL well above the morning mixed layer. Interestingly, the measurements within the 1.2-1.4km AGL layer are suggestive of an elevated but tightly constrained plume; this layer is also characterized by non-zero cloud liquid water (not shown) potentially suggesting condensation associated with steam or perhaps a very thin cloud layer.

Figure 7. Vertical profiles of selected P-3 pollutants during 10:18:11-10:24:24 CST on September 25, 2013 (corresponding to the morning Deer Park spiral).

Upwind/downwind analysis: Channelview and Moody Tower

In order to help quantify the potential impact of HSC emissions on measured concentrations in Houston, data collected in paired sets of Channelview/Moody Tower spirals were investigated. During periods of easterly wind flow in the lower atmosphere, Channelview is generally upwind of the HSC while Moody Tower is located in the downwind area. Changes in concentrations between these upwind and downwind locations would be expected, in part, to be associated with the accumulations of emissions from HSC sources. Because Moody Tower is located in urban Houston, the Moody Tower measurements might also be impacted by emissions from high density urban sources such as nearby and upwind on-road mobile vehicles.

Table 3 presents a summary of the eight sets of paired spirals used for the analysis. The predominant (easterly) low-level wind direction shown in Table 3 for each sampling period was determined based on a review of the wind measurements provided in Attachment 3 during the times of the spirals. Wind speeds during the HSC transects flown immediately prior to the Moody Tower spirals mostly averaged 10-15 mph. The spirals are separated by a distance of ~13 miles and the upwind Channelview spiral was typically flown 1.5 hours prior to the downwind Moody Tower spiral; for reference, transport time for an air parcel between the two locations is ~1 hour assuming an average easterly wind speed of 13 mph.

Table 3. Description of Channelview/Moody Tower paired spirals used for the upwind/downwind analysis.

Paired Spirals #

Date

Channelview

Start (CST)

Moody Tower Start (CST)

Wind Direction

Notes

1

9/6/2013

9:57:57

10:59:30

NE/E

2

9/11/2013

9:57:48

11:34:45

E

3

9/12/2013

9:58:19

11:37:39

ENE

4

9/12/2013

12:41:25

14:20:28

E/ESE

Missing VOC Data

5

9/13/2013

9:52:07

11:23:55

NE/ENE

6

9/13/2013

12:19:34

13:46:01

ENE

7

9/14/2013

9:02:05

10:44:01

NE/ENE

8

9/14/2013

11:48:39

13:08:39

E

The direct comparison of upwind/downwind concentrations averaged between 250-1000m at the Channelview and Moody Tower locations is affected by numerous uncertainties; for example, meteorological conditions that impact vertical mixing and horizontal dispersion and advection of pollutants (e.g., mixing heights, clouds, localized changes in wind speed and direction with respect to height AGL associated with features such as the land/sea breeze) might have substantial spatial and temporal variability between days as well as diurnally. Additionally, the impact of atmospheric chemistry between the spiral locations and along the HSC is not explicitly considered. Therefore, any differences in concentrations between the upwind and downwind locations could be related to a variety of environmental factors in addition to potential impacts from HSC emissions sources.

Figure 8 shows the average concentrations within the eight pairs of spiral for selected species. Ozone concentrations are consistently greater in the downwind spiral (i.e., Moody Tower) and range between 47 ppb and 76 ppb. The relatively higher downwind ozone concentrations are potentially due, in part, to ozone formed from HSC emissions and transported to Moody Tower; however, later time-of-day sampling at Moody Tower also provides more opportunity for enhanced ozone formation (due to daytime atmospheric chemistry) compared to the Channelview location.

The concentrations for the pollutant species other than ozone at Moody Tower indicate that downwind concentrations are often substantially greater compared to the Channelview measurements. SO2 is a likely tracer for industrial source emissions (e.g., combustion sources that burn fuels containing sulfur); note the large downwind enhancements in SO2 concentrations for spiral pairs 2, 4, 5, 7 and 8. Similar downwind enhancements often occur for other pollutant species including those associated with combustion (e.g., NO and NO2) as well as VOCs such as C8/9-alkylbenzenes. Acetaldehyde is present at concentrations greater than 1 ppbv and is consistently greater at the downwind (Moody Tower) location. Sources of acetaldehyde may include both biogenic and anthropogenic sources (Fischer, et al., 2014); in urban areas such as Houston, photochemical degradation of VOCs associated with combustion sources (both mobile and industrial) are likely important contributors especially during the summer season (Luecken et al., 2012).

Figure 8 indicates that the paired spirals flown on the morning of September 14, 2013 (corresponding to spiral pair “7”) had relatively high concentrations for multiple pollutant species. In order to investigate the variability of concentrations throughout the lower atmosphere, Figure 9 shows the vertical profiles of one-second measurements at Channelview (plotted in blue) and Moody Tower (plotted in red). For all species, concentrations are typically greater throughout the lower atmosphere at Moody Tower compared to Channelview with maximum differences often at heights AGL 400-1000m. At Channelview, the greatest concentrations are found at heights less than 600m AGL. An investigation of available meteorological observations suggests mixing heights were relatively lower at Channelview compared to Moody Tower; this difference in mixing heights likely contributes to differences in the vertical profiles of concentrations between the two locations.

Below 1km AGL, the Moody Tower ozone concentrations are substantially greater than those at Channelview with greatest differences exceeding 20 ppb. For other species, rapid increases and decreases in concentrations with respect to height suggest individual source plumes; for example, note the low-level vertical concentration profiles for benzene and NOy at Channelview. A relative peak in Moody Tower SO2 concentrations at ~420m AGL has co-located peaks in acetaldehyde and toluene suggesting potential impacts from HSC emissions.

Figure 8. For the eight paired spirals shown in Table 3, the vertically-averaged 250-1000m AGL concentrations for selected compound species at Channelview (plotted in blue labelled as “upwind”) and Moody Tower (plotted in red labelled as “dnwind”).

Figure 9. Vertical profiles of selected P-3 pollutants on September 14, 2013 for the morning paired spirals “7” (ref. Table 3) at Channelview (plotted in blue) and Moody Tower (plotted in red).

In order to quantify the variability of downwind concentration enhancements across the eight sets of paired spirals between the Channelview and Moody Tower locations, Figure 10 presents the minimum/median/maximum downwind-to-upwind ratios grouped by pollutant. Across all paired datasets, NOy, NO2, CO, acetaldehyde, and ozone are consistently greater at the downwind (i.e., Moody Tower) location. Based on the median ratios, SO2 and toluene (though the latter had concentrations <0.3 ppbv on all days except September 14, 2013) exceed a factor of 2; maximum enhancements larger than 3 occur for combustion source tracer compounds NO, NOy, NO2, and SO2 as well as toluene.

Figure 10. The minimum/median/maximum Moody Tower (downwind) to Channelview (upwind) concentration ratios for selected gas phase species across the eight sets of paired sets of spirals summarized in Table 3.

Upwind/downwind analysis: HSC transects

Because the HSC is oriented along an east/west directional axis, periods of easterly winds within the boundary layer, which are common during Houston summers, would be expected to accumulate emissions from HSC sources as air parcels travel westward. As summarized in Table 4, the P-3 flew twelve east-to-west HSC Transects during periods of generally easterly or east-northeasterly winds in the lower atmosphere; the flights were consistently at low-level altitudes of 250-350m AGL.

Table 4. Description of HSC Transects used for the upwind/downwind analysis.

HSC Transect #

Date

Start (CST)

Stop (CST)

Wind Direction

Notes

1

9/4/2013

12:09:42

12:13:05

E

2

9/6/2013

10:55:29

10:58:49

ENE

3

9/6/2013

13:33:22

13:36:40

ESE

4

9/11/2013

8:46:45

8:50:06

E

5

9/11/2013

11:31:02

11:34:10

E

6

9/11/2013

14:03:53

14:07:16

ESE

7

9/12/2013

8:49:11

8:52:34

ENE

8

9/12/2013

14:16:35

14:19:54

E

9

9/13/2013

11:20:02

11:23:21

ENE

Missing VOC Data

10

9/13/2013

13:41:54

13:45:26

ENE

11

9/14/2013

7:46:36

7:50:03

ENE

12

9/14/2013

13:04:39

13:08:06

E

Missing VOC Data

Across all HSC Transects shown in Table 4, large variability in measured concentrations might be associated with temporal and spatial differences in emissions, chemistry and meteorology; additionally, measured concentrations are highly sensitivity to the spatial locations of important emissions sources along and nearby to the flight track. Specifically, the changes in concentrations along the HSC Transects are likely affected by contributions from specific emissions sources along the flight track as well as a general increase in concentrations associated with downwind accumulation.

In order to quantify changes in concentrations, the 1-second measurement data collected across all days and Transects shown in Table 4 were combined. The concentration measurements were binned using longitude increments of 0.01 degrees (corresponding to a horizontal distance of ~0.96 km at HSC’s latitude). Median concentrations were then calculated for each 0.01 degree longitude bin and pollutant species.

Results grouped by pollutant species are presented in Figure 11; because the x-axis shows longitude, the differences in median concentrations moving right-to-left represent a measure of the central tendency of changes in concentrations moving east-to-west through the HSC. Because a generally linear relationship between concentrations and longitude is often apparent, a linear regression was calculated for each species and the best fit results and R2 values are also displayed in Figure 11.

Figure 11. Binned by 0.01 degree longitude along-track segments, the median one-second concentrations for selected compound species collected in the twelve HSC Transects (ref. Table 4). A best-fit linear regression is also shown.

Figure 11 (continued)

For all pollutant species, there is a strong and obvious tendency for increases moving east-to-west through the HSC. Visually, the weakest relationship occurs for ozone and benzene compared to a more pronounced and continuous westward increase in median concentrations for other species such as CO and acetaldehyde. The coefficients of correlation (“R2”) are displayed in Figure 11 and range from lows of 0.15 for ozone and 0.44 for benzene to 0.85 for acetaldehyde.

Based on the best fit linear regression equations shown in Figure 11, Table 5 quantifies the median concentration values at the eastern (upwind) and western (downwind) ends of the HSC as well as the concentration gradient moving east-to-west between these endpoints. The rate of concentration increases (using the best fit linear regression) varies from 0.05 ppbv/km for ozone and CO to 0.45 ppbv/km for C8/9-alkylbenzenes. The rates of eastern-to-western enhancements for most other compounds range 0.1-0.2 ppbv/km.

Table 5 also provides the ratio of median concentration values between the western and eastern portions of the HSC. For ozone, the median western HSC concentrations are 4.3% greater compared to the eastern values. The west-to-east ratio for NOy is 2; median ratios are 2-3 for most other compounds except toluene (4.3) and C8/9-alkylbenzenes that are 10 times the very low upwind median concentration of 0.031 ppbv.

Table 5. The median HSC concentrations at the eastern and western ends of the HSC Transects (ref. Table 4) using the best fit linear regressions displayed in Figure 11.

Species

Eastern HSC (ppbv)

Western HSC (ppbv)

Western-to-Eastern Ratio

East-to-West Enhancement

(ppbv/km)

O3

55.675

58.087

1.043

0.047

CO

120.734

139.151

1.153

0.052

NO

0.332

1.082

3.259

0.148

NO2

1.512

4.490

2.969

0.134

NOy

4.590

9.394

2.047

0.093

SO2

1.092

3.496

3.200

0.145

Acetaldehyde

0.761

1.788

2.349

0.106

Benzene

0.160

0.397

2.473

0.112

Propene

0.420

0.868

2.068

0.094

Toluene

0.073

0.317

4.341

0.197

C8/9-Alkylbenzenes

0.031

0.313

10.009

0.453

Upwind/downwind analysis: Channelview and Deer Park

In order to help quantify the potential impact of HSC emissions in the immediate vicinity of a portion of the HSC, data collected in paired sets of Channelview/Deer Park spirals were investigated. During periods of northerly wind flow in the lower atmosphere, Channelview is immediately upwind of the HSC and Deer Park is immediately downwind; southerly winds place Channelview downwind of Deer Park. Differences in concentrations between the upwind and downwind locations would be expected, in part, to be associated with impacts from HSC sources. The spirals are separated by a distance of ~7 miles and the Deer Park spiral was typically flown 15-25 minutes after the Channelview spiral. Because the aircraft sampling between locations is relatively similar in time and space, differences in concentrations between the spirals caused by differences in meteorological conditions should be relatively minimal.

Table 6 presents a summary of the fourteen paired spirals used for the analysis. The predominant low-level wind direction shown in Table 6 for each sampling period was determined based on a review of the wind direction measurements provided in Attachment 3. Based on the measurement data collected during the previously flown HSC Transect, wind speeds were mostly greater than 10 mph except on September 25, 2013.

Table 6. Description of Channelview/Deer Park paired spirals used for the upwind/downwind analysis.

Paired Spirals #

Date

Channelview

Start (CST)

Deer Park Start (CST)

Wind Direction

Notes

1

9/4/2013

13:24:25

13:43:35

SE

2

9/6/2013

9:57:57

10:15:52

NE

3

9/11/2013

15:05:47

15:19:14

SE

4

9/12/2013

9:58:19

10:17:49

NE

5

9/13/2013

9:52:07

10:06:39

NE

6

9/14/2013

9:02:05

9:19:23

NE

7

9/24/2013

9:53:54

10:09:24

N

8

9/24/2013

12:19:03

12:33:33

N

9

9/24/2013

14:45:19

15:02:38

N

10

9/25/2013

10:02:19

10:20:01

NW

Nearly calm winds

11

9/25/2013

12:33:20

12:48:14

N

Nearly calm winds

12

9/25/2013

15:02:48

15:17:10

NE

Nearly calm winds

13

9/26/2013

12:39:08

12:53:35

SE

14

9/26/2013

15:02:44

15:23:14

SE

Figure 12 shows the vertically-averaged (250-1000m AGL) concentrations for selected compound species within the fourteen paired HSC spirals shown in Table 6. Ozone concentrations are often but not always greater at the downwind location. For all other species, even though the absolute concentration values are often quite low, downwind concentrations are typically substantially larger compared to the upwind concentrations. SO2 concentrations greater than 2 ppb occur within 10 of the 14 paired spirals; NO concentrations are mostly less than 1.5 ppb. Maximum concentrations of toluene and alkylbenzenes are typically extremely low (<0.2 ppbv) as well as benzene (<0.5 ppbv); six spirals have propene concentrations greater than 1.0 ppbv.

In order to quantify the variability of concentration enhancements potentially associated with HSC emissions across the fourteen paired spirals, Figure 13 summarizes the minimum/median/maximum downwind-to-upwind ratios grouped by pollutant. NO and SO2 are consistently greater at the downwind location. The median downwind-to-upwind ratios exceed a factor of 2 for C8/9-alkylbenzenes, SO2, benzene, NO2, and NO; ratios for NOy, propene, and toluene are ~1.7-1.8. Maximum downwind enhancements greater than 5 occur for more than half the species (propene, toluene, C8/9-alkylbenzenes, SO2, benzene, NO2 and NO) suggesting potentially large impacts associated with HSC emissions.

The greatest downwind-to-upwind concentration enhancements across most species occurred on the morning of September 25, 2013. Vertical concentration profiles for the downwind Deer Park location (ref. Figure 7) demonstrate relatively high concentrations throughout a deep layer between the surface and 600m AGL. Winds were light and variable and generally from the northwest on this day placing portions of the HSC directly upwind of Deer Park; low mixing heights in the morning likely helped to accumulate emissions near the surface for all pollutant species.

Figure 14 shows the vertical profiles of one-second concentrations on the afternoon of September 25, 2013, a period more representative of results across the fourteen paired HSC spirals. Substantially higher concentrations were measured at Deer Park (plotted in red) compared to Channelview (plotted in blue) throughout a deep layer (0.6-2.3km AGL); concentrations are near zero above the mixed layer at both the upwind and downwind locations for all species except ozone.

Two distinct vertical layers of enhanced SO2 concentrations centered at ~750m and 2.1km AGL suggest emissions associated with industrial sources; note the co-located peaks for other compounds including VOC species such as benzene and propene. Figure 15 shows that the highest SO2 concentrations (>5 ppb) are found within the northern portions of the Deer Park spiral. This result suggests that the relatively large diameters of the spiral patterns (~10 km) captures potentially both horizontal and vertical variations associated with nearby and spatially heterogeneous industrial HSC emissions sources. As such, the downwind-to-upwind enhancements calculated from vertically-averaged concentrations would be expected to be sensitive to the sampling of plumes that are not well-mixed throughout the spirals as well as short-term variations in meteorology (e.g., local transport conditions in the lower atmosphere).

Figure 12. For the fourteen paired spirals shown in Table 6, the vertically-averaged 250-1000m AGL concentrations for selected compound species at Channelview and Deer Park (the downwind locations is plotted in red; upwind in blue; refer to Table 6 for the downwind location.)


Figure 13. The minimum/median/maximum downwind-to-upwind concentration ratios for selected gas phase species across the fourteen paired sets of HSC spirals summarized in Table 6.

Figure 14. Vertical profiles of selected P-3 pollutants on September 26, 2013 for the late afternoon paired spirals “14” (ref. Table 6) at Channelview (plotted in red) and Deer Park (plotted in blue).


Figure 15. SO2 concentrations during the September 25, 2013 late afternoon spiral flown at Deer Park.

Comparison of median upwind/downwind concentration ratios across HSC regions

In order to provide a direct comparison of the upwind/downwind results across the three HSC analysis regions, the median downwind-to-upwind concentration ratios are summarized in Figure 16 grouped by pollutant species. The ratios are often lowest for the Channelview/Moody Tower paired spirals and highest for HSC Transects. Results for HSC Transects and the HSC spirals are often similar; for example, the NO and NO2 median ratios are 3.3-3.5 and 2.7-3 compared to 1.4-1.6 at Moody Tower. Benzene and propene ratios are ~1 at Moody Tower compared to 2.4-2.5 and 1.8-2.1 for the HSC spirals and HSC Transects, respectively. The median downwind-to-upwind ratios for toluene, acetaldehyde and C8/9-alkybenzenes are far greater for HSC Transects compared to the paired sets of spirals suggesting substantial along-wind enhancement of concentrations at relatively low-levels in the boundary layer for these compounds compared to the results for spirals that vertically span a substantially deeper portion of the lower atmosphere.

Figure 16. Comparison of median downwind-to-upwind concentration ratios (ref. Figure 10, Figure 13, and Table 6) between the three HSC analysis regions.

Comparison to predictions from photochemical modeling

Concurrent with the analyses of P-3 observational data performed for our project, efforts to develop a Community Multi-scale Air Quality (CMAQ) episode covering September 2013 were being led by DISCOVER-AQ project scientist Kenneth Pickering (NASA Goddard Space Flight Center). The development of the CMAQ application incorporated results from the Weather Research and Forecasting (WRF) meteorological modeling developed in support of an AQRP project entitled “Emission Source region contributions to a high surface ozone episode during DISCOVER-AQ” (Loughner and Follette-Cook, 2015). As of June 2015, evaluation of the CMAQ and WRF modeling applications continues (e.g., Fried and Loughner, 2015). Details on the final configuration of the WRF and CMAQ applications, as well as any refinements to the HSC emissions inventory performed by the AQRP research teams, will be described in the final reports due to be submitted to AQRP later this summer.

Figure 17 shows the WRF/CMAQ nested domains with horizontal resolutions of 36, 12, and 4 km. Simulations are also being developed for a nested 1km grid domain covering the Houston area (not shown in Figure 17) that were not available at the time of our analysis. We used the latest CMAQ predictions on the 4km grid domain (obtained from Christopher Loughner in March 2015) for comparison to P-3 observations during the eight paired spirals flown on September 24-26, 2013; as summarized in Table 6, winds placed the Channelview and Deer Park locations directly upwind/downwind of portions of the nearby HSC on these days. Because September 25th and 26th had relative high maximum ozone concentrations (124 ppb and 89 ppb, respectively; ref. Attachment 1), these days are the focus of intensive investigation by DISCOVER-AQ investigators.

Figure 18 presents the one-second P-3 sampling locations within the DISCOVER-AQ Channelview and Deer Park spiral patterns. An overlay of a portion of the CMAQ 4km grid domain has also been included in Figure 18. At each spiral location, the P-3 mostly flew within four adjacent 4km grid cells (refer to the black box outlines in Figure 18).

Figure 17. Locations of the 36km, 12km, and 4km grid domains used in the WRF modeling (Source: http://aqrp.ceer.utexas.edu/projectinfoFY14_15/14-004/14-004%20Scope.pdf).

Figure 18. One-second P-3 locations (across all nine P-3 flight days during September 2013) for the Channelview (bright green) and Deer Park (dark blue) spiral patterns as well as an overlay of a portion of the 4km CMAQ grid (in red).

A detailed comparison of the CMAQ-predicted and P3-observed concentrations revealed that CMAQ was mostly characterized by an under-prediction bias at both the upwind and downwind spiral locations. For the purposes of an overall comparison of CMAQ and P-3 results, the model predictions were extracted for the grid cell (of the four adjacent grid cells within each spiral pattern) that had the highest vertically-averaged (250-1000m AGL) concentration for each pollutant of interest. Figure 19 compares the vertically-averaged (250-1000m AGL) upwind/downwind concentrations using the P-3 and CMAQ datasets. For each pollutant species, results are provided for each of the eight sets of paired HSC spirals flown during September 24-26, 2013.

As shown in Figure 19a, ozone concentrations are predicted too high for the first two sets of spirals flown on September 24, 2013 and the late afternoon spirals on September 26, 2013; the observed very high ozone concentrations on the afternoon of September 25, 2013 (spiral pairs “11” and “12”) are substantially under-predicted by CMAQ. Across all spirals, the predicted ozone concentrations also have less variability compared to observations. For all other pollutant species, the CMAQ predicted concentrations are generally lower than observed with the exception of acetaldehyde.

Figure 19. For the eight paired spirals shown in Table 6 flown September 24-26, 2013, the vertically-averaged 250-1000m AGL observed (P-3) and simulated (CMAQ) concentrations for selected compound species at Channelview and Deer Park (For each paired set of spirals the upwind values are presented first; CMAQ is plotted in red; P-3 in blue.)


The results for NO and NO2 shown in Figure 19 demonstrate that concentrations are consistently under-predicted at the upwind and downwind locations while the upwind NOy concentrations were sometimes more similar to observations (e.g., refer to September 24, 2013 spirals “7-9” and September 26, 2013 spirals “13-14”). Vertical profiles were investigated for NOy that assumed the grid cell (of the four adjacent cells at the upwind location) with the lowest CMAQ concentrations was representative of upwind conditions while the grid cell at the downwind location with the highest concentrations was representative of downwind conditions. Figure 20 presents the upwind and downwind vertical profiles of both observed and predicted NOy concentrations for the late afternoon paired spirals on September 26, 2013. Although the CMAQ downwind concentrations are slightly greater throughout a deep layer between the surface and 2km AGL compared to the CMAQ upwind concentrations, the predicted differences in upwind/downwind concentrations are much lower than observed.

The predictions for CO (ref. Figure 19f) show little consistency between predicted and observed concentrations with large under-prediction of the highest concentrations on September 25, 2013. In contrast, the SO2 results (ref. Figure 19e) indicate that CMAQ often predicts general agreement with both the absolute and relative directional changes in observed upwind/downwind concentrations. Figure 21 presents example vertical profile results for SO2 that are similar to those presented for NOy in Figure 20 but for SO2. Although the predicted SO2 concentrations do not replicate the observed relative maximum in concentrations centered at ~600m AGL that suggests an individual plume, the overall predicted enhancements in CMAQ downwind-to-upwind concentrations are comparable to those observed.

The comparison of selected VOC species shown in Figure 19 demonstrates that CMAQ consistently under-predicts the observed very low benzene concentrations. Because propene was not explicitly simulated within the current CMAQ application developed for DISCOVER-AQ, Figure 19h compares observed propene concentrations to predicted concentrations for the CMAQ chemical species “olefins”; note that the predicted and observed downwind and upwind concentrations often show relative similarity in both absolute and directional differences. Figure 22 provides example vertical profiles results similar to those for NOy in Figure 20 but for propene/olefins for the paired spirals flown on the morning of September 24, 2013; the relative agreement between observations and predictions for this specific set of paired spirals is generally good.

Figure 20. Vertical P-3 (dashed lines) and representative CMAQ (solid lines) profiles of NOy concentrations for the late afternoon paired spirals on September 26, 2013. Upwind concentrations are plotted in blue; downwind in red.

Figure 21. Vertical P-3 (dashed lines) and representative CMAQ (solid lines) profiles of SO2 concentrations for the late afternoon paired spirals on September 26, 2013. Upwind concentrations are plotted in blue; downwind in red.

Figure 22. Vertical P-3 (dashed lines) and representative CMAQ (solid lines) profiles of propene (P-3) and Olefins (CMAQ) concentrations for the morning paired spirals on September 24, 2013. Upwind concentrations are plotted in blue; downwind in red.

Summary of comparisons between P-3 observations and CMAQ predictions

Overall, the comparisons of upwind/downwind results across the eight paired sets of HSC spirals flown on September 24-26, 2013 indicate that predicted CMAQ concentrations for most pollutant species are lower than observed and that the differences in predictions between upwind and downwind locations is also lower than observed. The CMAQ NO and NO2 concentrations are consistently and substantially lower compared to observations potentially suggesting that the model is currently under-predicting the impact of both regional NOx sources (that impact background concentrations entering the HSC) as well as the impact of local (i.e., HSC) NOx emissions. The predicted and observed concentrations show somewhat better agreement for SO2 and VOC species such as toluene and propene (on some days).

Although the comparisons suggest that the simulated impact of HSC sources is mostly under-estimated, a more rigorous analysis would be beneficial when final CMAQ modeling outputs become available, including a potential comparison to predictions at 1km horizontal grid resolution. Additionally, TCEQ might support photochemical modeling for the DISCOVER-AQ period (i.e., September 2013) using the Comprehensive Air Quality Model with Extensions (CAMx). The upwind/downwind results presented previously in this report cover all nine DISCOVER-AQ flight days using data collected within three HSC regions (i.e., paired sets of Channelview/Moody Tower spirals, paired sets of Channelview/Deer Park spirals, results along the east-west HSC Transects). Future work could pair these observational results with the available photochemical modeling datasets to further evaluate the temporal and spatial differences between predictions and observations for the HSC pollutant species of interest.

References

Fischer, E. V., Jacob, D. J., Yantosca, R. M., Sulprizio, M. P., Millet, D. B., Mao, J., Paulot, F., Singh, H. B., Roiger, A., Ries, L., Talbot, R.W., Dzepina, K., and Pandey Deolal, S.: Atmospheric peroxyacetyl nitrate (PAN): a global budget and source attribution, Atmos. Chem. Phys., 14, 2679-2698, doi:10.5194/acp-14-2679-2014, 2014.

Fried, A. and C. Loughner, 2015. AQRP Project 14-002 entitled “Analysis of airborne formaldehyde data over Houston Texas acquired during the 2013 DISCOVER-AQ and SEAC4RS campaigns”, in-progress, http://aqrp.ceer.utexas.edu/aprojectsFY14-15.cfm?Category=Discover AQ.

Kim, S.-W., McKeen, S. A., Frost, G. J., Lee, S.-H., Trainer, M., Richter, A., Angevine, W. M., Atlas, E., Bianco, L., Boersma, K. F., Brioude, J., Burrows, J. P., de Gouw, J., Fried, A., Gleason, J., Hilboll, A., Mellqvist, J., Peischl, J., Richter, D., Rivera, C., Ryerson, T., te Lintel Hekkert, S., Walega, J., Warneke, C., Weibring, P., and Williams, E.: Evaluations of NOx and highly reactive VOC emission inventories in Texas and their implications for ozone plume simulations during the Texas Air Quality Study 2006, Atmos. Chem. Phys., 11, 11361-11386, doi:10.5194/acp-11-11361-2011, 2011.

Loughner, C., and Follette-Cook, M, 2015. AQRP Project 14-004 entitled “Emission source contributions to a high surface ozone episode during DISCOVER-AQ”, in-progress, http://aqrp.ceer.utexas.edu/aprojectsFY14-15.cfm?Category=Discover AQ.

LUECKEN, D. J., W. T. HUTZELL, M. STRUM, AND G. POULIOT. Regional Sources of Atmospheric Formaldehyde and Acetaldehyde, and Implications for Atmospheric Modeling. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, 47(February):477-490, (2012).

Washenfelder, R. A., et al. (2010), Characterization of NOx, SO2, ethene, and propene from industrial emission sources in Houston, Texas, J. Geophys. Res., 115, D16311, doi:10.1029/2009JD013645.

Attachment 1: NASA P-3 flight dates during DISCOVER-AQ Houston. The red numbers indicate the HGB maximum 8-hour ozone concentration in ppbv as provided by TCEQ (http://www.tceq.state.tx.us/cgi-bin/compliance/monops/8hr_monthly.pl).

Attachment 2: Summary of selected NASA P3 datasets relevant to our study.

Instrumentation

Observations

P-3B

NASA LaRC P3B Data System (PDS)

Meteorological (temperature, pressure, wind speed, wind direction) and navigational (GPS) data

Non-dispersive IR Spectrometer (NASA/LaRC)

CO2

NCAR Difference Frequency Generation Absorption Spectrometer (DFGAS)

CH2O

NCAR 4-Channel Chemiluminescence

O3, NO2, NO, NOy

Proton Transfer Reaction Mass Spectrometer (PTR-MS; Universität Innsbruck)

NMHCs

(Routinely measured species: methanol, acetonitrile, acetaldehyde, acetone, isoprene, MVK, MACR, benzene, toluene, sum of isomers of C8-aromatics, C9-aromatics, C10-aromatics, monoterpenes; Others: CH2O; propene, methyl ethyl ketone, PAN, DMS)

Pulsed UV Fluorescence (CIRES/NOAA)

SO2

Attachment 3: Scatter plot of selected wind direction data on the DISCOVER-AQ P-3 flight days. Refer to Figure 3 caption for more information on data shown in these Attachment 3 figures.

Attachment 3 (continued)




0306090120150180210240270300330360 Wind DirectionTime (CST)

Wind direction at selected Houston locations: September 26, 2013

Moody TowerLP: 0.1-0.5kmLP: 0.5-1.0kmLP: 1.0-1.5kmLP: 1.5-2.0kmChannelviewDeer ParkHSC TransectsMoody SpiralsHSC Spirals

02468101214Concentration (ppbv)

(a) HSC Transects

15.25 ppbv26.10 ppbv


(b) Moody Tower Spirals


(c) Channelview Spirals


(d) Deer Park Spirals

051015202530-95.285-95.235-95.185-95.135-95.085 Concentration (ppbv)LongitudeNOySO2PropeneAcetaldehyde

Sep13, 2013:13:41:54 -13:45:26 CST

0.00.20.40.60.81.01.21.40.005.0010.0015.0020.00Height (km)Mixing Ratio (g/kg)

Sep 25:10:18:11-10:24:24CST; MIXINGRATIO

0.00.20.40.60.81.01.21.4020406080100Height (km)Concentration (ppbv)

Sep 25:10:18:11-10:24:24CST; NOy

NOy


Sep 25:10:18:11-10:24:24CST; SO2

SO2


Sep 25:10:18:11-10:24:24CST; Propene

Propene


Sep 25:10:18:11-10:24:24CST; Benzene

Benzene

0102030405060708012345678Concentration (ppbv)Spiral PairUpwindDnwind

(a) Ozone

0.00.20.40.60.81.01.21.412345678Concentration (ppbv)Spiral PairUpwindDnwind

(b) NO

0.00.51.01.52.02.53.03.54.04.55.012345678Concentration (ppbv)Spiral PairUpwindDnwind

(c) NO2

0.00.51.01.52.02.53.03.54.04.512345678Concentration (ppbv)Spiral PairUpwindDnwind

(d) SO2

0.00.51.01.52.02.53.012345678Concentration (ppbv)Spiral PairUpwindDnwind

(e) Acetaldehyde

0.00.10.10.20.20.30.30.40.412345678Concentration (ppbv)Spiral PairUpwindDnwind

(f) C8/9-Alkylbenzenes


O3


NOy


SO2


Acetaldehyde

0.00.20.40.60.81.01.21.400.511.52Height (km)Concentration (ppbv)

Benzene


Toluene

0123456 Concentration (ppbv)

y = -3.2602x -309.55

R² = 0.6895

0.000.200.400.600.801.001.201.40

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

NO

y = -12.947x -1229.1

R² = 0.7202

0.001.002.003.004.005.006.00

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

NO2

y = -20.891x -1981.1

R² = 0.7334

0.002.004.006.008.0010.0012.00

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

NOy

y = -80.074x -7490.3

R² = 0.5881

0.0020.0040.0060.0080.00100.00120.00140.00160.00

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

CO

y = -10.45x -992.18

R² = 0.6296

0.000.501.001.502.002.503.003.504.004.505.00

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

SO2

y = -10.49x -941.4

R² = 0.1476

52.0053.0054.0055.0056.0057.0058.0059.0060.0061.0062.00

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

O3

y = -4.4644x -423.58

R² = 0.8439

0.000.501.001.502.002.50

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

Acetaldehyde

y = -1.027x -97.456

R² = 0.4471

0.000.050.100.150.200.250.300.350.400.450.50

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

Benzene

y = -1.9495x -184.88

R² = 0.575

0.000.200.400.600.801.001.20

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

Propene

y = -1.2264x -116.5

R² = 0.7976

0.000.050.100.150.200.250.300.350.40

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

Alkylbenzenes

y = -1.062x -100.87

R² = 0.7247

0.000.050.100.150.200.250.300.350.40

-95.35-95.3-95.25-95.2-95.15-95.1-95.05-95

Toluene

0204060801001201401234567891011121314Concentration (ppbv)Spiral Pair

(a) Ozone


(b) NO


(c) NOy


(d) NO2


(e) SO2


(f) CO

0.00.20.40.60.81.01.21234567891011121314Concentration (ppbv)Spiral Pair

(g) Benzene

0.00.51.01.52.02.53.01234567891011121314Concentration (ppbv)Spiral Pair

(h) Propene

0.00.20.40.60.81.01.21.41234567891011121314Concentration (ppbv)Spiral Pair

(i) Toluene


(j) Acetaldehyde

0.00.20.40.60.81.01.21.41.61234567891011121314Concentration (ppbv)Spiral Pair

(k) C8/9-Alkylbenzenes

012345678910 Concentration (ppbv)

0.00.51.01.52.02.53.0050100150Height (km)Concentration (ppbv)

O3


NO


NOy


NO2


SO2


CO


Acetaldehyde

0.00.51.01.52.02.53.00.000.200.400.600.801.001.20Height (km)Concentration (ppbv)

C8/9-Alkylbenzenes


Benzene


Propene

0.00.51.01.52.02.53.00.005.0010.0015.0020.00Height (km)Concentration (ppbv)

MixingRatio

0.00.51.01.52.02.53.000.20.40.60.81Height (km)Concentration (ppbv)

Toluene

020406080100120140Concentration (ppbv)Spiral NumberP3CMAQ

7 8 9 10 1112 13 14

(a) Ozone


7 8 9 10 1112 13 14

(b) NO


7 8 9 10 1112 13 14

(c) NO

2


7 8 9 10 1112 13 14

(d) NO

Y


7 8 9 10 1112 13 14

(e) SO

2


7 8 9 10 1112 13 14

(f) CO

00.20.40.60.811.2Concentration (ppbv)Spiral NumberP3CMAQ

7 8 9 10 1112 13 14

(g) Benzene

00.511.522.53Concentration (ppbv)Spiral NumberP3CMAQ

7 8 9 10 1112 13 14

(h) Propene (P-3) and Olefins (CMAQ)


7 8 9 10 1112 13 14

(j) Acetaldehyde

00.20.40.60.811.21.4Concentration (ppbv)Spiral NumberP3CMAQ

7 8 9 10 1112 13 14

(i) Toluene

0.00.51.01.52.02.505101520 Height (km AGL)Concentration (ppbv)CMAQ_UpCMAQ_DnP3_UpP3_Dn

Sep 26 Late Afternoon SpiralNO

y

0.00.51.01.52.02.500.511.522.533.54 Height (km AGL)Concentration (ppbv)CMAQ_UpCMAQ_DnP3_UpP3_Dn

Sep 26 LateAfternoon SpiralSO

2

0.00.51.01.52.02.500.511.522.533.5 Height (km AGL)Concentration (ppbv)CMAQ_UpCMAQ_DnP3_UpP3_Dn

Sep 24 Morning SpiralPropene (P-3) andOlefins (CMAQ)

6245516666645112489

engineering.lamar.edu€¦ · web viewmeasurements from multiple data platforms were utilized to...

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