1. Houston Lightning Mapping Array 1900-2000 UTC
Sources of Ozone in the Free Troposphere in Houston During DISCOVER-AQ 2013
Abstract
During the September 2013 DISCOVER-AQ Texas campaign, ozonesondes were launched from
the University of Houston-Main Campus and Smith Point, Texas. Surface ozone (O3) production
was not active during this campaign with the Houston region only recording two eight-hour
ozone exceedances. The potential sources of free tropospheric ozone include stratosphere-
troposphere exchange (STE), long-range transport of smoke, and lightning. We examined two
events of elevated free tropospheric ozone. Case study 1 focuses on a STE event from September
21st - 25th, and case study 2 focuses on a thunderstorm on September 5th. While there was
evidence of entrainment of biomass burning emissions, we conclude that the enhanced free
tropospheric ozone in case study 2 was most likely from coronal induced (CI) ozone production.
We calculated a CI ozone production rate of 1062+192 moles of O3 per flash.
Alexander Kotsakis1, Barry Lefer1, Gary Morris1,2, Anne Thompson3, Douglas Martins4, Andrew Weinheimer5, Richard Orville6
University of Houston1, St. Edwards University2, NASA Goddard Space Flight Center3, Penn State University4, National Center for Atmospheric Research5, Texas A&M University6
Case Study 2:
September 5th Lightning & Biomass Burning
Case Study 1:
September 21st – 25th Stratosphere-Troposphere Exchange
Data and Methods
Ozonesonde data from the University of Houston (UH) and Smith Point (SP) sites was used
for analysis in both case studies. Air parcel origins with respect to fire locations (detected
by MODIS) are identified by NOAA’s HYSPLIT trajectory model. Data from 14 AERONET
sites were used to determine the spatial variability in aerosol optical thickness. Ozone
production from lightning was estimated using the horizontal and vertical data from
Houston Lightning Mapping Array. The NASA Goddard Space Flight Center (GSFC) model
(L. C. Sparling, M. R. Schoeberl, 1995) was used to analyze the potential vorticity
throughout the column and identify the contribution of stratospheric ozone.
Conclusions
• In the days following the frontal passage (Case Study 1), strong
enhancements in PV and ozone as well as very low relative
humidity indicate the intrusion of stratospheric air into the free
troposphere.
• The NASA GSFC PV model also suggests possible entrainment of
stratospheric air into the boundary layer.
• While smoke was in the vicinity on September 5th, it is evident
that coronal induced production of ozone was the catalyst for
enhanced free tropospheric ozone.
• A calculated total ozone enhancement of 2 x 1028 molecules and
a ozone production rate from lightning of 1062+192 moles per
flash, agrees with previous work by Minschwaner et al. [2008].
• Future work:
• Simulation of Case Study 2 using a photochemical box
model
• Launch ozonesondes in the vicinity of strong convection
References & Acknowledgements
• NOAA HYSPLIT: Draxler, R.R. and Rolph, G.D., 2014. HYSPLIT (HYbrid Single-Particle
Lagrangian Integrated Trajectory) Model access via NOAA ARL READY Website (http://
ready.arl.noaa.gov/HYSPLIT.php). NOAA Air Resources Laboratory, Silver Spring, MD.
• WPC Surface Map: Fanning, 2014. 12Z Surface Analysis. Weather Prediction Center.
[accessed 2013 Sep 05] http://www.hpc.ncep.noaa.gov/archives/web_pages/sfc/
sfc_archive_maps.php?arcdate=09/21/2013&selmap=2013092112&maptype=lrgnamsfc
• NASA MODIS & Fire Data: https://earthdata.nasa.gov/labs/worldview/
• NASA AERONET: http://aeronet.gsfc.nasa.gov/new_web/DRAGON-
USA_2013_Houston.html
• NASA Goddard Model: Schoeberl, M. R., and L. C. Sparling (1993), Trajectory Modeling,
paper presented at Proceedings of the International School of Physics "Enrico Fermi", IOS
Press, 124, 289 - 306, Varenna on Lake Como, Villa Monastero, 22 June - 2 July,
• Matthew R. Cullen, Texas A&M University, College Station, TX; and D. R. Rodeheffer, P.
R. Krehbiel, W. Rison, and R. E. Orville(2008, January). The Houston Lightning Mapping
Array: Installation, Operation, and Preliminary Results, Austin, TX
• Funding provided by NASA and Texas Commission on Environmental Quality through
the 2013 DISCOVER-AQ field project.
• Thanks to Gary Huffines from Texas A&M for gathering and formatting the lightning data.
Coronal Induced Production of Ozone
A thunderstorm passed over the University of Houston ~10 minutes
after the ozonesonde launch. Lightning data from this storm was
used to determine the approximate CI ozone production using the
equation from Minschwaner et al. [2008]:
In this equation, dO3 is the mean ozone enhancement, ΔZ is the
cylindrical storm volume height, A is the cross sectional area, and
NL is the total number of flashes. The number of ozone molecules
was averaged throughout the layer of enhanced ozone (3 to 15 km)
to give a dO3 of 7.17 x 1011 cm-3. The number of recorded
significant flashes within the storm (NL) was 39. The calculated
total ozone enhancement (P(O3)) from lightning discharge for this
storm was 2.5 x 1028 molecules which amounts to 1062+192
moles per flash. This agrees with previous work by Minschwaner et
al. [2008], who calculated a total ozone enhancement of 2 x 1028
molecules and a range of 300-3000 moles per flash. As far as we
know, this is the first time Minschwaner’s results have been
evaluated by new field measurements.
Smith
Point:
University
of
Houston:
Figure 7: 48 hour back trajectories from the NOAA HYSPLIT
for UH and SP. The trajectories were calculated starting at
1800Z (1300 LST) on 5 September, 2013. Based on the
trajectories, SP was sampling clean Gulf of Mexico air while
UH was receiving smoke from Lake Charles, LA.
Figure 2: The mean potential vorticity (PV) profile
with one standard deviation (orange) graphed with the
7 day PV (black). Ozone (red) and relative humidity
(green) from the ozonesonde launched at the
University of Houston on September 21st, 2013. This
launch occurred ~6 hours after the frontal passage
occurred and there is a noticeable enhancement in
ozone at 14km, which is most likely stratospheric in
origin.
Figure 3: Data displayed is the same as in Figure 2 for
September 22nd, 2013. Compared to the 21st, the free
troposphere is much drier. Anomalously high PV
values and 2 ozone enhancements up to 100 ppbv
indicates the presence of stratospheric air. A slight PV
enhancement is evident from 0.5-2 km (in the
boundary layer).
Figure 4: Data displayed is the same as in Figure 2 for
September 25th, 2013. While the PV does not align
with the large ozone enhancement at 7.5 km, very dry
free tropospheric air is still present along with a peak
in ozone at 7.5km. A slight PV enhancement is again
evident in the boundary layer (0-2 km).
Figure 1: A meteorological surface map from 1200Z
(700 LST) on September 21st shows the cold front
having passed through the Houston area. Due to
strong dynamics associated with a cold front,
sometimes ozone can be pulled down from the ozone
rich stratosphere.
Figure 5: Ozonesonde ascent (markers) and descent (lines)
data from SP and UH. The ozonesondes were launched
within 30 minutes of each other and at a distance of 57 km.
The large free tropospheric enhancement of ozone was only
present on the ascent of the UH ozonesonde.
UH
Sept. 25Sept. 22
Sept. 21
Figure 6: Contours colored by daily average AOT. The ascent and
descent of both UH and SP ozonesondes are indicated by the
colored lines. There is a noticeable gradient in aerosol optical
thickness between SP and UH. Large values of aerosol optical
thickness are associated with smoke that was transported into
Houston.
Figure 8: Lightning data from the Houston Lightning
Mapping Array displays lightning flash distribution in the
horizontal and vertical. Note the storm’s vertical extent in
the red circle spans ~3-15 km and horizontal dimension
of ~10-12 km.
15
10
5
0
UH
5 0 5