Principal Component Analysis (PCA) is used to isolate the common modes of behavior in the daily maximum 8‐h average ozone mixing ratios measured at 30 Continuous Ambient Monitoring Stations in the ...Houston‐Galveston‐Brazoria area during the Second Texas Air Quality Study field intensive (1 August to 15 October 2006). Three principal components suffice to explain 93% of the total variance. Nearly 84% is explained by the first component, which is attributed to changes in the “regional background” determined primarily by the large‐scale winds. The second component (6%) is attributed to changes in the “local background,” that is, ozone photochemically produced in the Houston area and spatially and temporally averaged by local circulations. Finally, the third component (3.5%) is attributed to short‐lived plumes containing high ozone originating from industrial areas along Galveston Bay and the Houston Ship Channel. Regional background ozone concentrations derived using the first component compare well with mean ozone concentrations measured above the Gulf of Mexico by the tunable profiler for aerosols and ozone lidar aboard the NOAA Twin Otter. The PCA regional background values also agree well with background values derived using the lowest daily 8‐h maximum method of Nielsen‐Gammon et al. (2005), provided the Galveston Airport data (C34) are omitted from that analysis. The differences found when Galveston is included are caused by the sea breeze, which depresses ozone at Galveston relative to sites further inland. PCA removes the effects of this and other local circulations to obtain a regional background value representative of the greater Houston area.
The Tropospheric Ozone Lidar Network (TOLNet) was used to validate retrievals of ozone (O.sub.3) profiles in the troposphere from the TROPOspheric Monitoring Instrument (TROPOMI) ultraviolet (UV), ...Cross-track Infrared Sounder (CrIS) infrared (IR), and a combined UV + IR wavelength retrieval from TROPOMI/CrIS. Observations from six separate ground-based lidar systems and various locations of ozonesondes distributed throughout North America and in the Netherlands were used to quantify systematic bias and random errors for each satellite retrieval. Furthermore, TOLNet data were used to intercompare idealized UV, IR, and UV + IR convolved lidar profiles of O.sub.3 in the troposphere during case studies representative of high-O.sub.3 events. This study shows that the improved sensitivity and vertical resolution in UV + IR retrievals in the middle- and upper-troposphere resulted in tropospheric degree of freedom (DOF) values â¼ 33 % higher compared to UV- and IR-only retrievals. The increased DOFs in the UV + IR retrievals allowed for improved reproduction of mid- and upper-tropospheric O.sub.3 enhancements and, to a lesser degree, near-surface pollution enhancements compared to single-wavelength satellite products.
Ground-based lidars and ozonesondes belonging to the NASA-supported Tropospheric Ozone Lidar Network (TOLNet) are used in conjunction with the NASA Alpha Jet Atmospheric eXperiment (AJAX) to ...investigate the transport of stratospheric ozone and entrained pollution into the lower troposphere above the United States on May 24–25, 2013. TOLNet and AJAX measurements made in California, Nevada, and Alabama are compared to tropospheric ozone retrievals from the Atmospheric Infrared Sounder (AIRS), to back trajectories from the NOAA Air Resources Laboratory (ARL) Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model, and to analyses from the NOAA/NESDIS Real-time Air Quality Modeling System (RAQMS) and FLEXPART particle dispersion model. The measurements and model analyses show much deeper descent of ozone-rich upper tropospheric/lower stratospheric air above the Desert Southwest than above the Southeast, and comparisons to surface measurements from regulatory monitors reporting to the U.S. EPA Air Quality System (AQS) suggest that there was a much greater surface impact in the Southwest including exceedances of the 2008 National Ambient Air Quality Standard (NAAQS) of 0.075 ppm in both Southern California and Nevada. Our analysis demonstrates the potential benefits to be gained by supplementing the existing surface ozone network with coordinated upper air observations by TOLNet.
•Coordinated lidar and aircraft measurements used to study stratospheric intrusions.•Measurements in good agreement with predictions by the RAQMS and FLEXPART models.•The impact on surface ozone was greater in the Desert Southwest than the Southeast.•Coordinated ozone lidar measurements can help agencies identify ozone sources.
Abstract
The NOAA airborne ozone lidar system Tunable Optical Profiler for Aerosol and Ozone (TOPAZ) is compared with the fast-response chemiluminescence sensor flown aboard the NOAA WP-3D during the ...2006 Texas Air Quality Study (TexAQS). TOPAZ measurements made from the NOAA Twin Otter, flying at an altitude of ~3300 m MSL in the Houston, Texas, area on 31 August, and the Dallas, Texas, area on 13 September, show that the overall uncertainty in the 10-s (~600-m horizontal resolution) TOPAZ profiles is dominated by statistical uncertainties (1σ) of ~8 ppbv (6%–10%) at ranges of ~2300 m from the aircraft (~1000 m MSL), and ~11–27 ppbv (12%–30%) at ranges of ~2800 m (~500 m MSL). These uncertainties are substantially reduced by spatial averaging, and the averages of 11 profiles (of 110 s or 6.6-km horizontal resolution) at ~1000 m MSL are in excellent agreement (±2%) with the in situ measurements at ~500 m MSL. The TOPAZ measurements at lower altitudes on 31 August exhibit a negative bias of up to ~15%, however, when the lidar signals were strongly attenuated by very high ozone levels in the plume from the Houston Ship Channel. This bias appears to result from nonlinear behavior in the TOPAZ signal amplifiers, which is described in the companion paper by Alvarez et al. An empirical correction is presented.
The North America-based Tropospheric Ozone Lidar Network (TOLNet)
was recently established to provide high spatiotemporal vertical profiles of
ozone, to better understand physical processes driving ...tropospheric ozone
variability and to validate the tropospheric ozone measurements of upcoming
spaceborne missions such as Tropospheric Emissions: Monitoring Pollution
(TEMPO). The network currently comprises six tropospheric ozone lidars, four
of which are mobile instruments deploying to the field a few times per year,
based on campaign and science needs. In August 2016, all four mobile TOLNet
lidars were brought to the fixed TOLNet site of JPL Table Mountain Facility
for the 1-week-long Southern California Ozone Observation Project (SCOOP).
This intercomparison campaign, which included 400 h of lidar measurements
and 18 ozonesonde launches, allowed for the unprecedented simultaneous
validation of five of the six TOLNet lidars. For measurements between 3 and
10 km a.s.l., a mean difference of 0.7 ppbv (1.7 %), with a
root-mean-square deviation of 1.6 ppbv or 2.4 %, was found between the
lidars and ozonesondes, which is well within the combined uncertainties of
the two measurement techniques. The few minor differences identified were
typically associated with the known limitations of the lidars at the profile
altitude extremes (i.e., first 1 km above ground and at the instruments'
highest retrievable altitude). As part of a large homogenization and quality
control effort within the network, many aspects of the TOLNet in-house data
processing algorithms were also standardized and validated. This thorough
validation of both the measurements and retrievals builds confidence as to the
high quality and reliability of the TOLNet ozone lidar profiles for many
years to come, making TOLNet a valuable ground-based reference network for
tropospheric ozone profiling.
We have used NOAA’s Tunable Optical Profiler for Aerosol and oZone (TOPAZ) ozone lidar to investigate the sources of high surface ozone concentrations in two different regions of the western United ...States (US): the Uintah Basin in northeast Utah and Clark County in southern Nevada, which includes the city of Las Vegas. The Uintah Basin is a booming oil and gas producing region that often suffers from very high wintertime ozone concentrations. Clark County experiences violations of the US ozone standard primarily in spring and early summer despite a lack of any major local pollution sources. TOPAZ lidar observations, in conjunction with surface in situ measurements and model results, provided strong evidence that the high wintertime ozone concentrations in the Uintah Basin are primarily driven by local emissions associated with oil and gas exploration, whereas the Clark County ozone exceedances are often caused by ozone-rich air that is transported from the lower stratosphere all the way down to the earth’s surface.
The California Baseline Ozone Transport Study (CABOTS) was
conducted in the late spring and summer of 2016 to investigate the influence
of long-range transport and stratospheric intrusions on surface ...ozone
(O3) concentrations in California with emphasis on the San Joaquin
Valley (SJV), one of two extreme ozone non-attainment areas in the US.
One of the major objectives of CABOTS was to characterize the vertical
distribution of O3 and aerosols above the SJV to aid in the
identification of elevated transport layers and assess their surface
impacts. To this end, the NOAA Earth System Research Laboratory (ESRL)
deployed the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) mobile
lidar to the Visalia Municipal Airport (36.315∘ N,
119.392∘ E) in the central SJV between 27 May and 7 August 2016.
Here we compare the TOPAZ ozone retrievals with co-located in situ surface
measurements and nearby regulatory monitors and also with airborne in situ measurements
from the University of California at Davis–Scientific Aviation (SciAv)
Mooney and NASA Alpha Jet Atmospheric eXperiment (AJAX) research aircraft.
Our analysis shows that the lidar and aircraft measurements agree, on
average to within 5 ppbv, the sum of their stated uncertainties of 3 and 2 ppbv, respectively.
Aerosol retrieval using ozone lidars in the ultraviolet spectral region is
challenging but necessary for correcting aerosol interference in ozone
retrieval and for studying the ozone–aerosol ...correlations. This study
describes the aerosol retrieval algorithm for a tropospheric ozone lidar,
quantifies the retrieval error budget, and intercompares the aerosol
retrieval products at 299 nm with those at 532 nm from a high spectral
resolution lidar (HSRL) and with those at 340 nm from an AErosol RObotic NETwork radiometer. After the cloud-contaminated data are filtered out, the
aerosol backscatter or extinction coefficients at 30 m and 10 min resolutions retrieved by the ozone lidar are highly correlated with the HSRL
products, with a coefficient of 0.95 suggesting that the ozone lidar can
reliably measure aerosol structures with high spatiotemporal resolution
when the signal-to-noise ratio is sufficient. The actual uncertainties of
the aerosol retrieval from the ozone lidar generally agree with our
theoretical analysis. The backscatter color ratio (backscatter-related
exponent of wavelength dependence) linking the coincident data measured by
the two instruments at 299 and 532 nm is 1.34±0.11, while the
Ångström (extinction-related) exponent is 1.49±0.16 for a
mixture of urban and fire smoke aerosols within the troposphere above
Huntsville, AL, USA.
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