Quantifying TOLNet ozone lidar accuracy during the 2014 DISCOVER-AQ and FRAPPÉ campaigns

Abstract. The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure high-resolution atmospheric profiles of ozone. The accurate characterization of these lidars is necessary to determine the uniformity of the network calibration. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission and the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) to measure ozone variations from the boundary layer to the top of the troposphere. This study presents the analysis of the intercomparison between the TROPOZ, TOPAZ, and LMOL lidars, along with comparisons between the lidars and other in situ ozone instruments including ozonesondes and a P-3B airborne chemiluminescence sensor. The TOLNet lidars measured vertical ozone structures with an accuracy generally better than ±15 % within the troposphere. Larger differences occur at some individual altitudes in both the near-field and far-field range of the lidar systems, largely as expected. In terms of column average, the TOLNet lidars measured ozone with an accuracy better than ±5 % for both the intercomparison between the lidars and between the lidars and other instruments. These results indicate that these three TOLNet lidars are suitable for use in air quality, satellite validation, and ozone modeling efforts.

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Quantifying TOLNet Ozone Lidar Accuracy during the 2014 DISCOVER-AQ and FRAPPÉ Campaigns

10.5194/amt-2017-106 ◽

2017 ◽

Author(s):

Lihua Wang ◽

Michael J. Newchurch ◽

Raul J. Alvarez II ◽

Timothy A. Berkoff ◽

Steven S. Brown ◽

...

Keyword(s):

Air Quality ◽

Tropospheric Ozone ◽

Near Field ◽

Front Range ◽

Field Range ◽

Satellite Validation ◽

Good Measurement ◽

Better Than

Abstract. The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure high-resolution atmospheric profiles of ozone. The accurate characterization of these lidars is necessary to determine the uniformity of cross-instrument calibration. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission and the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ) to measure ozone variations from the boundary layer to the top of the troposphere. This study presents the analysis of the intercomparison between the TROPOZ, TOPAZ, and LMOL lidars, along with comparisons between the lidars and other in situ ozone instruments including ozonesondes and a P-3B airborne chemiluminescence sensor. In terms of the range-resolving capability, the TOLNet lidars measured vertical ozone structures with an accuracy generally better than ±15 % within the troposphere. Larger differences occur at some individual altitudes in both the near-field and far-field range of the lidar systems, largely as expected. In terms of column average, the TOLNet lidars measured ozone with an accuracy better than ±5 % for both the intercomparison between the lidars and between the lidars and other instruments. These results indicate very good measurement accuracy for these three TOLNet lidars, making them suitable for use in air quality, satellite validation, and ozone modeling efforts.

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TOLNet ozone lidar intercomparison during the discover-aq and frappé campaigns

EPJ Web of Conferences ◽

10.1051/epjconf/201817610007 ◽

2018 ◽

Vol 176 ◽

pp. 10007

Author(s):

Michael J. Newchurch ◽

Raul J. Alvarez ◽

Timothy A. Berkoff ◽

William Carrion ◽

Russell J. DeYoung ◽

...

Keyword(s):

Air Quality ◽

Tropospheric Ozone ◽

Measurement Accuracy ◽

Near Field ◽

Atmospheric Modeling ◽

Front Range ◽

Field Range ◽

Surface Conditions ◽

Satellite Validation

The Tropospheric Ozone Lidar Network (TOLNet) is a unique network of lidar systems that measure atmospheric profiles of ozone and aerosols, to contribute to air-quality studies, atmospheric modeling, and satellite validation efforts. The accurate characterization of these lidars is of critical interest, and is necessary to determine cross-instrument calibration uniformity. From July to August 2014, three lidars, the TROPospheric OZone (TROPOZ) lidar, the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar, and the Langley Mobile Ozone Lidar (LMOL), of TOLNet participated in the “Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality” (DISCOVER-AQ) mission and the “Front Range Air Pollution and Photochemistry Éxperiment” (FRAPPÉ) to measure sub-hourly ozone variations from near the surface to the top of the troposphere. Although large differences occur at few individual altitudes in the near field and far field range, the TOLNet lidars agree with each other within ±4%. These results indicate excellent measurement accuracy for the TOLNet lidars that is suitable for use in air-quality and ozone modeling efforts.

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Preparation and Characterization of In Situ Carbide Particle Reinforced Fe-Based Gradient Materials by Laser Melt Deposition

Coatings ◽

10.3390/coatings9080467 ◽

2019 ◽

Vol 9 (8) ◽

pp. 467 ◽

Cited By ~ 2

Author(s):

Weian Zong ◽

Song Zhang ◽

Chunhua Zhang ◽

Chenliang Wu ◽

Jingbo Zhang ◽

...

Keyword(s):

Wear Resistance ◽

Steel Powder ◽

Gradient Material ◽

Wear Resistant ◽

Gradient Materials ◽

Melt Deposition ◽

Surface Rigidity ◽

Better Than

To obtain the wear-resistant camshaft with surface rigidity and core toughness and improve the service life of camshaft, wear-resistant Fe-based alloy gradient material was prepared by laser melt deposition. The traditional camshaft was forged by 12CrNi2V. In this paper, four types of wear-resistant Fe-based powders were designed by introducing various content of Cr3C2 and V-rich Fe-based alloy (FeV50) into stainless steel powder. The results showed that the gradient materials formed a satisfactory metallurgical bond. The composition of the phases was mainly composed of α-Fe, Cr23C6, and V2C phases. The increasing of Cr3C2 and FeV50 led to transform V2C into the V8C7. The microstructures were mainly cellular dendrite and intergranular structure. Due to the addition of Cr3C2 and FeV50, the average microhardness and wear resistance of gradient materials were significantly better than that of 12CrNi2V. The sample with 8% V had the highest microhardness of 853 ± 18 HV, which was 2.6 times higher than that of 12CrNi2V. The sample with 6% V had the best wear resistance, which was 21 times greater than that of 12CrNi2V.

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Specimen heating stage with in-situ evaporator in UHV-STEM for the observation and characterization of monolayered superstructures

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075336 ◽

1983 ◽

Vol 41 ◽

pp. 308-309

Author(s):

M. Ohtsuki ◽

J.J. Schuler ◽

A.V. Crewe ◽

T. Ichinokawa

Keyword(s):

Heavy Atom ◽

High Vacuum ◽

Ultra High Vacuum ◽

Solid Surfaces ◽

Thin Specimen ◽

Heating Stage ◽

Specimen Holder ◽

Better Than

In-situ evaporating experiments on solid surfaces become meaningful only when the evaporation takes place after the surface of the object is fully cleaned in ultra high vacuum (UHV). A specimen heating stage is usually used for the cleaning process.For the observation of single heavy atom superstructures at atomic resolution in UHV, we have constructed a new specimen heating stage equipped with an insitu evaporator. The device is built into the specimen ante-chamber of the high-resolution UHV-STEM as shown in Figures 1 and 2. The vacuum of the chamber has been tested at 4 × 10-10 torr. with two 20 ℓ/ sec ion pumps attached close to the chamber. The vacuum of the STEM column is better than 1 × 10-10 torr. The heating stage is built into the specimen holder so that direct heating of the specimen is possible. In the detail shown in Figure 2, a thin specimen is mounted between two supporting grids which are then fastened together by two semi-circular tantalum clips. These clips are also used as contacts which carry the current to heat the specimen directly.

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Upgrade and automation of the JPL Table Mountain Facility tropospheric ozone lidar (TMTOL) for near-ground ozone profiling and satellite validation

Atmospheric Measurement Techniques ◽

10.5194/amt-12-569-2019 ◽

2019 ◽

Vol 12 (1) ◽

pp. 569-583

Author(s):

Fernando Chouza ◽

Thierry Leblanc ◽

Mark Brewer ◽

Patrick Wang

Keyword(s):

Tropospheric Ozone ◽

Surface Ozone ◽

Stratospheric Intrusion ◽

Satellite Validation ◽

Table Mountain ◽

The Stability ◽

Near Future ◽

Better Than ◽

Good Agreement ◽

Measurement Period

Abstract. As part of international efforts to monitor air quality, several satellite missions such as the Tropospheric Monitoring Instrument (TROPOMI) were deployed and others, like Tropospheric Emissions: Monitoring Pollution (TEMPO), are planned for the near future. In support of the validation of these missions, major upgrades to the tropospheric ozone lidar located at the Jet Propulsion Laboratory Table Mountain Facility (TMF) were recently performed. These modifications include the full automation of the system, which now allows unattended measurements during frequent satellite overpasses, and a new receiver that extends the measurement capabilities of the system down to 100 m above surface. The automation led to the systematic operation of the lidar during daily TROPOMI overpasses, providing more than 139 reference profiles since January 2018. Ozone profiles retrieved using the new lidar receiver were compared to ozonesonde profiles obtained from a co-located tethered balloon. An agreement of about 5 % with the ozonesonde down to an altitude range of 100 m a.g.l. was observed. Furthermore, the stability of the receiver configuration was investigated. Comparisons between the lowest point retrieved by the lidar and a co-located surface ozone photometer showed no sign of drift over a 2-month test period and an agreement better than 10 %. Finally, measurements from a 24 h intensive measurement period during a stratospheric intrusion event showed good agreement with two free-flying ozonesondes. These comparisons revealed localized differences between sonde and lidar, possibly owing to the differing vertical resolutions (between 52 and 380 m for lidar and about 100 m for the sonde).

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Robust Inferential Techniques Applied to the Analysis of the Tropospheric Ozone Concentration in an Urban Area

Sensors ◽

10.3390/s21010277 ◽

2021 ◽

Vol 21 (1) ◽

pp. 277

Author(s):

Wilmar Hernandez ◽

Alfredo Mendez ◽

Vicente González-Posadas ◽

José Luis Jiménez-Martín ◽

Iván Menes Camejo

Keyword(s):

Air Quality ◽

Confidence Intervals ◽

Tropospheric Ozone ◽

Air Quality Monitoring ◽

Robust Methods ◽

Time Period ◽

Measurement Results ◽

Robust Techniques ◽

The City ◽

Better Than

This paper analyzes 12 years of tropospheric ozone (O3) concentration measurements using robust techniques. The measurements were taken at an air quality monitoring station called Belisario, which is in Quito, Ecuador; the data collection time period was 1 January 2008 to 31 December 2019, and the measurements were carried out using photometric O3 analyzers. Here, the measurement results were used to build variables that represented hours, days, months, and years, and were then classified and categorized. The index of air quality (IAQ) of the city was used to make the classifications, and robust and nonrobust confidence intervals were used to make the categorizations. Furthermore, robust analysis methods were compared with classical methods, nonparametric methods, and bootstrap-based methods. The results showed that the analysis using robust methods is better than the analysis using nonrobust methods, which are not immune to the influence of extreme observations. Using all of the aforementioned methods, confidence intervals were used to both establish and quantify differences between categories of the groups of variables under study. In addition, the central tendency and variability of the O3 concentration at Belisario station were exhaustively analyzed, concluding that said concentration was stable for years, highly variable for months and hours, and slightly changing between the days of the week. Additionally, according to the criteria established by the IAQ, it was shown that in Quito, the O3 concentration levels during the study period were not harmful to human health.

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Sources and characteristics of summertime organic aerosol in the Colorado Front Range: perspective from measurements and WRF-Chem modeling

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-8293-2018 ◽

2018 ◽

Vol 18 (11) ◽

pp. 8293-8312 ◽

Cited By ~ 6

Author(s):

Roya Bahreini ◽

Ravan Ahmadov ◽

Stu A. McKeen ◽

Kennedy T. Vu ◽

Justin H. Dingle ◽

...

Keyword(s):

Boundary Layer ◽

Colorado Front Range ◽

Weather Research And Forecasting ◽

Front Range ◽

Top Down ◽

Mixing Ratios ◽

Oil And Natural Gas ◽

Lower Production

Abstract. The evolution of organic aerosols (OAs) and their precursors in the boundary layer (BL) of the Colorado Front Range during the Front Range Air Pollution and Photochemistry Éxperiment (FRAPPÉ, July–August 2014) was analyzed by in situ measurements and chemical transport modeling. Measurements indicated significant production of secondary OA (SOA), with enhancement ratio of OA with respect to carbon monoxide (CO) reaching 0.085±0.003 µg m−3 ppbv−1. At background mixing ratios of CO, up to ∼  1.8 µg m−3 background OA was observed, suggesting significant non-combustion contribution to OA in the Front Range. The mean concentration of OA in plumes with a high influence of oil and natural gas (O&G) emissions was ∼  40 % higher than in urban-influenced plumes. Positive matrix factorization (PMF) confirmed a dominant contribution of secondary, oxygenated OA (OOA) in the boundary layer instead of fresh, hydrocarbon-like OA (HOA). Combinations of primary OA (POA) volatility assumptions, aging of semi-volatile species, and different emission estimates from the O&G sector were used in the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) simulation scenarios. The assumption of semi-volatile POA resulted in greater than a factor of 10 lower POA concentrations compared to PMF-resolved HOA. Including top-down modified O&G emissions resulted in substantially better agreements in modeled ethane, toluene, hydroxyl radical, and ozone compared to measurements in the high-O&G-influenced plumes. By including emissions from the O&G sector using the top-down approach, it was estimated that the O&G sector contributed to <  5 % of total OA, but up to 38 % of anthropogenic SOA (aSOA) in the region. The best agreement between the measured and simulated median OA was achieved by limiting the extent of biogenic hydrocarbon aging and consequently biogenic SOA (bSOA) production. Despite a lower production of bSOA in this scenario, contribution of bSOA to total SOA remained high at 40–54 %. Future studies aiming at a better emissions characterization of POA and intermediate-volatility organic compounds (IVOCs) from the O&G sector are valuable.

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Preparation and Characterization of Polyacrylonitrile-Metal-O-MMT Nanocomposites

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.221.316 ◽

2011 ◽

Vol 221 ◽

pp. 316-320

Author(s):

Hui Xia Feng ◽

Gong Wei Fu ◽

Yi Wang ◽

Na Li Chen ◽

Rui Chen Yang

Keyword(s):

Thermal Stability ◽

Powder Diffraction ◽

Interlayer Space ◽

In Situ Polymerization ◽

X Ray ◽

Thermal Stability Of ◽

Better Than ◽

Montmorillonite Nanocomposites

Polyacrylonitrile-metal-O-montmorillonite nanocomposites were prepared by means of in situ polymerization. The Na-montmorillonite was modified by quaternary ammonium salt after the exchange of its interlayer cations with Ni2+. Infrared spectra and X-ray powder diffraction were employed to characterize the obtained polyacrylonitrile-metal-O-montmorillonite. The results of FTIR show that metal-O-montmorillonite has been concerned with the polymerization of PAN. The result of X-ray powder diffraction shows that the inserting of the acrylonitrile monomer can enlarge the interlayer space of montmorillonite. It is also shown that the polyacrylonitrile-metal-O- montmorillonite nanocomposites have been synthesized. The thermal stability of PAN /MMT is better than that of pure PAN.

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TROPOMI tropospheric ozone column data: geophysical assessment and comparison to ozonesondes, GOME-2B and OMI

Atmospheric Measurement Techniques ◽

10.5194/amt-14-7405-2021 ◽

2021 ◽

Vol 14 (12) ◽

pp. 7405-7433

Author(s):

Daan Hubert ◽

Klaus-Peter Heue ◽

Jean-Christopher Lambert ◽

Tijl Verhoelst ◽

Marc Allaart ◽

...

Keyword(s):

Air Quality ◽

Tropospheric Ozone ◽

Sampling Error ◽

Horizontal Resolution ◽

Correlated Errors ◽

Climate Data ◽

Uncertainty Estimates ◽

Low Earth Orbits ◽

Ozone Column ◽

Better Than

Abstract. Ozone in the troposphere affects humans and ecosystems as a pollutant and as a greenhouse gas. Observing, understanding and modelling this dual role, as well as monitoring effects of international regulations on air quality and climate change, however, challenge measurement systems to operate at opposite ends of the spatio-temporal scale ladder. Aboard the ESA/EU Copernicus Sentinel-5 Precursor (S5P) satellite launched in October 2017, the TROPOspheric Monitoring Instrument (TROPOMI) aspires to take the next leap forward by measuring ozone and its precursors at unprecedented horizontal resolution until at least the mid-2020s. In this work, we assess the quality of TROPOMI's first release (V01.01.05–08) of tropical tropospheric ozone column (TrOC) data. Derived with the convective cloud differential (CCD) method, TROPOMI daily TrOC data represent the 3 d moving mean ozone column between the surface and 270 hPa under clear-sky conditions gridded at 0.5∘ latitude by 1∘ longitude resolution. Comparisons to almost 2 years of co-located SHADOZ ozonesonde and satellite data (Aura OMI and MetOp-B GOME-2) conclude to TROPOMI biases between −0.1 and +2.3 DU (<+13 %) when averaged over the tropical belt. The field of the bias is essentially uniform in space (deviations <1 DU) and stable in time at the 1.5–2.5 DU level. However, the record is still fairly short, and continued monitoring will be key to clarify whether observed patterns and stability persist, alter behaviour or disappear. Biases are partially due to TROPOMI and the reference data records themselves, but they can also be linked to systematic effects of the non-perfect co-locations. Random uncertainty due to co-location mismatch contributes considerably to the 2.6–4.6 DU (∼14 %–23 %) statistical dispersion observed in the difference time series. We circumvent part of this problem by employing the triple co-location analysis technique and infer that TROPOMI single-measurement precision is better than 1.5–2.5 DU (∼8 %–13 %), in line with uncertainty estimates reported in the data files. Hence, the TROPOMI precision is judged to be 20 %–25 % better than for its predecessors OMI and GOME-2B, while sampling at 4 times better spatial resolution and almost 2 times better temporal resolution. Using TROPOMI tropospheric ozone columns at maximal resolution nevertheless requires consideration of correlated errors at small scales of up to 5 DU due to the inevitable interplay of satellite orbit and cloud coverage. Two particular types of sampling error are investigated, and we suggest how these can be identified or remedied. Our study confirms that major known geophysical patterns and signals of the tropical tropospheric ozone field are imprinted in TROPOMI's 2-year data record. These include the permanent zonal wave-one pattern, the pervasive annual and semiannual cycles, the high levels of ozone due to biomass burning around the Atlantic basin, and enhanced convective activity cycles associated with the Madden–Julian Oscillation over the Indo-Pacific warm pool. TROPOMI's combination of higher precision and higher resolution reveals details of these patterns and the processes involved, at considerably smaller spatial and temporal scales and with more complete coverage than contemporary satellite sounders. If the accuracy of future TROPOMI data proves to remain stable with time, these hold great potential to be included in Climate Data Records, as well as serve as a travelling standard to interconnect the upcoming constellation of air quality satellites in geostationary and low Earth orbits.

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A Dual-Droplet Approach for Measuring the Hygroscopicity of Aqueous Aerosol

10.5194/amt-2021-108 ◽

2021 ◽

Author(s):

Jack M. Choczynski ◽

Ravleen Kaur Kohli ◽

Craig S. Sheldon ◽

Chelsea L. Price ◽

James F. Davies

Keyword(s):

Chemical Reactivity ◽

Aerosol Particles ◽

High Viscosity ◽

Tetraethylene Glycol ◽

Hygroscopic Growth ◽

Electrodynamic Balance ◽

Sample Droplet ◽

Better Than

Abstract. Accurate characterization of the water activity and hygroscopicity of aqueous aerosol material allows us to predict the chemical and physical state of aerosol particles exposed to humid conditions in the environment. The hygroscopicity of aerosol determines the size, phase morphology, viscosity, chemical reactivity, and optical properties of constituent particles, and directly impacts their ability to form clouds in the atmosphere. In this work, we describe measurements of hygroscopicity using a linear quadrupole electrodynamic balance (LQ-EDB). We levitate two droplets, one droplet that acts as a relative humidity (RH) probe and one sample droplet, and expose them to controlled environmental conditions. We describe the development of a RH measurement using probe droplets of aqueous NaCl or LiCl, allowing for precise in-situ measurements of RH in the LQ-EDB chamber. We demonstrate that the RH may be determined with an accuracy of 0.5 % at 50 % RH and better than 0.1 % at 90 % RH using NaCl, and show that LiCl is effective at characterizing the RH from ~10 % RH up to ~90 %. We simultaneously measure the response of sample droplets containing aqueous material (including ammonium sulfate, citric acid, 1,2,6-hexanetriol, and tetraethylene glycol) and report hygroscopic growth via their radial growth factors. We use established thermodynamic models to validate the accuracy of the RH probe and to compare with the measured hygroscopicity of the samples. This approach shows significant advantages over other methods for accurately characterizing the hygroscopicity of samples with a range of characteristics, such as high viscosity and vapor pressure.

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