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The Tropospheric Ozone Lidar Network (TOLNet) was used to validate retrievals of ozone (O 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 3 in the troposphere during case studies representative of high-O 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 ∼ 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 3 enhancements and, to a lesser degree, near-surface pollution enhancements compared to single-wavelength satellite products. The validation of O 3 profiles in the troposphere retrieved with the UV-only, IR-only, and UV + IR Tikhonov regularised Ozone Profile retrievAl with SCIATRAN (TOPAS) algorithm developed at the Institute for Environmental Physics, University of Bremen, demonstrated the utility of using TOLNet as a satellite evaluation data set. TOPAS UV-only, IR-only, and UV + IR wavelength retrievals had systematic biases, quantified with normalized mean bias, throughout the troposphere of 11.2 ppb (22.1 %), -1.7 ppb (-0.3 %), and 3.5 ppb (7.8 %), respectively, which meet the tropospheric systematic bias requirements defined by the science teams for the TROPOMI and CrIS sensors. The primary drivers of systematic bias were determined to be solar zenith angle, surface albedo, and cloud fraction. Random errors, representative of uncertainty in the retrievals and quantified by root mean squared errors (RMSEs), were large for all three retrievals, with UV-only, IR-only, and UV + IR wavelength retrievals having RMSEs throughout the troposphere of 17.4 ppb (19.8 % of mean tropospheric column values), 10.5 ppb (12.6 % of mean tropospheric column values), and 14.0 ppb (14.6 % of mean tropospheric column values), respectively. TOPAS UV-only profiles did not meet the uncertainty requirements defined for TROPOMI for the troposphere; however, CrIS IR-only retrievals did meet the uncertainty requirements defined by this mission. The larger random errors reflect the challenge of retrieving daily O 3 profiles due to the limited sensitivity and vertical resolution of these retrievals in the troposphere. Tropospheric systematic biases and random error were lower in IR-only and combined UV + IR retrievals compared to UV-only products due to the increased sensitivity in the troposphere allowing the retrievals to deviate further from the a priori profiles. Observations from TOLNet demonstrated that the performance of the three satellite products varied by season and altitude in the troposphere. TOLNet was shown to result in similar validation statistics compared to ozonesonde data, which are a commonly used satellite evaluation data source, demonstrating that TOLNet is a sufficient source of satellite O 3 profile validation data in the troposphere, which is critical as this data source is the primary product identified for the tropospheric O 3 validation of the recently launched Tropospheric Emissions: Monitoring of Pollution (TEMPO) mission. [ABSTRACT FROM AUTHOR]

The Tropospheric Ozone Lidar Network (TOLNet) was applied to validate retrievals of ozone (O3) 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 Europe were applied 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 profiles of O3 in the troposphere during case studies representative of high O3 events. This study shows that the combination of wavelengths in satellite retrievals (i.e., UV+IR) increases the sensitivity and vertical resolution of the retrievals of O3 in the troposphere compared to single-wavelength products. The improved sensitivity and vertical resolution in UV+IR retrievals in the middle- and upper-troposphere resulted in tropospheric degree of freedom (DOF) values ~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 O3 enhancements, and to a lesser degree near-surface pollution enhancements, compared to single wavelength satellite products. The validation of O3 profiles in the troposphere retrieved with the UV-only, IR-only, and UV+IR Tikhonov regularised Ozone Profile retrievAl with SCIATRAN (TOPAS) algorithm developed at the Institute for Environmental Physics, University of Bremen demonstrated the utility of using TOLNet as a satellite evaluation data set. TOPAS UV-only, IR-only, and UV+IR wavelength retrievals had systematic biases throughout the troposphere of 11.2 ppb (22.1 %), -1.7 ppb (-0.3 %), and 3.5 ppb (7.8 %), respectively, which meet the tropospheric systematic bias requirements of TROPOMI and CrIS. The primary drivers of systematic bias were determined to be the a priori vertical profile shape, solar zenith angle, and surface albedo. Random errors, representative of uncertainty in the retrievals, were large for all three retrievals with UV-only, IR-only, and UV+IR wavelength retrievals having root mean squared errors (RMSE) throughout the troposphere of 17.4 ppb (19.8 % of mean tropospheric column values), 10.5 ppb (12.6 % of mean tropospheric column values), and 14.0 ppb (14.6 % of mean tropospheric column values), respectively. TOPAS UV-only profiles did not meet the uncertainty requirements defined for TROPOMI for the troposphere; however, CrIS IR-only retrievals did meet the uncertainty requirements defined by this mission. The larger random biases reflect the challenge of retrieving daily O3 profiles due to the limited sensitivity and vertical resolution of these retrievals in the troposphere. Tropospheric systematic biases and random error were lower in IR-only and combined UV+IR retrievals compared to UV-only products due to the increased sensitivity in the troposphere allowing the retrievals to deviate further from the a priori profiles. Consistent daily observations from TOLNet demonstrated that the performance of the three satellite products varied by season and altitude in the troposphere. TOLNet was shown in this study to be a sufficient source of satellite O3 profile validation data in the troposphere which is critical as this data source is the primary product identified for the tropospheric O3 validation of the recently-launched Tropospheric Emissions: Monitoring of Pollution (TEMPO) mission. [ABSTRACT FROM AUTHOR]

During the SALTRACE field experiment, conducted during June/July 2013, the Saharan dust transport across the Atlantic was analyzed by a set of ground based, in-situ and airborne instruments, including a 2-μm coherent DWL (Doppler wind lidar) mounted onboard the DLR Falcon 20 research aircraft. An overview of the measurements of aerosol backscatter and extinction, horizontal and vertical winds retrieved from the DWL are presented together with a brief description of the applied methods. The retrieved measurements provide direct observation of Saharan dust transport mechanisms across the Atlantic as well as island induced lee waves in the Barbados region.

The impact of aerosol fluorescence on the measurement of water vapor by UV (355 nm emission) Raman lidar in the upper troposphere and lower stratosphere (UTLS) is investigated using the long-term records of three high-performance Raman lidars contributing to the Network for the Detection of Atmospheric Composition Change (NDACC). Comparisons with co-located radiosondes and aerosol backscatter profiles indicate that laser-induced aerosol fluorescence in smoke layers injected into the stratosphere by pyrocumulus events can introduce very large and chronic wet biases above 15 km, thus impacting the ability of these systems to accurately estimate long-term water vapor trends in the UTLS. In order to mitigate the fluorescence contamination, a correction method based on the addition of an aerosol fluorescence channel was developed and tested on the water vapor Raman lidar TMWAL located at the JPL Table Mountain Facility, in California. The results of this experiment, conducted between 27 August and 4 November 2021 and involving 22 co-located lidar and radiosonde profiles, suggest that the proposed correction method is able to effectively reduced the fluorescence25 induced wet bias. After correction, the average difference between the lidar and co-located radiosonde water vapor measurements was reduced to 5%, consistent with the difference observed during periods of negligible aerosol fluorescence interference. The present results provide confidence that, after a correction is applied, water vapor long-term trends can be reasonably well estimated in the upper troposphere, but they also call for further refinements, or the use of alternate Raman lidar approaches (e.g., 308 nm or 532 nm emission) to confidently detect long-term trends in the lower stratosphere. These findings may have important implications on NDACC's water vapor measurements strategy in the years to come. [ABSTRACT FROM AUTHOR]

In this work, the impact of Los Angeles basin pollution transport and stratospheric intrusions on the surface ozone levels observed in the San Gabriel Mountains is investigated based on a combination of surface and lidar measurements as well as WRF-Chem (Weather Research and Forecasting with Chemistry) and WACCM (Whole Atmosphere Community Climate Model) model runs. The number of days with observed surface ozone levels exceeding the National Ambient Air Quality Standards exhibit a clear seasonal pattern, with a maximum during summer, when models suggest a minimum influence of stratospheric intrusions and the largest impact from Los Angeles basin pollution transport. Additionally, measured and modeled surface ozone and PM10 were analyzed as a function of season, time of the day and wind direction. Measurements and models are in good qualitative agreement, with maximum surface ozone observed for south-west and west winds. For the prevailing summer wind direction, slightly south of the ozone maximum and corresponding to south south-west winds, lower ozone levels were observed. Back-trajectories suggest that this is associated with transport from the central Los Angeles basin, where titration limits the amount of surface ozone. A quantitative comparison of the lidar profiles with WRF-Chem and WACCM models revealed good agreement near the surface, with models showing an increasing positive bias as function of altitude, reaching 75 % at 15 km above sea level. Finally, three selected case studies covering the different mechanisms affecting the near-surface ozone concentration over the San Gabriel mountains, namely stratospheric intrusions and pollution transport, are analyzed based on surface and ozone lidar measurements, as well as co-located ceilometer measurements and models. [ABSTRACT FROM AUTHOR]

Aerosol backscatter coefficients were calculated using multi-wavelength aerosol extinction products from the SAGE II and SAGE III/ISS instruments. The conversion methodology is presented followed by an evaluation of the conversion algorithm's robustness. The SAGE-based backscatter products were compared to backscatter coefficients derived from ground-based lidar at three sites (Table Mountain Facility, Mauna Loa, and Observatoire de Haute-Provence). This evaluation includes the major eruption of Mt. Pinatubo in 1991 followed by the atmospherically quiescent period beginning in the late nineties. Recommendations are made regarding the use of this method for evaluation of aerosol extinction profiles collected using the occultation method. [ABSTRACT FROM AUTHOR]

As part of the international efforts to monitor air quality, several satellite missions were deployed (e.g. TROPOMI) and others, like 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 collocated tethered balloon. An agreement of 5 % or better with the ozonesonde down to an altitude range of 100-m above ground was demonstrated. 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 two-month test period. Finally, measurements from a 24-hour 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 (about 52 m for lidar and at least 120 m for sonde). [ABSTRACT FROM AUTHOR]