Learning about the vertical structure of radar reflectivity using hydrometeor classes and neural networks in the Swiss Alps
Floor van den Heuvel, Loris Foresti, Marco Gabella, Urs Germann, and Alexis Berne
Atmos. Meas. Tech., 13, 2481–2500, https://doi.org/10.5194/amt-13-2481-2020, 2020
In areas with reduced visibility at the ground level, radar precipitation measurements higher up in the atmosphere need to be extrapolated to the ground and be corrected for the vertical change (i.e. growth and transformation) of precipitation. This study proposes a method based on hydrometeor proportions and machine learning (ML) to apply these corrections at smaller spatiotemporal scales. In comparison with existing techniques, the ML methods can make predictions from higher altitudes.
Assessment of NO2 observations during DISCOVER-AQ and KORUS-AQ field campaigns
Sungyeon Choi, Lok N. Lamsal, Melanie Follette-Cook, Joanna Joiner, Nickolay A. Krotkov, William H. Swartz, Kenneth E. Pickering, Christopher P. Loughner, Wyat Appel, Gabriele Pfister, Pablo E. Saide, Ronald C. Cohen, Andrew J. Weinheimer, and Jay R. Herman
Atmos. Meas. Tech., 13, 2523–2546, https://doi.org/10.5194/amt-13-2523-2020, 2020
NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ, conducted in 2011–2014) campaign in the United States and the joint NASA and National Institute of Environmental Research (NIER) Korea–United States Air Quality Study (KORUS-AQ, conducted in 2016) in South Korea were two field study programs that provided comprehensive, integrated datasets of airborne and surface observations of atmospheric constituents, including nitrogen dioxide (NO2), with the goal of improving the interpretation of spaceborne remote sensing data. Various types of NO2 measurements were made, including in situ concentrations and column amounts of NO2 using ground- and aircraft-based instruments, while NO2 column amounts were being derived from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This study takes advantage of these unique datasets by first evaluating in situ data taken from two different instruments on the same aircraft platform, comparing coincidently sampled profile-integrated columns from aircraft spirals with remotely sensed column observations from ground-based Pandora spectrometers, intercomparing column observations from the ground (Pandora), aircraft (in situ vertical spirals), and space (OMI), and evaluating NO2 simulations from coarse Global Modeling Initiative (GMI) and high-resolution regional models. We then use these data to interpret observed discrepancies due to differences in sampling and deficiencies in the data reduction process. Finally, we assess satellite retrieval sensitivity to observed and modeled a priori NO2 profiles. Contemporaneous measurements from two aircraft instruments that likely sample similar air masses generally agree very well but are also found to differ in integrated columns by up to 31.9 %. These show even larger differences with Pandora, reaching up to 53.9 %, potentially due to a combination of strong gradients in NO2 fields that could be missed by aircraft spirals and errors in the Pandora retrievals. OMI NO2 values are about a factor of 2 lower in these highly polluted environments due in part to inaccurate retrieval assumptions (e.g., a priori profiles) but mostly to OMI's large footprint (>312 km2).
A technical description of the Balloon Lidar Experiment BOLIDE
Bernd Kaifler, Dimitry Rempel, Philipp Roßi, Christian Büdenbender, Natalie Kaifler, and Volodymyr Baturkin
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-150,2020
Preprint under review for AMT (discussion: open, 0 comments)
The Balloon Lidar Experiment was the first lidar dedicated to measurements in the mesosphere flown on a balloon. During a 6 day flight it made high resolution observations of polar mesospheric clouds which form at high latitudes during summer in ~83 km altitude and are the highest clouds in Earth's atmosphere. We describe the instrument and assess its performance. We could detect fainter clouds with higher resolution than what is possible with ground-based instruments.
Learning about the vertical structure of radar reflectivity using hydrometeor classes and neural networks in the Swiss Alps
Floor van den Heuvel, Loris Foresti, Marco Gabella, Urs Germann, and Alexis Berne
Atmos. Meas. Tech., 13, 2481–2500, https://doi.org/10.5194/amt-13-2481-2020, 2020
In areas with reduced visibility at the ground level, radar precipitation measurements higher up in the atmosphere need to be extrapolated to the ground and be corrected for the vertical change (i.e. growth and transformation) of precipitation. This study proposes a method based on hydrometeor proportions and machine learning (ML) to apply these corrections at smaller spatiotemporal scales. In comparison with existing techniques, the ML methods can make predictions from higher altitudes.
Assessment of NO2 observations during DISCOVER-AQ and KORUS-AQ field campaigns
Sungyeon Choi, Lok N. Lamsal, Melanie Follette-Cook, Joanna Joiner, Nickolay A. Krotkov, William H. Swartz, Kenneth E. Pickering, Christopher P. Loughner, Wyat Appel, Gabriele Pfister, Pablo E. Saide, Ronald C. Cohen, Andrew J. Weinheimer, and Jay R. Herman
Atmos. Meas. Tech., 13, 2523–2546, https://doi.org/10.5194/amt-13-2523-2020, 2020
NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ, conducted in 2011–2014) campaign in the United States and the joint NASA and National Institute of Environmental Research (NIER) Korea–United States Air Quality Study (KORUS-AQ, conducted in 2016) in South Korea were two field study programs that provided comprehensive, integrated datasets of airborne and surface observations of atmospheric constituents, including nitrogen dioxide (NO2), with the goal of improving the interpretation of spaceborne remote sensing data. Various types of NO2 measurements were made, including in situ concentrations and column amounts of NO2 using ground- and aircraft-based instruments, while NO2 column amounts were being derived from the Ozone Monitoring Instrument (OMI) on the Aura satellite. This study takes advantage of these unique datasets by first evaluating in situ data taken from two different instruments on the same aircraft platform, comparing coincidently sampled profile-integrated columns from aircraft spirals with remotely sensed column observations from ground-based Pandora spectrometers, intercomparing column observations from the ground (Pandora), aircraft (in situ vertical spirals), and space (OMI), and evaluating NO2 simulations from coarse Global Modeling Initiative (GMI) and high-resolution regional models. We then use these data to interpret observed discrepancies due to differences in sampling and deficiencies in the data reduction process. Finally, we assess satellite retrieval sensitivity to observed and modeled a priori NO2 profiles. Contemporaneous measurements from two aircraft instruments that likely sample similar air masses generally agree very well but are also found to differ in integrated columns by up to 31.9 %. These show even larger differences with Pandora, reaching up to 53.9 %, potentially due to a combination of strong gradients in NO2 fields that could be missed by aircraft spirals and errors in the Pandora retrievals. OMI NO2 values are about a factor of 2 lower in these highly polluted environments due in part to inaccurate retrieval assumptions (e.g., a priori profiles) but mostly to OMI's large footprint (>312 km2).
A technical description of the Balloon Lidar Experiment BOLIDE
Bernd Kaifler, Dimitry Rempel, Philipp Roßi, Christian Büdenbender, Natalie Kaifler, and Volodymyr Baturkin
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-150,2020
Preprint under review for AMT (discussion: open, 0 comments)
The Balloon Lidar Experiment was the first lidar dedicated to measurements in the mesosphere flown on a balloon. During a 6 day flight it made high resolution observations of polar mesospheric clouds which form at high latitudes during summer in ~83 km altitude and are the highest clouds in Earth's atmosphere. We describe the instrument and assess its performance. We could detect fainter clouds with higher resolution than what is possible with ground-based instruments.
Measurement of ammonia, amines and iodine compounds using protonated water cluster chemical ionization mass spectrometry
Joschka Pfeifer, Mario Simon, Martin Heinritzi, Felix Piel, Lena Weitz, Dongyu Wang, Manuel Granzin, Tatjana Müller, Steffen Bräkling, Jasper Kirkby, Joachim Curtius, and Andreas Kürten
Atmos. Meas. Tech., 13, 2501–2522, https://doi.org/10.5194/amt-13-2501-2020, 2020
Ammonia is an important atmospheric trace gas that affects secondary aerosol formation and, together with sulfuric acid, the formation of new particles. A measurement technique is presented that uses high-resolution mass spectrometry and protonated water clusters for the ultrasensitive detection of ammonia at single-digit parts per trillion by volume levels. The instrument is further capable of measuring amines and a suite of iodine compounds at sub-parts per trillion by volume levels.
Measurement of ammonia, amines and iodine compounds using protonated water cluster chemical ionization mass spectrometry
Joschka Pfeifer, Mario Simon, Martin Heinritzi, Felix Piel, Lena Weitz, Dongyu Wang, Manuel Granzin, Tatjana Müller, Steffen Bräkling, Jasper Kirkby, Joachim Curtius, and Andreas Kürten
Atmos. Meas. Tech., 13, 2501–2522, https://doi.org/10.5194/amt-13-2501-2020, 2020
Ammonia is an important atmospheric trace gas that affects secondary aerosol formation and, together with sulfuric acid, the formation of new particles. A measurement technique is presented that uses high-resolution mass spectrometry and protonated water clusters for the ultrasensitive detection of ammonia at single-digit parts per trillion by volume levels. The instrument is further capable of measuring amines and a suite of iodine compounds at sub-parts per trillion by volume levels.
A low-activity ion source for measurement of atmospheric gases by chemical ionization mass spectrometry
Young Ro Lee, Yi Ji, David J. Tanner, and L. Gregory Huey
Atmos. Meas. Tech., 13, 2473–2480, https://doi.org/10.5194/amt-13-2473-2020, 2020
In this work we show how to construct a radioactive ion source for a chemical ionization mass spectrometer (CIMS) from commercially available components. The source is low activity and can be shipped with a minimum of complications. This facilitates the deployment of CIMS to measure atmospheric pollutants at remote ground sites.
Characterization of anthropogenic organic aerosols by TOF-ACSM with the new capture vaporizer
Yan Zheng, Xi Cheng, Keren Liao, Yaowei Li, Yong Jie Li, Ru-Jin Huang, Weiwei Hu, Ying Liu, Tong Zhu, Shiyi Chen, Limin Zeng, Douglas R. Worsnop, and Qi Chen
Atmos. Meas. Tech., 13, 2457–2472, https://doi.org/10.5194/amt-13-2457-2020, 2020
This paper provides important information to help researchers to understand the mass quantification and source apportionment by Aerodyne aerosol mass spectrometers.
MICRU background map and effective cloud fraction algorithms designed for UV/vis satellite instruments with large viewing angles
Holger Sihler, Steffen Beirle, Steffen Dörner, Marloes Gutenstein-Penning de Vries, Christoph Hörmann, Christian Borger, Simon Warnach, and Thomas Wagner
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-182,2020
Preprint under review for AMT (discussion: open, 0 comments)
MICRU is an algorithm for the retrieval of effective cloud fractions (CF) from satellite measurements. CF describe the amount of clouds, which have a significant impact on the vertical sensitivity profile of trace-gases like NO2 and HCHO. MICRU retrieves small CF with an accuracy of 0.04 over the entire satellite swath. It features an empirical surface reflectivity model accounting for physical anisotropy (BRDF, sun glitter) and instrumental effects. MICRU is also applicable to imager data.
A new OCO-2 cloud flagging and rapid retrieval of marine boundary layer cloud properties
Mark Richardson, Matthew D. Lebsock, James McDuffie, and Graeme L. Stephens
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-140,2020
Preprint under review for AMT (discussion: open, 0 comments)
We previously combined data from a lidar on the CALIPSO satellite and measurements of reflected sunlight from the OCO-2 satellite to get new information about low clouds over oceans. The satellites are no longer formation flying, so this work is a step towards getting unique new information about these clouds using OCO-2 data only. We show we can rapidly and accurately identify liquid oceanic clouds and obtain their height better than a widely-used passive sensor.
A low-activity ion source for measurement of atmospheric gases by chemical ionization mass spectrometry
Young Ro Lee, Yi Ji, David J. Tanner, and L. Gregory Huey
Atmos. Meas. Tech., 13, 2473–2480, https://doi.org/10.5194/amt-13-2473-2020, 2020
In this work we show how to construct a radioactive ion source for a chemical ionization mass spectrometer (CIMS) from commercially available components. The source is low activity and can be shipped with a minimum of complications. This facilitates the deployment of CIMS to measure atmospheric pollutants at remote ground sites.
Characterization of anthropogenic organic aerosols by TOF-ACSM with the new capture vaporizer
Yan Zheng, Xi Cheng, Keren Liao, Yaowei Li, Yong Jie Li, Ru-Jin Huang, Weiwei Hu, Ying Liu, Tong Zhu, Shiyi Chen, Limin Zeng, Douglas R. Worsnop, and Qi Chen
Atmos. Meas. Tech., 13, 2457–2472, https://doi.org/10.5194/amt-13-2457-2020, 2020
This paper provides important information to help researchers to understand the mass quantification and source apportionment by Aerodyne aerosol mass spectrometers.
MICRU background map and effective cloud fraction algorithms designed for UV/vis satellite instruments with large viewing angles
Holger Sihler, Steffen Beirle, Steffen Dörner, Marloes Gutenstein-Penning de Vries, Christoph Hörmann, Christian Borger, Simon Warnach, and Thomas Wagner
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-182,2020
Preprint under review for AMT (discussion: open, 0 comments)
MICRU is an algorithm for the retrieval of effective cloud fractions (CF) from satellite measurements. CF describe the amount of clouds, which have a significant impact on the vertical sensitivity profile of trace-gases like NO2 and HCHO. MICRU retrieves small CF with an accuracy of 0.04 over the entire satellite swath. It features an empirical surface reflectivity model accounting for physical anisotropy (BRDF, sun glitter) and instrumental effects. MICRU is also applicable to imager data.
A new OCO-2 cloud flagging and rapid retrieval of marine boundary layer cloud properties
Mark Richardson, Matthew D. Lebsock, James McDuffie, and Graeme L. Stephens
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2020-140,2020
Preprint under review for AMT (discussion: open, 0 comments)
We previously combined data from a lidar on the CALIPSO satellite and measurements of reflected sunlight from the OCO-2 satellite to get new information about low clouds over oceans. The satellites are no longer formation flying, so this work is a step towards getting unique new information about these clouds using OCO-2 data only. We show we can rapidly and accurately identify liquid oceanic clouds and obtain their height better than a widely-used passive sensor.
An intercomparison of CH3O2 measurements by fluorescence assay by gas expansion and cavity ring-down spectroscopy within HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry)
Lavinia Onel, Alexander Brennan, Michele Gianella, James Hooper, Nicole Ng, Gus Hancock, Lisa Whalley, Paul W. Seakins, Grant A. D. Ritchie, and Dwayne E. Heard
Atmos. Meas. Tech., 13, 2441–2456, https://doi.org/10.5194/amt-13-2441-2020, 2020
Simultaneous measurements of CH3O2 radical concentrations have been performed using two different methods in the Leeds HIRAC (Highly Instrumented Reactor for Atmospheric Chemistry) chamber at 295 K and in 80 mbar of a mixture of 3:1 He∕O2 and 100 or 1000 mbar of synthetic air. The first detection method consisted of the indirect detection of CH3O2 using the conversion of CH3O2 into CH3O by excess NO with subsequent detection of CH3O by fluorescence assay by gas expansion (FAGE). The FAGE instrument was calibrated for CH3O2 in two ways. In the first method, a known concentration of CH3O2 was generated using the 185 nm photolysis of water vapour in synthetic air at atmospheric pressure followed by the conversion of the generated OH radicals to CH3O2 by reaction with CH4∕O2. This calibration can be used for experiments performed in HIRAC at 1000 mbar in air. In the second method, calibration was achieved by generating a near steady state of CH3O2 and then switching off the photolysis lamps within HIRAC and monitoring the subsequent decay of CH3O2, which was controlled via its self-reaction, and analysing the decay using second-order kinetics. This calibration could be used for experiments performed at all pressures. In the second detection method, CH3O2 was measured directly using cavity ring-down spectroscopy (CRDS) using the absorption at 7487.98 cm−1 in the A←X (ν12) band with the optical path along the ∼1.4 m chamber diameter. Analysis of the second-order kinetic decays of CH3O2 by self-reaction monitored by CRDS has been used for the determination of the CH3O2 absorption cross section at 7487.98 cm−1, both at 100 mbar of air and at 80 mbar of a 3:1 He∕O2 mixture, from which σCH3O2=(1.49±0.19)×10-20 cm2 molecule−1 was determined for both pressures. The absorption spectrum of CH3O2 between 7486 and 7491 cm−1 did not change shape when the total pressure was increased to 1000 mbar, from which we determined that σCH3O2 is independent of pressure over the pressure range 100–1000 mbar in air. CH3O2 was generated in HIRAC using either the photolysis of Cl2 with UV black lamps in the presence of CH4 and O2 or the photolysis of acetone at 254 nm in the presence of O2. At 1000 mbar of synthetic air the correlation plot of [CH3O2]FAGE against [CH3O2]CRDS gave a gradient of 1.09±0.06. At 100 mbar of synthetic air the FAGE–CRDS correlation plot had a gradient of 0.95±0.024, and at 80 mbar of 3:1 He∕O2 mixture the correlation plot gradient was 1.03±0.05. These results provide a validation of the FAGE method to determine concentrations of CH3O2.
Laboratory evaluation of particle-size selectivity of optical low-cost particulate matter sensors
Joel Kuula, Timo Mäkelä, Minna Aurela, Kimmo Teinilä, Samu Varjonen, Óscar González, and Hilkka Timonen
Atmos. Meas. Tech., 13, 2413–2423, https://doi.org/10.5194/amt-13-2413-2020, 2020
Particle-size-dependent detection ranges of low-cost particulate matter sensors were evaluated in a laboratory experiment. Six different sensor models were evaluated altogether. The results showed that none of the sensor models adhered to the technical specifications provided by the manufacturers, and thus a high risk of sensor misuse is posed. It is paramount that the limitations regarding the particle size discrimination of low-cost sensors are acknowledged properly.
First validation of Aeolus wind observations by airborne Doppler wind lidar measurements
Benjamin Witschas, Christian Lemmerz, Alexander Geiß, Oliver Lux, Uwe Marksteiner, Stephan Rahm, Oliver Reitebuch, and Fabian Weiler
Atmos. Meas. Tech., 13, 2381–2396, https://doi.org/10.5194/amt-13-2381-2020, 2020
Aeolus, the first ever wind lidar in space, has been providing wind profiles on a global scale since its launch. In order to validate the quality of Aeolus wind observations, the German Aerospace Center (DLR) recently performed two airborne campaigns over central Europe deploying two different Doppler wind lidars. A total of 10 satellite underflights were performed and used to validate the early-stage wind data product of Aeolus by means of collocated airborne wind lidar observations.
Nitrate radical generation via continuous generation of dinitrogen pentoxide in a laminar flow reactor coupled to an oxidation flow reactor
Andrew T. Lambe, Ezra C. Wood, Jordan E. Krechmer, Francesca Majluf, Leah R. Williams, Philip L. Croteau, Manuela Cirtog, Anaïs Féron, Jean-Eudes Petit, Alexandre Albinet, Jose L. Jimenez, and Zhe Peng
Atmos. Meas. Tech., 13, 2397–2411, https://doi.org/10.5194/amt-13-2397-2020, 2020
We present a new method to continuously generate N2O5 in the gas phase that is injected into a reactor where it decomposes to generate nitrate radicals (NO3). To assess the applicability of the method towards different chemical systems, we present experimental and model characterization of the integrated NO3 exposure and other metrics as a function of operating conditions. We demonstrate the method by characterizing secondary organic aerosol particles generated from the β-pinene + NO3 reaction.
