Atmospheric Measurements Techniques Discussions

Toward a variational assimilation of polarimetric radar observations in a convective-scale numerical weather prediction (NWP) model
Guillaume Thomas, Jean-François Mahfouf, and Thibaut Montmerle
Atmos. Meas. Tech., 13, 2279–2298, https://doi.org/10.5194/amt-13-2279-2020, 2020
This paper presents the potential of a polarimetric weather radar observation operator for hydrometeor content initialization. The non-linear operator allows to simulate ZHH, ZDR, KDP and ρHV, using the T-Matrix method, prognostic variables forecasted by the AROME-France NWP model and a one-moment microphysical scheme. After sensitivity studies, it has been found that ZHH and ZDR are good candidates for hydrometeor initialization and that KDP seems useful for rain content only.

Validation of the vertical profiles of HCl over the wide range of the stratosphere to the lower thermosphere measured by SMILES
Seidai Nara, Tomohiro O. Sato, Takayoshi Yamada, Tamaki Fujinawa, Kota Kuribayashi, Takeshi Manabe, Lucien Froidevaux, Nathaniel J. Livesey, Kaley A. Walker, Jian Xu, Franz Schreier, Yvan J. Orsolini, Varavut Limpasuvan, Nario Kuno, and Yasuko Kasai
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-105,2020
Preprint under review for AMT (discussion: open, 0 comments)
In the atmosphere, more than 80 % of chlorine compounds are anthropogenic. Hydrogen chloride (HCl), the main stratospheric chlorine reservoir, is useful to estimate the total budget of the atmospheric chlorine compounds. We for the first time report the HCl vertical distribution from the middle troposphere to the lower thermosphere using a high sensitive SMILES measurement; the data quality is quantified by comparisons with other measurements and via theoretical error analysis.

A convolutional neural network for classifying cloud particles recorded by imaging probes
Georgios Touloupas, Annika Lauber, Jan Henneberger, Alexander Beck, and Aurélien Lucchi
Atmos. Meas. Tech., 13, 2219–2239, https://doi.org/10.5194/amt-13-2219-2020, 2020
Images of cloud particles give important information for improving our understanding of microphysical cloud processes. For phase-resolved measurements, a large number of water droplets and ice crystals need to be classified by an automated approach. In this study, a convolutional neural network was designed, which exceeds the classification ability of traditional methods and therefore shortens the analysis procedure of cloud particle images.

Intercomparison study of atmospheric 222Rn and 222Rn progeny monitors
Claudia Grossi, Scott D. Chambers, Olivier Llido, Felix R. Vogel, Victor Kazan, Alessandro Capuana, Sylvester Werczynski, Roger Curcoll, Marc Delmotte, Arturo Vargas, Josep-Anton Morguí, Ingeborg Levin, and Michel Ramonet
Atmos. Meas. Tech., 13, 2241–2255, https://doi.org/10.5194/amt-13-2241-2020, 2020
The sustainable support of radon metrology at the environmental level offers new scientific possibilities for the quantification of greenhouse gas (GHG) emissions and the determination of their source terms as well as for the identification of radioactive sources for the assessment of radiation exposure. This study helps to harmonize the techniques commonly used for atmospheric radon and radon progeny activity concentration measurements.

Validation of XCO2 and XCH4 retrieved from a portable Fourier transform spectrometer with those from in-situ profiles from aircraft borne instruments
Hirofumi Ohyama, Isamu Morino, Voltaire A. Velazco, Theresa Klausner, Gerry Bagtasa, Matthäus Kiel, Matthias Frey, Akihiro Hori, Osamu Uchino, Tsuneo Matsunaga, Nicholas Deutscher, Joshua P. DiGangi, Yonghoon Choi, Glenn S. Diskin, Sally E. Pusede, Alina Fiehn, Anke Roiger, Michael Lichtenstern, Hans Schlager, Pao K. Wang, Charles C.-K. Cho, Maria Dolores Andrés-Hernández, and John P. Burrows
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-170,2020
Preprint under review for AMT (discussion: open, 0 comments)
Column-averaged dry-air mole fractions of CO2 and CH4 measured by a solar viewing portable Fourier transform spectrometer (EM27/SUN) were validated with in-situ profile data obtained during the transfer flights of two aircraft campaigns. Atmospheric dynamical properties based on ERA5 and WRF-Chem were used as criteria for selecting the best aircraft profiles for the validation. The resulting air mass independent correction factors for the EM27/SUN data were 0.9878 for CO2 and 0.9833 for CH4.

Evaluation of single-footprint AIRS CH4 Profile Retrieval Uncertainties Using Aircraft Profile Measurements
Susan S. Kulawik, John R. Worden, Vivienne H. Payne, Dejian Fu, Steve C. Wofsy, Kathryn McKain, Colm Sweeney, Bruce C. Daube Jr., Alan Lipton, Igor Polonsky, Yuguang He, Karen E. Cady-Pereira, Edward J. Dlugokencky, Daniel J. Jacob, and Yi Yin
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-145,2020
Preprint under review for AMT (discussion: open, 0 comments)
This paper shows comparisons of a new methane product from the AIRS satellite to aircraft-based observations. We show that this AIRS methane product provides useful information to study seasonal and global methane trends of this important greenhouse gas.

Mapping ice formation to mineral-surface topography using a micro mixing chamber with video and atomic-force microscopy
Raymond W. Friddle and Konrad Thürmer
Atmos. Meas. Tech., 13, 2209–2218, https://doi.org/10.5194/amt-13-2209-2020, 2020
An obstacle to predicting ice content in mixed-phase clouds is the inability to directly view atmospheric ice nucleation at the nanoscale, where this process occurs. Here we show how a cloud-like environment can be created in a small atomic-force microscopy (AFM) sample cell. By colocating video microscopy of ice formation with high-resolution AFM images, we quantitatively show how the surface topography, down to nanometer-length scales, can determine the preferential locations of ice formation.

Improved chloride quantification in quadrupole aerosol chemical speciation monitors (Q-ACSMs)
Anna K. Tobler, Alicja Skiba, Dongyu S. Wang, Philip Croteau, Katarzyna Styszko, Jarosław Nęcki, Urs Baltensperger, Jay G. Slowik, and André S. H. Prévôt
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-117,2020
Preprint under review for AMT (discussion: open, 0 comments)
Some quadrupole aerosol chemical speciation monitors (Q-ACSMs) have shown issues with the quantification of particulate chloride, resulting in apparent negative chloride concentrations. We can show that this is due to the different behavior of Cl+ and HCl+ and we present a correction for more accurate quantification of chloride. The correction can be applied for measurements in environments where the particulate chloride is dominated by NH4Cl.

TomoSim: a tomographic simulator for DOAS
Rui Valente de Almeida, Nuno Matela, and Pedro Vieira
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-26,2020
Preprint under review for AMT (discussion: open, 0 comments)
Air pollution is quite literally one of the most present concerns of modern day Western societies. It is widely recognized (namely by the European Union) that technology plays a very important role in the fighting of this problem. One of such technologies is the spectroscopic measurement of air pollutant concentration known as DOAS. In this paper, the technique is applied with an Unmanned Aerial Vehicle, using tomographic techniques to map pollutant concentration in two dimensions.

Variability of the Brunt-Väisälä frequency at the OH-airglow layer height at low and mid latitudes
Sabine Wüst, Michael Bittner, Jeng-Hwa Yee, Martin G. Mlynczak, and James M. Russell III
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-73,2020
Preprint under review for AMT (discussion: open, 0 comments)
With airglow spectrometers the temperature in the upper mesosphere/lower thermosphere can be derived each night. The data allow to estimate the amount of energy which is transported by small-scale atmospheric waves, known as gravity waves. In order to do this, information about the Brunt–Väisälä frequency and its evolution during the year is necessary. This is provided here for low and mid latitudes based on 18 years of satellite data.

Three Decades of Tropospheric Ozone Lidar Development at Garmisch-Partenkirchen
Thomas Trickl, Helmuth Giehl, Frank Neidl, Matthias Perfahl, and Hannes Vogelmann
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-89,2020
Preprint under review for AMT (discussion: open, 0 comments)
Lidar sounding of ozone and other atmospheric constituents has proved to be invaluable tool for atmospheric studies. The ozone lidar systems developed at Garmisch-Partenkirchen have reached an accuracy level almost matching that of in situ sensors. Since the late 1990s numerous important scientific discoveries have been made such as the first observation of intercontinental transport of ozone and the very high occurrence of intrusions of stratospheric air into the troposphere.

Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV–visible spectrometers during CINDI-2
Karin Kreher, Michel Van Roozendael, Francois Hendrick, Arnoud Apituley, Ermioni Dimitropoulou, Udo Frieß, Andreas Richter, Thomas Wagner, Johannes Lampel, Nader Abuhassan, Li Ang, Monica Anguas, Alkis Bais, Nuria Benavent, Tim Bösch, Kristof Bognar, Alexander Borovski, Ilya Bruchkouski, Alexander Cede, Ka Lok Chan, Sebastian Donner, Theano Drosoglou, Caroline Fayt, Henning Finkenzeller, David Garcia-Nieto, Clio Gielen, Laura Gómez-Martín, Nan Hao, Bas Henzing, Jay R. Herman, Christian Hermans, Syedul Hoque, Hitoshi Irie, Junli Jin, Paul Johnston, Junaid Khayyam Butt, Fahim Khokhar, Theodore K. Koenig, Jonas Kuhn, Vinod Kumar, Cheng Liu, Jianzhong Ma, Alexis Merlaud, Abhishek K. Mishra, Moritz Müller, Monica Navarro-Comas, Mareike Ostendorf, Andrea Pazmino, Enno Peters, Gaia Pinardi, Manuel Pinharanda, Ankie Piters, Ulrich Platt, Oleg Postylyakov, Cristina Prados-Roman, Olga Puentedura, Richard Querel, Alfonso Saiz-Lopez, Anja Schönhardt, Stefan F. Schreier, André Seyler, Vinayak Sinha, Elena Spinei, Kimberly Strong, Frederik Tack, Xin Tian, Martin Tiefengraber, Jan-Lukas Tirpitz, Jeroen van Gent, Rainer Volkamer, Mihalis Vrekoussis, Shanshan Wang, Zhuoru Wang, Mark Wenig, Folkard Wittrock, Pinhua H. Xie, Jin Xu, Margarita Yela, Chengxin Zhang, and Xiaoyi Zhao
Atmos. Meas. Tech., 13, 2169–2208, https://doi.org/10.5194/amt-13-2169-2020, 2020
In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants during an instrument intercomparison campaign (CINDI-2) at Cabauw, the Netherlands. Here we report on the outcome of this intercomparison exercise. The three major goals were to characterise the differences between the participating instruments, to define a robust methodology for performance assessment, and to contribute to the harmonisation of the measurement settings and retrieval methods.

Global Cloud Property Models for Real Time Triage Onboard Visible-Shortwave Infrared Spectrometers
Macey W. Sandford, David R. Thompson, Robert O. Green, Brian H. Kahn, Raffaele Vitulli, Steve Chien, Amruta Yelamanchili, and Winston Olson-Duvall
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-139,2020
Preprint under review for AMT (discussion: open, 0 comments)
We demonstrate an onboard cloud screening approach to significantly reduce the amount of cloud-contaminated data transmitted from orbit. We have produced location-specific models that improve performance by taking into account the unique cloud statistics in different latitudes. We have shown that screening clouds based on their location or surface type will improve the ability for a cloud-screening tool to improve the volume of usable science data.

The influence of the baseline drift on the resulting extinction values of a cavity attenuated phase shift-based extinction monitor (CAPS PMex)
Sascha Pfeifer, Thomas Müller, Andrew Freedman, and Alfred Wiedensohler
Atmos. Meas. Tech., 13, 2161–2167, https://doi.org/10.5194/amt-13-2161-2020, 2020
The effect of the baseline drift on the resulting extinction values of three CAPS PMex monitors with different wavelengths was analysed for an urban background station. A significant baseline drift was observed, which leads to characteristic measurement artefacts for particle extinction. Two alternative methods for recalculating the baseline are shown. With these methods the extinction artefacts are diminished and the effective scattering of the resulting extinction values is reduced.

How to estimate total differential attenuation due to hydrometeors with ground-based multi-frequency radars?
Frédéric Tridon, Alessandro Battaglia, and Stefan Kneifel
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-159,2020
Preprint under review for AMT (discussion: open, 0 comments)

At millimeter wavelengths, attenuation by hydrometeors, such as liquid droplets or large snowflakes, is generally not negligible. When using multi-frequency ground-based radar measurements, it is common practice to use the Rayleigh targets at cloud top as a reference in order to derive attenuation-corrected reflectivities and meaningful dual-frequency ratios (DFR). By capitalizing on this idea, this study describes a new quality-controlled approach aiming at identifying regions of the cloud where particle growth is negligible. The core of the method is the identification of a Rayleigh plateau, i.e. a large enough region near cloud top where the vertical gradient of DFR remains small.

By analyzing collocated Ka-W band radar and microwave radiometer (MWR) observations taken at two European sites under various meteorological conditions, it is shown how the resulting estimates of differential path-integrated attenuation (DeltaPIA) can be used to characterize hydrometeor properties. When the DeltaPIA is predominantly produced by cloud liquid droplets, this technique alone can provide accurate estimates of the liquid water path. When combined with MWR observations, this methodology paves the way towards profiling the cloud liquid water and/or quality flagging the MWR retrieval for rain/drizzle contamination and/or estimating the snow differential attenuation.

An inter-laboratory comparison of aerosol in organic ion measurements by Ion Chromatography: implications for aerosol pH estimate
Jingsha Xu, Shaojie Song, Roy M. Harrison, Congbo Song, Lianfang Wei, Qiang Zhang, Yele Sun, Lu Lei, Chao Zhang, Xiaohong Yao, Dihui Chen, Weijun Li, Miaomiao Wu, Hezhong Tian, Lining Luo, Shengrui Tong, Weiran Li, Junling Wang, Guoliang Shi, Yanqi Huangfu, Yingze Tian, Baozhu Ge, Shaoli Su, Chao Peng, Yang Chen, Fumo Yang, Aleksandra Mihajlidi-Zelić, Dragana Đorđević, Stefan J. Swift, Imogen Andrews, Jacqueline F. Hamilton, Ye Sun, Agung Kramawijaya, Jinxiu Han, Supattarachai Saksakulkrai, Clarissa Baldo, Siqi Hou, Feixue Zheng, Kaspar R. Daellenbach, Chao Yan, Yongchun Liu, Markku Kulmala, Pingqing Fu, and Zongbo Shi
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-156,2020
Preprint under review for AMT (discussion: open, 0 comments)
An inter-laboratory comparison exercise was conducted for the first time to examine the difference of water-soluble inorganic ions (WSII) measured by 10 labs using Ion Chromatography and by 2 online Aerosol Chemical Speciation Monitor method. Major ions including SO42−, NO3−, NH4+ agreed well in 10 IC labs, and correlated well with ACSM. WSII inter-lab variability strongly affected aerosol acidity results based on ion balance, but aerosol pH computed by ISORROPIA-II were very similar.

Three-dimensional radiative transfer effects on airborne, satellite and ground-based trace gas remote sensing
Marc Schwaerzel, Claudia Emde, Dominik Brunner, Randulph Morales, Thomas Wagner, Alexis Berne, Brigitte Buchmann, and Gerrit Kuhlmann
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-146,2020
Preprint under review for AMT (discussion: open, 0 comments)
Horizontal homogeneity is often assumed for trace gases remote sensing, although it is not valid where trace gas concentrations have high spatial variability, e.g. in cities. We show the importance of 3D effects for MAX-DOAS and airborne imaging spectrometers using 3D-box air mass factors implemented in the MYSTIC radiative transfer solver. In both cases, 3D information is invaluable for interpreting the measurements, as not considering 3D effects can lead to misinterpretation of measurements.

Ground-based FTIR O3 retrievals from the 3040 cm−1 spectral range at Xianghe, China
Minqiang Zhou, Pucai Wang, Bavo Langerock, Corinne Vigouroux, Christian Hermans, Nicolas Kumps, Ting Wang, Yang Yang, Denghui Ji, Liang Ran, Jinqiang Zhang, Yuejian Xuan, Hongbin Chen, Françoise Posny, Valentin Duflot, Jean-Marc Metzger, and Martine De Mazière
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-127,2020
Preprint under review for AMT (discussion: open, 0 comments)
We study O3 retrievals in the 3040 cm−1 spectral range from FTIR measurements at Xianghe China (39.75N, 116.96E, 50 m a.s.l.) between June 2018 and December 2019. It is found that the FTIR O3 (3040 cm−1) retrievals capture very well the seasonal and synoptic variations of O3. The systematic and random uncertainties of FTIR O3 (3040 cm−1) total column are about 5.5–9.0 % and 1.4%, respectively. The DOF is 2.4±0.3 (1σ), with 2 individual pieces of information in surface-20 km and 20–40 km.

Detecting turbulent structures on single Doppler lidar large datasets: an automated classification method for horizontal scans
Ioannis Cheliotis, Elsa Dieudonné, Hervé Delbarre, Anton Sokolov, Egor Dmitriev, Patrick Augustin, and Marc Fourmentin
Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2020-82,2020
Preprint under review for AMT (discussion: open, 0 comments)
The current study presents an automated method to classify turbulent structures near the surface, based on the observations recorded by a single scanning Doppler lidar. This methodology combines texture analysis with a supervised machine learning algorithm in order to study large datasets. The algorithm classified correctly about 91 % cases of a training ensemble (150 scans). Furthermore the results of a two-months classified dataset (4577 scans) by the algorithm are presented.

Assessment of the quality of TROPOMI high-spatial-resolution NO2 data products in the Greater Toronto Area
Xiaoyi Zhao, Debora Griffin, Vitali Fioletov, Chris McLinden, Alexander Cede, Martin Tiefengraber, Moritz Müller, Kristof Bognar, Kimberly Strong, Folkert Boersma, Henk Eskes, Jonathan Davies, Akira Ogyu, and Sum Chi Lee
Atmos. Meas. Tech., 13, 2131–2159, https://doi.org/10.5194/amt-13-2131-2020, 2020
Pandora NO2 measurements made at three sites located in the Toronto area are used to evaluate the TROPOspheric Monitoring Instrument (TROPOMI) NO2 data products, including standard NO2 and research data developed using a high-resolution regional air quality forecast model. TROPOMI pixels located upwind and downwind from the Pandora sites were analyzed by a new wind-based validation method, which revealed the spatial patterns of local and transported emissions and regional air quality changes.