ALBERT

Description: 〈b〉Retrieval of liquid water cloud properties from POLDER-3 measurements using a neural network ensemble approach〈/b〉〈br〉 Antonio Di Noia, Otto P. Hasekamp, Bastiaan van Diedenhoven, and Zhibo Zhang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-345,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This paper describes a neural network algorithm for the estimation of liquid water cloud optical properties from the Polarization and Directionality of Earth's Reflectances-3 (POLDER-3) instrument, on board the Polarization & Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. The algorithm has been trained on synthetic multi-angle, multi-wavelength measurements of reflectance and polarization, and has been applied to the processing of one year of POLDER-3 data. Comparisons of the retrieved cloud properties with Moderate resolution Imaging Spectroradiometer (MODIS) products show negative biases around −2 in retrieved cloud optical thicknesses (COTs) and between −1 and −2 μm in retrieved cloud effective radii. Comparisons with existing POLDER-3 datasets suggest that the proposed scheme may have enhanced capabilities for cloud effective radius retrieval at least over land. An additional feature of the presented algorithm is that it provides COT and effective radius retrievals at the native POLDER-3 Level 1B pixel level.〈/p〉

Description: 〈b〉Recovery of the three-dimensional wind and sonic temperature data from a physically deformed sonic anemometer〈/b〉〈br〉 Xinhua Zhou, Qinghua Yang, Xiaojie Zhen, Yubin Li, Guanghua Hao, Hui Shen, Tian Gao, Yirong Sun, and Ning Zheng〈br〉 Atmos. Meas. Tech., 11, 5981-6002, https://doi.org/10.5194/amt-11-5981-2018, 2018〈br〉 The three-dimensional wind and sonic temperature data from a physically deformed sonic anemometer was successfully recovered by developing equations, algorithms, and related software. Using two sets of geometry data from production calibration and return re-calibration, this algorithm can recover wind with/without transducer shadow correction and sonic temperature with crosswind correction, and then obtain fluxes at quality as expected. This study is applicable as a reference for related topics.

Description: 〈b〉Doppler W-band polarization diversity space-borne radar simulator for wind studies〈/b〉〈br〉 Alessandro Battaglia, Ranvir Dhillon, and Anthony Illingworth〈br〉 Atmos. Meas. Tech., 11, 5965-5979, https://doi.org/10.5194/amt-11-5965-2018, 2018〈br〉 A new technique is proposed to simulated winds in clouds as they could be observed by a space-borne Doppler 3 mm wavelength radar. Results show that, in the presence of cloud inhomogeneity and of vertical wind shear, measured winds can be corrected and produce unbiased estimates of line-of-sight winds that can then be assimilated in numerical models to improve weather forecasts.

Description: 〈b〉Potential of INSAT-3D sounder-derived total precipitable water product for weather forecast〈/b〉〈br〉 Shailesh Parihar, Ashim Kumar Mitra, Mrutyunjay Mohapatra, and Rajjev Bhatla〈br〉 Atmos. Meas. Tech., 11, 6003-6012, https://doi.org/10.5194/amt-11-6003-2018, 2018〈br〉 This paper is based on operational work carried out at IMD, New Delhi using the INSAT-3D satellite-derived sounder product TPW for weather events such as rainfall and thunderstorms. The INSAT-3D TPW has been used by forecasters as well as many other users over the last 2 years. This work mainly brings out an in-depth validation with in situ ground measurement data as well as a GNSS system for its suitability in weather prediction. This paper can be utilized operationally for weather purposes.

Description: 〈b〉High-precision measurements of nitrous oxide and methane in air with cavity ring-down spectroscopy at 7.6 μm〈/b〉〈br〉 Jing Tang, Bincheng Li, and Jing Wang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-385,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A high-sensitivity CH〈sub〉4〈/sub〉 and N〈sub〉2〈/sub〉O sensor based on mid-IR (7.6 µm) cavity ring-down spectroscopy was developed. The effect of temperature fluctuation on measurement sensitivity was analyzed and corrected, and detection limits of 3.62 pptv for CH〈sub〉4〈/sub〉 and 4.67 pptv for N〈sub〉2〈/sub〉O were experimentally achieved. Separate and continuous measurements of CH〈sub〉4〈/sub〉 and N〈sub〉2〈/sub〉O concentrations of in-/out-door air at different locations showed the spatial and temporal concentration variations of CH〈sub〉4〈/sub〉 and N〈sub〉2〈/sub〉O in air.

Description: 〈b〉Calibration of isotopologue-specific optical trace gas analysers: a practical guide〈/b〉〈br〉 David W. T. Griffith〈br〉 Atmos. Meas. Tech., 11, 6189-6201, https://doi.org/10.5194/amt-11-6189-2018, 2018〈br〉 In recent years optical spectroscopic techniques have become commonly used in the determination of mole fractions of trace gases in air. These techniques in many cases determine the mole fractions of only individual isotopic variants (〈q〉isotopologues〈/q〉) of the trace gas, while for many applications the total mole fraction of all isotopologues is required. This paper sets out the measurements and calculations required to convert between individual isotopologue and total trace gas amounts.

Description: 〈b〉Improving the Mean and Uncertainty of Ultraviolet Multi-Filter Rotating Shadowband Radiometer In-Situ Calibration Factors: Utilizing Gaussian Process Regression with a New Method to Estimate Dynamic Input Uncertainty〈/b〉〈br〉 Maosi Chen, Zhibin Sun, John M. Davis, Yan-An Liu, Chelsea A. Corr, and Wei Gao〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-295,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉To recover the actual responsivity for Ultraviolet Multi-Filter Rotating Shadowband Radiometer (UV-MFRSR), the complex (e.g. unstable, noisy, and with gaps) time series of its in-situ calibration factors (Vo) need to be smoothed. Many smoothing techniques require accurate input uncertainty of the time series. A new method is proposed to estimate the dynamic input uncertainty by examining overall variation and subgroup means within a moving time window. Using this calculated dynamic input uncertainty within Gaussian Process regression (GP) provides the mean and uncertainty functions of the time series. This proposed GP solution was first applied on a synthetic signal and showed significant smaller RMSEs than a Gaussian Process regression performed with constant values of input uncertainty and the mean function. GP was then applied to three UV-MFRSR Vo time series at three ground sites; The method appropriately accounted for variation in slopes, noises, and gaps at all sites. The validation results demonstrated that the agreement between aerosol optical depths (AODs) calculated using Vo determined by the GP mean function and AERONET AODs were consistently better than those calculated using Vo from standard techniques (e.g. moving average). The improved accuracy of in-situ UVMRP Vo values suggests the GP solution is a robust technique for accurate analysis of complex time series and may be applicable to other fields.〈/p〉

Description: 〈b〉An inter-comparison of total column-averaged nitrous oxide between ground-based FTIR TCCON and NDACC measurements at seven sites and comparisons with the GEOS-Chem model〈/b〉〈br〉 Minqiang Zhou, Bavo Langerock, Kelley C. Wells, Dylan B. Millet, Corinne Vigouroux, Mahesh Kumar Sha, Christian Hermans, Jean-Marc Metzger, Rigel Kivi, Pauli Heikkinen, Dan Smale, David F. Pollard, Nicholas Jones, Nicholas M. Deutscher, Thomas Blumenstock, Matthias Schneider, Mathias Palm, Justus Notholt, James W. Hannigan, and Martine De Mazière〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-340,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 N〈sub〉2〈/sub〉O is an important atmospheric gas, which is observed by two ground-based FTIR networks (TCCON and NDACC).The difference between NDACC and TCCON X〈sub〉N〈sub〉2〈/sub〉O〈/sub〉 measurements are discussed. It is found that the bias between two networks are within their combined uncertainties. However, TCCON measurements are affected by a priori profiles. In addition, the TCCON and NDACC N〈sub〉2〈/sub〉O measurements are compared with the GEOS-Chem model simulations.

Description: 〈b〉Joint retrieval of surface reflectance and aerosol properties with continuous variation of the state variables in the solution space – Part 1: theoretical concept〈/b〉〈br〉 Yves Govaerts and Marta Luffarelli〈br〉 Atmos. Meas. Tech., 11, 6589-6603, https://doi.org/10.5194/amt-11-6589-2018, 2018〈br〉 This paper presents a new algorithm for the joint retrieval of surface reflectance and aerosol properties with continuous variations of the state variables in the solution space. This algorithm, named CISAR (Combined Inversion of Surface and AeRosol), relies on a simple atmospheric vertical structure composed of two layers and an underlying surface. Surface anisotropic reflectance effects are taken into account and radiatively coupled with atmospheric scattering.

Description: 〈b〉Evaluating the performance of five different chemical ionization techniques for detecting gaseous oxygenated organic species〈/b〉〈br〉 Matthieu Riva, Pekka Rantala, Jordan E. Krechmer, Otso Peräkylä, Yanjun Zhang, Liine Heikkinen, Olga Garmash, Chao Yan, Markku Kulmala, Douglas Worsnop, and Mikael Ehn〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-407,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The impact of aerosol particles on climate and air quality remains poorly understood due to multiple factors. One of the current limitations is the incomplete understanding of the contribution of oxygenated species, formed from the oxidation of volatile organic compounds (VOC), to aerosol formation. Taking advantage of recent mass spectrometric developments, we have evaluated and compared the capability of multiple state-of-the-art mass spectrometers to detect a wide variety of oxygenated VOC.

Description: 〈b〉Atomic oxygen number densities in the MLT region measured by solid electrolyte sensors on WADIS-2〈/b〉〈br〉 Martin Eberhart, Stefan Löhle, Boris Strelnikov, Jonas Hedin, Mikhail Khaplanov, Stefanos Fasoulas, Jörg Gumbel, Franz-Josef Lübken, and Markus Rapp〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-341,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This paper describes the measurement of atomic oxygen in the upper atmosphere onboard sounding rockets using solid electrolyte sensors. Calibration of the sensors in the laboratory is explained in detail. Results from the WADIS-2 rocket campaign show profiles of atomic oxygen density with a high spatial resolution.

Description: 〈b〉Analysis of a warehouse fire smoke plume over Paris with an N〈sub〉2〈/sub〉 Raman lidar and an optical thickness matching algorithm〈/b〉〈br〉 Xiaoxia Shang, Patrick Chazette, and Julien Totems〈br〉 Atmos. Meas. Tech., 11, 6525-6538, https://doi.org/10.5194/amt-11-6525-2018, 2018〈br〉 For the first time, a ground-based N〈sub〉2〈/sub〉 Raman lidar sampled smoke plumes originating from a large accidental warehouse fire in the Paris area. We developed a new algorithm, dubbed top-down aerosol optical thickness matching, to characterize the optical properties of the smoke aerosols, without a pre-determined reference zone and in the presence of clouds. The industrial pollution episode was concomitant with the long-range transport of dust aerosols and the presence of an extended stratus cloud.

Description: 〈b〉Pre-launch calibration results of the TROPOMI payload on-board the Sentinel-5 Precursor satellite〈/b〉〈br〉 Quintus Kleipool, Antje Ludewig, Ljubiša Babić, Rolf Bartstra, Remco Braak, Werner Dierssen, Pieter-Jan Dewitte, Pepijn Kenter, Robin Landzaat, Jonatan Leloux, Erwin Loots, Peter Meijering, Emiel van der Plas, Nico Rozemeijer, Dinand Schepers, Daniel Schiavini, Joost Smeets, Giuseppe Vacanti, Frank Vonk, and Pepijn Veefkind〈br〉 Atmos. Meas. Tech., 11, 6439-6479, https://doi.org/10.5194/amt-11-6439-2018, 2018〈br〉 This paper reports on the pre-launch calibration of the TROPOMI instrument on board ESA's Sentinel 5P satellite. This calibration is needed to convert the raw instrument digital data to physical quantities like Earth radiance and Sun irradiance. From these quantities atmospheric properties can be derived. The paper shows that the chosen approach to calibration and analysis was successful and that the achieved accuracy makes high-quality observations of the Earth's atmosphere feasible.

Description: 〈b〉Better turbulence spectra from VAD scanning wind lidar〈/b〉〈br〉 Felix Kelberlau and Jakob Mann〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-410,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Lidars are devices that can measure wind velocities remotely from the ground. Their estimates are very accurate in the mean but wind speed fluctuations lead to measurement errors. The presented data processing methods mitigate several of the error causes. First, by making use of knowledge about the mean wind direction. And second, by determining the location of air packages and sensing them in the best moment. Both methods can be applied to existing wind lidars and results are very promising.

Description: 〈b〉Reactive mercury flux measurements using cation exchange membranes〈/b〉〈br〉 Matthieu B. Miller, Mae S. Gustin, and Grant C. Edwards〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-360,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 In the atmosphere there are 2 gaseous forms of mercury (Hg), elemental (Hgo) and oxidized compounds (GOM). Hgo is oxidized by gases such as ozone and chlorine compounds. GOM is readily deposited to ecosystems and converted to methylmercury (a subtle neurotoxin). Here we explain development of a method for measurement of GOM deposition and emission associated with surfaces, and demonstrate that both occur. This has significant implications, because no one has been able to do this successfully.

Description: 〈b〉Comparative analysis of low-Earth orbit (TROPOMI) and geostationary (GeoCARB, GEO-CAPE) satellite instruments for constraining methane emissions on fine regional scales: application to the Southeast US〈/b〉〈br〉 Jian-Xiong Sheng, Daniel J. Jacob, Joannes D. Maasakkers, Yuzhong Zhang, and Melissa P. Sulprizio〈br〉 Atmos. Meas. Tech., 11, 6379-6388, https://doi.org/10.5194/amt-11-6379-2018, 2018〈br〉 We conduct Observing System Simulation Experiments to compare the ability of future satellite measurements of atmospheric methane columns for constraining methane emissions at the 25 km scale. We find that the geostationary instruments can do much better than TROPOMI and are less sensitive to cloud cover. GeoCARB observing twice a day would provide 70 % of the information from the nominal GEO-CAPE mission considered by NASA in response to the Decadal Survey of the US National Research Council.

Description: 〈b〉LISA: a lightweight stratospheric air sampler〈/b〉〈br〉 Joram J. D. Hooghiem, Marcel de Vries, Henk A. Been, Pauli Heikkinen, Rigel Kivi, and Huilin Chen〈br〉 Atmos. Meas. Tech., 11, 6785-6801, https://doi.org/10.5194/amt-11-6785-2018, 2018〈br〉 We have developed a lightweight stratospheric air sampler, named LISA, for measurements of CO〈sub〉2〈/sub〉, CH〈sub〉4〈/sub〉 and CO mole fractions. The LISA sampler is capable of grabbing stratospheric air samples at an altitude of up to 30 km and provides a useful tool for routine stratospheric measurements of both mole fractions and isotopic composition of trace gases.

Description: 〈b〉Radiometric correction of observations from microwave humidity sounders〈/b〉〈br〉 Isaac Moradi, James Beauchamp, and Ralph Ferraro〈br〉 Atmos. Meas. Tech., 11, 6617-6626, https://doi.org/10.5194/amt-11-6617-2018, 2018〈br〉 Microwave (MW) satellite instruments are used for a variety of applications such as retrieving geophysical variables such as temperature and humidity. They are also assimilated into NWP models to improve the weather forecast. However, MW instruments are subject to radiometric and geometric errors. This study evaluates the observations from several MW instruments for radiometric errors and provides correction coefficients for the data that are biased.

Description: 〈b〉A novel approach to calibrating a photo-acoustic absorption spectrometer using polydisperse absorbing aerosol〈/b〉〈br〉 Katie Foster, Rudra Pokhrel, Matthew Burkhart, and Shane Murphy〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-413,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Optical properties of absorbing aerosol significantly impact global climate. Photoacoustic absorption spectrometers (PAS) have emerged as a popular technique for measuring aerosol absorption. There are no particle-based calibration methods for PAS instruments. We present a calibration approach utilizing polydisperse particles and a cavity attenuation phase shift instrument. This technique does not rely on specific substances with known refractive indices and is easily deployable in the field.

Description: 〈b〉Using computational fluid dynamics and field experiments to improve vehicle-based wind measurements for environmental monitoring〈/b〉〈br〉 Tara Hanlon and David Risk〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-354,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 In this study, we aimed to improve accuracy of wind speed and direction measurements from an anemometer mounted atop a research vehicle. Controlled field tests and computer simulations showed that the vehicle shape biases airflow above the vehicle. The results indicate that placing an anemometer at a significant height (〉 1 m) above the vehicle, and calibrating anemometer measurements for vehicle shape and wind angle, can be effective in reducing bias in measurements of wind speed and direction.

Description: 〈b〉BOREAS – a new MAX-DOAS profile retrieval algorithm for aerosols and trace gases〈/b〉〈br〉 Tim Bösch, Vladimir Rozanov, Andreas Richter, Enno Peters, Alexei Rozanov, Folkard Wittrock, Alexis Merlaud, Johannes Lampel, Stefan Schmitt, Marijn de Haij, Stijn Berkhout, Bas Henzing, Arnoud Apituley, Mirjam den Hoed, Jan Vonk, Martin Tiefengraber, Moritz Müller, and John Philip Burrows〈br〉 Atmos. Meas. Tech., 11, 6833-6859, https://doi.org/10.5194/amt-11-6833-2018, 2018〈br〉 A new MAX-DOAS profiling algorithm for aerosols and trace gases was developed. The performance of this novel algorithm was tested with the help of synthetic data and measurements from the CINDI-2 campaign in Cabauw, the Netherlands, in 2016.

Description: 〈b〉Apparatus for dry deposition of aerosols on snow〈/b〉〈br〉 Nicholas D. Beres and Hans Moosmüller〈br〉 Atmos. Meas. Tech., 11, 6803-6813, https://doi.org/10.5194/amt-11-6803-2018, 2018〈br〉 Particulate matter found in the atmosphere, or aerosols, can deposit on snow and ice and significantly change its reflectivity. Consequently, the timing of snow melt and snow water runoff is also changed. To study these processes, it is important to be able to deposit aerosols in a controlled manner on snow surfaces. Here, we present the design and demonstrate the use of an apparatus for deposition of common mineral dust and combustion aerosols.

Description: 〈b〉Low-pressure gas chromatography with chemical ionization mass spectrometry for quantification of multifunctional organic compounds in the atmosphere〈/b〉〈br〉 Krystal T. Vasquez, Hannah M. Allen, John D. Crounse, Eric Praske, Lu Xu, Anke C. Noelscher, and Paul O. Wennberg〈br〉 Atmos. Meas. Tech., 11, 6815-6832, https://doi.org/10.5194/amt-11-6815-2018, 2018〈br〉 Oxygenated volatile organic compounds (OVOCs) are difficult to measure in the atmosphere due to their high reactivity and low concentrations. This hinders our understanding of their impact on air quality and climate. Therefore, we have developed a field-deployable instrument capable of providing isomer-resolved measurements of OVOCs in the ambient air. Its performance is assessed through data collected both in the laboratory and during two field studies.

Description: 〈b〉Detecting layer height of smoke aerosols over vegetated land and water surfaces via oxygen absorption bands: Hourly results from EPIC/DSCOVR satellite in deep space〈/b〉〈br〉 Xiaoguang Xu, Jun Wang, Yi Wang, Jing Zeng, Omar Torres, Jeffrey S. Reid, Steven D. Miller, J. Vanderlei Martins, and Lorraine A. Remer〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-414,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Detecting aerosol layer height from space has been challenging. Tradition method relies on active sensors such as lidar that provides detailed vertical structure of aerosol profile, but is costly and has limited spatial coverage (it needs more than one year to have a global coverage). Here we developed a PASSIVE remote sensing technique that uses backscattered sunlight to retrieve smoke aerosol layer height over both water and vegetated surfaces from a sensor that is 1.5 M kms from the Earth.

Description: 〈b〉Aerosol optical properties derived from POLDER-3/PARASOL (2005–2013) over the western Mediterranean Sea – Part 1: Quality assessment with AERONET and in situ airborne observations〈/b〉〈br〉 Paola Formenti, Lydie Mbemba Kabuiku, Isabelle Chiapello, Fabrice Ducos, François Dulac, and Didier Tanré〈br〉 Atmos. Meas. Tech., 11, 6761-6784, https://doi.org/10.5194/amt-11-6761-2018, 2018〈br〉 Aerosol particles from natural and anthropogenic sources are climate regulators as they can counteract or amplify the warming effect of greenhouse gases, but are difficult to observe due to their temporal and spatial variability. Satellite sensors can provide the needed global coverage but need validation. In this paper we explore the capability of the POLDER-3 advanced space-borne sensor to observe aerosols over the western Mediterranean region.

Description: 〈b〉Investigation of observational error sources in multi Doppler radar vertical air motion retrievals: Impacts and possible solutions〈/b〉〈br〉 Mariko Oue, Pavlos Kollias, Alan Shapiro, Aleksandra Tatarevic, and Toshihisa Matsui〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-442,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This study investigated impacts of the selected radar volume coverage pattern, the sampling time period, the number of radars used, and the added value of advection correction on the retrieval of vertical air motion from a multi-Doppler radar technique. The results suggest that the use of rapid-scan radars can substantially improve the quality of wind retrievals and that the retrieved wind field needs to be carefully used considering the limitations of the radar observing system.

Description: 〈b〉Intercomparison of MAX-DOAS Vertical Profile Retrieval Algorithms: Studies using Synthetic Data〈/b〉〈br〉 Udo Frieß, Steffen Beirle, Leonardo Alvarado Bonilla, Tim Bösch, Martina M. Friedrich, Francois Hendrick, Ankie Piters, Andreas Richter, Michel van Roozendael, Vladimir V. Rozanov, Elena Spinei, Jan-Lukas Tirpitz, Tim Vlemmix, Thomas Wagner, and Yang Wang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-423,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a widely used measurement technique for the detection of a variety of atmospheric trace gases. It enables the retrieval of aerosol and trace gas vertical profiles in the atmospheric boundary layer using appropriate retrieval algorithms. In this study, the ability of eight profile retrieval algorithms to reconstruct vertical profiles is assessed on the basis of synthetic measurements.

Description: 〈b〉Improving algorithms and uncertainty estimates for satellite NO〈sub〉2〈/sub〉 retrievals: results from the quality assurance for the essential climate variables (QA4ECV) project〈/b〉〈br〉 K. Folkert Boersma, Henk J. Eskes, Andreas Richter, Isabelle De Smedt, Alba Lorente, Steffen Beirle, Jos H. G. M. van Geffen, Marina Zara, Enno Peters, Michel Van Roozendael, Thomas Wagner, Joannes D. Maasakkers, Ronald J. van der A, Joanne Nightingale, Anne De Rudder, Hitoshi Irie, Gaia Pinardi, Jean-Christopher Lambert, and Steven C. Compernolle〈br〉 Atmos. Meas. Tech., 11, 6651-6678, https://doi.org/10.5194/amt-11-6651-2018, 2018〈br〉 This paper describes a new, improved data record of 22+ years of coherent nitrogen dioxide (NO〈sub〉2〈/sub〉) pollution measurements from different satellite instruments. Our work helps to ensure that climate data are of sufficient quality to draw reliable conclusions and shape decisions. It shows how dedicated intercomparisons of retrieval sub-steps have led to improved NO〈sub〉2〈/sub〉 measurements from the GOME, SCIAMACHY, GOME-2(A), and OMI sensors, and how quality assurance of the new data product is achieved.

Description: 〈b〉Retrieval of aerosol microphysical and optical properties over land using a multimode approach〈/b〉〈br〉 Guangliang Fu and Otto Hasekamp〈br〉 Atmos. Meas. Tech., 11, 6627-6650, https://doi.org/10.5194/amt-11-6627-2018, 2018〈br〉 We implement a multimode approach in which each mode has fixed effective radius and effective variance. In this way the algorithm obtains more flexibility in describing the aerosol size distribution and avoids the high nonlinear dependence of the forward model on the aerosol size parameters. The synthetic and real data experiments show that multimode retrievals are good alternatives to the parametric two-mode approach.

Description: 〈b〉Characterization and application of artificial light sources for nighttime aerosol optical depth retrievals using the VIIRS Day/Night Band〈/b〉〈br〉 Jianglong Zhang, Shawn L. Jaker, Jeffrey S. Reid, Steven D. Miller, Jeremy Solbrig, and Travis D. Toth〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-424,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Using nighttime observations from Visible/Infrared Imager/Radiometer Suite (VIIRS) Day/Night band (DNB), the characteristics of artificial light sources are evaluated as functions of observation conditions, and incremental improvements are documented on nighttime aerosol retrievals using VIIRS DNB data on a regional scale. Results from the study indicate the potential of this method to begin filling critical gaps in diurnal AOT information at both regional and global scales.

Description: 〈b〉An open platform for Aerosol InfraRed Spectroscopy analysis – AIRSpec〈/b〉〈br〉 Matteo Reggente, Rudolf Höhn, and Satoshi Takahama〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-332,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 1 comment)〈br〉 The infrared spectra of atmospheric particles are rich in chemical information, but require sophisticated statistical methods to extract information on account of their complex absorption profiles. We present an open software suite which makes current algorithms used for analysis of such spectra available to the community, with a browser-based interface for general users and modular architecture that facilitates addition of new methods by developers.

Description: 〈b〉Study of the diffraction pattern of cloud particles and respective response of Optical Array Probes〈/b〉〈br〉 Thibault Vaillant de Guélis, Alfons Schwarzenböck, Valery Shcherbakov, Christophe Gourbeyre, Bastien Laurent, Régis Dupuy, Pierre Coutris, and Christophe Duroure〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-437,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉Optical array probes (OAPs) are classical instrumental means to derive shape, size, and number concentration of cloud and precipitation particles from 2D images. However, recorded 2D images are subject to distortion based on the diffraction of light when particles are imaged out of the object plane of the optical device. This phenomenon highly affects retrievals of microphysical properties of cloud particles. Previous studies of this effect mainly focused on spherical droplets. In this study we propose a theoretical method to compute diffraction pattern of all kind of cloud particle shapes in order to simulate the response recorded by an OAP. To check the validity of this method, a series of experimental measurements have been performed with a 2D-S probe mounted on a test bench. Measurements are performed using spinning glass discs with imprinted non-circular opaque particle shapes.〈/p〉

Description: 〈b〉Development of an incoherent broadband cavity-enhanced absorption spectrometer for measurements of ambient glyoxal and NO〈sub〉2〈/sub〉 in a polluted urban environment〈/b〉〈br〉 Shuaixi Liang, Min Qin, Pinhua Xie, Jun Duan, Wu Fang, Yabai He, Jin Xu, Ke Tang, Fanhao Meng, Kaidi Ye, Jianguo Liu, and Wenqing Liu〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-430,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A home-built instrument of an incoherent broadband cavity-enhanced absorption spectrometer for sensitive detection of CHOCHO and NO〈sub〉2〈/sub〉 in China's highly polluted environment is reported. NO〈sub〉2〈/sub〉 spectral profile measured using the same spectrometer is applied as a reference spectral profile in subsequent atmospheric spectral analysis and retrieval of NO〈sub〉2〈/sub〉 and CHOCHO. This will provide an idea for solving the problem of cross-interference of strongly absorbing gases in weakly absorbing gases.

Description: 〈b〉Analysis of spatial and temporal patterns of on-road NO〈sub〉2〈/sub〉 concentrations in Hong Kong〈/b〉〈br〉 Ying Zhu, Ka Lok Chan, Yun Fat Lam, Martin Horbanski, Denis Pöhler, Johannes Boll, Ivo Lipkowitsch, Sheng Ye, and Mark Wenig〈br〉 Atmos. Meas. Tech., 11, 6719-6734, https://doi.org/10.5194/amt-11-6719-2018, 2018〈br〉 The paper presents an investigation of spatio-temporal variability of street-level NO〈sub〉2〈/sub〉 in Hong Kong using mobile cavity-enhanced differential optical absorption spectroscopy (DOAS) and long-path DOAS. Measurements were conducted in December 2010 and March 2017. A significant decreasing trend in on-road NO〈sub〉2〈/sub〉 was found by comparing measurements taken in 2010 and 2017. Influences of changes in bus companies' operation strategies can also be observed from the measured NO〈sub〉2〈/sub〉 concentration maps.

Description: 〈b〉Chemical ionisation quadrupole mass spectrometer with an electrical discharge ion source for atmospheric trace gas measurement〈/b〉〈br〉 Philipp G. Eger, Frank Helleis, Gerhard Schuster, Gavin J. Phillips, Jos Lelieveld, and John N. Crowley〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-428,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We present a Chemical Ionisation Quadrupole Mass Spectrometer (CI-QMS) with a novel discharge ion source. In addition to the expected detection of PAN, peracetic acid and ClNO〈sub〉2〈/sub〉, the instrument is also sensitive to SO〈sub〉2〈/sub〉, HCl and acetic acid through ion chemistry unique for our ion source. We present ionisation schemes along with illustrative data sets from field campaigns underlining the potential of the CI-QMS as an alternative to polonium, especially for application in the marine boundary layer.

Description: 〈b〉A fully autonomous ozone, aerosol and nighttime water vapor lidar: a synergistic approach to profiling the atmosphere in the Canadian oil sands region〈/b〉〈br〉 Kevin B. Strawbridge, Michael S. Travis, Bernard J. Firanski, Jeffrey R. Brook, Ralf Staebler, and Thierry Leblanc〈br〉 Atmos. Meas. Tech., 11, 6735-6759, https://doi.org/10.5194/amt-11-6735-2018, 2018〈br〉 Environment and Climate Change Canada has recently developed a fully autonomous, mobile lidar system to simultaneously measure the vertical profile of tropospheric ozone, aerosol and water vapor from near the ground to altitudes reaching 10–15 km. These atmospheric constituents play an important role in climate, air quality, and human and ecosystem health. Using an autonomous multi-lidar approach provides a continuous dataset rich in information for atmospheric process studies.

Description: 〈b〉First high resolution BrO column retrievals from TROPOMI〈/b〉〈br〉 Sora Seo, Andreas Richter, Anne-Marlene Blechschmidt, Ilias Bougoudis, and John Philip Burrows〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-365,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The TROPOMI onboard the Copernicus Sentinel-5 Precursor platform can measure various atmospheric compositions at high spatial resolution and improved spectral resolution compared to its predecessors. Bromine monoxide (BrO) is one of the gases that can be derived from the measured radiances of TROPOMI using Differential Optical Absorption Spectroscopy (DOAS) method. In this paper, we present first retrieval results of BrO column amounts from TROPOMI observations on global and regional scales.

Description: 〈b〉Lidar temperature series in the middle atmosphere as a reference data set – Part 2: Assessment of temperature observations from MLS/Aura and SABER/TIMED satellites〈/b〉〈br〉 Robin Wing, Alain Hauchecorne, Philippe Keckhut, Sophie Godin-Beekmann, Sergey Khaykin, and Emily M. McCullough〈br〉 Atmos. Meas. Tech., 11, 6703-6717, https://doi.org/10.5194/amt-11-6703-2018, 2018〈br〉 We have compared 2433 nights of OHP lidar temperatures (2002–2018) to temperatures derived from the satellites SABER and MLS. We have found a winter stratopause cold bias in the satellite measurements with respect to the lidar (−6 K for SABER and −17 K for MLS), a summer mesospheric warm bias for SABER (6 K near 60 km), and a vertically structured bias for MLS (−4 to 4 K). We have corrected the satellite data based on the lidar-determined stratopause height and found a significant improvement.

Description: 〈b〉Footprint-scale cloud type mixtures and their impacts on Atmospheric Infrared Sounder cloud property retrievals〈/b〉〈br〉 Alexandre Guillaume, Brian H. Kahn, Eric J. Fetzer, Qing Yue, Gerald J. Manipon, Brian D. Wilson, and Hook Hua〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-415,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉A method is described to classify cloud mixtures of cloud top types, termed cloud scenes, using cloud type classification derived from the CloudSat radar (2B-CLDCLASS). The scale dependence of those cloud scenes is studied. For spatial scales near 45 km, only 16 out of 256 possible cloud scenes account for 90 % of all observations and contain either one, two, or three cloud types. The number of possible cloud scenes is shown to depend on spatial scale with a maximum number of 194 out of 256 possible scenes at a scale of 105 km and fewer cloud scenes at smaller and larger scales. The cloud scenes are used to assess the characteristics of spatially collocated Atmospheric Infrared Sounder (AIRS) thermodynamic phase and ice cloud property retrievals within scenes of varying cloud type complexity. The likelihood of ice and liquid phase detection strongly depends on the CloudSat-identified cloud scene type collocated with the AIRS footprint. Cloud scenes primarily consisting of cirrus, nimbostratus, altostratus and deep convection are dominated by ice phase detection, while stratocumulus, cumulus, and altocumulus are dominated by liquid and undetermined phase detection. Ice cloud particle size and optical thickness are largest for cloud scenes containing deep convection and cumulus, and are smallest for cirrus. Cloud scenes with multiple cloud types have small reductions in information content and slightly higher residuals of observed and modelled radiance compared to cloud scenes with single cloud types. These results will help advance the development of temperature, specific humidity, and cloud property retrievals from hyperspectral infrared sounders that include cloud microphysics in forward radiative transfer models.〈/p〉

Description: 〈b〉A physics-based approach to oversample multi-satellite, multispecies observations to a common grid〈/b〉〈br〉 Kang Sun, Lei Zhu, Karen Cady-Pereira, Christopher Chan Miller, Kelly Chance, Lieven Clarisse, Pierre-François Coheur, Gonzalo González Abad, Guanyu Huang, Xiong Liu, Martin Van Damme, Kai Yang, and Mark Zondlo〈br〉 Atmos. Meas. Tech., 11, 6679-6701, https://doi.org/10.5194/amt-11-6679-2018, 2018〈br〉 An agile, physics-based approach is developed to oversample irregular satellite observations to a high-resolution common grid. Instead of assuming each sounding as a point or a polygon as in previous methods, the proposed physical oversampling represents soundings as distributions of sensitivity on the ground. This sensitivity distribution can be determined by the spatial response function of each satellite sensor, parameterized as generalized 2-D super Gaussian functions.

Description: 〈b〉Aerosol Optical Depth comparison between GAW-PFR and AERONET-Cimel radiometers from long term (2005–2015) 1-minute synchronous measurements〈/b〉〈br〉 Emilio Cuevas, Pedro Miguel Romero-Campos, Natalia Kouremeti, Stelios Kazadzis, Rosa Delia García, Africa Barreto, Carmen Guirado-Fuentes, Ramón Ramos, Carlos Toledano, Fernando Almansa, and Julian Gröbner〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-438,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A comprehensive comparison of more than 70000 synchronous 1-minute aerosol optical depth (AOD) data from three Global Atmosphere Watch-Precision Filter Radiometer (GAW-PFR) and 15 Aerosol Robotic Network-Cimel (AERONET-Cimel) radiometers was performed for the four nearby wavelengths (380, 440, 500 and 870 nm) in the period 2005–2015. The goal of this study is to assess whether their long term AOD data are comparable and consistent.

Description: 〈b〉Particle wall-loss correction methods in smog chamber experiments〈/b〉〈br〉 Ningxin Wang, Spiro D. Jorga, Jeffery R. Pierce, Neil M. Donahue, and Spyros N. Pandis〈br〉 Atmos. Meas. Tech., 11, 6577-6588, https://doi.org/10.5194/amt-11-6577-2018, 2018〈br〉 The interaction of particles with the chamber walls has been a significant source of uncertainty when analyzing results of secondary organic aerosol formation experiments performed in Teflon chambers. We evaluated the performance of several particle wall-loss correction methods for aging experiments of 〈i〉α〈/i〉-pinene ozonolysis products. Experimental procedures are proposed for the characterization of particle losses during different stages of these experiments.

Description: 〈b〉Using collision-induced dissociation to constrain sensitivity of ammonia chemical ionization mass spectrometry (NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉-CIMS) to oxygenated volatile organic compounds〈/b〉〈br〉 Alexander Zaytsev, Martin Breitenlechner, Abigail R. Koss, Christopher Y. Lim, James C. Rowe, Jesse H. Kroll, and Frank N. Keutsch〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-425,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We present the development of a chemical ionization mass spectrometer which can be operated with either hydronium (H〈sub〉3〈/sub〉O〈sup〉+〈/sup〉) or ammonium (NH〈sub〉4〈/sub〉〈sup〉+〈/sup〉) as the reagent ion. We describe a mass spectrometric voltage scanning procedure based on collision-induced dissociation that allows us to determine the stability of detected ammonium-organic ions and hence constrain the sensitivity of the instrument to a wide range of organic compounds that cannot be calibrated directly.

Description: 〈b〉Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm〈/b〉〈br〉 Christopher W. O'Dell, Annmarie Eldering, Paul O. Wennberg, David Crisp, Michael R. Gunson, Brendan Fisher, Christian Frankenberg, Matthäus Kiel, Hannakaisa Lindqvist, Lukas Mandrake, Aronne Merrelli, Vijay Natraj, Robert R. Nelson, Gregory B. Osterman, Vivienne H. Payne, Thomas E. Taylor, Debra Wunch, Brian J. Drouin, Fabiano Oyafuso, Albert Chang, James McDuffie, Michael Smyth, David F. Baker, Sourish Basu, Frédéric Chevallier, Sean M. R. Crowell, Liang Feng, Paul I. Palmer, Mavendra Dubey, Omaira E. García, David W. T. Griffith, Frank Hase, Laura T. Iraci, Rigel Kivi, Isamu Morino, Justus Notholt, Hirofumi Ohyama, Christof Petri, Coleen M. Roehl, Mahesh K. Sha, Kimberly Strong, Ralf Sussmann, Yao Te, Osamu Uchino, and Voltaire A. Velazco〈br〉 Atmos. Meas. Tech., 11, 6539-6576, https://doi.org/10.5194/amt-11-6539-2018, 2018〈br〉 〈p〉Since September 2014, NASA's Orbiting Carbon Observatory-2 (〈span〉OCO-2〈/span〉) satellite has been taking measurements of reflected solar spectra and using them to infer atmospheric carbon dioxide levels. This work provides details of the 〈span〉OCO-2〈/span〉 retrieval algorithm, versions 7 and 8, used to derive the column-averaged dry air mole fraction of atmospheric CO〈sub〉2〈/sub〉 (X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉) for the roughly 100 000 cloud-free measurements recorded by 〈span〉OCO-2〈/span〉 each day. The algorithm is based on the Atmospheric Carbon Observations from Space (ACOS) algorithm which has been applied to observations from the Greenhouse Gases Observing SATellite (GOSAT) since 2009, with modifications necessary for 〈span〉OCO-2〈/span〉. Because high accuracy, better than 0.25 %, is required in order to accurately infer carbon sources and sinks from X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉, significant errors and regional-scale biases in the measurements must be minimized. We discuss efforts to filter out poor-quality measurements, and correct the remaining good-quality measurements to minimize regional-scale biases. Updates to the radiance calibration and retrieval forward model in version 8 have improved many aspects of the retrieved data products. The version 8 data appear to have reduced regional-scale biases overall, and demonstrate a clear improvement over the version 7 data. In particular, error variance with respect to TCCON was reduced by 20 % over land and 40 % over ocean between versions 7 and 8, and nadir and glint observations over land are now more consistent. While this paper documents the significant improvements in the ACOS algorithm, it will continue to evolve and improve as the CO〈sub〉2〈/sub〉 data record continues to expand.〈/p〉

Description: 〈b〉Studies of the horizontal inhomogeneities in NO〈sub〉2〈/sub〉 concentrations above a shipping lane using ground-based MAX-DOAS and airborne imaging DOAS measurements〈/b〉〈br〉 André Seyler, Andreas C. Meier, Folkard Wittrock, Lisa Kattner, Barbara Mathieu-Üffing, Enno Peters, Andreas Richter, Thomas Ruhtz, Anja Schönhardt, Stefan Schmolke, and John P. Burrows〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-348,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 1 comment)〈br〉 This study describes a novel application of an 〈q〉onion peeling〈/q〉 like approach to MAX-DOAS measurements of shipping emissions aiming at investigating the inhomogenous NO〈sub〉2〈/sub〉 field over a shipping lane. Case studies for different wind conditions demonstrate the ability to derive the approximate plume positions in the observed area, which are in good agreement with simultaneous air-borne imaging DOAS measurements. NO〈sub〉2〈/sub〉 concentrations in a plume retrieved from both measurement techniques agree very well.

Description: 〈b〉NO〈sub〉2〈/sub〉 vertical profiles and column densities from MAX-DOAS measurements in Mexico City〈/b〉〈br〉 Martina Michaela Friedrich, Claudia Rivera, Wolfgang Stremme, Zuleica Ojeda, Josué Arellano, Alejandro Bezanilla, José Agustín García-Reynoso, and Michel Grutter〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-358,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We present a new numerical code to retrieve NO〈sub〉2〈/sub〉 vertical column densities (vcd) and concentrations from previously retrieved slanted columns from spectroscopic measurements in visible and ultraviolet spectral range in different vertical viewing directions. We use this code on roughly 1.5 years of data from a measurement station located in the south of Mexico city and compare daily and monthly averages to averages of in-situ measurements. We show daily NO〈sub〉2〈/sub〉 vcd time series for a few example days.

Description: 〈b〉The impact of bath gas composition on the calibration of photoacoustic spectrometers with ozone at discrete visible wavelengths spanning the Chappuis band〈/b〉〈br〉 Michael I. Cotterell, Andrew J. Orr-Ewing, Kate Szpek, Jim M. Haywood, and Justin M. Langridge〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-409,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Photoacoustic spectroscopy provides measurements of absorption coefficient for aerosol and gas samples, but requires careful calibration and researchers often use concentrations of ozone. Recent work has shown that the bath gas composition impacts on the accuracy of this calibration at visible wavelengths. We explore further the role of bath gas, demonstrating that the calibration accuracy is optimal for a bath gas composed of 20 % oxygen and 80 % nitrogen at wavelengths of 405, 514 and 658 nm.

Description: 〈b〉Improvement of stratospheric aerosol extinction retrieval from OMPS/LP using a new aerosol model〈/b〉〈br〉 Zhong Chen, Pawan K. Bhartia, Robert Loughman, Peter Colarco, and Matthew DeLand〈br〉 Atmos. Meas. Tech., 11, 6495-6509, https://doi.org/10.5194/amt-11-6495-2018, 2018〈br〉 We describe the derivation of an improved aerosol size distribution (ASD) for the OMPS/LP retrieval algorithm. The new ASD uses a gamma function distribution that is derived from CARMA-calculated results. The new ASD also explains the spectral dependence of LP-measured radiances well. Initial comparisons with collocated extinction profiles retrieved at 676 nm from the SAGE III/ISS instrument show a significant improvement in agreement for the LP retrievals.

Description: 〈b〉Boundary-layer water vapor profiling using differential absorption radar〈/b〉〈br〉 Richard J. Roy, Matthew Lebsock, Luis Millán, Robert Dengler, Raquel Rodriguez Monje, Jose V. Siles, and Ken B. Cooper〈br〉 Atmos. Meas. Tech., 11, 6511-6523, https://doi.org/10.5194/amt-11-6511-2018, 2018〈br〉 The measurement of water vapor profiles inside clouds with high spatial resolution represents an outstanding problem in atmospheric remote sensing. Here we present measurements from a proof-of-concept millimeter-wave (170 GHz) cloud radar aimed at filling this observational gap, and demonstrate the ability to retrieve in-cloud water vapor profiles with high precision and resolution. This technology could meaningfully impact future satellite-based measurements of water vapor.

Description: 〈b〉Evolution of DARDAR-CLOUD ice cloud cloud retrieval: new parameters and impacts on the retrieved microphysical properties〈/b〉〈br〉 Quitterie Cazenave, Marie Ceccaldi, Julien Delanoë, Jacques Pelon, Silke Groß, and Andrew Heymsfield〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-397,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The impact of ice clouds on the water cycle and radiative budget is still uncertain due to the complexity of cloud processes that makes it difficult to acquire adequate observations of ice cloud properties and parameterize them into climate and weather prediction models. In this paper we present the latest refinements brought to the DARDAR-CLOUD product, which contains ice cloud microphysical properties retrieved from the cloud radar and lidar measurements from the A-Train space mission.

Description: 〈b〉A machine learning approach to aerosol classification for single-particle mass spectrometry〈/b〉〈br〉 Costa D. Christopoulos, Sarvesh Garimella, Maria A. Zawadowicz, Ottmar Möhler, and Daniel J. Cziczo〈br〉 Atmos. Meas. Tech., 11, 5687-5699, https://doi.org/10.5194/amt-11-5687-2018, 2018〈br〉 Compositional analysis of atmospheric and laboratory aerosols is often conducted with mass spectrometry. In this study, machine learning is used to automatically differentiate particles on the basis of chemistry and size. The ability of the machine learning algorithm was then tested on a data set for which the particles were not initially known to judge its ability.

Description: 〈b〉MODIS Collection 6 MAIAC algorithm〈/b〉〈br〉 Alexei Lyapustin, Yujie Wang, Sergey Korkin, and Dong Huang〈br〉 Atmos. Meas. Tech., 11, 5741-5765, https://doi.org/10.5194/amt-11-5741-2018, 2018〈br〉 MAIAC algorithm used for the MODIS C6 processing is described. MAIAC combines time series analysis and pixel/image-based processing to improve the accuracy of cloud detection, aerosol retrievals and atmospheric correction. MAIAC offers an interdisciplinary suite of atmospheric, land surface and snow products. Due to generally high quality, high resolution and high coverage, MAIAC AOD and surface reflectance/BRDF have been widely used for air quality and land research and applications.

Description: 〈b〉Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015〈/b〉〈br〉 Matthias Wiegner, Ina Mattis, Margit Pattantyús-Ábrahám, Juan Antonio Bravo-Aranda, Yann Poltera, Alexander Haefele, Maxime Hervo, Ulrich Görsdorf, Ronny Leinweber, Josef Gasteiger, Martial Haeffelin, Frank Wagner, Jan Cermak, Katerina Komínková, Mike Brettle, Christoph Münkel, and Kornelia Pönitz〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-307,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Ceilometers are often influenced by water vapor absorption in the spectral range around 910 nm. Thus, a correction is required to retrieve aerosol optical properties. Validation of this correction scheme was performed in the framework of CeiLinEx2015 for several ceilometers with good agreement in case of CL51 ceilometers. For future applications we recommend to monitor the emitted wavelength and to provide 〈q〉dark〈/q〉 measurements on a regular basis to be able to correct for signal artefacts.

Description: 〈b〉The Disdrometer Verification Network (DiVeN): a UK network of laser precipitation instruments〈/b〉〈br〉 Ben S. Pickering, Ryan R. Neely III, and Dawn Harrison〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-302,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A new network of precipitation instruments has been established for the UK. The instruments are capable of detecting the fall velocity and diameter of each particle that falls through a laser beam. The particle characteristics are derived from the duration and amount of decrease in beam brightness as perceived by a receiving diode. 14 instruments make up the network and all instruments upload 60-second frequency data in near real time to a publicly available website with plots.

Description: 〈b〉Level 1b error budget for MIPAS on ENVISAT〈/b〉〈br〉 Anne Kleinert, Manfred Birk, Gaétan Perron, and Georg Wagner〈br〉 Atmos. Meas. Tech., 11, 5657-5672, https://doi.org/10.5194/amt-11-5657-2018, 2018〈br〉 We present the error budget for the calibrated and geolocated spectra of the MIPAS limb sounder which flew on the ENVISAT satellite from 2002 to 2012. The impact of the different error sources on the spectra is characterized in terms of spectral, vertical, and temporal correlation. The radiometric error is in the order of 1 to 2.4 %, the spectral accuracy is better than 0.3 ppm, and the line of sight accuracy at the tangent point is around 400 m. All errors are well within the requirements.

Description: 〈b〉A bulk-mass-modeling-based method for retrieving Particulate Matter Pollution using CALIOP observations〈/b〉〈br〉 Travis D. Toth, Jianglong Zhang, Jeffrey S. Reid, and Mark A. Vaughan〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-335,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 An innovative method is presented for deriving particulate matter (PM) concentrations using CALIOP measurements. Deviating from conventional approaches of relying on passive satellite column-integrated aerosol measurements, PM concentrations are derived from near surface CALIOP measurements through a bulk-mass-modeling method. This proof-of-concept study shows that, while limited in spatial and temporal coverage, CALIOP exhibits reasonable skill for PM applications.

Description: 〈b〉An instrument for quantifying heterogeneous ice nucleation in multiwell plates using infrared emissions to detect freezing〈/b〉〈br〉 Alexander D. Harrison, Thomas F. Whale, Rupert Rutledge, Stephen Lamb, Mark D. Tarn, Grace C. E. Porter, Michael P. Adams, James B. McQuaid, George J. Morris, and Benjamin J. Murray〈br〉 Atmos. Meas. Tech., 11, 5629-5641, https://doi.org/10.5194/amt-11-5629-2018, 2018〈br〉 The detection of low concentrations of ice-nucleating particles (INPs) is challenging. Here we present a new technique (IR-NIPI) that is sensitive to low concentrations of INPs (〉 0.01 L〈sup〉−1〈/sup〉) and uses an infrared camera with a novel calibration to detect the freezing of experimental suspensions. IR-NIPI temperature measurements prove to be robust with a series of comparisons to thermocouple measurements. Experimental comparisons to other freezing assay instruments are also in agreement.

Description: 〈b〉Towards imaging of atmospheric trace gases using Fabry Perot Interferometer Correlation Spectroscopy in the UV and visible spectral range〈/b〉〈br〉 Jonas Kuhn, Ulrich Platt, Nicole Bobrowski, and Thomas Wagner〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-350,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We study a novel remote sensing technique for atmospheric trace gases absorbing in the UV and visible spectral range. Using Fabry Perot interferometers with a spectral transmission matched to the trace gas's spectral absorption allows for imaging trace gases with high sensitivity and selectivity. The thereby achieved high spatio temporal resolution enables the study of small scale and dynamic processes in the atmosphere. We present sample calculations and a proof of concept study.

Description: 〈b〉Empirical high-resolution wind field and gust model in mountainous and hilly terrain based on the dense WegenerNet station networks〈/b〉〈br〉 Christoph Schlager, Gottfried Kirchengast, and Juergen Fuchsberger〈br〉 Atmos. Meas. Tech., 11, 5607-5627, https://doi.org/10.5194/amt-11-5607-2018, 2018〈br〉 In this work we further developed and evaluated an operational weather diagnostic application, the WegenerNet Wind Product Generator (WPG), and applied it to the WegenerNet Johnsbachtal (JBT), a dense meteorological station network located in a mountainous Alpine region. The WPG automatically generates gridded high-resolution wind fields in near-real time with a temporal resolution of 30 min and a spatial resolution of 100 m x 100 m.

Description: 〈b〉Calibration of a 35-GHz Airborne Cloud Radar: Lessons Learned and Intercomparisons with 94-GHz Cloud Radars〈/b〉〈br〉 Florian Ewald, Silke Groß, Martin Hagen, Lutz Hirsch, Julien Delanoë, and Matthias Bauer-Pfundstein〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-269,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉In this study, we will give an overview of lessons learned during the radiometric calibration of the airborne, high-power Ka-band cloud radar on board the German research aircraft HALO. Within this context, a number of flight experiments over Europe and over the tropical and extra-tropical North-Atlantic have been conducted, where the ocean surface backscatter was used as an external reference reflector. Measurements of signal linearity and signal saturation complement this characterization. To validate the external calibration, joint flights of HALO and the French Falcon 20 aircraft, which was equipped with the RASTA cloud radar at 94 GHz and underflights of the spaceborne CloudSat at 94 GHz have been conducted. Finally, the influence of different radar wavelengths was explored with numerical studies.〈/p〉

Description: 〈b〉Is a scaling factor required to obtain closure between measured and modelled atmospheric O〈sub〉4〈/sub〉 absorptions? – A case study for two days during the MADCAT campaign〈/b〉〈br〉 Thomas Wagner, Steffen Beirle, Nuria Benavent, Tim Bösch, Kai Lok Chan, Sebastian Donner, Steffen Dörner, Caroline Fayt, Udo Frieß, David García-Nieto, Clio Gielen, David González-Bartolome, Laura Gomez, François Hendrick, Bas Henzing, Jun Li Jin, Johannes Lampel, Jianzhong Ma, Kornelia Mies, Mónica Navarro, Enno Peters, Gaia Pinardi, Olga Puentedura, Janis Puķīte, Julia Remmers, Andreas Richter, Alfonso Saiz-Lopez, Reza Shaiganfar, Holger Sihler, Michel Van Roozendael, Yang Wang, and Margarita Yela〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-238,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 In this study the consistency between MAX-DOAS measurements and radiative transfer simulations of the atmospheric O〈sub〉4〈/sub〉 absorption is investigated. The study is based on measurements (two days during the MADCAT campaign) as well as synthetic spectra. The uncertainties of all relevant aspects (spectral retrieval and radiative transfer simulations) are quantified. For one of the selected days, measurements and simulations do not agree within their uncertainties.

Description: 〈b〉An algorithm to retrieve ice water content profiles in cirrus clouds from the synergy of ground-based lidar and thermal infrared radiometer measurements〈/b〉〈br〉 Friederike Hemmer, Laurent C.-Labonnote, Frédéric Parol, Gérard Brogniez, Bahaiddin Damiri, and Thierry Podvin〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-320,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The paper presents a novel method to retrieve microphysical properties of cirrus clouds from the synergy of lidar and thermal infrared radiometer measurements. It highlights the advantages of combining two independent data sets resulting in a better characterization of the considered cloud type. Our algorithm may improve the description of the backscattering features of the ice crystals composing the cloud and thereby improve our understanding of their interactions with atmospheric radiation.

Description: 〈b〉Derivation of Flow Rate and Calibration Method for High-Volume Air Samplers〈/b〉〈br〉 Richard Hann and Mark Hermanson〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-301,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 High-volume air sampling is a key measurement technique to investigate the concentration of atmospheric pollutants. Although being a mature technique, a detailed description of how to derive flow rates and how to calibrate these samplers is missing in the literature. This paper uses basics in fluid mechanics to derive the equations in question. This allows for a deeper understanding of the measurement process and opens up for a more differentiated assessment of potential error sources.

Description: 〈b〉Extinction and optical depth retrievals for CALIPSO's Version 4 data release〈/b〉〈br〉 Stuart A. Young, Mark A. Vaughan, Anne Garnier, Jason L. Tackett, James D. Lambeth, and Kathleen A. Powell〈br〉 Atmos. Meas. Tech., 11, 5701-5727, https://doi.org/10.5194/amt-11-5701-2018, 2018〈br〉 This paper describes comprehensive upgrades to the algorithms used to retrieve altitude-resolved profiles of cloud and aerosol extinction coefficients from the elastic backscatter measurements made by the space-based CALIPSO lidar. The CALIPSO version 4 data products generated by these new algorithms are explored in detail, and the many areas of improvement are highlighted using extensive comparisons both to previous versions and to collocated measurements made by space-based passive sensors.

Description: 〈b〉Field measurements of methylglyoxal using proton transfer reaction time-of-flight mass spectrometry and comparison to the DNPH–HPLC–UV method〈/b〉〈br〉 Vincent Michoud, Stéphane Sauvage, Thierry Léonardis, Isabelle Fronval, Alexandre Kukui, Nadine Locoge, and Sébastien Dusanter〈br〉 Atmos. Meas. Tech., 11, 5729-5740, https://doi.org/10.5194/amt-11-5729-2018, 2018〈br〉 This study presents the first measurements of ambient methylglyoxal, an important atmospheric α-dicarbonyl, using proton transfer reaction time-of-flight mass spectrometry. These measurements mostly agree with concomitant measurements from a reference technique: the DNPH derivatization technique and high-performance liquid chromatography with UV detection. In addition, a careful investigation of the differences between the two techniques is carried out to explain the disagreements observed.

Description: 〈b〉Quantifying methane point sources from fine-scale satellite observations of atmospheric methane plumes〈/b〉〈br〉 Daniel J. Varon, Daniel J. Jacob, Jason McKeever, Dylan Jervis, Berke O. A. Durak, Yan Xia, and Yi Huang〈br〉 Atmos. Meas. Tech., 11, 5673-5686, https://doi.org/10.5194/amt-11-5673-2018, 2018〈br〉 Methane is a powerful greenhouse gas emitted from numerous human activities. Space-based observation of point sources would be a cost-effective monitoring solution, but the resolution of most current and planned methane-observing satellites is too coarse to resolve individual emitters. We simulate fine-resolution (50 m) satellite observations of methane plumes as would be measured by GHGSat (to be launched in 2019) and show that such data can usefully quantify large methane point sources.

Description: 〈b〉Development and field testing of an online instrument for measuring the real-time oxidative potential of ambient particulate matter based on dithiothreitol assay〈/b〉〈br〉 Joseph V. Puthussery, Chen Zhang, and Vishal Verma〈br〉 Atmos. Meas. Tech., 11, 5767-5780, https://doi.org/10.5194/amt-11-5767-2018, 2018〈br〉 The oxidative potential (OP) of ambient particulate matter (PM) has recently gained attention as an alternative metric for assessing the ambient PM toxicity. However, a major constraint in measuring the OP is its labor-intensive protocol. Here, we developed a new online instrument by coupling a mist chamber to an automated analytical system which can measure the real-time OP of ambient PM. We also report for the first time, the hourly averaged diurnal profile of ambient PM OP at an urban site.

Description: 〈b〉Large volume sample system for measuring sulfur isotopic compositions of carbonyl sulfide〈/b〉〈br〉 Kazuki Kamezaki, Shohei Hattori, Enno Bahlmann, and Naohiro Yoshida〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-324,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Knowledge related to sulfur isotopic composition of carbonyl sulfide (OCS or COS), the most abundant atmospheric sulfur species, remains scarce. We present a new sampling system for collecting approx. 10 nmol of OCS from ambient air coupled with a purification system. The system presented herein is useful for application of sulfur isotopic compositions for investigation of OCS sources and sinks in the troposphere to elucidate its cycle and its contribution to background stratospheric sulfate.

Description: 〈b〉An in situ flow tube system for direct measurement of N〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 heterogeneous uptake coefficients in polluted environments〈/b〉〈br〉 Weihao Wang, Zhe Wang, Chuan Yu, Men Xia, Xiang Peng, Yan Zhou, Dingli Yue, Yubo Ou, and Tao Wang〈br〉 Atmos. Meas. Tech., 11, 5643-5655, https://doi.org/10.5194/amt-11-5643-2018, 2018〈br〉 This study introduces an in situ experimental approach to direct measurement of N〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 heterogeneous reactivity in polluted environments. Laboratory tests, model simulations, and field deployment of the method at a polluted site in south China demonstrated its applicability in accurately measuring N〈sub〉2〈/sub〉O〈sub〉5〈/sub〉 uptake coefficient with high ambient pollutants levels and air mass changes. The introduced method is also applicable to in situ measurement of reactivity of other trace gases on ambient aerosols.

Description: 〈b〉Nitrogen dioxide and formaldehyde measurements from the GEOstationary Coastal and Air Pollution Events (GEO-CAPE) Airborne Simulator over Houston, Texas〈/b〉〈br〉 Caroline R. Nowlan, Xiong Liu, Scott J. Janz, Matthew G. Kowalewski, Kelly Chance, Melanie B. Follette-Cook, Alan Fried, Gonzalo González Abad, Jay R. Herman, Laura M. Judd, Hyeong-Ahn Kwon, Christopher P. Loughner, Kenneth E. Pickering, Dirk Richter, Elena Spinei, James Walega, Petter Weibring, and Andrew J. Weinheimer〈br〉 Atmos. Meas. Tech., 11, 5941-5964, https://doi.org/10.5194/amt-11-5941-2018, 2018〈br〉 The GEO-CAPE Airborne Simulator (GCAS) was developed in support of future air quality and ocean color geostationary satellite missions. GCAS flew in its first field campaign on NASA's King Air B-200 aircraft during DISCOVER-AQ Texas in 2013. In this paper, we determine nitrogen dioxide and formaldehyde columns over Houston from the GCAS air quality sensor and compare those results with measurements made from ground-based Pandora spectrometers and in situ airborne instruments.

Description: 〈b〉Validation of OCO-2 error analysis using simulated retrievals〈/b〉〈br〉 Susan S. Kulawik, Chris O'Dell, Robert R. Nelson, and Thomas E. Taylor〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-368,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This work investigates errors in CO〈sub〉2〈/sub〉 near-infrared estimates retrieved from simulated radiances. We find that interferent errors are underpredicted and that non-linearity causes significant errors.

Description: 〈b〉Cloud Products from the Earth Polychromatic Imaging Camera (EPIC): Algorithms and Initial Evaluaiton〈/b〉〈br〉 Yuekui Yang, Kerry Meyer, Galina Wind, Yaping Zhou, Alexander Marshak, Steven Platnick, Qilong Min, Anthony B. Davis, Joanna Joiner, Alexander Vasilkov, David Duda, and Wenying Su〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-316,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The physical basis of the EPIC cloud product algorithms and an initial evaluation of their performance are presented. EPIC cloud products include cloud mask, effective height, and optical depth. Comparison with co-located retrievals from Geosynchronous Earth Orbit (GEO) and Low Earth Orbit (LEO) satellites shows that the algorithms are performing well and are consistent with theoretical expectations. These products are publicly available at the NASA Langley Atmospheric Sciences Data Center.

Description: 〈b〉Spectral Intensity Bioaerosol Sensor (SIBS): A new Instrument for Spectrally Resolved Fluorescence Detection of Single Particles in Real-Time〈/b〉〈br〉 Tobias Könemann, Nicole Savage, Thomas Klimach, David Walter, Janine Fröhlich-Nowoisky, Hang Su, Ulrich Pöschl, Alex Huffman, and Christopher Pöhlker〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-390,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This study presents a comprehensive assessment of the SIBS, a new instrument for spectrally resolved fluorescence detection of single particles. Exemplary ambient data and fluorescence spectra obtained for 16 reference compounds (biofluorophores and PSLs) show that the SIBS has the ability to expand the scope of fluorescent bioaerosol quantification and classification. Detailed technical insights will be broadly beneficial for users of various WIBS generations and other LIF instruments.

Description: 〈b〉Using the tracer flux ratio method with flight measurements to estimate dairy farm CH〈sub〉4〈/sub〉 emissions in central California〈/b〉〈br〉 Conner Daube, Stephen Conley, Ian C. Faloona, Claudia Arndt, Tara I. Yacovitch, Joseph R. Roscioli, and Scott C. Herndon〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-356,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This study describes aircraft measurements of methane from dairy farms in central California. A small deliberate release of a tracer gas is done on the ground and measured from the air and the ratio of methane to tracer used to quantify emissions. Farm-scale methane emissions are determined as well as the fraction of those emissions coming from animal activity versus liquid manure management. These findings were within the uncertainty of two established methods.

Description: 〈b〉Simulating precipitation radar observations from a geostationary satellite〈/b〉〈br〉 Atsushi Okazaki, Takumi Honda, Shunji Kotsuki, Moeka Yamaji, Takuji Kubota, Riko Oki, Toshio Iguchi, and Takemasa Miyoshi〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-278,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The JAXA is now surveying the feasibility of a potential satellite mission equipped with a precipitation radar on a geostationary orbit, as a successor of GPM core observatory. We investigate what kind of observation data will be available from the radar using simulation techniques. Although the quality of the observation depends on the radar specifications and the position of precipitation systems, the results demonstrate that it would be possible to obtain three-dimensional precipitation data.

Description: 〈b〉A multiwavelength numerical model in support of quantitative retrievals of aerosol properties from automated lidar ceilometers and test applications for AOT and PM〈sub〉10〈/sub〉 estimation〈/b〉〈br〉 Davide Dionisi, Francesca Barnaba, Henri Diémoz, Luca Di Liberto, and Gian Paolo Gobbi〈br〉 Atmos. Meas. Tech., 11, 6013-6042, https://doi.org/10.5194/amt-11-6013-2018, 2018〈br〉 〈p〉The use of automated lidar ceilometer (ALC) systems for the aerosol vertically resolved characterization has increased in recent years thanks to their low construction and operation costs and their capability of providing continuous unattended measurements. At the same time there is a need to convert the ALC signals into usable geophysical quantities. In fact, the quantitative assessment of the aerosol properties from ALC measurements and the relevant assimilation in meteorological forecast models is amongst the main objectives of the EU COST Action TOPROF (〈q〉Towards operational ground-based profiling with ALCs, Doppler lidars and microwave radiometers for improving weather forecasts〈/q〉). Concurrently, the E-PROFILE program of the European Meteorological Services Network (EUMETNET) focuses on the harmonization of ALC measurements and data provision across Europe. Within these frameworks, we implemented a model-assisted methodology to retrieve key aerosol properties (extinction coefficient, surface area, and volume) from elastic lidar and/or ALC measurements. The method is based on results from a large set of aerosol scattering simulations (Mie theory) performed at UV, visible, and near-IR wavelengths using a Monte Carlo approach to select the input aerosol microphysical properties. An average 〈q〉continental aerosol type〈/q〉 (i.e., clean to moderately polluted continental aerosol conditions) is addressed in this study. Based on the simulation results, we derive mean functional relationships linking the aerosol backscatter coefficients to the abovementioned variables. Applied in the data inversion of single-wavelength lidars and/or ALCs, these relationships allow quantitative determination of the vertically resolved aerosol backscatter, extinction, volume, and surface area and, in turn, of the extinction-to-backscatter ratios (i.e., the lidar ratios, LRs) and extinction-to-volume conversion factor (〈i〉c〈/i〉〈sub〉v〈/sub〉) at 355, 532, and 1064 nm. These variables provide valuable information for visibility, radiative transfer, and air quality applications. This study also includes (1) validation of the model simulations with real measurements and (2) test applications of the proposed model-based ALC inversion methodology. In particular, our model simulations were compared to backscatter and extinction coefficients independently retrieved by Raman lidar systems operating at different continental sites within the European Aerosol Research Lidar Network (EARLINET). This comparison shows good model–measurement agreement, with LR discrepancies below 20 %. The model-assisted quantitative retrieval of both aerosol extinction and volume was then tested using raw data from three different ALCs systems (CHM 15k Nimbus), operating within the Italian Automated LIdar-CEilometer network (ALICEnet). For this purpose, a 1-year record of the ALC-derived aerosol optical thickness (AOT) at each site was compared to direct AOT measurements performed by colocated sun–sky photometers. This comparison shows an overall AOT agreement within 30 % at all sites. At one site, the model-assisted ALC estimation of the aerosol volume and mass (i.e., PM〈sub〉10〈/sub〉) in the lowermost levels was compared to values measured at the surface level by colocated in situ instrumentation. Within this exercise, the ALC-derived daily-mean mass concentration was found to reproduce the corresponding (EU regulated) PM〈sub〉10〈/sub〉 values measured by the local air quality agency well in terms of both temporal variability and absolute values. Although limited in space and time, the good performances of the proposed approach suggest it could possibly represent a valid option to extend the capabilities of ALCs to provide quantitative information for operational air quality and meteorological monitoring.〈/p〉

Description: 〈b〉Improvements to a long-term Rayleigh-scatter lidar temperature climatology by using an optimal estimation method〈/b〉〈br〉 Ali Jalali, Robert J. Sica, and Alexander Haefele〈br〉 Atmos. Meas. Tech., 11, 6043-6058, https://doi.org/10.5194/amt-11-6043-2018, 2018〈br〉 We use 16 years of lidar (laser radar) temperature measurements of the middle atmosphere to form a climatology for use in studying atmospheric temperature change using an optimal estimation method (OEM). Using OEM allows us to calculate a complete systematic and random uncertainty budget and allows for an additional 10–15 km in altitude for the measurement to be used, improving our ability to detect atmospheric temperature change up to 100 km of altitude.

Description: 〈b〉Detecting cloud contamination in passive microwave satellite measurements over land〈/b〉〈br〉 Samuel Favrichon, Catherine Prigent, Carlos Jimenez, and Filipe Aires〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-352,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Land surface parameters (such as temperature) can be extracted from passive microwave satellite observations, with less cloud contamination than in the infrared. A cloud contamination index is proposed to detect cloud contamination for multiple frequency ranges (from 10 to 190 GHz), to be applicable to the successive generations of MW instruments. Even with a reduced number of low frequency channels over land, the index reaches an accuracy ≥ 70 %, in detecting contaminated observations.

Description: 〈b〉An instrument for the rapid quantification of PM oxidative potential: the Particle Into Nitroxide Quencher (PINQ)〈/b〉〈br〉 Reece Alexander Brown, Svetlana Stevanovic, Steven Bottle, and Zoran Ristovski〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-333,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Presence or generation of reactive oxygen species (ROS) on/by particulate matter (PM) have been implicated in PM-induced health effects. Methodologies to quantify ROS concentrations vary widely both in detection and collection methods. However, there is currently an increasing emphasis on rapid collection and measurement due to observations of short half-live ROS. To address this problem, this manuscript details the design and characterization of a novel instrument named the Particle Into Nitroxide Quencher (PINQ). This instrument combines the BPEAnit ROS assay in conjunction with a purpose-built aerosol collection device, the insoluble aerosol collector (IAC). The IAC continuously collects PM regardless of size or chemistry directly into a liquid sample with a collection efficiency of 0.98 and a low cut-off size of −3 in equivalent BPEAnit-Me concentration per volume of air. This high sample time resolution and sensitivity is achieved due a combination of the highly concentrated IAC liquid sample and the rapid reaction and stability of the BPEAnit probe.

Description: 〈b〉The OCO-3 mission; measurement objectives and expected performance based on one year of simulated data〈/b〉〈br〉 Annmarie Eldering, Tommy E. Taylor, Chris W. O'Dell, and Ryan Pavlick〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-357,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 NASA's Orbiting Carbon Observatory-3 (OCO-3) is scheduled for a 2019 launch to the International Space Station (ISS). It is expected to continue the record of column carbon dioxide (XCO〈sub〉2〈/sub〉) and solar induced chlorophyll fluorescence (SIF) measurements from space used to study and constrain the earth's carbon cycle. This work highlights the measurement objectives and uses simulated data to show that the expected instrument performance is on par with those from OCO-2.

Description: 〈b〉The SPARC water vapour assessment II: Profile-to-profile comparisons of stratospheric and lower mesospheric water vapour data sets obtained from satellites〈/b〉〈br〉 Stefan Lossow, Farahnaz Khosrawi, Michael Kiefer, Kaley A. Walker, Jean-Loup Bertaux, Laurent Blanot, James M, Russell, Ellis E. Remsberg, John C. Gille, Takafumi Sugita, Christopher E. Sioris, Bianca M. Dinelli, Enzo Papandrea, Piera Raspollini, Maya Garcia-Comas, Gabriele P. Stiller, Thomas von Clarmann, Anu Dudhia, William G. Read, Gerald E. Nedoluha, Robert P. Damadeo, Joseph M. Zawodny, Katja Weigel, Alexei Rozanov, Faiza Azam, Klaus Bramstedt, Stefan Noël, John P. Burrows, Hideo Sagawa, Yasuko Kasai, Joachim Urban, Patrick Eriksson, Donal P. Murtagh, Mark E. Hervig, Charlotta Högberg, Dale F. Hurst, and Karen H. Rosenlof〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-380,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Within the framework of the second SPARC (Stratosphere-troposphere Processes And their Role in Climate) water vapour assessment (WAVAS-II), profile-to-profile comparisons of stratospheric and lower mesospheric water vapour were performed considering 33 data sets derived from satellite observations of 15 different instruments. These comparisons aimed to provide a picture of the typical biases and drifts in the observational database and to identify data set specific problems. The observational database typically exhibits the largest biases below 70 hPa, both in absolute and relative terms. The smallest biases are often found between 50 hPa and 5 hPa. Typically, they range from 0.25 ppmv to 0.5 ppmv (5 % to 10 %) in this altitude region, based on the 50 % percentile over the different comparison results. Higher up, the biases are overall increasing with altitude but this general behaviour is accompanied by considerable variations. Characteristic values vary between 0.3 ppmv and 1 ppmv (4 % to 20 %). Obvious data set specific bias issues are found for a number of data sets. In our work we performed a drift analysis for data sets overlapping for a period of at least 36 months. This assessment shows a wide range of drifts among the different data sets that are statistically significant at the 2σ uncertainty level. In general, the smallest drifts are found in the altitude range between about 30 hPa to 10 hPa. Histograms considering results from all altitudes indicate the largest occurrence for drifts between 0.05 ppmv decade〈sup〉−1〈/sup〉 and 0.3 ppmv decade〈sup〉−1〈/sup〉. Comparisons of our drift estimates to those derived from comparisons of zonal mean time series only exhibit statistically significant differences in slightly more than 3 % of the comparisons. Hence, drift estimates from profile-to-profile and zonal mean time series comparisons are largely interchangeable. Like for the biases, a number of data sets exhibit prominent drift issues. In our analyses we found that the large number of MIPAS data sets included in the assessment affects our general results as well as the bias summaries we provide for the individual data sets. This is because these data sets exhibit a relative similarity with respect to the remaining data sets, despite that they are based on different measurement modes and different processors implementing different retrieval choices. Because of that, we have by default considered an aggregation of the comparison results obtained from MIPAS data sets. Results without this aggregation are provided on multiple occasions to characterise the effects due to the numerous MIPAS data sets. Among other effects, they cause a reduction of the typical biases in the observational database.

Description: 〈b〉Revisiting the differential freezing nucleus spectra derived from drop freezing experiments; methods of calculation, applications and confidence limits〈/b〉〈br〉 Gabor Vali〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-309,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The abundance of freezing nuclei in water samples is routinely determined by experiments involving the cooling of sample drops and observing the temperatures at which the drops freeze. This can be used for characterizing the nucleating abilities of materials in laboratory preparations or to determine the numbers of nucleating particles in rain, snow river water or other natural waters. The evaluation of drop freezing experiments in terms of differential nucleus spectra is advocated in the paper.

Description: 〈b〉Processing and quality control with FY-3C/GNOS data used in numerical weather prediction applications〈/b〉〈br〉 Mi Liao, Sean Healy, and Peng Zhang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-271,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This paper describes a new method for improving the data of Chinese radio occultation sounder, GNOS, with large biases. The new method can effectively eliminate about 90 % of the large departures. In addition, this paper also describes the quality control (QC) for the GNOS data. The GNOS data with the new L2 extrapolation is suitable for assimilation into numerical weather prediction systems.

Description: 〈b〉Initial report on polar mesospheric cloud observations by Himawari-8〈/b〉〈br〉 Takuo T. Tsuda, Yuta Hozumi, Kento Kawaura, Keisuke Hosokawa, Hidehiko Suzuki, and Takuji Nakamura〈br〉 Atmos. Meas. Tech., 11, 6163-6168, https://doi.org/10.5194/amt-11-6163-2018, 2018〈br〉 Polar mesospheric clouds (PMCs) or noctilucent clouds (NLCs) are the highest clouds in the Earth's atmosphere. In this paper, we introduce new PMC observations by the Japanese Geostationary Earth Orbit (GEO) meteorological satellite Himawari-8, which was launched in October 2014.

Description: 〈b〉Validation of the TOLNet lidars: the Southern California Ozone Observation Project (SCOOP)〈/b〉〈br〉 Thierry Leblanc, Mark A. Brewer, Patrick S. Wang, Maria Jose Granados-Muñoz, Kevin B. Strawbridge, Michael Travis, Bernard Firanski, John T. Sullivan, Thomas J. McGee, Grant K. Sumnicht, Laurence W. Twigg, Timothy A. Berkoff, William Carrion, Guillaume Gronoff, Ali Aknan, Gao Chen, Raul J. Alvarez, Andrew O. Langford, Christoph J. Senff, Guillaume Kirgis, Matthew S. Johnson, Shi Kuang, and Michael J. Newchurch〈br〉 Atmos. Meas. Tech., 11, 6137-6162, https://doi.org/10.5194/amt-11-6137-2018, 2018〈br〉 This article reviews the capability of five ozone lidars from the North American TOLNet lidar network. These ground-based laser remote-sensing instruments typically measure ozone in the troposphere with a precision of 5 % and vertical and time resolutions of 100 m and 10 min, respectively. Understanding ozone variability at high spatiotemporal scales is essential for monitoring air quality, human health, and climate. The article shows that the TOLNet lidars are very well suited for this purpose.

Description: 〈b〉Novel aerosol extinction coefficients and lidar ratios over the ocean from CALIPSO-CloudSat: Evaluation and global statistics〈/b〉〈br〉 David Painemal, Marian Clayton, Richard Ferrare, Sharon Burton, Damien Josset, and Mark Vaughan〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-363,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 One year of a new CALIOP-based aerosol extinction coefficient and lidar ratio dataset over the ocean is presented, with the goal of providing a flexible dataset for climate research as well as independent retrievals that can be helpful for refining CALIPSO Science Team algorithms. The retrievals are derived by constraining the lidar equation with aerosol optical depth estimated from cross-calibrated CALIOP and CloudSat surface echos.

Description: 〈b〉Dried, closed-path eddy covariance method for measuring carbon dioxide flux over sea ice〈/b〉〈br〉 Brian J. Butterworth and Brent G. T. Else〈br〉 Atmos. Meas. Tech., 11, 6075-6090, https://doi.org/10.5194/amt-11-6075-2018, 2018〈br〉 This study measured how quickly carbon dioxide was absorbed/released from sea ice to the air. We used a method that had never been tested over landlocked sea ice. To avoid water vapor ruining the carbon dioxide measurement, we dried the sample air before it went to the gas analyzer. This gave values that were more credible than those found by previous studies. We showed that this method will be useful for studying the processes which affect carbon dioxide exchange between sea ice and air.

Description: 〈b〉Albedo-Ice regression method for determining ice water content of Polar Mesospheric Clouds using ultraviolet observations from space〈/b〉〈br〉 Gary E. Thomas, Jerry Lumpe, Charles Bardeen, and Cora E. Randall〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-330,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Polar Mesospheric Clouds are an upper atmospheric phenomenon of great interest in that they provide information about a previously inaccessible atmospheric region, the coldest of the planet. This paper provides the basis for converting raw radiance measurements of clouds, made by diverse satellite instrumentation, into a physically-based quantity, the cloud ice water content. The new algorithm allows inter-comparisons of data collected by diverse optical methods.

Description: 〈b〉Evaluation of microwave radiances of GPM/GMI for the all-sky assimilation in RTTOV framework〈/b〉〈br〉 Rohit Mangla and Indu Jayaluxmi〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-319,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 〈p〉This study evaluates the all-sky GPM/GMI radiances towards assimilation in regional mesoscale model at 183 ± 7 GHz. The radiative transfer model (RTM) namely RTTOV-SCATT is used for the simulation of three tropical cyclones (hudhud, vardah and kyant respectively). Within the RTM, the performance of non-spherical Discrete Dipole Approximation (DDA) shapes (sector snowflake, 6-bullet rosette, block-column and thinplate) are evaluated. The input data used in RTTOV-SCATT includes vertical hydrometeor profiles, humidity and surface fluxes. In addition, the first guess simulations from Weather Research Forecast (WRF) model were executed at 15 km resolution using ERA-Interim reanalysis datasets. Results indicate that observed minus first guess (FG departures) are symmetric with DDA shapes. The normalized probability density function of FG departures shows large number of spatially correlated samples between clear-sky and poorly forecasted region. Quality control (QC) method was performed to eliminate large FG departures due to instrumental anomalies or poor forecast of clouds and precipitation. The goodness of fit test, h-statistics and skewness of observed and simulated distribution show optimum results for thinplate shape in all the convective events. We also tested the high resolution ERA-5 reanalysis datasets for the simulation of all-sky radiances using thinplate shape. Results illustrate a potential to integrate the GMI sensor data within a WRF data assimilation system.〈/p〉

Description: 〈b〉Machine learning for improved data analysis of biological aerosol using the WIBS〈/b〉〈br〉 Simon Ruske, David O. Topping, Virginia E. Foot, Andrew P. Morse, and Martin W. Gallagher〈br〉 Atmos. Meas. Tech., 11, 6203-6230, https://doi.org/10.5194/amt-11-6203-2018, 2018〈br〉 Pollen, bacteria and fungal spores are common in the environment, can have very important implications for public health and may influence the weather. Biological sensors potentially could be used to monitor quantities of these types of particles. However, it is important to transform the measurements from these instruments into counts of these biological particles. The paper tests a variety of approaches for achieving this aim on data collected in a laboratory.

Description: 〈b〉Evaluation of GPM-DPR precipitation estimates with WegenerNet gauge data〈/b〉〈br〉 Martin Lasser, Sungmin O, and Ulrich Foelsche〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-395,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 This paper evaluates the rain rate estimates from the Global Precipitation Measurement (GPM) mission's radar instrument by comparing them to the data of the WegenerNet, a local-scale high resolution network of meteorological stations. Our results show that the GPM-DPR estimates basically match with the WegenerNet measurements, but absolute quantities are biased.

Description: 〈b〉Homogeneity criteria within IASI pixels for the preparation of an all-sky assimilation〈/b〉〈br〉 Imane Farouk, Nadia Fourrie, and Vincent Guidard〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-288,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A selection for homogeneous scenes for the all-sky infrared radiance assimilation is proposed by using information of the collocated imager pixels inside each infrared observation. A revised method for the selection, which is a compromise between two methods to select homogeneous scenes using homogeneity criteria already proposed en the literature has a positive impact on the observation minus the simulation statistic. It has been tested in a numerical weather prediction model for clear sky.

Description: 〈b〉The Fifth International Workshop on Ice Nucleation phase 2 (FIN-02): laboratory intercomparison of ice nucleation measurements〈/b〉〈br〉 Paul J. DeMott, Ottmar Möhler, Daniel J. Cziczo, Naruki Hiranuma, Markus D. Petters, Sarah S. Petters, Franco Belosi, Heinz G. Bingemer, Sarah D. Brooks, Carsten Budke, Monika Burkert-Kohn, Kristen N. Collier, Anja Danielczok, Oliver Eppers, Laura Felgitsch, Sarvesh Garimella, Hinrich Grothe, Paul Herenz, Thomas C. J. Hill, Kristina Höhler, Zamin A. Kanji, Alexei Kiselev, Thomas Koop, Thomas B. Kristensen, Konstantin Krüger, Gourihar Kulkarni, Ezra J. T. Levin, Benjamin J. Murray, Alessia Nicosia, Daniel O'Sullivan, Andreas Peckhaus, Michael J. Polen, Hannah C. Price, Naama Reicher, Daniel A. Rothenberg, Yinon Rudich, Gianni Santachiara, Thea Schiebel, Jann Schrod, Teresa M. Seifried, Frank Stratmann, Ryan C. Sullivan, Kaitlyn J. Suski, Miklós Szakáll, Hans P. Taylor, Romy Ullrich, Jesus Vergara-Temprado, Robert Wagner, Thomas F. Whale, Daniel Weber, André Welti, Theodore W. Wilson, Martin J. Wolf, and Jake Zenker〈br〉 Atmos. Meas. Tech., 11, 6231-6257, https://doi.org/10.5194/amt-11-6231-2018, 2018〈br〉 The ability to measure ice nucleating particles is vital to quantifying their role in affecting clouds and precipitation. Methods for measuring droplet freezing were compared while co-sampling relevant particle types. Measurement correspondence was very good for ice nucleating particles of bacterial and natural soil origin, and somewhat more disparate for those of mineral origin. Results reflect recently improved capabilities and provide direction toward addressing remaining measurement issues.

Description: 〈b〉How bias correction goes wrong: Measurement of X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉 affected by erroneous surface pressure estimates〈/b〉〈br〉 Matthäus Kiel, Christopher W. O'Dell, Brendan Fisher, Annmarie Eldering, Ray Nassar, Cameron G. MacDonald, and Paul O. Wennberg〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-353,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 1 comment)〈br〉 Currently all measurements of X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉 from space have systematic errors. To reduce a large fraction of these errors, a bias correction is applied to X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉 retrieved from GOSAT and OCO-2 spectra using the ACOS retrieval algorithm. The bias correction uses, among other parameters, the surface pressure difference between the retrieval and the meteorological reanalysis. Erroneous surface pressure estimates, however, propagate nearly 1 : 1 into bias-corrected X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉. For OCO-2, small errors in the knowledge of the pointing of the observatory (up to ∼ 130 arcsec) introduce a bias in X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉 in regions with rough topography. Erroneous surface pressure estimates are also caused by a bug in ACOS version 8, sampling meteorological analyses at wrong times (up to three hours after the overpass time). Here, we derive new geolocations for OCO-2's eight footprints and show how using improved knowledge of surface pressure estimates in the bias correction reduces errors in OCO-2's v9 X〈sub〉CO〈sub〉2〈/sub〉〈/sub〉 data.

Description: 〈b〉Simulation study for ground-based Ku-band microwave observations of ozone and hydroxyl in the polar middle atmosphere〈/b〉〈br〉 David A. Newnham, Mark A. Clilverd, Michael Kosch, and Pekka T. Verronen〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-334,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A simulation study has been carried out to investigate the potential for observing ozone and hydroxyl radical abundances in the mesosphere and lower thermosphere using ground based passive microwave radiometry. In the polar middle atmosphere these chemical species respond strongly to geomagnetic activity associated with space weather. The results show that measuring diurnal variations in ozone and hydroxyl from high latitude northern hemisphere and Antarctic locations would be possible.

Description: 〈b〉Correlated observation error models for assimilating all-sky infrared radiances〈/b〉〈br〉 Alan J. Geer〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-379,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 Using more satellite data in cloudy areas will help improve weather forecasts. All-sky assimilation of microwave radiances is common but of infrared radiances less so. To allow the all-sky use of hyperspectral infrared sounders, an error model is developed to represent the effect of cloud in broadening the correlations between channels as well as increasing error variances. After fixing problems of gravity wave and bias amplification, the results of all-sky assimilation trials were promising.

Description: 〈b〉Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: functional group quantification in US measurement networks〈/b〉〈br〉 Matteo Reggente, Ann M. Dillner, and Satoshi Takahama〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-331,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 We compare state-of-the-art models for predicting functional group composition in atmospheric particulate matter across urban and rural samples collected in a US monitoring network. While trends across models are consistent, absolute abundances can be sensitive to selection of calibration standards, spectral processing, and calibration algorithms. Recommendations for further method development for reducing uncertainties are outlined.

Description: 〈b〉Stratospheric aerosol characteristics from space-borne observations: extinction coefficient and Ångström exponent〈/b〉〈br〉 Elizaveta Malinina, Alexei Rozanov, Landon Rieger, Adam Bourassa, Heinrich Bovensmann, John P. Burrows, and Doug Degenstein〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-328,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The paper covers the problems related to the derivation of aerosol extinction coefficients and Ångström exponents from space-borne instruments working in limb and occultation viewing geometries. Aerosol extinction coefficients and Ångström exponents were calculated from SCIAMACHY aerosol particle size data set. The results were compared with the data from SAGE II and OSIRIS instruments. The Ångström exponent in the tropical regions and its dependency on particle size parameters are discussed.

Description: 〈b〉A novel study of the morphology and effective density of externally mixed black carbon aerosols in ambient air using a size-resolved single-particle soot photometer (SP2)〈/b〉〈br〉 Yunfei Wu, Yunjie Xia, Rujin Huang, Zhaoze Deng, Ping Tian, Xiangao Xia, and Renjian Zhang〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-408,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 A novel system composing of a DMA and SP2 was designed to investigate the morphology and effective density of externally-mixed BC (extBC) in ambient atmosphere. Based on 19-day in-situ measurement in urban Beijing using the system, the fractal dimension of extBC was determined as 2.36 indicating the dominant contribution of diesel exhausts. The loosely chain-like structure of extBC was identified with effective density decreasing from 0.34 to 0.12 g cm〈sup〉−3〈/sup〉 in the mobility size range of 140–700 nm.

Description: 〈b〉FRESCO-B: A fast cloud retrieval algorithm using oxygen B-band measurements from GOME-2〈/b〉〈br〉 Marine Desmons, Ping Wang, Piet Stammes, and L. Gijsbert Tilstra〈br〉 Atmos. Meas. Tech. Discuss., https//doi.org/10.5194/amt-2018-420,2018〈br〉 〈b〉Manuscript under review for AMT〈/b〉 (discussion: open, 0 comments)〈br〉 The FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A-band) algorithm is a simple, fast and robust algorithm used to retrieve cloud information in operational satellite data processing. It has been applied to GOME-1, SCIAMACHY, GOME-2 and more recently to TROPOMI. FRESCO retrieves effective cloud fraction and cloud pressure from measurements in the oxygen A-band around 761 nm. In this paper, we propose a new version of the algorithm, called FRESCO-B, which is based on measurements in the oxygen B-band around 687 nm. Such a method is interesting for vegetated surfaces where the surface albedo is much lower in the B-band than in the A-band, which limits the ground contribution to the top-of-atmosphere reflectances. In this study we first perform retrieval simulations. These show that the retrieved cloud pressures from FRESCO-B and FRESCO differ only between −10 hPa and +10 hPa, except for high thin clouds over vegetation where the difference is larger, about +15 to +30 hPa, with FRESCO-B yielding higher pressures. Next, inter-comparison between FRESCO-B and FRESCO retrievals over one month of GOME-2B data reveals that the effective cloud fractions retrieved in the O〈sub〉2〈/sub〉 A and B bands are very similar (mean difference of 0.003) while the cloud pressures show a mean difference of 11.5 hPa, with FRESCO-B retrieving higher pressures than FRESCO. This agrees with the simulations and is partly due to deeper photons penetrations of O〈sub〉2〈/sub〉 B-band in clouds as compared to the O〈sub〉2〈/sub〉 A-band photons, and partly due to the surface albedo bias in FRESCO. Finally, validation with ground-based measurements shows that the FRESCO-B cloud pressure represents an altitude within the cloud boundaries for clouds that are not too far from the Lambertian reflector model, which occurs in about 50 % of the cases.