Intercomparison of MAX-DOAS vertical profile retrieval algorithms: studies on field data from the CINDI-2 campaign

Atmospheric Measurement Techniques Discussions

article

Tirpitz, Jan-Lukas¹  Bognar, Kristof²  Bösch, Tim³  Bruchkouski, Ilya⁴  Cede, Alexander⁵  Chan, Ka Lok⁷  den Hoed, Mirjam⁹  Donner, Sebastian^1,10  Drosoglou, Theano^1,11  Fayt, Caroline^1,12  Friedrich, Martina M.^1,12  Frieß, Udo¹  Frumau, Arnoud^1,13  Gast, Lou^1,14  Gielen, Clio^1,12  Gomez-Martín, Laura^1,16  Hao, Nan^1,17  Hensen, Arjan^1,13  Henzing, Bas^1,13  Hermans, Christian^1,12  Jin, Junli^1,18  Kreher, Karin^1,19  Hendrick, François^1,12  Kuhn, Jonas¹  Lampel, Johannes¹  Li, Ang^2,21  Liu, Cheng^2,22  Liu, Haoran^2,22  Ma, Jianzhong^2,23  Merlaud, Alexis^1,12  Peters, Enno³  Pinardi, Gaia^1,12  Piters, Ankie⁹  Alberti, Carlos⁷  Platt, Ulrich¹  Puentedura, Olga^1,16  Richter, Andreas³  Schmitt, Stefan¹  Spinei, Elena⁶  Stein Zweers, Deborah⁹  Strong, Kimberly²  Swart, Daan^1,14  Tack, Frederik^1,12  Tiefengraber, Martin⁵  Allaart, Marc⁹  van der Hoff, René^1,14  van Roozendael, Michel^1,12  Vlemmix, Tim⁹  Vonk, Jan^1,14  Wagner, Thomas^1,10  Wang, Yang^1,10  Wang, Zhuoru^1,17  Wenig, Mark⁷  Wiegner, Matthias⁷  Wittrock, Folkard³  Apituley, Arnoud⁹  Xie, Pinhua^2,21  Xing, Chengzhi^2,22  Xu, Jin^2,21  Yela, Margarita^1,16  Zhang, Chengxin^2,22  Zhao, Xiaoyi²  Bais, Alkis^1,11  Beirle, Steffen^1,10  Berkhout, Stijn^1,14 

[1] Institute of Environmental Physics, University of Heidelberg;Department of Physics, University of Toronto;Institute for Environmental Physics, University of Bremen;National Ozone Monitoring Research and Education Center (NOMREC), Belarusian State University;LuftBlick Earth Observation Technologies;NASA-Goddard Space Flight Center;Meteorological Institute, Ludwig-Maximilians-Universität München;now at: Remote Sensing Technology Institute (IMF), German Aerospace Center (DLR);Royal Netherlands Meteorological Institute (KNMI);Max Planck Institute for Chemistry;Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki;Royal Belgian Institute for Space Aeronomy;Netherlands Organisation for Applied Scientific Research (TNO);National Institute for Public Health and the Environment (RIVM);now at: Institute for Astronomy;National Institute of Aerospatial Technology (INTA);Remote Sensing Technology Institute, German Aerospace Center (DLR);Meteorological Observation Centre, China Meteorological Administration;BK Scientific GmbH;Airyx GmbH;Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences;School of Earth and Space Sciences, University of Science and Technology of China;Chinese Academy of Meteorology Science, China Meteorological Administration;now at: Institute for Protection of Maritime Infrastructures;now at: Institute of Meteorology and Climate Research (IMK-ASF), Karlsruhe Institute of Technology (KIT);now at: Virginia Polytechnic Institute and State University;Department of Atmospheric and Cryospheric Sciences, University of Innsbruck;now at: Air Quality Research Division

DOI  :  10.5194/amt-14-1-2021

学科分类：大气科学

来源: Copernicus Publications

【 摘 要 】

The second Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI-2) took place in Cabauw (the Netherlands) in September 2016 with the aim of assessing the consistency of multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of tropospheric species (NO 2 , HCHO, O 3 , HONO, CHOCHO and O 4 ). This was achieved through the coordinated operation of 36 spectrometers operated by 24 groups from all over the world, together with a wide range of supporting reference observations (in situ analysers, balloon sondes, lidars, long-path DOAS, direct-sun DOAS, Sun photometer and meteorological instruments). In the presented study, the retrieved CINDI-2 MAX-DOAS trace gas (NO 2 , HCHO) and aerosol vertical profiles of 15 participating groups using different inversion algorithms are compared and validated against the colocated supporting observations, with the focus on aerosol optical thicknesses (AOTs), trace gas vertical column densities (VCDs) and trace gas surface concentrations. The algorithms are based on three different techniques: six use the optimal estimation method, two use a parameterized approach and one algorithm relies on simplified radiative transport assumptions and analytical calculations. To assess the agreement among the inversion algorithms independent of inconsistencies in the trace gas slant column density acquisition, participants applied their inversion to a common set of slant columns. Further, important settings like the retrieval grid, profiles of O 3 , temperature and pressure as well as aerosol optical properties and a priori assumptions (for optimal estimation algorithms) have been prescribed to reduce possible sources of discrepancies. The profiling results were found to be in good qualitative agreement: most participants obtained the same features in the retrieved vertical trace gas and aerosol distributions; however, these are sometimes at different altitudes and of different magnitudes. Under clear-sky conditions, the root-mean-square differences (RMSDs) among the results of individual participants are in the range of 0.01–0.1 for AOTs, (1.5–15)  × 10 14 molec . cm - 2 for trace gas (NO 2 , HCHO) VCDs and (0.3– 8 ) × 10 10 molec . cm - 3 for trace gas surface concentrations. These values compare to approximate average optical thicknesses of 0.3 , trace gas vertical columns of 90 × 10 14 molec . cm - 2 and trace gas surface concentrations of 11 × 10 10 molec . cm - 3 observed over the campaign period. The discrepancies originate from differences in the applied techniques, the exact implementation of the algorithms and the user-defined settings that were not prescribed. For the comparison against supporting observations, the RMSDs increase to a range of 0.02–0.2 against AOTs from the Sun photometer, (11– 55 ) × 10 14 molec . cm - 2 against trace gas VCDs from direct-sun DOAS observations and (0.8– 9 ) × 10 10 molec . cm - 3 against surface concentrations from the long-path DOAS instrument. This increase in RMSDs is most likely caused by uncertainties in the supporting data, spatiotemporal mismatch among the observations and simplified assumptions particularly on aerosol optical properties made for the MAX-DOAS retrieval. As a side investigation, the comparison was repeated with the participants retrieving profiles from their own differential slant column densities (dSCDs) acquired during the campaign. In this case, the consistency among the participants degrades by about 30  % for AOTs, by 180  % ( 40  % ) for HCHO (NO 2 ) VCDs and by 90  % ( 20  % ) for HCHO (NO 2 ) surface concentrations. In former publications and also during this comparison study, it was found that MAX-DOAS vertically integrated aerosol extinction coefficient profiles systematically underestimate the AOT observed by the Sun photometer. For the first time, it is quantitatively shown that for optimal estimation algorithms this can be largely explained and compensated by considering biases arising from the reduced sensitivity of MAX-DOAS observations to higher altitudes and associated a priori assumptions.

【 授权许可】

CC BY