The Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI): design, execution, and early results

Abstract

Published by Copernicus Publications on behalf of the European Geosciences Union. 458 A. J. M. Piters et al.: The CINDI campaign: design, execution and early resultsAbstract. From June to July 2009 more than thirty different in-situ and remote sensing instruments from all over the world participated in the Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The campaign took place at KNMI's Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands. Its main objectives were to determine the accuracy of state-ofthe-art ground-based measurement techniques for the detection of atmospheric nitrogen dioxide (both in-situ and remote sensing), and to investigate their usability in satellite data validation. The expected outcomes are recommendations regarding the operation and calibration of such instruments, retrieval settings, and observation strategies for the use in ground-based networks for air quality monitoring and satellite data validation. Twenty-four optical spectrometers participated in the campaign, of which twenty-one had the capability to scan different elevation angles consecutively, the so-called Multi-axis DOAS systems, thereby collecting vertical profile information, in particular for nitrogen dioxide and aerosol. Various in-situ samplers and lidar instruments simultaneously characterized the variability of atmospheric trace gases and the physical properties of aerosol particles. A large data set of continuous measurements of these atmospheric constituents has been collected under various meteorological conditions and air pollution levels. Together with the permanent measurement capability at the CE-SAR site characterizing the meteorological state of the atmosphere, the CINDI campaign provided a comprehensive observational data set of atmospheric constituents in a highly polluted region of the world during summertime. First detailed comparisons performed with the CINDI data show that slant column measurements of NO 2 , O 4 and HCHO with MAX-DOAS agree within 5 to 15 %, vertical profiles of NO 2 derived from several independent instruments agree within 25 % of one another, and MAX-DOAS aerosol optical thickness agrees within 20-30 % with AERONET data. For the in-situ NO 2 instrument using a molybdenum converter, a bias was found as large as 5 ppbv during day time, when compared to the other in-situ instruments using photolytic converters.

The use of NO<sub>2</sub> absorption cross section temperature sensitivity to derive NO<sub>2</sub> profile temperature and stratospheric–tropospheric column partitioning from visible direct-sun DOAS measurements

“…The Cabauw Experimental Site for Atmospheric Research, a rural site in the heart of the Netherlands, is characterized by relatively large regional NO 2 pollution. Observations during the Cabauw Intercomparison campaign for Nitrogen Dioxide Measuring Instruments (CINDI, June-July 2009; Piters et al, 2012) are presented here. NASA Goddard Space Flight Center (NASA/GSFC) is located in Greenbelt, MD, which is part of the Baltimore-Washington metropolitan area.…”

Evaluation of OMI operational standard NO<sub>2</sub> column retrievals using in situ and surface-based NO<sub>2</sub> observations

“…cm −2 . NO 2 column retrievals from Pandora have been previously validated against direct-sun multifunction DOAS (MFDOAS) and Fourier transform ultraviolet spectrometer (UVFTS) data and have been found to agree to within 12 % (Piters et al, 2012;Wang et al, 2010;Herman et al, 2009). Here, we compute 30 min Pandora column averages close to the OMI overpass time to compare with the nearest OMI NO 2 columns representing individual field of view (FOV).…”

Investigating differences in DOAS retrieval codes using MAD-CAT campaign data

“…was the first to also have a focus on MAX-DOAS observations of tropospheric species (Roscoe et al, 2010;Piters et al, 2012;Pinardi et al, 2013) and has recently been followed by the CINDI-2 campaign carried out in 2016, also in Cabauw. However, these intercomparison exercises concentrated mostly on results originating from different retrieval codes and instruments, and separation of instrument and retrieval effects was not easily possible.…”