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

[摘要] From June to July 2009 more than thirty different in-situ and remote sensinginstruments from all over the world participated in the CabauwIntercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI).The campaign took place at KNMI's Cabauw Experimental Site for AtmosphericResearch (CESAR) in the Netherlands. Its main objectives were to determine theaccuracy of state-of-the-art ground-based measurement techniques for thedetection of atmospheric nitrogen dioxide (both in-situ and remote sensing),and to investigate their usability in satellite data validation. The expectedoutcomes are recommendations regarding the operation and calibration of suchinstruments, retrieval settings, and observation strategies for the use inground-based networks for air quality monitoring and satellite datavalidation. Twenty-four optical spectrometers participated in the campaign,of which twenty-one had the capability to scan different elevation anglesconsecutively, the so-called Multi-axis DOAS systems, thereby collectingvertical profile information, in particular for nitrogen dioxide and aerosol.Various in-situ samplers and lidar instruments simultaneously characterized the variability ofatmospheric trace gases and the physical properties of aerosol particles. Alarge data set of continuous measurements of these atmospheric constituentshas been collected under various meteorological conditions and air pollutionlevels. Together with the permanent measurement capability at the CESAR sitecharacterizing the meteorological state of the atmosphere, the CINDI campaignprovided a comprehensive observational data set of atmospheric constituentsin a highly polluted region of the world during summertime. First detailedcomparisons performed with the CINDI data show that slant column measurementsof NO₂, O₄ and HCHO with MAX-DOAS agree within 5 to 15%,vertical profiles of NO₂ derived from several independent instrumentsagree within 25% of one another, and MAX-DOAS aerosol optical thickness agrees within20–30% with AERONET data. For the in-situ NO₂ instrument using amolybdenum converter, a bias was found as large as 5 ppbv during day time,when compared to the other in-situ instruments using photolytic converters.

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