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Titel Ground-based MAXDOAS retrievals of formaldehyde during the CINDI campaign
VerfasserIn Katrijn Clemer, Isabelle De Smedt, Folkard Wittrock, Caroline Fayt, Francois Hendrick, Christian Hermans, Gaia Pinardi, Rob Spurr, Michel Van Roozendael
Konferenz EGU General Assembly 2010
Medientyp Artikel
Sprache Englisch
Digitales Dokument PDF
Erschienen In: GRA - Volume 12 (2010)
Datensatznummer 250037099
 
Zusammenfassung
Over the last years, ground-based multi-axis differential absorption spectroscopy (MAXDOAS) has been proved to be a very promising tool for the automated retrieval of tropospheric pollutants. The MAXDOAS instruments are designed to allow for the quasi simultaneous observation of the scattered sun light in a range of different line-of-sight (LOS) directions from the horizon to the zenith, resulting in an increased sensitivity towards atmospheric absorbers present close to the surface. One of the main obstacles for the tropospheric trace gas vertical profile retrievals is the sensitivity of the length of the light path –and thus the observed slant column densities (SCD) of an atmospheric absorber– to the presence of aerosol in the atmosphere. To overcome this difficulty we developed an algorithm to retrieve, in a first step, the aerosol extinction vertical profiles from measurements of the O4 absorptions for different LOS. In a second step, the obtained aerosol profiles are used as input for the retrieval of tropospheric trace gas (e.g., CH2O, NO2) vertical profiles. The retrieval of minor trace gases such as CH2O remains quite challenging, due the overall faintness of the signal. The CINDI campaign held in June-July 2009 in Cabauw offered the opportunity to explore the possibilities of the MAXDOAS technique for the retrieval of CH2O slant columns and, in a second step, vertical profile information. Here we will present the first results of the inter-comparison of slant columns and vertical CH2O profiles. We will discuss the strengths, limitation, and information content of the retrievals. In addition we will show the first results of the inter-comparison of the total tropospheric CH2O columns retrieved from ground-based MAXDOAS measurements and from satellite UV-VIS nadir sounders. We will explore the possibility of using the CH2O MAXDOAS measurements for satellite validation.