Measurement of formaldehyde total content in troposphere using DOAS technique: improvements in version 1.3a of IAP retrieval algorithm

Formaldehyde (HCHO) is a significant constituent of the atmospheric chemistry involved in a lot of chemical reactions. It is directly emitted by anthropogenic and biogenic sources and, more significantly, by production during oxidation of methane and other VOCs. So HCHO is used as an indicator of local pollution by VOCs. HCHO has a sufficiently large absorption cross-section in the UV spectral region to be detected by the technique of the differential optical absorption spectroscopy (DOAS). We present here new version 1.3a of the algorithm for retrieval of the HCHO total content in the troposphere from DOAS observations of the scattered solar radiation developed in A.M. Obukhov Institute of Atmospheric Physics (IAP). The new version has reduced retrieval error but negligible bias with respect to the previous versions. DOAS measurements of scattered solar radiation are performed at Zvenigorod Scientific Station (ZSS, 55°41'49''N, 36°46'29''E) located in 38 km west from Moscow Ring Road by a MAX-DOAS instrument since 2008. We provide preliminary results of the HCHO total content measurements in the troposphere observed in 2010-2012 obtained by the revised retrieval algorithm.