MAX-DOAS measurements of formaldehyde in the Po-Valley

[摘要] During the first measurement campaign of the EU FORMAT project in summer 2002near Milan, northern Italy, ground-based scattered light differential opticalabsorption spectroscopy (DOAS) measurements wereperformed using a new multi-axis instrument. From the data set of this four weekmeasurement period, the detailed analysis results of three days, 12–14 August, are presented exemplary.Slant column densities for formaldehyde (HCHO) and the oxygen dimer (O₄)have been retrieved, employing fitting windows from 335 nm to 357 nm and 350 nm to360 nm respectively. In order to convert slant into vertical columns radiativetransfer calculations were perfomred using aerosol parameters derived from the actualO₄ measurements. By analysing the measurements from differentviewing directions (zenith, 4x off-axis) vertical profile information, and inparticular mixing ratios for the boundary layer have been derived forthe first time for HCHO with a multi-axis DOAS (MAX-DOAS) instrument.HCHO vertical columns are in the range of 5 to20·10¹⁵ molec/cm² with an relative error of about 15%.This corresponds to HCHO mixing ratios in the boundarylayer of0.7 ppb to 4.2 ppb, which is inexcellent agreement with simultaneous measurements from both a Hantzsch in-situand a long-path DOAS instrument operated at the same place.

[学科分类] 大气科学