Tropospheric profile of NO_2 over the Po Valley measured with scanDOAS spectrometer

摘要

A simple method to determine the vertical distribution of a pollutant gas, namely NO_2, by means of the spectralmeasurements obtained with a scan-DOAS spectrometer, is presented. The developed technique can be summarized asfollows: i) a series of quasi simultaneous measurements in the zenith and in others directions allowing for thedetermination of the Slant Column Density of NO_2for different elevation angles; ii) an active DOAS measurement forthe determination of the NO_2concentration at the ground; iii) a set of Radiative Transfer Model (RTM) calculation of thescattering distance from the spectrometer, for a set of visibility values; iv) a recursive procedure of profile calculationstarting from the first measurement and subtracting the value of NO_2Slant Column Density (SCD) retrieved from themeasurement taken at the previous angle of sight. Measurements are carried out during summer 2007 in S. PietroCapofiume (Bologna-Italy). The vertical distribution for NO_2obtained with the above described method has beencompared with the profiles calculated with the GAMES (Gas Aerosol Modelling Evaluation System) model. The resultsof this comparison show some differences between the modelled and the measured profiles, probably due to boxapproximations in RTM calculation for measured profiles and to the large pixel grid (about 10x10 km2), for modelevaluation.