Tropospheric profile of NO 2 over the Po Valley measured with scan DOAS spectrometer

Abstract

A simple method to determine the vertical distribution of a pollutant gas, namely NO 2 , by means of the spectral measurements obtained with a scan-DOAS spectrometer, is presented. The developed technique can be summarized as follows: i) a series of quasi simultaneous measurements in the zenith and in others directions allowing for the determination of the Slant Column Density of NO 2 for different elevation angles; ii) an active DOAS measurement for the determination of the NO 2 concentration at the ground; iii) a set of Radiative Transfer Model (RTM) calculation of the scattering distance from the spectrometer, for a set of visibility values; iv) a recursive procedure of profile calculation starting from the first measurement and subtracting the value of NO 2 Slant Column Density (SCD) retrieved from the measurement taken at the previous angle of sight. Measurements are carried out during summer 2007 in S. Pietro Capofiume (Bologna-Italy). The vertical distribution for NO 2 obtained with the above described method has been compared with the profiles calculated with the GAMES (Gas Aerosol Modelling Evaluation System) model. The results of this comparison show some differences between the modelled and the measured profiles, probably due to box approximations in RTM calculation for measured profiles and to the large pixel grid (about 10x10 km2), for model evaluation.

TROPOMI NO2 Tropospheric Column Data: Regridding to 1 km Grid-Resolution and Assessment of their Consistency with In Situ Surface Observations

“…Moreover, we know (e.g., [8][9][10][11][12][13][14][15][16]) that the daily evolution of the Planetary Boundary Layer (PBL) height can affect the vertical mixing ration profile of NO 2 and its diurnal cycle. The PBL height can at most reach an altitude of 1-3 km (e.g., [11,12]); usually, it rapidly increases in the morning because of sunlight and tends to stay at or below ≈1000 m at night.…”

Towards a New MAX-DOAS Measurement Site in the Po Valley: NO2 Total VCDs

“…Despite being the most polluted Italian area, no continuous DOAS/MAX-DOAS measurements compliant with FRM4DOAS standards are performed in the Po Valley. DOAS measurements not compliant with the standards were performed in the framework of a few campaigns (e.g., [18,19]) and from two DOAS/MAX-DOAS instruments, developed at CNR-ISAC and located in the Emilia Romagna Region: one at Mount Cimone and the other in Bologna. The instrument located in Bologna is the Tropospheric Gas Analyser Spectrometer (TROPOGAS) and has measured diffuse solar spectra on the roof of the CNR-ISAC building since 2018.…”