Ground-based remote sensing of O<sub>3</sub> by high and medium resolution FTIR spectrometers over the Mexico City basin

Abstract

Abstract. We present atmospheric ozone (O3) profiles measured over central Mexico between November 2012 and February 2014 by two different ground-based FTIR (Fourier transform infrared) solar absorption experiments. The first instrument offers very high resolution spectra and contributes to NDACC (Network for the Detection of Atmospheric Composition Change). It is located at a mountain observatory about 1700 m above the Mexico City basin. The second instrument has a medium spectral resolution and is located inside of Mexico City at a horizontal distance of about 60 km to the mountain observatory. It is documented that the retrieval with the high and medium resolution experiments give O3 variations for three and four independent atmospheric altitude ranges, respectively, whereby the theoretically estimated errors of these profile data are mostly within 10 %. The good quality of the data is empirically demonstrated: above the tropopause by intercomparing the two FTIR O3 data and for the boundary layer by comparing the Mexico City FTIR O3 data with in-situ O3 surface data. Furthermore, we develop a combined boundary layer O3 remote sensing product that uses the retrieval results of both FTIR experiments and demonstrate theoretically and empirically the improvements achieved by such combination.