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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/amt-2018-358
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-2018-358
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 13 Dec 2018

Research article | 13 Dec 2018

Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Measurement Techniques (AMT).

NO2 vertical profiles and column densities from MAX-DOAS measurements in Mexico City

Martina Michaela Friedrich1,2, Claudia Rivera1,3, Wolfgang Stremme1, Zuleica Ojeda1, Josué Arellano1,4, Alejandro Bezanilla1, José Agustín García-Reynoso1, and Michel Grutter1 Martina Michaela Friedrich et al.
  • 1Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México
  • 2Belgian Institute for Space Aeronomie (BIRA-IASB)
  • 3Facultad de Química, Universidad Nacional Autónoma de México
  • 4Instituto de Geofísica, Universidad Nacional Autónoma de México

Abstract. We present a new numerical code, Mexican Maxdoas Fit (MMF), developed to retrieve profiles of different trace gases from the network of MAX-DOAS instruments operated in Mexico City. MMF uses differential slant column densities (dSCDs) retrieved with the QDOAS (Danckaert et al., 2013) software. The retrieval is comprised of two steps, an aerosol retrieval and the trace gas retrieval that uses the retrieved aerosol profile in the forward model for the trace gas. For forward model simulations, VLIDORT is used (e.g. Spurr et al., 2001; Spurr, 2006, 2013). Both steps use constrained least square fitting, but the aerosol retrieval uses Tikhonov regularization and the trace gas retrieval optimal estimation. Aerosol optical depth and scattering properties from the AERONET database, averaged ceilometer data, WRF-Chem model data as well as temperature and pressure sounding data are used for different steps in the retrieval chain.

The MMF code was applied to retrieve NO2 profiles with two degrees of freedom (DOFs = 2) from spectra of the MAX-DOAS instrument located at the UNAM campus. We describe the full error analysis of the retrievals and include a sensitivity exercise to quantify the contribution of the uncertainties in the aerosol extinction profiles to the total error. A dataset comprised of measurements from January 2015 to July 2016 was processed and the results compared to independent surface measurements. We concentrate on the analysis of 4 single days and additionally present diurnal and annual variabilities from averaging the 1.5 years of data. Even though the total error is considerably large (depending on the exact counting 14–20 %) this work still provides new and relevant information about NO2 in the boundary layer of Mexico City.

Martina Michaela Friedrich et al.
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Martina Michaela Friedrich et al.
Martina Michaela Friedrich et al.
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Short summary
We present a new numerical code to retrieve NO2 vertical column densities (vcd) and concentrations from previously retrieved slanted columns from spectroscopic measurements in visible and ultraviolet spectral range in different vertical viewing directions. We use this code on roughly 1.5 years of data from a measurement station located in the south of Mexico city and compare daily and monthly averages to averages of in-situ measurements. We show daily NO2 vcd time series for a few example days.
We present a new numerical code to retrieve NO2 vertical column densities (vcd) and...
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