Abstract
Abstract. We present a new numerical code, Mexican MAX-DOAS 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 a 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, and temperature and pressure sounding data are used for different steps in the retrieval chain. The MMF code was applied to retrieve NO2 profiles with 2 degrees of freedom (DOF = 2) from spectra of the MAX-DOAS instrument located at the Universidad Nacional Autónoma de México (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 data set 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 four single days and additionally present diurnal and annual variabilities from averaging the 1.5 years of data. The total error, depending on the exact counting, is 14 %–20 % and this work provides new and relevant information about NO2 in the boundary layer of Mexico City.
Highlights
Air pollution is a serious environmental problem due to its negative impacts on human health and ecosystems
We present results of the NO2 variability measured at one of the stations comprising the MAX-DOAS network operated in Mexico City, and compare them with in situ measurements performed at the surface
In this contribution we describe the methodology used to analyze the data produced by the network of MAX-DOAS instruments (Arellano et al, 2016) operating in the Mexico City metropolitan area
Summary
Air pollution is a serious environmental problem due to its negative impacts on human health and ecosystems. The multi-axis differential optical absorption spectroscopy (MAX-DOAS) technique (e.g., Hönninger et al, 2004; Platt and Stutz, 2008) has rapidly developed in recent years and has proven extremely valuable in tropospheric chemistry and air pollution studies since it provides vertical distribution of trace gases with high temporal resolution This remote-sensing technique is based on the spectroscopically resolved measurement of scattered sunlight at different elevation angles, allowing for the retrieval of total column amounts of aerosols and trace gases with profiling capability. In 2014, a MAX-DOAS network, initially consisting of four instruments, was established in the Mexico City metropolitan area (MCMA) and has been operating since (Arellano et al, 2016) In this contribution, we describe the MMF (Mexican MAX-DOAS Fit) code that has been implemented to retrieve vertical distribution of aerosols and trace gases with emphasis on the errors and diagnostics of the results.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
