Comparisons between satellite and ground-based measurements of the atmosphere are inevitably affected by natural variability due to mismatches in spatial and temporal co-location. These additional terms in the comparison error budget are quantified here for total ozone column comparisons using an Observing System Simulation Experiment. Even when using tight co-location criteria, atmospheric variability is found to impact the comparisons significantly. ; Part of this work was funded by the Belgian Science Policy Office (BELSPO) and ESA via the ProDEx projects A3C and ACROSAT, and by the EU H2020 project GAIA-CLIM (Ares(2014)3708963/Project 640276). The authors acknowledge the pioneering research carried out in 2008–2012 by C. De Clercq and S. Vandenbussche and funded by the EU FP6 project GEOmon (FP6-2005-Global-4-036677) and ProDEx project SECPEA.
Comparisons between satellite and ground-based measurements of the atmosphere are inevitably affected by natural variability due to mismatches in spatial and temporal co-location. These additional terms in the comparison error budget are quantified here for total ozone column comparisons using an Observing System Simulation Experiment. Even when using tight co-location criteria, atmospheric variability is found to impact the comparisons significantly. ; Part of this work was funded by the Belgian Science Policy O ce (BELSPO) and ESA via the ProDEx projects A3C and ACROSAT, and by the EU H2020 project GAIA-CLIM (Ares(2014)3708963/Project 640276). Finally, the 20 authors acknowledge the pioneering research carried out in 2008–2012 by C. De Clercq and S. Vandenbussche and funded by the EU FP6 project GEOmon (FP6-2005-Global-4-036677) and ProDEx project SECPEA.
Recent studies show that air pollution also affects Africa. Air quality is worsening in large cities with growing populations. Satellite observations over some Central African cities seem to confirm this pollution for species such as NO2, HCHO and aerosols. The sources of pollution are generally different from those found in Europe for example. In Central Africa, particularly in the Congo Basin, the main sources of NO2 and HCHO emissions are forest fires and the use of embers in cooking. Kinshasa, the capital of the Democratic Republic of Congo, a large megalopolis of about 11 million inhabitants, like several other large cities in Africa, lack ground-based atmospheric measurement systems. To improve this situation, the researchers of the University of Kinshasa (Unikin) in collaboration with the UV-Vis group of the Belgian Institute for Space Aeronomy (IASB) have set up a first installation of a simple atmospheric observation equipment. This equipment was installed on the roof of the Faculty of Sciences of Unikin ( -4.42°S, 15.31°E) in May 2017 and has operated until November 2019. The instrument is based on a compact AVANTES spectrometer covering the spectral range 290 - 450 nm with 0.7 nm resolution. The spectrometer is a Czerny-Turner type with an entry slit of 50 µm wide, and an array of 1200 l/mm. A 10 m long and 600 µm thick diameter optical fiber is connected to the spectrometer to receive the incident light beam from the sky. Measurements were mainly made by looking in a fixed direction. In November 2019, a Multi-Axis DOAS instrument (MAX-DOAS) has been installed to replace the first instrument. The measurements clearly show the signature of polluting species such as NO2 and HCHO in Kinshasa's atmosphere. In this study, we therefore show all the different steps of the algorithm we used to obtain the vertical columns from the observations of the instrument installed in Kinshasa. We present a first comparison of these ground-based observations of NO2 in Kinshasa with those from the OMI and TROPOMI satellites for clear days between May and November 2017.
