Comparison between economic growth and satellite-based measurements of NO2 pollution over northern Italy

Abstract

The aim of this study is to investigate to what extent spatiotemporal fluctuations in the tropospheric NO2 column concentration can map variations in economic output. To do so satellite based tropospheric NO2 column measurements obtained from the ERS-2, ENVISAT, MetOp-A, and MetOp-B satellite missions covering the period from 1996 to 2017 over the Po valley in northern Italy is analyzed. A harmonic analysis is carried out in order to exclude influences such as the annual or semi-annual cycle. Afterwards the residues of the tropospheric NO2 time series are further investigated by means of a wavelet analysis method. The result is a spectrogram which implies the NO2 variability for the study area between 1996 and 2017. Therefore, the gross domestic product (GDP) is used as an indicator for economic performance and thus, as an approximation, of anthropogenically induced NO2 pollution. Clear conspicuous signatures occurred almost simultaneously both within the temporal development of the GDP growth rate and the spectral characteristic of the NO2 variability during the studied period. The comparison of the temporal course of the GDP shows that the period of systematically reduced spectral intensity in NO2 coincides strikingly well with the period of the global financial crisis in 2008 which was then followed by a second crisis in 2014. The economic growth decreased by 7.9% between 2007 and 2009 and by 5.2% between 2011 and 2014 in comparison to the same quarter of the previous year. It is found that during the crises (2007–2013) the variability of NO2 is reduced by about 80%.