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Negative Ozone Anomalies at a High Mountain Site in Northern Italy during 2020: a Possible Role of COVID-19 Lockdowns?

P. Cristofanelli1, D. Putero1, F. Serva2, J. Arduini3, M. Sprenger4, M. Maione3,1, P. Bonasoni1, F. Calzolari1, M. Busetto1 and P. Trisolino1

1Institute of Atmospheric Sciences and Climate, National Research Council of Italy, Bologna, Italy; +39 051 6399597, E-mail: p.cristofanelli@isac.cnr.it
2Institute of Marine Sciences, National Research Council of Italy, Rome, Italy
3University of Urbino, Department of Basic Sciences and Foundations, Urbino, Italy
4ETH Zurich, Institute for Atmospheric and Climate Science, Zurich, Switzerland

Several studies investigated the possible impacts of the restriction measures related to the containment of the spread of the COrona VIrus Disease (COVID-19) to atmospheric ozone (O3) at global, regional, and local scales during 2020. O3 is a secondary pollutant with adverse effects on population health and ecosystems and with negative impacts on regional climate, acting as greenhouse gas. Most of these studies focused on spring 2020 (i.e., March–May) and on observations in the planetary boundary layer (PBL), mostly in the vicinity of urban agglomerates. Here, we analyzed the variability of O3 above the PBL of northern Italy in 2020 by using continuous observations carried out at a high mountain World Meteorological Organization/Global Atmosphere Watch global station in Italy (Mt. Cimone–CMN; 44°12' N, 10°42' E, 2165 m a.s.l.). Low O3 monthly anomalies were observed during spring (MAM) and summer (JJA), when periods of low O3 intertwined with periods with higher O3, within climatological ranges. Concurrent differences were not observed for nitrogen dioxide and non-methane volatile organic compounds, while the analysis of meteorological variables and diel O3 cycles did not suggest major changes in the vertical transport related to the thermal circulation system in the mountain area. The characterization of two transport regimes (i.e., air masses from the regional PBL or from the free troposphere) and the analysis of 5-day back-trajectories suggested an important contribution of transport from the continental PBL during the periods with the lowest O3 at CMN. Our study suggested for the first time that, during MAM and JJA 2020, the reduced anthropogenic emissions related to the COVID-19 restrictions lowered the amount of this short-lived climate forcer/pollutant at remote locations and above the PBL over northern Italy. This work suggests the importance of limiting anthropogenic precursor emissions for decreasing the O3 amount at remote locations and in atmospheric layers above the PBL

Figure 1

Figure 1. Monthly average O3 at CMN from 1996 to 2020 (the vertical shaded bars denote the 95% confidence levels of the monthly mean values).