Urban eddy covariance measurements of air pollutant fluxes during the SARS-CoV2 lockdown in Europe

Following the initial SARS-CoV2 outbreak in China, the pandemic struck Europe shortly after in 2020. As a consequence most European nations implemented strict lockdown policies to suppress exponential growth of infection rates starting in March 2020. For example the mandatory quarantine in the state of Tyrol resulted in a 95% mobility reduction of puplic life early on. Such a drastic mobility reduction during the suppression period allows performing a granular assessment of processes impacting emissions and the distribution of urban air pollutant and climate gases in context of PBL dynamics and chemistry. We present a new integrated observational analysis based on long-term in-situ multispecies eddy flux measurements, allowing to quantify near real time changes of urban surface emissions for key air quality and climate tracers during the lockdown. We find a non-linear relationship between the reduction of carbon dioxide and air pollution gases, which declined much more significantly. The observed changes are put into context of urban emission sources and climate driven variability, which is key for accurately assessing quantitative emission changes in response to the SARS-CoV2 lockdown.