Abstract
‘Lockdown’ periods in response to COVID-19 have provided a unique opportunity to study the impacts of economic activity on environmental pollution (e.g., NO2, aerosols, noise, light). The effects on NO2 and aerosols have been very noticeable and readily demonstrated, but that on light pollution has proven challenging to determine. The main reason for this difficulty is that the primary source of nighttime satellite imagery of the earth is the SNPP-VIIRS/DNB instrument, which acquires data late at night after most human nocturnal activity has already occurred and much associated lighting has been turned off. Here, to analyze the effect of lockdown on urban light emissions, we use ground and satellite data for Granada, Spain, during the COVID-19 induced confinement of the city’s population from 14 March until 31 May 2020. We find a clear decrease in light pollution due both to a decrease in light emissions from the city and to a decrease in anthropogenic aerosol content in the atmosphere which resulted in less light being scattered. A clear correlation between the abundance of PM10 particles and sky brightness is observed, such that the more polluted the atmosphere the brighter the urban night sky. An empirical expression is determined that relates PM10 particle abundance and sky brightness at three different wavelength bands.
Highlights
The COVID-19 pandemic has caused dramatic changes in human habits and activities across much of the world
We focused on the concentration of PM10 particles and nitrogen dioxide, two pollutants directly related to vehicle emissions and to urban activity
We found a clear decrease in light pollution within the city of Granada during the lockdown
Summary
The COVID-19 pandemic has caused dramatic changes in human habits and activities across much of the world. Periods, when the local, regional or national activities and movements of people have been markedly curtailed to reduce rates and levels of viral transmission The details of these restrictions, and the extent and vigour with which they have been enforced, have varied greatly between different countries. These unusual situations have acted as valuable ‘natural experiments’, allowing novel analyses to be conducted of the relationships between levels of human activity and levels of change to the environment, by comparing important potential impacts prior to and during lockdown periods.
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