Travel restrictions to reduce the spread of the COVID-19 pandemic have led to a massive reduction in global air traffic. For April 2020, the European air traffic control authority, EUROCONTROL has reported a 90% decrease in compared to March 2020. Researchers at the Institute for Physics of the Atmosphere of the German Aerospace Center have now analysed the impact of reduced air traffic on the formation of contrails over Europe using data measured on 16 April 2020 by the ‘Spinning Enhanced Visible and Infrared Imager' (SEVIRI) sensor on a Meteosat Second Generation (MSG) weather satellite. On that day, the atmosphere over Europe was cold and humid enough for persistent contrail formation. The analyses show a 90% decrease in the number of contrails compared to normal operations.
Cover and optical thickness of contrails and natural cirrus for air traffic on 16 April 2020 compared to 16 April 2019 for the same meteorology.
(Graphics: DLR, CC-BY3.0)
The researchers compared the satellite measurements with a model developed at the DLR Institute of Atmospheric Physics, which calculates the coverage from natural clouds and cirrus clouds produced by aircraft contrails, based on current air traffic movements and weather data. The findings based on the satellite imagery are largely consistent with the model data, and the model reflects the regional structures and gives a good representation of the measured values of the optical thicknesses of clouds. In addition, the scientists used the model to calculate a scenario with an air traffic volume 10 times higher, based on air traffic data on the same day in 2019, with the meteorological conditions kept the same in order to pinpoint the effect of different traffic levels. The calculations clearly show far greater coverage from contrail cirrus clouds, with an increased optical thickness of the ice clouds. Weighted with the optical thicknesses, the degree of coverage of the partially overlapping contrails would be four times greater.
Over the coming months, scientists will determine more precisely how much the reduced contrail coverage and the related cirrus clouds will affect Earth's radiation budget.