Decreased Aviation Leads to Increased Ice Crystal Number and a Positive Radiative Effect in Cirrus Clouds

Jialei Zhu, Joyce E. Penner, Anne Garnier, Olivier Boucher, Meng Gao, Lei Song, Junjun Deng, Cong‐qiang Liu, Pingqing Fu

Research output: Contribution to journalJournal articlepeer-review

Abstract

Travel restrictions in the wake of the COVID-19 pandemic resulted in an unprecedented decrease of 73% in global flight mileage in April–May 2020 compared to 2019. Here we examine the CALIPSO satellite observations and find a significant increase in ice crystal number concentrations (Ni) in cirrus clouds in the mid-latitudes of the Northern Hemisphere, which we attribute to an increase in homogeneous freezing when soot from aircraft emissions is reduced. A relatively small positive global average radiative effect of 21 mW m−2 is estimated if a decrease in aircraft traffic continues, with an average of up to 64 mW m−2 over the area where aviation is most active. We infer from this analysis that the worldwide adoption of biofuel blending in aircraft fuels that lead to smaller soot emissions could lead to a significant change in the microphysical properties of cirrus clouds but a rather small positive radiative effect.
Original languageEnglish
Article numbere2021AV000546
JournalAGU Advances
Volume3
Issue number2
DOIs
Publication statusPublished - Apr 2022

User-Defined Keywords

  • cirrus clouds
  • aircraft soot
  • COVID-19
  • radiative effects

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