Aerosols Reduction during the COVID-19 Pandemic Substantially Increased Diurnal Temperature Range in China

Abstract:

Aerosols scatter sunlight radiation and increase low-level cloudiness, which reflect short-wave radiation during daytime and discharge long-wave radiation back to the surface at night. Hypothetically, these effects combine to reduce diurnal temperature range (DTR). . Prolonged period of quarantine in China due to the COVID -19 pandemic, which significantly reduced emission of aerosols, offers a unique opportunity to examine this theory. We collected maximum and minimum temperature from January to June for every weather stations in China that have complete records during 2000-2020 from the Global Summary of the Day dataset. Then we compared national mean DTRs of 2000-2019 with that of 2020. For every month from January to June, monthly mean DTRs showed remarkable increase in 2020 compared to the average of 2000-2019, showing a large increase in January and gradually further increases, peaks at April, and then decreases in May and June. Except for January, when quarantine had just begun, other five months all show record-high DTRs in 20th century, surpassing the climatological mean DTR with more than three standard deviations. This significant change is partly caused by the substantial reduction of aerosols, which partly validates the theory that aerosols reduce DTRs. Further studies after this finding may have crucial implications on aerosol’s climatic effect, which remains the largest uncertainty in appraising global climate change.