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arXiv · 2008.13497

Record high solar irradiance in Western Europe during first COVID-19 lockdown largely due to unusual weather

Chiel C. van Heerwaarden·Wouter B. Mol·Menno A. Veerman·Imme B. Benedict·Bert G. Heusinkveld·Wouter H. Knap·Stelios Kazadzis·Natalia Kouremeti·Stephanie Fiedler
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Abstract

Spring 2020 broke sunshine duration records across western Europe. The Netherlands recorded the highest surface irradiance since 1928, exceeding the previous extreme of 2011 by 13 %, and the diffuse fraction of the irradiance measured a record low percentage (38 %). The coinciding irradiance extreme and a reduction in anthropogenic pollution due to COVID-19 measures triggered the hypothesis that cleaner-than-usual air contributed to the record. Based on analyses of ground-based and satellite observations and experiments with a radiative transfer model, we estimate a 1.3 % (2.3 W m$^{-2}$) increase in surface irradiance with respect to the 2010-2019 mean due to a low median aerosol optical depth, and a 17.6 % (30.7 W m$^{-2}$) increase due to several exceptionally dry days and a very low cloud fraction overall. Our analyses show that the reduced aerosols and contrails due to the COVID-19 measures are far less important in the irradiance record than the dry and particularly cloud-free weather.

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Chiel C. van Heerwaarden, Wouter B. Mol, Menno A. Veerman, Imme B. Benedict, Bert G. Heusinkveld, Wouter H. Knap, Stelios Kazadzis, Natalia Kouremeti, Stephanie Fiedler. 2020-08-31. Record high solar irradiance in Western Europe during first COVID-19 lockdown largely due to unusual weather. https://doi.org/10.1038/s43247-021-00110-0

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