The diurnal cycle and temporal trends of surface winds

Winds play an essential role in the climate system. In this study, we analyze the global pattern of the diurnal cycle of surface (10 m) winds from the ERA5 reanalysis data. We find that over the land and especially over sand dune regions, the maximal wind speed and wind drift potential (DP) occur during the hours around midday. However, over the ocean, the wind also peaks at night. Using the sensible heat flux, we show that the weaker winds over land at night are due to a nocturnal cooling that decouples upper atmospheric levels and their associated stronger winds from the surface-nocturnal cooling is much smaller over the ocean. We also analyze wind data from more than 400 meteorological stations in the USA and find a similar diurnal trend as in the reanalysis data. The timing (during the day) of the maximum wind speed has not varied much over the past 70 years. Yet, the wind speed, wind power, and wind drift potential exhibit significant increases with time over the ocean and, to a much lesser degree, over the land and sand dune regions. We compare the USA and Europe DP and wind speed of the ERA5 to that of meteorological stations and find that the ERA5 significantly underestimates real winds; however, the temporal patterns of the two are similar.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, the researchers analyze the global pattern of surface winds using ERA5 reanalysis data. They find that the maximum wind speed occurs during midday over land and especially over sand dune regions, while over the ocean, the wind peaks at night. The weakening of winds over land at night is attributed to nocturnal cooling, which decouples upper atmospheric levels from the surface. Comparisons with meteorological stations show that ERA5 underestimates real winds but exhibits similar temporal patterns.