The contribution of large-scale atmospheric circulation to variations of observed near-surface wind speed across Sweden since 1926

This study investigates the centennial-scale (i.e., since 1926) variability of observed near-surface wind speed across Sweden. Results show that wind speed underwent various phases of change during 1926-2019, i.e., (a) a clear slowdown during 1926-1960; (b) a stabilization from 1960 to 1990; (c) another clear slowdown during 1990-2003; (d) a slight recovery/stabilization period for 2003-2014, which may continue with a possible new slowdown. Furthermore, the performance of three reanalysis products in representing past wind variations is evaluated. The observed low-frequency variability is properly simulated by the selected reanalyses and is linked to the variations of different large-scale atmospheric circulation patterns (e.g., the North Atlantic Oscillation). However, the evident periods of decreasing trend during 1926-1960 and 1990-2003, which drive most of the stilling in the last century, are missing in the reanalyses and cannot be realistically modeled through multiple linear regression by only using indexes of atmospheric circulation. Therefore, this study reveals that changes in large-scale atmospheric circulation mainly drive the low-frequency variability of observed near-surface wind speed, while other factors (e.g., changes in surface roughness) are crucial for explaining the periods of strong terrestrial stilling across Sweden.

Automated summary

This study examines the long-term variability of wind speed in Sweden since 1926. The results show distinct phases of change, including slowdowns and stabilization periods. Three reanalysis products are evaluated for their ability to simulate past wind variations, and it is found that large-scale atmospheric circulation patterns play a significant role in driving the low-frequency variability. However, changes in factors such as surface roughness are crucial for explaining periods of strong terrestrial stilling.