Significant trend in vertical wind velocity variability over the last 40 years

Abstract

Vertical air motion influences cloud formation, mixing and transport processes. Due to limitations in spatial resolution, global atmospheric models cannot resolve the sub-kilometer scale component of this motion. Instead it is represented using the standard deviation in vertical wind velocity within a grid cell, σW. Using a novel deep learning model constrained by observational data, we reveal significant trends in σW over the period 1980-2023. These trends, reaching up to 1% yr-1 in low and mid-level oceanic regions, indicate a more turbulent atmosphere with enhanced cloud formation over the last few decades. We attribute these trends to global shifts in water vapor, temperature and convection, suggesting a connection between enhanced warming, turbulence and cloud microphysics. Over the industrial era we estimate that increased cloud formation from enhanced σW yields a radiative forcing of about -0.1 ± 0.21 W m-2, slightly mitigating greenhouse warming.