Global climatology of synoptically‐forced downslope winds

Abstract

Downslope winds are mesoscale mountain meteorological phenomena that contribute to localized temperature extremes and contribute to numerous societal and environmental impacts. Whereas previous studies have examined local downslope winds, no known efforts have attempted to identify and characterize meso‐ to synoptic‐scale downslope winds globally using a common approach. We use a conceptual model for downslope winds that employs cross‐barrier wind speed, near‐mountain top static stability, and downward vertical velocity using thresholds guided by a chronology of local downslope winds and meta‐analysis of downslope wind case studies. This approach was applied to ERA‐5 reanalysis during 1979–2018 to develop a global atlas of downslope winds. Downslope winds adhered to distinct geographic and seasonal patterns, with peak occurrence in north–south oriented midlatitude mountains in the winter hemisphere associated with strong cross‐mountain winds and stability. However, we identify numerous locations from the tropics to the high‐latitudes where downslope winds occur at least 60 days a year as a byproduct of the general circulation and local‐scale circulation interacting with topography. The four‐decade‐long data set is also used to examine statistical relationships between the occurrence of downslope winds and El Niño‐Southern Oscillation as well as long‐term trends in downslope wind occurrence.

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