Historical Occurrence of and Shift in Snow Drought Drivers in Global
Snow droughts are a new way to understand changes in snowpack and
subsequent runoff. Globally, we do not have a good understanding of the
drivers of snow droughts or how those drivers have changed historically.
Here, we identify what has been the dominant driver of global snow
droughts in mountain ranges, how it shifted historically, and what
similarities exist in similar snow types. We explore this in all global
mountain ranges, ones that are highly dependent on winter precipitation
for summer water, and two regional case studies in the Cascade Range and
the Himalayan Mountains. We found that in both the northern and southern
hemispheres, dry snow droughts (driven by precipitation) are the most
common. In both the northern and southern hemisphere, more mountain
ranges shifted to having temperature be the main driver of snow droughts
in the historical record. In the northern hemisphere, tundra, boreal,
prairie, and ice snow type areas had the most area with dry snow
droughts. In the southern hemisphere, all snow types except for tundra
had the most area with temperature as the main driver of snow droughts.
With this global, multivariate methodology, we were able to identify
common drivers and patterns of historical snow droughts that exist
across similar geographical areas (i.e., northern and southern
hemisphere and mountain ranges) and snow type areas. More research is
needed to better understand snow droughts, their drivers, and the risk
they pose regionally to food and water security.