What is drought?

Drought. What comes to mind when you hear “drought”? Is it parched soils, massive dust storms, water restrictions, decadent tree stands, shriveled plant life, failed crops, deepening water wells, raging wildfires, empty lakes, dry riverbeds, closed ski resorts, endless sunny skies, or perhaps old memories of wetter times when you were younger? There is a lot to think about when it comes to drought impacts! Individual perspectives likely vary quite a bit based on your lifetime experience with any “drought conditions” and where you were geographically during a drought event.

I purposely put “drought conditions” in quotes because this gets at the heart of what I am hoping to share with everyone introducing this explainer topic. Yes, in weather the term drought essentially refers to a deficit of precipitation of some kind, however, it is important to be aware that the use of drought should always be rooted in relative context! The underlying precipitation deviation (observed or forecasted) must be in reference to a specific location’s climatology, that inherently changes with time (climate baselines are typically adjusted in moving 30-year intervals with observed weather data; these are communicated as new “climate normals”).

We already know that the world is represented by a patchwork of contrasting climates. For some, the long-term precipitation record indicates your average annual totals are measured in feet (e.g., windward side of the Cascades, Amazon Basin, or India’s monsoon), while others may struggle to get measurable precipitation in any given year (Chili’s Atacama Desert and the world’s polar deserts like Antarctica). Expected extreme climate contrasts occur within much smaller regions, too! For example, the state of Arizona is often described as an arid place. You are probably thinking of a saguaro cactus right now! But, the annual precipitation average range across Arizona is ~3 inches in sandy Yuma southwest of Phoenix to ~40 inches in the forested White Mountains east of Phoenix.

The main point here is that contrasting regional climates with a myriad of embedded microclimates make holistic drought evaluation and projection tasks over time complex!

Photo Credit: Jonny William Malloy