The University of Arizona

Background | CLIMAS


Dry and hot! For many people, these two words sum up the climate of the Southwestern United States, but the climate of the Southwest is much more complex. While low deserts of the Southwest experience searing heat and desiccating winds in the early summer, its forested mountains and plateaus endure biting cold and drifting snow in the heart of winter. The Southwest may be drenched by torrential monsoon thunderstorms in July and August, yet it can warm gently under fair skies from fall to spring.

Rainfall in the Southwest is especially variable, with regional floods or droughts severe enough to affect both indigenous and modern civilizations on time scales ranging from single growing seasons to multiple years, even decades.

Interannual and decadal precipitation variability plays major societal and ecological roles in western North America, for example in areas such as ranching, farming, tourism, urban water management, and regional power production within the Southwest. Moreover, not all parts of the Southwest are affected to the same degree, or even at the same time, by weather events and long-term climate patterns. During some summers rainfall might be abundant in southwestern New Mexico, but scanty in northwestern Arizona. Long-term droughts, such as the one that gripped the region during the 1950s, might be far more severe in one part of the 2-state region—as evidenced by the profound effect of the 1950s drought on the forests of eastern New Mexico.

Thus, data were needed by researchers to investigate climate and weather at a variety of time scales and over spatial scales ranging from tens to thousands of square kilometers. Individuals and agencies that use climate information to make decisions also need data that allow them to look at past climate variations that affect businesses and land management operations ranging from a few square kilometers to all of Arizona and New Mexico.

Currently, free climate data for Arizona and New Mexico consist of records for individual meteorological stations, regional records for large climate divisions (some of which are as large as several counties) and coarse-scale gridded records developed from interpolation of station records, without regard to elevation—which may vary dramatically over very short distances.