Research shows that Arizona’s monsoon storms are diminishing in number but increasing in severity.

Most severe weather in Arizona and the rest of the Southwestern United States occurs during the region’s summer monsoon season, but the nature of those monsoon storms is changing. New research led by University of Arizona scientists indicates that global warming has resulted in fewer monsoon storms but with heavier rainfall and stronger winds.

Christopher L. Castro, an associate professor at the UA Department of Hydrology and Atmospheric Sciences, will describe the new findings in a 3:30 p.m. Wednesday (Nov. 1) talk in the Arizona Senior Academy’s Great Room.

The researchers compared precipitation records from 1950-1970 to those from 1991-2010 for Arizona. They also used those records to verify that their climate model generated realistic results. “This is one of the first studies to look at long-term changes in monsoon precipitation,” Castro said.

The region of Arizona with more extreme storms includes Bullhead City, Kingman, the Phoenix metropolitan area, the Colorado River valley and Arizona’s low deserts, including the towns of Casa Grande, Gila Bend, Ajo, Lukeville, Yuma, and the Tohono O’odham Reservation. Tucson is just outside of the zone with more extreme storms.

Having less frequent but more intense storms is consistent with what is expected throughout the world due to climate change, according to Castro. “Our work shows that it certainly holds true for the monsoon in Arizona,” he says.

Christopher L. Castro

The findings were published July 3 in a paper, “The More Extreme Nature of North American Monsoon Precipitation in the Southwestern U.S. as Revealed by a Historical Climatology of Simulated Severe Weather Events,” in the early online edition of the Journal of Applied Meteorology and Climatology.

First author Thang M. Luong conducted the research as part of his doctoral work at the UA. He is now a postdoctoral researcher at King Abdullah University of Science and Technology in Saudi Arabia. Castro was the co-author.

Written by Charles Prewitt, Academy Village Volunteer


As Climate Changes, Arizona Monsoons Intensify:Nov.2017