Science Source
Thang M. Luong, Christopher L. Castro, Hsin-I Chang, Timothy Lahmers, David K. Adams, and Carlos A. Ochoa-Moya
Journal of Applied Meteorology and Climatology
Published date July 3, 2017

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

What's going on in the changes to the extremes is very different from what goes on in the changes to the mean. Big storms, heavy flooding -- we found out those types of extreme precipitation events are becoming more intense and are becoming more intense downwind of the mountain ranges.

Christopher L. Castro, co-author and University of Arizona associate professor of hydrology and atmospheric sciences

  • Evaluates long-term changes in North American monsoon (NAM) precipitation intensity in the Southwest U.S. through the use of convective-permitting model simulations of objectively identified severe weather events during “historical past” (1950-1970) and “present day” (1991-2010) periods
  • Defines severe weather events as days when the highest atmospheric instability and moisture occur within a long-term regional climate simulation
  • Performs severe weather event day simulations and compares them to available observed precipitation data to evaluate the model performance and verify model-simulated trends
  • Finds that a statistically significant long-term increase in atmospheric moisture and instability is associated with an increase in extreme monsoon precipitation in observations and severe weather event simulations
  • Finds that precipitation is becoming more intense within the context of the diurnal cycle of convection
  • Concludes that a more favorable thermodynamic environment in the Southwest U.S. is facilitating stronger organized monsoon convection during at least the last 20 years

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