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

The More Extreme Nature of North American Monsoon Precipitation in the Southwestern U.S. as... AbstractLong-term changes in North American monsoon (NAM) precipitation intensity in the Southwest U.S. are evaluated 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. Severe weather events are days when the highest atmospheric instability and moisture occur within a long-term regional climate simulation. Severe weather event day simulations are performed with convective-permitting (2.5 km) grid spacing, and these simulations are compared to available observed precipitation data to evaluate the model performance and verify any statistically significant model simulated trends in precipitation. Statistical evaluation of precipitation extremes is performed using peaks-over-threshold approach with a generalized Pareto distribution. 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, corresponding to similar behavior in station-based precipitation observations in the Southwest. Precipitation is becoming more intense within the context of the diurnal cycle of convection. The largest modeled increases in extreme event precipitation occur in central and southwest Arizona, where mesoscale convective systems account for a majority of monsoon precipitation and where relatively large modeled increases in precipitable water occur. Therefore, we conclude that a more favorable thermodynamic environment in the Southwest U.S. is facilitating stronger organized monsoon convection during at least the last twenty years. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Meteorology and Climatology American Meteorological Society

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

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Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1558-8432
D.O.I.
10.1175/JAMC-D-16-0358.1
Publisher site
See Article on Publisher Site

Abstract

AbstractLong-term changes in North American monsoon (NAM) precipitation intensity in the Southwest U.S. are evaluated 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. Severe weather events are days when the highest atmospheric instability and moisture occur within a long-term regional climate simulation. Severe weather event day simulations are performed with convective-permitting (2.5 km) grid spacing, and these simulations are compared to available observed precipitation data to evaluate the model performance and verify any statistically significant model simulated trends in precipitation. Statistical evaluation of precipitation extremes is performed using peaks-over-threshold approach with a generalized Pareto distribution. 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, corresponding to similar behavior in station-based precipitation observations in the Southwest. Precipitation is becoming more intense within the context of the diurnal cycle of convection. The largest modeled increases in extreme event precipitation occur in central and southwest Arizona, where mesoscale convective systems account for a majority of monsoon precipitation and where relatively large modeled increases in precipitable water occur. Therefore, we conclude that a more favorable thermodynamic environment in the Southwest U.S. is facilitating stronger organized monsoon convection during at least the last twenty years.

Journal

Journal of Applied Meteorology and ClimatologyAmerican Meteorological Society

Published: Jul 3, 2017

References

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