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The More Extreme Nature of North American Monsoon Precipitation in the Southwestern United States as Revealed by a Historical Climatology of Simulated Severe Weather Events.
- Source :
- Journal of Applied Meteorology & Climatology; Sep2017, Vol. 56 Issue 9, p2509-2529, 21p, 3 Charts, 3 Graphs, 12 Maps
- Publication Year :
- 2017
-
Abstract
- Long-term changes in North American monsoon (NAM) precipitation intensity in the southwestern United States are evaluated through the use of convective-permitting model simulations of objectively identified severe weather events during 'historical past' (1950-70) and 'present day' (1991-2010) periods. Severe weather events are the days on which the highest atmospheric instability and moisture occur within a long-term regional climate simulation. Simulations of severe weather event days are performed with convective-permitting (2.5 km) grid spacing, and these simulations are compared with available observed precipitation data to evaluate the model performance and to verify any statistically significant model-simulated trends in precipitation. Statistical evaluation of precipitation extremes is performed using a 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 simulations of severe weather events, 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 southwestern Arizona, where mesoscale convective systems account for a majority of monsoon precipitation and where relatively large modeled increases in precipitable water occur. Therefore, it is concluded that a more favorable thermodynamic environment in the southwestern United States is facilitating stronger organized monsoon convection during at least the last 20 years. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 15588424
- Volume :
- 56
- Issue :
- 9
- Database :
- Complementary Index
- Journal :
- Journal of Applied Meteorology & Climatology
- Publication Type :
- Academic Journal
- Accession number :
- 126890296
- Full Text :
- https://doi.org/10.1175/JAMC-D-16-0358.1