NWC REU 2011
May 23 - July 29



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Quantifying Changes in Extreme Precipitation at Houston and Oklahoma City by 2041–2065 Using the Canadian Regional Climate Model (CRCM)

Daniel Brouillette, Yang Hong, and Lu Liu


What is already known:

  • Extreme precipitation has been increasing in frequency and intensity in the southern Great Plains in the last 50 years and is likely to continue to do so according to many studies.
  • Daily-projection climate model output can be used to study such changes in the future by the 2041-2065 period (over an historic 1971-1995 period) quantitatively for Houston and Oklahoma City.

What this study adds:

  • Extreme precipitation may increase in intensity in the future at Oklahoma City and, particularly, Houston.
  • There is indication that overall precipitation may decrease in the future at the two locations.
  • The overall suggestion is that drought will be more common and interspersed by more intense extreme precipitation events in the future at the two locations.


One-half-degree gridded daily-projection precipitation model output from two combinations of the Canadian Regional Climate Model (CRCM)—one driven by the Community Climate System Model (CCSM) and another by the Canadian Global Climate Model 3 (CGCM3)—was obtained from the North American Regional Climate Change Assessment Program (NARCCAP). Gridded observational daily precipitation data were used as a reference to a 1971-1995 historic period and as a basis for validating the projection data. Validation suggested strong bias in the projection data, which necessitated that they be bias-corrected using a mean-value technique. Both the observational and projection data were ranked and assigned percentile values as a means of identifying and quantifying possible changes in extreme precipitation during a historic 1971-1995 and a future 2041-2065 period over two 1/2-degree grid squares centered over Houston and Oklahoma City. Overall results of the percentile analysis suggested that, for the highest percentile rankings, the daily precipitation values associated with a given percentile ranking will increase by the 2041-2065 period. For more moderate percentile rankings, the tendency toward change was less clear. For lower percentile rankings (approximately the 80th), there was indication that the values associated with a given percentile ranking will decrease by the future period. Analysis also suggested that a more sophisticated bias-correction procedure based on rain rate is necessary.

Full Paper [PDF]