Apr 15, 2008

Changes in North American extremes derived from daily weather data

Thomas C. Peterson, Xuebin Zhang, Manola Brunet‐India, Jorge Luis Vázquez‐Aguirre
Journal of Geophysical Research: Atmospheres
  • Analyses changes in North American extremes starting in 1950 based on detailed homogeneity assessments of daily weather observing station data from Canada, the United States, and Mexico
  • The approach used a number of indices derived from the daily data, primarily based on the number of days per year that temperature or precipitation observations were above or below percentile thresholds
  • The authors grid station level indices to produce North American area‐averaged time series
  • The results indicated that the increase in the number of days exceeding the 90th percentile is about the same magnitude as the decrease in the number of days below the 10th percentile
  • Analysis of extremes farther out on the tails of the distribution (e.g., 95th and 97.5th percentiles) reveals changes very similar to the 90th and 10th percentiles
  • Finds that annual extreme lowest temperatures are warming faster than annual extreme highest temperatures when the index assessed is the actual temperature, but cold and hot extremes are changing about the same when examined on a normalized basis
  • Finds, on the basis of several measures, heavy precipitation has been increasing over the last half century, and the average amount of precipitation falling on days with precipitation has also been increasing
  • Concludes that these observed changes since the late 1960s, decrease in cold extremes, increases in warm extremes, and increases in heavy precipitation, are consistent with a warming planet