Changes in North American extremes derived from daily weather data

Abstract

[1] Detailed homogeneity assessments of daily weather observing station data from Canada, the United States, and Mexico enabled analysis of changes in North American extremes starting in 1950. 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. Station level indices were gridded 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. 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. 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. 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.

Climate change impacts on extreme events in the United States: an uncertainty analysis

“…In addition, there have been increases in the number of heavy precipitation events over the last half of the 20th century in more regions than there have been decreases (IPCC 2013). The overall most consistent trends toward increases in heavier precipitation events are found in North America (Peterson et al 2008;DeGaetano 2009;Pryor et al 2009;Gleason et al 2008). Models project substantial increases in temperature extremes by the end of the 21st century with the length, frequency, and/or intensity of warm spells and heat waves increasing over most land areas (Kharin et al 2007;Sterl et al 2008;Orlowsky and Seneviratne 2012).…”

“…Regional and global analyses of temperature extremes on land report statistically significant increases in the numbers of warm days and nights and decreases in the numbers of cold days and nights (Brown et al 2008;Peterson et al 2008;Meehl et al 2009). In addition, there have been increases in the number of heavy precipitation events over the last half of the 20th century in more regions than there have been decreases (IPCC 2013).…”

Trends and Variability in Extreme Rainfall Events in British Columbia

“…Again these results are generally consistent with the results from this work. Peterson et al (2008) examined changes in extreme precipitation for North America based on gridded daily precipitation data. They found generally increasing trends in heavy precipitation for the 1950 to 2004 analysis period although the results were more prominent in the northern part of North America.…”

“…They focused on seasonal variations in precipitation intensity and noted that in winter the number of medium and light events decreased while the number of heavy events increased, while the opposite was observed for summer. Karl and Knight (1998) found increases in heavy and extreme precipitation for the United States while Peterson et al (2008) found increases in heavy precipitation for North America over the last half century. Markus et al (2007) investigated changes in design precipitation in north-eastern Illinois resulting from the analysis of different periods of record and the selection of different methods for estimating the design values.…”

How do variations in the temporal distribution of rainfall events affect ecosystem fluxes in seasonally water-limited Northern Hemisphere shrublands and forests?

“…There was a globally consistent increase in metrics of rainfall extremes (Tank and Konnen, 2003;Karl et al, 1996;Peterson et al, 2008;Alexander et al, 2006). Anthropogenic climate change is expected to intensify this shift towards fewer, larger rainfall events (Trenberth et al, 2003).…”