Dec 30, 2020

A Global, Continental, and Regional Analysis of Changes in Extreme Precipitation

by
Qiaohong Sun, Xuebin Zhang, Francis Zwiers, Seth Westra, and Lisa V. Alexander
,
AMS Journal of Climate

Study key findings & significance

  • The study examines changes in 1-day and 5-day extreme precipitation accumulations
  • Results are reported for two periods, 1950–2018 and 1900–2018
  • Intensification of extreme precipitation is evident throughout global land areas for which station data are available
  • At the continental scale, a significant intensification of extreme precipitation has been observed in Europe, Asia, and North America. 
  • At the regional scale, intensification in extreme precipitation is observed in central and eastern North America, northern Central America, northern Europe, the Russian Far East, eastern central Asia, and East Asia; a decreasing trend in 5-day precipitation is observed in southern Australia
  • The data also indicate a weakening of extreme precipitation in the Canadian Prairies, some parts of the western United States, Australia, and northern China
  • 11.6% of stations show a statistically significant increase in 1-day precipitation extremes with warming, significantly higher than what would be expected from random chance alone (the percentage of stations showing a significant negative relation is only about 2.4%, consistent with expectations from random chance)

Abstract

This paper provides an updated analysis of observed changes in extreme precipitation using high-quality station data up to 2018. We examine changes in extreme precipitation represented by annual maxima of 1-day (Rx1day) and 5-day (Rx5day) precipitation accumulations at different spatial scales and attempt to address whether the signal in extreme precipitation has strengthened with several years of additional observations. Extreme precipitation has increased at about two-thirds of stations and the percentage of stations with significantly increasing trends is significantly larger than that can be expected by chance for the globe, continents including Asia, Europe, and North America, and regions including central North America, eastern North America, northern Central America, northern Europe, the Russian Far East, eastern central Asia, and East Asia. The percentage of stations with significantly decreasing trends is not different from that expected by chance. Fitting extreme precipitation to generalized extreme value distributions with global mean surface temperature (GMST) as a covariate reaffirms the statistically significant connections between extreme precipitation and temperature. The global median sensitivity, percentage change in extreme precipitation per 1 K increase in GMST is 6.6% (5.1% to 8.2%; 5%–95% confidence interval) for Rx1day and is slightly smaller at 5.7% (5.0% to 8.0%) for Rx5day. The comparison of results based on observations ending in 2018 with those from data ending in 2000–09 shows a consistent median rate of increase, but a larger percentage of stations with statistically significant increasing trends, indicating an increase in the detectability of extreme precipitation intensification, likely due to the use of longer records.