May 31, 2013

Global Increasing Trends in Annual Maximum Daily Precipitation

Seth Westra, Lisa Alexander, and Francis Zwiers
Journal of Climate
  • This study investigates the presence of trends in annual maximum daily precipitation time series obtained from a global dataset of 8326 high-quality land-based observing stations with more than 30 years of record over the period from 1900 to 2009
  • The outcomes are that statistically significant increasing trends can be detected at the global scale, with close to two-thirds of stations showing increases
  • Finds that there is a statistically significant association with globally averaged near-surface temperature, with the median intensity of extreme precipitation changing in proportion with changes in global mean temperature at a rate of between 5.9% and 7.7% K−1, depending on the method of analysis
  • Finds that this ratio was robust irrespective of record length or time period considered and was not strongly biased by the uneven global coverage of precipitation data.
  • Finds there is a distinct meridional variation, with the greatest sensitivity occurring in the tropics and higher latitudes and the minima around 13°S and 11°N
  • Notes that the greatest uncertainty was near the equator because of the limited number of sufficiently long precipitation records, and there remains an urgent need to improve data collection in this region to better constrain future changes in tropical precipitation