title: Characterizing differences in precipitation regimes of extreme wet and dry years: implications for climate change experiments.
abstract: Climate change is intensifying the hydrologic cycle and is expected to increase the frequency of extreme wet and dry years. Beyond precipitation amount, extreme wet and dry years may differ in other ways, such as the number of precipitation events, event size, and the time between events. We assessed 1614 long-term (100 year) precipitation records from around the world to identify key attributes of precipitation regimes, besides amount, that distinguish statistically extreme wet from extreme dry years. In general, in regions where mean annual precipitation (MAP) exceeded 1000 mm, precipitation amounts in extreme wet and dry years differed from average years by ~40% and 30%, respectively. The magnitude of these deviations increased to >60% for dry years and to >150% for wet years in arid regions (MAP<500 mm). Extreme wet years were primarily distinguished from average and extreme dry years by the presence of multiple extreme (large) daily precipitation events (events >99th percentile of all events); these occurred twice as often in extreme wet years compared to average years. In contrast, these large precipitation events were rare in extreme dry years. Less important for distinguishing extreme wet from dry years were mean event size and frequency, or the number of dry days between events. However, extreme dry years were distinguished from average years by an increase in the number of dry days between events. These precipitation regime attributes consistently differed between extreme wet and dry years across 12 major terrestrial ecoregions from around the world, from deserts to the tropics. Thus, we recommend that climate change experiments and model simulations incorporate these differences in key precipitation regime attributes, as well as amount into treatments. This will allow experiments to more realistically simulate extreme precipitation years and more accurately assess the ecological consequences.
authors: Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA.
authors: Alan K
authors: AK
authors: Knapp
authors: Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA.
authors: David L
authors: DL
authors: Hoover
authors: Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA.
authors: Kevin R
authors: http://orcid.org/0000-0001-6829-1148
authors: KR
authors: Wilcox
authors: Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA.
authors: Meghan L
authors: ML
authors: Avolio
authors: Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA.
authors: Sally E
authors: SE
authors: Koerner
authors: Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors: Kimberly J
authors: KJ
authors: La Pierre
authors: Department of Environmental Studies, University of California, Santa Cruz, CA 95064, USA.
authors: Michael E
authors: ME
authors: Loik
authors: Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK 73019, USA.
authors: Yiqi
authors: Y
authors: Luo
authors: School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA.
authors: Osvaldo E
authors: OE
authors: Sala
authors: Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA.
authors: Melinda D
authors: MD
authors: Smith
keywords: climate change experiments; climate extremes; drought; ecoregions; global patterns; precipitation; rainfall patterns