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Disconnection Between Trends of Atmospheric Drying and Continental Runoff
Author(s) -
Yang Yuting,
Zhang Shulei,
McVicar Tim R.,
Beck Hylke E.,
Zhang Yongqiang,
Liu Bing
Publication year - 2018
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2018wr022593
Subject(s) - evapotranspiration , arid , surface runoff , aridity index , precipitation , environmental science , climate change , climatology , coupled model intercomparison project , water cycle , atmosphere (unit) , climate model , atmospheric sciences , hydrology (agriculture) , physical geography , meteorology , geography , geology , ecology , paleontology , oceanography , geotechnical engineering , biology
The ratio of potential evapotranspiration ( E 0 ) over precipitation ( P ), known as the aridity index (AI), has been commonly used to stratify global aridity zones and widely adopted to assess changes in aridity globally. Anthropogenic climate change, in particular atmospheric warming, is projected to increase AI, which has in most cases been interpreted as increasing terrestrial aridity. In this study we demonstrate, for both past and future conditions, that such an interpretation requires reconsideration. Using catchment observations over the past 30 years and climate model projections for the 21st century, we show that increased AI does not ubiquitously lead to a decreased water availability over land, using surface runoff ( Q ) as an indicator. This is primarily caused by a higher Q sensitivity to changes in P ( S P ) and a lower Q sensitivity to changes in E 0 ( S E 0 ), with the ratio of S P over S E 0 being higher than the relative changes of E 0 compared to P (i.e., | P × S P | > | E 0 × S E 0 |). Assessment of Coupled Model Intercomparison Project Phase 5 model outputs indicates that both Q and AI change‐induced Q changes are increasing over the majority of the globe for the 21st century despite increasing AI (a drying atmosphere). Our findings demonstrate a disconnection between the atmospheric drying trends and surface runoff trends and call for caution when interpreting retrospective and future changes in terrestrial aridity based on AI and related measures.