Dynamical and thermodynamical modulations on future changes of landfalling atmospheric rivers over western North America

• Published in: Geophysical research letters Vol. 42; no. 17; pp. 7179 - 7186
• Main Authors: Gao, Yang, Lu, Jian, Leung, L. Ruby, Yang, Qing, Hagos, Samson, Qian, Yun
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 16.09.2015; John Wiley & Sons, Inc; American Geophysical Union
• Subjects: Americas; atmospheric rivers; Atmospheric water; Atmospherics; Basins; climate change; Constraining; dynamical effects; ENVIRONMENTAL SCIENCES; increased moisture; Meteorology; Modulation; Moisture; Rivers; thermodynamic effects; Water vapor; North America; IN, North Pacific
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL065435

This study examines future changes of landfalling atmospheric rivers (ARs) over western North America using outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5). The result reveals a strikingly large increase of AR days by the end of the 21st century in the RCP8.5 scenario, with fractional increases between 50% and 600%, depending on the seasons and landfall locations. These increases are predominantly controlled by the super‐Clausius‐Clapeyron rate of increase of atmospheric water vapor with warming, while changes of winds that transport moisture in the ARs, or dynamical effect, mostly counter the thermodynamical effect of increasing water vapor, limiting the increase of AR events in the future. The consistent negative effect of wind changes on AR days during spring and fall can be linked to the robust poleward shift of the subtropical jet in the North Pacific basin. Key Points Atmospheric river events increase in the future Increase in moisture contributes largely to AR changes Dynamical effects counter the thermodynamical changes