Global Analysis of Climate Change Projection Effects on Atmospheric Rivers

May 24, 2018

Vicky Espinoza (UC Merced) and CW3E collaborators Bin Guan (UCLA), Duane Waliser (NASA/JPL), along with CW3E director Marty Ralph and David Lavers European Centre for Medium‐Range Weather Forecast, recently published a paper in Geophysical Research Letters, titled Global Analysis of Climate Change Projection Effects on Atmospheric Rivers.

Atmospheric rivers (ARs) are elongated strands of horizontal water vapor transport, accounting for over 90% of the poleward water vapor transport across midlatitudes. ARs have important implications for extreme precipitation when they make landfall, particularly along the west coasts of many midlatitude continents (e.g., North America, South America, and West Europe) due to orographic lifting. ARs are important contributors to extreme weather and precipitation events, and while their presence can contribute to beneficial rainfall and snowfall, which can mitigate droughts, they can also lead to flooding and extreme winds. This study takes a uniform, global approach that is used to quantify how ARs change between Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations and future projections under the Representative Concentration Pathway (RCP) 4.5 and RCP8.5 warming scenarios globally. The projections indicate that while there will be ~10% fewer ARs in the future, the ARs will be ~25% longer, ~25% wider, and exhibit stronger integrated water vapor transports under RCP8.5 (Figure 1). These changes result in pronounced increases in the frequency (integrated water vapor transport strength) of AR conditions under RCP8.5: ~50% (25%) globally, ~50% (20%) in the northern midlatitudes, and ~60% (20%) in the southern midlatitudes (Figure 2).

Figure 2 from Espinoza et al., 2018. AR frequency (shading; percent of time steps) and IVT (vectors; kg · m−1 · s−1) for (a) ERA‐Interim reanalysis for the historical period (1979–2002) with six green boxes depicting regions analyzed in Figures S2 and S3, (b) the MMM for the 21 CMIP5 models analyzed in this study for the historical period (1979–2002), (c) RCP4.5 warming scenario (2073–2096), and (d) RCP8.5 warming scenario (2073–2096).

This research was supported by the NASA Energy and Water cycle Study (NEWS) program. Vicky Espinoza’s contribution to this study was made possible by NASA Jet Propulsion Laboratory’s Year-Round Internship Program during her graduate studies at the University of Southern California. Please contact Duane Waliser at duane.waliser@jpl.nasa.gov with inquiries. More information can be found from the NASA website https://www.jpl.nasa.gov/news/news.php?feature=7141.

Espinoza, V., Waliser, D. E., Guan, B., Lavers, D. A., & Ralph, F. M. 2018: Global Analysis of Climate Change Projection Effects on Atmospheric Rivers. Geophysical Research Letters. 45. https://doi.org/10.1029/2017GL076968