Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Sensitivity of Atmospheric River Vapor Transport and Precipitation to Uniform Sea‐Surface Temperature Increases

TitleSensitivity of Atmospheric River Vapor Transport and Precipitation to Uniform Sea‐Surface Temperature Increases
Publication TypeJournal Article
Year of Publication2020
JournalJournal of Geophysical Research: Atmospheres
Abstract / Summary

Filaments of intense vapor transport called atmospheric rivers (ARs) are responsible for the majority of poleward vapor transport in the midlatitudes. Despite their importance to the hydrologic cycle, there remain many unanswered questions about changes to ARs in a warming climate. In this study, we perform a series of escalating uniform SST increases (+2, +4, and +6K, respectively) in the Community Atmosphere Model version 5 in an aquaplanet configuration to evaluate the thermodynamic and dynamical response of AR vapor content, transport, and precipitation to warming SSTs. We find that AR column integrated water vapor (IWV) is especially sensitive to SST and increases by 6.3‐9.7 percent per degree warming despite decreasing relative humidity through much of the column. Further analysis provides a more nuanced view of AR IWV changes: since SST warming is modest compared to that in the mid‐troposphere, computing fractional changes in IWV with respect to SST results in finding spuriously large increases. Meanwhile, results here show that AR IWV transport increases relatively uniformly with temperature and at consistently lower rates than IWV, as modulated by systematically decreasing low‐level wind speeds. Similarly, changes in AR precipitation are related to a compensatory relationship between enhanced near‐surface moisture and damped vertical motions.

URLhttp://dx.doi.org/10.1029/2020jd033421
DOI10.1029/2020jd033421
Journal: Journal of Geophysical Research: Atmospheres
Year of Publication: 2020
Publication Date: 10/2020

Filaments of intense vapor transport called atmospheric rivers (ARs) are responsible for the majority of poleward vapor transport in the midlatitudes. Despite their importance to the hydrologic cycle, there remain many unanswered questions about changes to ARs in a warming climate. In this study, we perform a series of escalating uniform SST increases (+2, +4, and +6K, respectively) in the Community Atmosphere Model version 5 in an aquaplanet configuration to evaluate the thermodynamic and dynamical response of AR vapor content, transport, and precipitation to warming SSTs. We find that AR column integrated water vapor (IWV) is especially sensitive to SST and increases by 6.3‐9.7 percent per degree warming despite decreasing relative humidity through much of the column. Further analysis provides a more nuanced view of AR IWV changes: since SST warming is modest compared to that in the mid‐troposphere, computing fractional changes in IWV with respect to SST results in finding spuriously large increases. Meanwhile, results here show that AR IWV transport increases relatively uniformly with temperature and at consistently lower rates than IWV, as modulated by systematically decreasing low‐level wind speeds. Similarly, changes in AR precipitation are related to a compensatory relationship between enhanced near‐surface moisture and damped vertical motions.

DOI: 10.1029/2020jd033421
Citation:
McClenny, E, P Ullrich, and R Grotjahn.  2020.  "Sensitivity of Atmospheric River Vapor Transport and Precipitation to Uniform Sea‐Surface Temperature Increases."  Journal of Geophysical Research: Atmospheres.  https://doi.org/10.1029/2020jd033421.