Resolution Dependence and Rossby Wave Modulation of Atmospheric Rivers in an Aquaplanet Model

TitleResolution Dependence and Rossby Wave Modulation of Atmospheric Rivers in an Aquaplanet Model
Publication TypeJournal Article
Year of Publication2018
JournalJournal of Geophysical Research: Atmospheres
Volume123
Number12
Pages6297-6311
Date Published08/2018
Abstract / Summary

Atmospheric rivers (ARs) are examined in a set of aquaplanet simulations using the Model for Prediction Across Scales dynamical core run at multiple horizontal resolutions, namely, 240, 120, and 60 km. As the resolution is increased, there is an increase in the occurrence of long‐lasting ARs. At the same time there is also an increase in the local finite‐amplitude wave activity (LWA) of upper‐tropospheric absolute vorticity, a measure for Rossby wave phase and amplitude that is closely linked with wave breaking. Consistent with the notion that changes in ARs are driven by midlatitude dynamics, a strong relationship is identified between ARs and the equatorward component of LWA. A logistic regression model is used to quantify the probability of AR occurrence based solely on LWA and explains most of the change in AR frequency with resolution. LWA is a diagnostic that may be easily applied to the broadly available output of phase 6 of the Coupled Model Intercomparison project and other model simulations, thus enabling scientists to infer AR and Rossby wave characteristics. AR characteristics, in particular, require higher‐resolution moisture and winds at multiple levels that are not always easily available.

URLhttp://dx.doi.org/10.1029/2017jd027899
DOI10.1029/2017jd027899
Journal: Journal of Geophysical Research: Atmospheres
Year of Publication: 2018
Volume: 123
Number: 12
Pages: 6297-6311
Date Published: 08/2018

Atmospheric rivers (ARs) are examined in a set of aquaplanet simulations using the Model for Prediction Across Scales dynamical core run at multiple horizontal resolutions, namely, 240, 120, and 60 km. As the resolution is increased, there is an increase in the occurrence of long‐lasting ARs. At the same time there is also an increase in the local finite‐amplitude wave activity (LWA) of upper‐tropospheric absolute vorticity, a measure for Rossby wave phase and amplitude that is closely linked with wave breaking. Consistent with the notion that changes in ARs are driven by midlatitude dynamics, a strong relationship is identified between ARs and the equatorward component of LWA. A logistic regression model is used to quantify the probability of AR occurrence based solely on LWA and explains most of the change in AR frequency with resolution. LWA is a diagnostic that may be easily applied to the broadly available output of phase 6 of the Coupled Model Intercomparison project and other model simulations, thus enabling scientists to infer AR and Rossby wave characteristics. AR characteristics, in particular, require higher‐resolution moisture and winds at multiple levels that are not always easily available.

DOI: 10.1029/2017jd027899
Citation:
Swenson, E, J Lu, and D Straus.  2018.  "Resolution Dependence and Rossby Wave Modulation of Atmospheric Rivers in an Aquaplanet Model."  Journal of Geophysical Research: Atmospheres 123(12): 6297-6311.  https://doi.org/10.1029/2017jd027899.