Thermodynamic and dynamic controls on changes in the zonally anomalous hydrological cycle
The wet gets wetter, dry gets drier paradigm explains the expected moistening of the extratropics and drying of the subtropics as the atmospheric moisture content increases with global warming. Here we show, using precipitation minus evaporation (P − E) data from climate models, that it cannot be extended to apply regionally to deviations from the zonal mean. Wet and dry zones shift substantially in response to shifts in the stationary-eddy circulations that cause them. Additionally, atmospheric circulation changes lead to a smaller increase in the zonal variance of P − E than would be expected from atmospheric moistening alone. The P − E variance change can be split into dynamic and thermodynamic components through an analysis of the atmospheric moisture budget. This reveals that a weakening of stationary-eddy circulations and changes in the zonal variation of transient-eddy moisture fluxes moderate the strengthening of the zonally anomalous hydrological cycle with global warming.
© 2016 American Geophysical Union. Received 24 FEB 2016; Accepted 19 APR 2016; Accepted article online 25 APR 2016; Published online 14 MAY 2016. The data used in this study are publicly available as part of the Coupled Model Intercomparison Project Phase 5 (CMIP5) and accessible via the Earth System Grid Federation. We thank Ori Adam for his work in developing the data portal GOAT (www.goat-geo.org), which was used to obtain the data for this study. We thank Aaron Donohoe and an anonymous reviewer for useful input on this manuscript.
Supplemental Material - grl54353-sup-0001-supplementary.pdf