Abstract
Current climate models produce quite heterogeneous projections for the responses of precipitation extremes to future climate change. To help understand the range of projections from multimodel ensembles, a series of idealized ‘aquaplanet’ Atmospheric General Circulation Model (AGCM) runs have been performed with the Community Atmosphere Model CAM3. These runs have been analysed to identify the effects of horizontal resolution on precipitation extreme projections under two simple global warming scenarios. We adopt the aquaplanet framework for our simulations to remove any sensitivity to the spatial resolution of external inputs and to focus on the roles of model physics and dynamics. Results show that a uniform increase of sea surface temperature (SST) and an increase of low-to-high latitude SST gradient both lead to increase of precipitation and precipitation extremes for most latitudes. The perturbed SSTs generally have stronger impacts on precipitation extremes than on mean precipitation. Horizontal model resolution strongly affects the global warming signals in the extreme precipitation in tropical and subtropical regions but not in high latitude regions. This study illustrates that the effects of horizontal resolution have to be taken into account to develop more robust projections of precipitation extremes.
Highlights
Major changes in hydrological cycle are expected with the strong increase of atmospheric water vapor content under global warming
To aid in understanding the inconsistencies of the extreme precipitation projections across the climate models, a series of idealized Atmospheric General Circulation Model (AGCM) runs using the “aquaplanet” boundary conditions have been performed based on the Eulerian spectral transform Community Atmosphere Model Community Atmospheric Model Version 3.0 (CAM3) (Collins et al, 2004)
Two simple global warming scenarios are defined with the simplest modifications of prescribed sea surface temperature (SST) based on the SST profiles proposed by Neale and Hoskins (2000) in the Aqua-Planet
Summary
Major changes in hydrological cycle are expected with the strong increase of atmospheric water vapor content under global warming. The warming of the climate will likely lead to increases in the intensities and frequencies of extreme precipitation events, which result from anomalous horizontal moisture flux convergence (Trenberth et al, 2003; Held and Soden, 2006; O’Gorman and Schneider, 2009). The ability of the current generation of climate models to simulate and project these extreme precipitation events is still an open question at present (Randall et al, 2007).
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