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Publication Date
1 May 2014

Atmospheric Moisture Budget and Spatial Resolution Dependence of Precipitation Extremes in Aqua-planet Simulations



This study investigates the moisture budgets and resolution dependency of precipitation extremes in an aqua-planet framework based on the Community Atmosphere Model (CAM4). Moisture budgets from simulations using two different dynamical cores, the Model for Prediction Across Scales - Atmosphere (MPAS-A) and High Order Method Modeling Environment (HOMME), but the same physics parameterizations suggest that during precipitation extremes the intensity of precipitation is approximately balanced by the vertical advective moisture transport. The resolution dependency in extremes from simulations at their native grid resolution originates from that of vertical moisture transport, which is mainly explained by changes in dynamics (related to omega) with resolution. When assessed at the same grid scale by area-weighted averaging the fine-resolution simulations to the coarse grids, simulations with either dynamical core still demonstrate resolution dependency in extreme precipitation with no convergence over the tropics, but convergence occurs at a wide range of latitudes over the extra-tropics. The use of lower temporal frequency data (i.e., daily versus 6-hourly) reduces the resolution dependency. Although thermodynamic (moisture) changes become significant in offsetting the effect of dynamics when assessed at the same grid scale, especially over the extra-tropics, changes in dynamics with resolution are still large and explain most of the resolution dependency during extremes. This suggests that the effects of sub-grid scale variability of omega and vertical moisture transport during extremes are not adequately parameterized by the model at coarse resolution. The aqua-planet framework and analysis described in this study provide an important metric for assessing sensitivities of cloud parameterizations to spatial resolution and dynamical cores under extreme conditions.

“Atmospheric Moisture Budget And Spatial Resolution Dependence Of Precipitation Extremes In Aqua-Planet Simulations”. 2014. Journal Of Climate. doi:10.1175/JCLI-D-13-00468.1.
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