Using Idealized Tests to Diagnose the Impact of Physical Parameterizations on Atmospheric Simulations

Monday, May 12, 2014 - 07:00
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Assessing uncertainty in particular model processes is important to gaining a more complete understanding of complex climate simulations. Subgrid physical parameterizations act to simulate processes unresolved by the model's dynamical core. These mechanisms occur on spatial scales smaller than the model grid spacing and include processes such as convection, surface fluxes, and turbulence. Understanding the effect of these processes on the model solution becomes increasingly crucial as horizontal resolution is increased, allowing the model to more accurately represent previously unresolved phenomena. We explore the behavior of different subgrid physical parameterizations using the Community Atmosphere Model's Spectral Element (CAM-SE) dynamical core at multiple resolutions. Idealized setups are utilized to allow for easier isolation of specific processes through decreased complexity of the model system. We assess the impact of different convective parameterizations on simulated climatology using an aquaplanet framework. We also discuss the impact of the convective parameterizations on tropical cyclone intensity at high horizontal resolution. Special attention is also paid to the resolution signatures due to localized refinements in global simulations. In particular, we use variable-resolution CAM-SE grids in conjunction with the default CAM version 4 and CAM version 5 physics packages. We thereby assess the performance of these parameterizations across a wide range of horizontal scales and the implications of using multi-resolution grids in climate simulations with prescribed sea surface temperatures.

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