Development of the Atmospheric Component of the Next Generation Gfdl Climate Model

Abstract:

Development of the next generation GFDL climate model is an on-going multi-year effort. The goal is to develop a climate model suitable for: a) projecting future climate change up to several hundred years into the future, b) for the attribution of climate change over the past century, and c) prediction of climate variability at seasonal to decadal time scales. This effort represents a unification of modeling capability including forcing with aerosol precursor and carbon emissions and representation of extreme phenomena while reducing biases through physically meaningful development.

Prototype atmospheric configurations (AM4) are currently under active development. These configurations are rooted in previous generation GFDL models, but with increased resolution and updated physics. The target horizontal resolution for AM4 is 0.5 deg, with an option for a lower resolution version of 1 deg for certain applications. The reduction of long-standing systematic errors is also a focus of the development efforts through updates to the model physics. For example, an updated convective parameterization reduces the equatorial cold tongue SST biases as well as improves the representation of MJO. Modifications to the boundary layer and cloud parameterizations show promise in significantly reducing long-standing marine stratocumulus clouds biases. Most AM4 prototype configurations exhibit a higher climate sensitivity compared to previous generation models. Given uncertainties in climate sensitivity and aerosol cloud interactions, we are also investigating the feasibility and viability of creating an alternate lower climate sensitivity model configuration.