PRIMAVERA: High resolution climate processes. Evaluating the impact of resolution and stochastic physics parameterisations in climate simulations.

We present here the first results of the Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project, which was conducted in preparation of PRIMAVERA. Climate SPHINX (http://sansone.to.isac.cnr.it/sphinx/) is a comprehensive set of ensemble AGCM simulations aimed at evaluating the sensitivity of present and future climate to both model resolution and stochastic parameterization. The atmospheric component of the EC-Earth Earth-System Model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different horizontal resolutions (from 125km up to 16km for the atmosphere). The project includes more than 110 simulations in both a historical scenario (1979-2008) and a climate change projection (2039-2068), together with coupled transient runs (1850-2100). This paper presents the technical and scientific setup of the experiments and an overview of preliminary results. An improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increases is observed. It is also shown that including stochastic parameterization in the low resolution runs helps to improve some aspects of the tropical climate - specifically the Madden-Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small-scale processes on the large scale climate variability either explicitly (with high resolution simulations) or stochastically (in low resolution simulations). A sub-set of similar experiments with the EC-Earth couple system in which high resolution and stochastic physics will be tested in the ocean component as well are in preparation in the framework of the PRIMAVERA European Union-funded Horizon H2020 project.