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Global high-resolution modelling of the atmosphere and ocean (co-organized)
Conveners: Marie-Estelle Demory , Reinhard Schiemann  | Co-Conveners: Erich Fischer , Mio Matsueda , Pier-Luigi Vidale , Len Shaffrey , Malcolm Roberts 
 / Tue, 29 Apr, 13:30–17:00
 / Attendance Tue, 29 Apr, 17:30–19:00

Increasing computational resource has enabled global climate simulations at unprecedented resolutions, which are several factors higher than typical CMIP3/CMIP5 model resolutions. Atmospheric GCMs are being developed at resolutions similar to NWP models (40-20 km), while ocean GCMs are reaching resolutions that start to resolve eddies (20-10 km). A number of processes are shown to be sensitive to model resolution, while some systematic biases persist at high resolution. Here are examples of processes we are interested in:
- tropical cyclones
- transport of water and energy by eddies
- teleconnections and weather regimes in the extratropics, including blocking
- polar lows or “medicanes”
- high-impact events and their co-variability across the globe
- extratropical cyclones and the associated moisture transport in the warm conveyor belt (atmospheric rivers)
- ocean eddies
- simulation of precipitation (orographic precipitation, snow) and their impact on river flow
- diurnal cycle of precipitation over land

The aim of this session is to assess the consistency of sensitivity to resolution across GCMs, and to discuss the implications for climate model trustworthiness and planning of future simulation campaigns that will be useful for the next IPCC report.

We invite contributions on the sensitivity of key processes, such as those listed above, to horizontal or vertical resolution, and their role in the simulated present or future global climate system. Discussions on how to make use of high-resolution models to depict persistent biases across GCMs and identify their causes are also appreciated.

The focus is on global simulations, with a prescribed ocean, atmosphere, or fully coupled, both from so-called ensembles of opportunity and from well-designed experiments. We particularly welcome studies that delineate the resolution sensitivities of model parameterisation (‘physics’) and ‘dynamics’, and discussions of the desired/necessary amount of parameter changes (‘tuning’) as resolution is increased.

Presentations on the technical challenges associated with high-resolution simulations, and storage, transfer and analysis of large volumes of model data are also welcome.

Any studies using convection-permitted RCMs or GCMs (less than 10-km resolution) can be submitted to a complementary session on “Improving the representation of climate using high resolution climate and NWP models” (CL6.6/HS7.9).

This session includes solicited talks by Prof. Christiane Jablonowski (University of Michigan) and Dr Shian-Jiann Lin (GFDL, Princeton).