CSL Allocations 2014

These projects received CSL allocations for June 2014 to May 2015

Scale Interactions in the Climate System

Project lead: Greg Holland, NCAR
Yellowstone allocation: 5.5 million core-hours
Sponsor: NSF

This project has the potential to significantly advance climate science and the provision of climate advice for community planning and adaptation by supporting the development of a climate prediction approach that includes full multi-scale interaction between weather and climate. Central to this approach is full accounting for the upscale impact of small scales and intense weather systems back on the larger climate system. Scale interactions in the climate system have received little attention in the past few decades, largely due to the inadequacy of tools and resources to study them. However, recent advances in modeling and computational capacity permit investigations of this critical and potentially transformative area of climate science.

This project will utilize the variable grid resolution capability in the Model for Prediction Across Scales (MPAS) that supports the full range of multi-scale interactions between the regional and global scales. The project will proceed in two phases. Phase I will establish a base climate using uniform resolution MPAS at two different resolutions, one coarse resolution (60 km grid spacing) and one fine resolution (15 km grid spacing). Phase II will explore a series of MPAS runs with mesh refinement from the coarse (60 km) to the fine (15 km) resolution that captures different regional weather and climate phenomena previously identified as having important large-scale influence. Comparisons    between the uniform coarse and fine resolution runs and the mesh refined runs will elucidate the upscale impact of regional small-scales on the global climate.

Dynamical Seasonal Prediction

Project lead: Ben Cash, GMU/COLA
Yellowstone allocation: 25.9 million core-hours
Sponsor: NSF

Having established that there are limits to the gains in model fidelity and skill possible from increasing atmospheric horizontal resolution, and mindful of our goal to continue identifying and harvesting new sources of seasonal predictability, we turn our attention here to two different and promising avenues for improving model skill. A series of seasonal forecasts will be performed for the period 1982-2009, initialized in May and November with 15 ensemble members each, made using (a) the ‘super-parameterized’ (SP) version of CESM, in which the impact of convection on the resolved scales is calculated using an embedded cloud-resolving model and (b) ocean resolution of 0.1 degrees (HIRES), in which we test the impact of oceanic, rather than atmospheric, resolution, on model fidelity and skill. By performing similar suites of experiments exploring these two approaches, with an experimental design that conforms to our extensive catalog of existing integrations, we will be able to quantify the relative impact of these two approaches versus increasing atmospheric resolution and help to establish which approaches provide the most cost-effective increases in model fidelity and skill. Given the demanding nature of these calculations, which include both new processes (SP) and high resolution (HIRES) and the volume of data generated by the proposed suite of experiments (see Section D for details) these calculations can only be performed at a computational facility such as NWSC, which combines petaflop- and petabyte- scale computing resources.

CESM Allocation from Nov 2014 to Oct 2015

Community Earth System Model (CESM)
Project lead: Jean-Francois Lamarque, NCAR
Yellowstone allocation: 46 million core-hours
Sponsor: NSF and DOE

Over the period of performance for the present request, the main priority for the Community Earth System Model will be the development, testing and release of CESM2, targeted for June 2016. Two main streams of development are being proposed: 1) a workhorse version, based on CAM5 with limited physics updates (and therefore provisionally named CAM5.5) with a 1-degree horizontal resolution for both the atmosphere and ocean grids and 2) a bleeding edge version, based on CAM6, with the spectral element dynamical core, with a focus on high-resolution (approx. 0.25o globally) and a 1o ocean. Indeed, the analysis of the CMIP5 simulations (as documented in the special issues of J. Climate on CCSM4 and CESM1) has indicated that there was a significant improvement when performing climate simulations with an atmospheric and oceanic resolution of 1o As such, it is reasonable to use such configuration for the generation of the next CESM to be used in various asses sments. However, coarser versions of CESM will still be provided within the timeframe of CESM2 to enable long simulations at reduced computational expense, albeit their availability will possibly be later than the CESM2 June 2016 release to allow for additional testing. The CAM5.5 version will be mostly developed by June 2015, at which point it will be released, and testing and coupling of additional components (e. g. land, ocean, sea-ice, biogeochemistry, atmospheric chemistry and WACCM) will proceed between June 2015 and June 2016, to provide a thoroughly tested and evaluated model for release. The CAM6 extension will be mostly developed between June 2015 and June 2016. Overall, our approach for CESM2 development and therefore the present proposal is to focus on a limited set of model configurations to maximize the scrutiny put into the model evaluation for each released configuration. The timing in the development and release of CESM2 is somewhat tied to the upcoming Climate Model Intercomparison Project Phase 6 (CMIP6), but more generally represents the culmination of major updates to many parts of CESM that can now be provided to the broader community with a scientifically supported release.