A 24-hour simulation run at progressively higher resolutions captures finer and finer details of cloud “vortex streets” moving over Alaska’s Aleutian Islands. (NASA/William Putman, Max Suarez; NOAA/Shian-Jiann Lin)
Climate scientists need more powerful computers to process the sophisticated computer models used in climate forecasts. Such an expanded capability is now being developed at NASA’s Goddard Space Flight Center.

In August, Goddard added 4,128 new-generation Intel Nehalem processors to its Discover high-end computing system. The upgraded Discover will serve as the centerpiece of a new climate simulation capability at Goddard. Discover will host NASA’s modeling contributions to the Intergovernmental Panel on Climate Change (IPCC) - the leading scientific organization for assessing climate change.

Goddard will install another 4,128 Nehalem processors in the fall, bringing Discover to 15,160 processors.

"This new computing system represents a dramatic step forward in performance for climate simulations," said Phil Webster, chief of Goddard’s Computational and Information Sciences and Technology Office (CISTO).

According to CISTO lead architect Dan Duffy, the Nehalem architecture is especially well-suited to climate studies. "Speed is an inherent advantage for solving complex problems, but climate models also require large memory and fast access to memory," he said. Each Nehalem processor has 3 gigabytes of memory, and memory access is three to four times faster than Discover’s previous-generation processors.

In preliminary testing of the processors, NASA climate simulations performed up to twice as fast per processor compared with other nationally recognized high-end computing systems. The new computational capabilities allowed NASA climate scientists to run high-resolution simulations that reproduced atmospheric features not previously seen in their models, including well-defined hurricane eyewalls and convective cloud clusters.

For the IPCC studies, scientists will run both longer-term and shorter-term climate projections using different computer models. A climate model from the Goddard Institute for Space Studies will perform simulations going back a full millennium and forward to 2100. Goddard’s Global Modeling and Assimilation Office will use a climate model for projections of the next 30 years, and an atmospheric chemistry-climate model for short-term simulations of chemistry-climate feedbacks.

The IPCC will use information from climate simulations such as these in its Fifth Assessment Report, which should be published in 2014.