The Earth Simulator is a legend in computational meteorology and long-term climate simulations. For years it has been one of the fastest supercomputers, designed to evaluate the effects of global warming and problems in solid earth geophysics. In 2009, a comprehensive upgrade of the Earth Simulator will begin a new era for the history-making supercomputer.

For six years, the Earth Simulator has been a constant in the twice-yearly TOP500 list of the most powerful supercomputers. Currently ranked in 49th place, a significant enhancement is scheduled. A new and comprehensive reinstallation is underway to enable researchers to conduct enhanced climate simulations to produce results that are beyond the scope of any other computing system.

Again the NEC Corporation in Japan, responsible for the original version in 2002, is assigned to deliver the upgraded Earth Simulator. This new mega-simulator is being installed in the Japanese research centre JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and is destined to help scientists find answers to mitigate the impact of global climate change on the earth’s ecosystems. With a maximum processing power of 131 teraflops (131 billion arithmetic operations per second), a planned special SX-9-series will be able to accomplish so-called ultra-high-speed simulations in real time.

Until the new system is installed in 2009, the current Earth Simulator will continue to work on unique scientific topics. Simulations of the global climate both in the atmosphere and in the oceans made the Earth Simulator the expert in assessing climatology issues and the most important contributor to the Fourth IPCC Assessment report in 2007. The need for continuing this effort is obvious. In the period from 1950 to 2005, a massive increase in major weather-related natural catastrophes was observed, and between 1994 and 2005 there were almost three times as many weather-related natural catastrophes as in the 1960s.

The beginning: The fastest computer in the world

It all started in 2002. The fastest computer in the world was installed at the Yokohama Institute for Earth Sciences (YES). Its 640 nodes, with 8 vector processors each, occupy 3,250 square meters. The system is based on the SX-6 architecture and consists of 5,120 CPUs, 10 terabytes of main storage, 700 terabytes of hard disc storage units and 1.6 petabytes of streamer storage. An unrivalled accomplishment back then, the system is still very much in use today, and not only by Japanese researchers. International collaborative projects with institutes in the US, France and UK have attained unique results.

At first Japan used the supercomputer for its own interests. In 1923 the Kanto earthquake killed 130,000 people and destroyed Tokyo and Yokohama. In addition to that, the birth rate rose explosively, forcing the government to pay much more attention to potential national catastrophes. Today, however, the Earth Simulator is in demand worldwide, helping to clarify problems associated with a global climate. This field has indeed become a global issue, as evidenced by recent deadly natural disasters, such as the Tsunami in 2004 and the latest earthquake in China, which killed hundreds of thousands of people.

One important aim of climate supercomputers is not only understanding incidents like earthquakes, but predicting them as early as possible. Another field of activity, which the original Earth Simulator is perfect for, is the realization of coupled simulations of the atmosphere and the ocean or even complete earth simulations.

Same architecture — only smaller and more effective

“Currently there is no other platform that is able to run calculations of that kind in a comparable short time — even though there are machines capable of more output according to the available data,” says Dr. Sébastien Masson from L’Institut Pierre-Simon Laplace (IPSL) in Paris, France. For his climate models, he has been using the Earth Simulator for a long time now — not least because the interaction between hardware and software works out perfectly well. Another key aspect is the possibility of running coupled models. That means complicated ocean models, complex land models, and also climate models can be simultaneously simulated and then brought together.

“The Earth Simulator is almost identical in construction with the SX 6 machine we are using in Hamburg,” says Michael Böttinger, who is responsible for the application software at the German Climate Computing Centre (DKRZ). “Except the vector architecture is 25 times bigger than ours.” Its architecture is one of the key benefits of the Earth Simulator. The computer simulation of natural occurrences and the calculation of natural catastrophes and their climate impact require increasing processing power.

Vector processors — with their strong single processor performance associated with a very high bandwidth to the main memory — are particularly effective at meeting the special demands of computing in earth sciences. Clusters of vector computers have the advantage of using a mixture of both MPI and OpenMP with extremely strong SMP nodes. As an example of how well these codes map to the vector architecture, the AFES climate model delivers up to 60 percent of the Earth Simulator’s peak performance.

Since the first successful numerical weather forecast in 1950, the world has changed dramatically. With the increase of unusual weather events, computational meteorology has taken over a new role in assessing the future changes of the environment rather than solely forecasting tomorrow’s weather. Society recognizes the value of investing in these kinds of supercomputer systems and in their utilization. This support is evidenced by the scheduled reinstallation of the Earth Simulator.

“Oceans with their complex biological interaction play a key role in climate research, producing 50 percent of the oxygen and storing one third of the atmospheric CO2,” explains Dr. Onno Groß, marine biologist and founder of the Ocean Protection Organisation DEEPWAVE. “But the temperature change and the acidification of the sea by exhaust emissions threaten their organisms. The impact of these changes can only be made graspable with supercomputers like the Earth Simulator.”

Thanks to enhancements, the new computer allows extended applications, like cloud resolving physics and ensemble studies. Exact high-speed analysis is enabled, and with that even more precise forecasts for worldwide environmental phenomena are possible. Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures and rising global average sea level. However, with adequate adaptation and mitigation strategies associated with emission reduction concepts, scientists can provide guidance to try to minimize the impact to ecosystems and human society. Systems like the Earth Simulator will play a key role in defining and evaluating these strategies and scenarios. Neither emission reduction nor adaptation will avoid all climate change impacts, but together they can reduce the risks of climate change.

Looking Ahead

Another supercomputer is also being constructed in Japan. The RIKEN Institute (Institute of Physical and Chemical Research) is developing a 10 petaflop system. The enormous increase in processing power in the HPC-area shows the impressive book of supercomputing is never going to end.

About the Author

Markus Henkel is a geodesist, science writer and lives in Hamburg, Germany. He writes about supercomputing, environmental protection and clinical medicine. For more information, email him at [email protected] or visit the Web sites: http://laengsynt.de and http://netzwelt.de.