Throughout the world everyone — from experts in air, sea and land to the average citizen — relies on precise weather forecasts. Accurate weather forecasts are very much dependent on a careful and diligent collation of data, often organized and processed by the various national meteorological services around the globe.

One such national weather service is the German Meteorological Service, called Deutscher Wetterdienst (DWD), based in Offenbach, Germany. Here, on the southern banks of the river Main, researchers work around the clock forecastings storms, rain and hail showers — weather conditions that usually arrive on very short notice. In order to make these seemingly unpredictable events somewhat less so, the German Meteorological Service has installed a new NEC supercomputer. The SX-9 is the most powerful vector computer in the industry, and the German Meteorological Service plans to use it to improve the accuracy of its predictions by a factor of 45, all by the year 2010.

The excitement created in the German as well as international press in March suggested an announcement about a new deployment would soon be forthcoming. The official stamp of approval followed on the heels of the reports: the headquarters of German Meteorological Service had taken delivery of an NEC SX-9 supercomputer.

Due to the increased performance and speed of the computer, more complex forecasting models can now be used by researchers in Offenbach than was previously the case. The SX-9 is a veritable specialist in terms of dealing with Germany’s chaotic weather. The supercomputer is equipped with the world’s most powerful vector processor, operating at 102.4 gigaflop/s, and supports a memory bandwidth of 4 terabytes per second per node.

In terms of predicting weather conditions, this electronic weatherman certainly has a few tricks up its sleeve. As a result of the increased spatial resolution of the simulation model, climate and weather researchers are confronted with even larger amounts of data. The models being used often place a heavy demand on the connection between main memory and processor. As such, the processor is of very little use if the data is not loaded and returned to the main memory quickly enough. Here the SX-9 achieves a proven new high in relation to processor performance and simultaneous writing and reading access from main memory.

“We have satisfied all requirements made by the German Meteorological Service concerning the time-critical operational procedures of operational weather forecasting and developed a very effective and high availability solution concept,” states Dr. Thomas Schoenemeyer, NEC Germany’s head of HPC pre-sales. “The SX-9 is much more than just the average supercomputer,” he adds proudly.

What he means becomes clear when one views the accompanying hardware component list. The system consists of two independent computer clusters, which are installed in adjacent rooms. Since the Fall of 2008, both systems have been in use — initially as a transfer system with the SX-8R, similarly from NEC, and now in the final SX-9 configuration. Each system is capable of running 36 copies of the current short-term weather forecast for Germany, which is equivalent to a sustained performance of 4.5 teraflops.

Special strengths of the system include the optimised MPI library as well as the reliable workload manager, which allows a rapid changeover to short-term calculations even when the system is running at full pelt. The latter is the central component that guarantees execution times on work units and allows for reliable access to the databanks.

A Sun Fire X4600 M2 Linux cluster provides access to SX-9 system. The Sun cluster is where the meteorological data is pre-processed and collated depending on model calculation, maps or warnings.

The system employs dual StorageTek SL8500 tape libraries, each of which offers space for more than 10,000 magnetic tape cassettes. By 2012 the total volume should comprise around 40 petabytes — equal to the storage available on four million DVDs. Sixteen robotic hands will be used to access the more than 50 tape decks.

“Anyone computing weather models on supercomputers is dependent on two factors: performance and reliability,” claims Prof. Geerd-Rüdiger Hoffmann, the board member at the German Meteorological Service responsible for its technical infrastructure. Hoffman illustrates that the purchase of the SX-9 will be worth it due to the new opportunities it presents. ”In recent years NEC has demonstrated that in technological terms its vector supercomputers are practically unmatched in the field of climate research. For us the switch to the new technology is an important step that will allow us to work with ensemble forecasting in conjunction with high resolution weather models.”

The results obtained by the supercomputer provides early warnings of some weather events several days in advance. Each forecast is the result of 10, 20 or as many as 50 parallel calculated model simulations. On the basis of these ensemble calculations, the German Meteorological Service was able to predict hurricane Kyrill five days in advance. The new system allows for an even more precise prediction of such devastating occurrences. And it is this preciseness that can help save lives.

The supercomputer is also able to provide early warnings of extreme thunderstorms and torrential downpours. Such weather conditions are often very difficult to locate on account of their small structure and the short time span in which they occur. With COSMO-DE, a local weather model, and a resolution of 2.8 km, the German Meteorological Service is now capable of simulating isolated thunderstorms up to 18 hours in advance.

“The supercomputer hype of recent years has focused on ever more computing power — in theory. But users are primarily interested in the real application performance of the computers,” explains Dr. Schoenemeyer on the subject of the supercomputer and its development. “NEC’s supercomputer philosophy rests on two pillars: excellent performance in practice and a solely pacifist use.” A peacefulness lacking in all too many of the TOP500 systems.

The next generation of supercomputers will make it possible for meteorologists to look into the future and stay at least one step ahead of the weather. In this regard, the SX-9 is a very important step in the right direction. And although these events cannot be stopped, the damage they cause can be reduced to a minimum.

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 site: http://laengsynt.de.