Antarctic Mesoscale Prediction System (AMPS) on pegasus

	Pegasus is a 71-node IBM Cluster 1350 computer. It provides the production and development environments for the Antarctic Mesoscale Prediction System (AMPS). The production runs on the pegasus cluster produce twice-daily experimental real-time forecasts that support flight operations at McMurdo Station, Antarctica and scientific activities around the continent.

The pegasus cluster system became the sole production system at NCAR for the Antarctic Mesoscale Prediction System (AMPS) in December 2005. Pegasus was the second supercomputer-class Linux cluster deployed by CISL. The other Linux cluster, lightning, provides backup service if necessary to greatly reduce the potential for missed forecasts. Reliability has been excellent. AMPS is an experimental mesoscale numerical weather prediction (NWP) system providing support to forecasting for the United States Antarctic Program (USAP). For the USAP, AMPS provides forecasters with model guidance at the highest spatial and temporal resolution available for Antarctica. To researchers in Antarctic meteorology and climatology, AMPS offers a vehicle for process and event studies, a platform to test parameterizations in the polar regions, and a long-term database of high-resolution numerical output. AMPS also provides Antarctic NWP support for other nations.

This computing effort advances two of NCAR's strategic objectives: "Improving prediction of weather, climate, and other atmospheric phenomena" and "Supporting and conducting regional-scale investigations of climate and weather." To support flight operations and forecasters in Antarctica, the pegasus cluster runs the MM5 mesoscale weather model on a set of 60-km (Southern Ocean), 20-km (Antarctica), 6.67-km (western Ross Sea, South Pole, Antarctic Peninsula), and 2.3-km (Ross Island) grids twice daily, a significant improvement over the previous 90, 30, 10, and 3.3-km grids. AMPS employs the Polar MM5 weather model, a version of the MM5 developed primarily at the Byrd Polar Research Center. The Polar MM5 contains a number of modifications to better represent processes in the polar troposphere.

In FY 2006, pegasus' capacity allowed the development of a new capability: on-demand implementation of nested one-way, higher-resolution grids. This allows enhanced resolution over areas of new Antarctic activity without interfering with the basic forecast production of AMPS. The capability was enlisted three times in the 2005-2006 field season. This capability is nimble and has the potential to offer especially valuable assistance to emergency operations on the ice.

The capacity of pegasus allows AMPS to run two mesoscale models, both the MM5 and WRF. This has been important, allowing forecasters to transition from the older MM5 to the newer WRF and to begin understanding its performance. In addition, it provides time for the model developers to create and implement a polar version of WRF, while the existing polar MM5 remains available. This transition will continue through FY 2007.

Under sponsorship from the NSF Office of Polar Programs and in collaboration with the Byrd Polar Research Center of the Ohio State University, these real-time AMPS forecasts have been tailored to the needs of the forecasters at McMurdo Station, Antarctica. Additional information about the AMPS program is available from the AMPS web page.