ASSISTING ANTARCTIC RESCUES:
A specialized model produces lifesaving forecasts of some of the world’s harshest weatherTrapped in pack ice during Antarctica’s winter darkness in June 2002, more than 100 scientists and crew members aboard the Magdalena Oldendorff faced a grim situation. Snow and bitterly cold winds approaching hurricane force buffeted the supply ship, which had left the Antarctic coast bound for Cape Town. The scientists and crew appeared to have no means of escape.
Researchers need accurate forecasts for the Antarctic. (Photo by Digital Vision/Getty Images.)
Only a few years before, orchestrating a rescue in such conditions would have been nearly impossible. Weather reports were scarce across the Antarctic, and few computer forecast models had been tailored for the continent’s unique geography and cold, dry climate. Fortunately for those aboard the Oldendorff, NCAR was already developing a forecasting model in conjunction with Ohio State University designed to help researchers from around the world who work in the brutal Antarctic winter.
Forecasts from this Antarctic Mesoscale Prediction System (AMPS) helped the South African Weather Service guide a specially equipped ship from Cape Town to pick up the stranded ship’s 78 Russian scientists and most of its 28 German crew members. Two helicopters subsequently evacuated the last passengers on July 1, when AMPS had targeted a brief window of favorable weather.
The model, upgraded in 2004 to provide five-day forecasts for Antarctica, has enabled other dramatic rescues, including evacuations in 2001 and 2003 of ailing Americans from their South Pole assignments. NCAR scientists are planning further improvements that will increase the model’s resolution. “AMPS is not only breaking ground in the realm of real-time Antarctic weather modeling, but it is building a record of assisting in emergency rescues from Antarctica,” explains NCAR scientist Jordan Powers.
Constant forecasts
Every 12 hours for several years, AMPS has generated three-day forecasts for the continent. NCAR launched five-day forecasts in 2004.
The model is an important tool for the international research community in Antarctica. Research teams from several countries, including Australia, Great Britain, Chile, Germany, Italy, and South Africa, have come to rely on its forecasts for their flights in and out of Antarctic bases.
Scientists from these and other countries meet regularly with Powers and the rest of the AMPS team. These colleagues provide important feedback about climate conditions, which leads to improvements in the model.
“Their input has been very helpful,” Powers says. “They can let us know about aspects of performance that we might not otherwise focus on.”
AMPS can examine Antarctica’s unique weather in increasingly fine detail. To view the latest forecast or an animation, see the AMPS home page. (Image courtesy Jordan Powers, NCAR.)
Adapting to Antarctica
To develop AMPS, scientists turned to a leading regional forecasting system, the Pennsylvania State University/NCAR Mesoscale Model, version 5. Adapting the MM5 to Antarctica was not a simple task, because the physical processes in the model had been developed and tested over the years on midlatitude and tropical weather systems and were not tuned for polar regions. Scientists at Ohio State University and NCAR accordingly modified the computer code to simulate clouds, solar radiation, and sea ice in the Antarctic.
In order to incorporate the topography of Antarctica, which dramatically affects the continent’s weather, scientists used a series
of nested grids with varying degrees of resolution. The model calculates atmospheric conditions for points that are spaced anywhere from 3.3 to 90 kilometers (2 to 56 miles) apart, allowing users to focus on specific regions at a scale that would be too computationally intensive if applied to the entire continent. The finest resolution forecasts are provided for the region surrounding McMurdo Station, an important research and logistics base.
Each forecasting run begins with a global model making a first estimate of the state of the atmosphere above Antarctica. The system then takes into account surface observations, balloon-gathered data, and satellite-derived wind observations.
Thanks to improved modeling capabilities, better satellite coverage, and feedback from Antarctic scientific teams, AMPS is gradually becoming more powerful. Resolution for even the most remote areas of Antarctica will soon be boosted to 20 kilometers (12 miles), enabling the model to capture smaller-scale cloud systems and other atmospheric events.
Scientists are also preparing to adjust AMPS in late 2005 to incorporate the newest forecasting system developed with NCAR leadership: the Weather Research and Forecasting model (WRF). With these improvements, they hope to position AMPS to provide more accurate and detailed predictions of the ever-critical, and often life-threatening, Antarctic weather.
The CAWFE computer model simulates complex wildfire behavior. View an animation. (Image courtesy Janice Coen, NCAR.)
Once they begin to spread, wildfires are extremely difficult to predict. The speed and direction of the fire and the size of the flames are influenced by a number of factors, including weather conditions, local topography, and the type of fuel on the ground, as well as by complicated interactions between the atmosphere and gases that escape from vegetation.
NCAR scientists have developed the Coupled Atmosphere Wildland Fire Environment model (CAWFE) to simulate wildfire behavior. Such computer simulations may improve understanding of fires and eventually lead to tools that will help local officials better anticipate their speed and movement. But researchers need to test CAWFE on real wildfires in a variety of situations before it can be used for predictions.
To that end, NCAR is collaborating with Australia’s Bushfire Cooperative Research Center. Every year, Australia sets a number of prescribed burns to evaluate fire behavior under various conditions. These burns can help scientists gather data on such important issues as the distribution of smoke, the rate at which various fuels burn, and the intricate interplay between winds and the course of a fire.
NCAR researchers hope to use the burns to test the accuracy of their model predictions under typical conditions in Australia. The collaboration can benefit both countries in their ongoing efforts to combat wildfires.
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