Reanalysis Project targets
once-and-future weather
Posted September 29, 2009
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Gil Compo describes the 20th Century Reanalysis Project that he leads for the National Oceanic and Atmospheric Administration. The project relies on 150 years of weather data and simulations run on Department of Energy supercomputers. |
Alone near the South Pole in 1934, Admiral Richard Byrd documented his ice-bound despair. He also dutifully recorded the surface air pressure every hour.
As the Great Long Island Hurricane of 1938 ripped apart houses and turned towns into islands, meteorologists recorded crucial data – the sea-level pressure leading up to the terrible event.
Storms and blizzards made headlines throughout the late 19th and 20th centuries. But it’s the humble recordings of lows and highs during those unforgettable events that scientists are harvesting now. They hope a computationally intense reanalysis of weather over the past 150 years will tell them whether today’s storms are more extreme and if climate prediction models can be trusted for this purpose.
“It’s that connection to our scientific forbears that makes this project so exciting,” says Gil Compo, who leads the 20th Century Reanalysis Project at the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL) and the Cooperative Institute for Research in Environmenal Sciences (a joint project of NOAA and the University of Colorado).
“These guys went out at tremendous risk to life and limb” to collect the data. “Now, in ways they never could have imagined, we are going to use data from those dedicated meteorologists to figure out how much weather and climate have changed over the past 150 years.”
Compo and 28 international collaborators hope to gather pressure readings from the surface and from sea level on five continents for every six-hour period going back to 1850. They have cadged records from Jesuit monks, polar explorers, independent observers and trained meteorologists.
“We sent out the call: ‘We need more surface data. Do you have it?’” to universities and weather bureaus. Colleagues combed the records of Google and Microsoft, Compo says.
Before research aircraft
Before airplanes and weather balloons, meteorologists had just surface temperatures, wind speeds and barometric pressures to make forecasts.
The Reanalysis Project aims to use just those old tools to map the weather over 150 years, and in so doing determine whether the models of past and future climate correlate – or are likely to correlate – with the kind of events that happened in the past.
For example, the hurricane known as the Long Island Express roared inland from the Atlantic in 1938, killing up to 800 people and damaging or destroying 57,000 homes in New York, Connecticut, Rhode Island, Massachusetts and New Hampshire.
Can air-pressure readings from 1938, by themselves, indicate that a hurricane was inevitable and that it would be one for the ages? Can those readings help show that recent hurricanes are more vicious than even the worst ones of the early 20th century? It’s a daunting challenge.
Compo and his principal collaborators, Jeffrey Whitaker of NOAA ESRL and Prashant Sardeshmukh of CIRES and NOAA ESRL, believe new advanced data-assimilation methods can generate highly reliable estimates of conditions high in the air. And if that kind of analysis can be done for today’s weather, why not historically, provided there are enough ground-level readings?
