Understanding Past Weather to Improve Future Predictions
|Gilbert Compo, Jeffrey Whitaker, Prashant Sardeshmukh
Science Writer: Barb DeLuisi
The Quest for Data
There exists an enormous amount of weather observations describing the atmospheric circulation for the past 100 years collected by a variety of sources; from meteorologists and military personnel to volunteer observers and ships' crews. Until recently, however, this data was only available in paper manuscripts. Researchers had to rely on hand-drawn weather maps to study the past weather. Although these maps contain many errors, the value of this information was recognized and during the 1970s extensive efforts put these maps into a digital format. In recent years, organizations such as NOAA's National Climatic Data Center Climate Database Modernization Programs and the National Center for Atmospheric Research have formed partnerships with private industry and scientific organizations around the world to digitize the original manuscript weather observations, and make them available on the Web. Millions of images are available, but believe it or not, there is still a long way to go.
Since the weather we experience occurs in the troposphere — the area of the atmosphere from the Earth's surface to about 11 km (6.8 miles) up in the air — Compo, Whitaker, and Sardeshmukh decided to focus on surface air pressure and sea level pressure observations over the past 100 years. By studying recent pressure data, as shown in their article in the February issue of the Bulletin of the American Meteorological Society, it is possible to get a snapshot of the other variables, such as the winds and temperatures, throughout the troposphere. "This was a bit unexpected," says Compo, "but it means that we can use the surface pressure measurement to get a very good picture of the weather back to the 19th century. Climate change may alter a region's weather and its dominant weather patterns. We need to know if we can understand and simulate the variations in weather and weather patterns over the past 100 years to have confidence in our projections of changes in the future."
What Compo, Whitaker, and Sardeshmukh, have shown is that the international community has digitized enough pressure data over the Northern and Southern Hemispheres that they can recreate the weather maps over the past 100 years.