May 1, 2005 Traveling to the coast of Western Mexico, U.S. researchers are studying the North American Monsoon, which brings humid air and heavy rain by blowing winds from the ocean. Studying the monsoon will give forecasters a better gauge of the climate system during the summer.
BOULDER, Colo.--Summertime brings the right mix of conditions for thunderstorms, but pinning down their exact location makes forecasting summer weather unpredictable. A group of researchers is trying to change that, and the results could have a huge impact on our economy.
It's hard to believe local thunderstorms, heavy rains, or even drought we see across the United States can be caused by storm systems created off the coast of western Mexico.
At the National Center For Atmospheric Research, or NCAR, scientists discovered this link and are predicting how it will impact this summer's weather.
"What's going on to our south can have a, a very pronounced impact on the weather we get across the central United States," says David Gochis, of the Research Applications Program at NCAR in Boulder, Colo.
So meteorologists are traveling south of the border to study what they call the North American Monsoon. A monsoon is characterized by a seasonal shift in the wind direction. During the wet season -- or summer monsoon -- the winds blow from the ocean onto land, bringing humid air and heavy rains.
Gochis says, "It may sound like subtle differences but for the people in those areas it's a very significant difference. They're getting rain, it's affecting their climate, it's affecting their energy use in several different ways."
When the study is complete, it will give forecasters a better gauge of the climate system during the summer. "It should allow people to better plan their activities, whether they be economic activities, things like agriculture, things like energy production, whether they be recreational activities," Gochis says.
And because weather impacts everyone, that's a forecast that would be good for us all.
They've set up weather equipment all over Mexico to track patterns into the United States. This North American Monsoon Experiment began in 2004 and will continue through 2009.
Many people associate monsoons with heavy rain, but the term actually refers to a wind shift rather than precipitation -- although monsoons are often accompanied by rain and thunderstorms, usually from June through September.
Technically, monsoons are major wind patterns that reverse direction depending on the season. While monsoons are beneficial, even critical for survival in many regions -- they supply almost 90 percent of India's water supply, for example -- they can also cause floods, drought, damage, deaths, and destroy crops.
Monsoons are caused by sharp contrasts in temperature between the land and the water. There are two main types of monsoon, characterized by the earth's tilt in comparison to the sun. Because the monsoon is so closely tied to the movement of the sun, it occurs fairly regularly every year.
Summer monsoons form when the earth is tilted and the sun's rays heat the air in the northern hemisphere, so that the land heats up rapidly, drawing humid air in from surrounding bodies of water, which rises and condenses into rain.
Winter monsoons occur when the sun's rays shine mostly on the southern hemisphere, and when the water is warmer than the land. Dry air flows from the land out over the ocean. So monsoon climates typically experience drought in winter and rain in summer.
Monsoons primarily occur in Asia and India, although smaller monsoons are found in equatorial Africa, northern Australia, and even the southwestern United States. For instance, during the winter, wind flow in Arizona moves from the west or northwest, shifting in the summer to a southerly or southeasterly direction. This pulls in moisture from the surrounding oceans, eventually triggering intense rains.
The American Meteorological Society contributed to the information in the TV portion of this report.