Archive for Tuesday, January 21, 1992


January 21, 1992


— If a weather researcher's theory is right, most of Kansas will get about 10 percent more rain than normal this year.

Charles Perry, who works for the U.S. Geological Survey in Lawrence, thinks he has found a statistical connection between solar activity and rain that would mean heavier than normal rainfall.

The total might not be quite that much in northwest, northeast and southeast section of the state, Perry says, but he still predicts a wetter year than normal.

Perry believes his research will lead to better long-range forecasting of precipitation.

He said his work needs refinement, but adds, ``I have growing confidence in it.''

While cautious, other weather experts are interested in what Perry is doing. Dave Salmon, a meteorologist for Knight-Ridder Financial News in Leawood, said that if Perry can find that correlation between solar activity and rain, he's going to become famous.

Still, Salmon said that even if Perry's forecast for 31 inches of precipitation this year in the Wichita area and south central Kansas proves accurate, the information isn't too helpful to farmers unless they know when the rain is going to fall.

``IF IT ALL comes at once, it's a flood,'' Salmon said. ``If it doesn't come at the right time, it doesn't make any difference. If it's spread quite evenly over the year, which it never is, 3 inches wouldn't make any difference in a sorghum crop or a wheat crop.''

Perry, who describes himself as a hydroclimatologist, is aiming for the ability to make seasonal forecasts for every part of the country two or three months in advance.

He has had a long interest in weather cycles, and some of his research involves looking at drought cycles and their relationship to sunspot activity.

The problem with his and other work on sunspots, Perry said, is that it is based on a subjective evaluation of what is occurring on the sun.

``If you mention sunspots in the scientific community, you'll get a chuckle most of the time,'' he said.

The added element in his latest work is data from the Nimbus 7 satellite providing an objective measurement of the total amount of solar energy reaching the earth.

THE OTHER set of data Perry works with is actual precipitation amounts at particular locations on earth.

By comparing the two sets of data, Perry said, he can show that an increase in solar energy or irradiance will correspond to an increase in precipitation in a particular locale some number of years in the future.

He presented a paper to the American Geophysical Union in December showing a particularly strong relationship between changes in solar irradiance and corresponding changes in the precipitation in the Pacific Northwest four years later.

In other regions of the country, the length of the lag is different and the relationship is more complicated.

In Kansas, for example, the weather is influenced by what goes on in the Pacific, in the Gulf of Mexico and on the North American continent. In this case, Perry must meld solar irradiance data from one, two and three years ago to find his correlation to actual precipitation amounts in a given year.

ONCE HE has developed a mathematical relationship between solar activity and precipitation for a particular region, Perry can make a prediction of rainfall with current data from the Nimbus 7 satellite.

Stephen Welch, an agronomy professor at Kansas State who is the acting climatologist for the state of Kansas, said correlation methods have been used in the past to try to predict the weather. Most frequently they fall apart either because they work only for limited parts of the globe, or because they just don't hold up over time, he said.

``In statistics we say that correlation doesn't indicate causation,'' Welch said.

But Perry said the action of the oceans is the physical mechanism linking changes in solar irradiance and precipitation, and that's where he finds a cause-and-effect relationship.

IT OCCURS in three steps: absorption of solar energy by the transparent tropical oceans into a deep surface layer; transport of that energy, in the form of warmer water, from the tropics to the temperate regions by major ocean currents; and transfer of the energy into the atmosphere by evaporation of ocean water.

The evaporated water returns to the earth's surface as precipitation. The lag between the changes in solar irradiance and precipitation is related to the duration of ocean circulation patterns.

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