Experts Examine State's Weather Patterns

Sunday, July 1st 2007, 1:58 pm

By: News On 6

PONCA CITY, Okla. (AP) _ Ah, the lazy days of summer, when you can lie back, gaze at puffy white clouds lumbering overhead and wonder, ``Is continental cumulus convection modulated by land surface conditions?''

Well, you might if you're one of the 100 or so scientists who have gathered in Oklahoma for an international research project. The study could alter _ or at least tweak _ the way researchers calculate global climate change.

The $5 million project funded by the U.S. Department of Energy is actually two studies. The ``Cloud and Land Surface Interaction Campaign, or CLASIC, is looking at how surface activity _ forest growth, farming, urban sprawl _ affects formation of cumulus clouds. The second, the ``Cumulus Humilis Aerosol Processing Study, is focusing on how small airborne particles (aerosols) _ such as pollution from Oklahoma City _ interact with clouds.

Why Oklahoma?

``The weather and the climate here is highly variable,'' said Pete Lamb, professor of meteorology at the University of Oklahoma.

That's why the Atmospheric Radiation Measurement Program decided to base in Oklahoma one of its three sites for atmospheric testing. The Southern Great Plains Site is headquartered at a permanent research facility near Lamont in Grant County, west of Ponca City. The other two ARM sites are the North Slope of Alaska site and the Tropical Western Pacific site in Australia.

Information from the Southern Great Plains site is used to design computer models for weather in middle latitudes around the world, researchers said, while the other two sites cover upper and lower latitudes.

Oklahoma's site was established in 1992 as the first ARM location.

``It really is what would be considered the flagship research site for the program,'' said Lynn Roeder, spokeswoman for the ARM Climate Research Facility. ``It's been operating the longest and has the most data.''

The Southern Great Plains Site actually is a rectangle comprising 55,000 square miles, extending from about Sulphur to 40 miles north of Wichita, Kan., and roughly east to Muskogee and west to Sayre.

Scientists chose this time of year for the study because they're interested not so much in Oklahoma's renowned thunderstorms as in its small fair-weather clouds that dot summer skies, what scientists call cumulus humilis. They're looking at the stages that cause those clouds to become cumulus congestus, or storm clouds.

Researchers are conducting experiments across the region from the ground and in the air. The project is using three ground ``supersites:'' Lamont, in the oak forests around Okmulgee and in a pasture near Fort Cobb, along with numerous intermediate ground stations.

Also key will be at least nine aircraft _ from a helicopter and a Twin Otter to an ER-2, a descendent of the U2 spy plane _ each bristling with specialized equipment.

For the CLASIC study, aircraft will fly through and around clouds to actually measure heat exchanges that occur in and around those clouds. They also will analyze how much of the water vapor came from land surface beneath the clouds through evaporation and how much came from elsewhere, such as the Gulf of Mexico.

These measurements could reveal the effect of wheat crops, harvesting, forests and other land cover and land use might have on formation of clouds, and thus the absorption or reflection of solar heat.

``We don't really understand fully how our decisions may impact the climate system,'' said Mark Miller, scientist at Brookhaven National Laboratory, one of the labs involved in the study.

Currently, computer models that calculate the effect of solar energy on the atmosphere use generalized ``mathematical representations'' of clouds, researchers said.

``Computers assumed there was a kind of generic cloud there,'' said Lamb, who also is site scientist for the Southern Great Plains.

For the CHAPS study, scientists will examine the influence of manmade aerosols on clouds and the effects clouds have on these particles. Aerosols, along with dust and other tiny particles, serve as nuclei around which water vapor condenses, forming clouds and precipitation.

``Clouds in a sense live on aerosols,'' Miller said. And, he said, the Oklahoma City area provides ``a nice, well-defined plume'' of aerosols.

When this project ends, the work is just beginning. Data from the equipment, about 2 gigabytes per day during the three weeks, will take years to analyze.

``It's going to be a very, very large number of numbers,'' Lamb said.