Why it's dry

As forecasting improves, states may soon be able to prepare for droughts as many now do for hurricanes and earthquakes

By , Staff writer of The Christian Science Monitor

When poet Carl Sandburg wrote of fog coming in "on little cat feet," he could just as well have applied the image to another, more troubling weather event: drought. For more than 50 years, researchers have noted that drought is a "creeping" phenomenon. People recognize they're experiencing it only after it has been around for a while, and then struggle to cope with it.

But now, researchers are looking forward to new tools to help them improve drought forecasting, while in Washington, lawmakers are expected to introduce legislation in the next few weeks aimed at setting up machinery to help states, counties, and cities prepare for drought, much as many do already for hurricanes or earthquakes.

These efforts come as about 30 percent of the United States is shaded in yellows, tans, and browns on drought-severity maps.

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"In many places, the current drought is a 1-in-20- to a 1-in-50-year event," notes James Laver, director of the National Oceanic and Atmospheric Administration's Climate Prediction Center (CPC) in Camp Springs, Md. "It's not unprecedented, but it's pretty unusual."

Steven Turner needs no convincing of that. Standing inside the water-filtration plant alongside the Millham Reservoir, which ordinarily supplies a third of the drinking water to residents in Marlborough, Mass., Mr. Turner, a plant operator, notes that the water level is so low that the facility hasn't pumped a gallon since the end of last October.

Since then, he quips, "we've painted everything that doesn't move, and now we are chasing things that do move." Elsewhere in the state, neighborhood ponds have become occasionally malodorous mud flats. To tend nesting boxes for wood ducks, residents plod over planks rather than paddle canoes.

In New Jersey, this winter has been the driest on record. On Monday Gov. James McGreevey declared the state's first drought emergency.

In the Washington, D.C., area, conditions have been so dry that Cardinal Theodore McCarrick asked the half-million Roman Catholics in the area to pray for rain last month. US Army Corps of Engineers officials made the same suggestion to residents attending a meeting on water allocation in Anderson, S.C., last week, after saying the corps has done the best it could to manage water levels in nearby lakes. During the past four years, some parts of the state have accumulated a rainfall deficit of 48 inches.

Georgia has also endured drought for the past four years, notes Mark Svoboda, a climatologist at the National Drought Monitoring Center (NDMC) at the University of Nebraska at Lincoln. Out west, Montana and Wyoming are withering under three years of drought conditions. There, drought conditions stretch to southern Texas.

The tricky business of forecasting

Climatologists attribute the drought to several factors. Cooler-than-usual waters in the tropical Pacific, the flip side to El Niño, have triggered shifts in climate patterns during the past few years. Winters in the US Southeast have tended to be drier and warmer than normal, as have summers in the northern-tier states, particularly those along the Rocky Mountains. In addition, the atmospheric impact of the cool Pacific waters, known as La Niña, have driven the storm-steering jet stream toward the north.

Now, as La Niña has started to give way to what could be another El Niño, these "teleconnections" between ocean-atmosphere interactions in the tropical Pacific and seasonal weather patterns over North America and elsewhere are expected to shift as well. In its latest seasonal-drought outlook, the CPC anticipates "slow improvement" in the northern Rocky Mountain states, along the Eastern Seaboard, and along the Texas-New Mexico border. Drought conditions are expected to expand from the rest of New Mexico and Arizona into southern California, at least through May.

These federal forecasts are relatively new, notes Mr. Svoboda. While the CPC has issued seasonal outlooks for temperature and precipitation for years, he says, only in 2000 did it join forces with the US Department of Agriculture, which gathers data on soil moisture, to issue its first seasonal-drought outlook. The initial effort forecast drought conditions for the eastern Corn Belt, but the region received plenty of rain. For other parts of the country, however, "it did pretty well," Svoboda says.

For years, forecasters have noted that predicting rainfall amounts is fiendishly difficult. Part of the challenge lies in measuring and forecasting moisture in the atmosphere and soil. In the summer, researchers say, evaporating soil moisture, as well as moisture given off by plants, feeds thunderstorm activity.

Researchers are looking forward to the deployment of a range of new space- and ground-based sensors that will enable them to get a more detailed picture of the water cycle, says Robert Harris, a researcher at the National Center for Atmospheric Research (NCAR) in Boulder, Colo.

Next month, for example, NASA is scheduled to launch its Aqua satellite, which will gather data about the Earth's water cycle. NASA also plans to follow up its successful Tropical Rainfall Measuring Mission by launching a constellation of satellites to track global and regional rainfall patterns more comprehensively.

The TRMM satellite has led to unexpected discoveries regarding mechanisms that can aggravate drought. Last May, for example, researchers at Hebrew University in Jerusalem reported that desert dust from the Sahara suppresses rain in clouds that otherwise would generate downpours.

Conventional wisdom had held that large dust particles kicked up by grazing and farming would serve as seeds around which water vapor would condense. Instead, the team found that as dust enters a cloud mass, the moisture is spread over a larger number of seeds, forming smaller droplets. The dust-laden clouds would dissipate before the undersized droplets could collide to form an appreciable number of raindrops.

Legislation that's 'proactive'

Support for drought research and forecasting is a key element of the National Drought Preparedness Act, which is expected to be introduced in Congress within the next few weeks.

"It's a real paradigm shift," says the NDMC's Svoboda. Past efforts to deal with droughts typically occurred only after a drought was well under way, while the new legislation "is more proactive."

The measure would establish a council modeled after the Federal Emergency Management Agency to plan for droughts and set up a fund to help pay for mitigation measures - ranging from water efficiency standards for appliances to rewriting building codes so homes and businesses use less water.

These and other approaches constitute what NCAR's Dr. Harris calls "no regrets" or anticipatory, methods, to blunt the economic effect of droughts, a natural feature of the climate system. They also could offset the potential effects of global warming on already arid regions.

"Over the longer term, we're going to have to adapt," he says.

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