Weather station gets cool new digs Custom House site had too-hot readings

April 30, 1998|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

It might not be any cooler in downtown Baltimore this summer. But at least the weather reports will sound cooler.

The National Weather Service switched its downtown weather station yesterday from the chronically overheated roof of the Custom House on Gay Street to a grassy spot across the harbor at the Maryland Science Center.

The new station is expected to produce hourly temperature readings 3 to 5 degrees cooler than the old one.

"I think it's a real winner for people in Baltimore," said meteorologist John Newkirk, of the weather service's Sterling, Va., office, where the region's daily weather reports and forecasts are compiled.

"They've got a sensor sitting on top of a building about five stories high that usually reads about 5 degrees warmer than ambient temperature where people are actually walking around," he said. "That's not a true picture of the actual temperature readings."

The new station will also report barometric readings, humidity and rainfall, long absent from the Custom House data.

But not everyone is happy to see the end of 128 years of continuous weather data from the Custom House -- one of the longest climatological records in the United States.

"It's like switching from sugar to NutraSweet. It still tastes good, but it's not the same thing," said Sam Perugini, a meteorologist at Pennsylvania State University.

"Whether the temperature has been measured properly for the last 120 years is another argument, but you would still be able to pick out different trends, the 20- and 30-year cycles we know temperatures go through. You won't be able to do that anymore."

Meteorologists have known for years that the instruments atop the Custom House were sitting in an artificial "heat island" -- heat absorbed and generated by the Custom House, its rooftop utilities and by other buildings that have grown up around it over the decades.

The skewed readings were one reason Baltimore's official data has been recorded at Baltimore-Washington International Airport since 1950.

More than a year ago, the weather service began working with the city to find a better spot. The science center was chosen.

"We're delighted," said science center spokeswoman Gwen Fariss Newman. And why not? Instead of "the Custom House temperature," radio and television audiences will hear the hourly "temperature at the Maryland Science Center."

The $50,000, state-of-the-art instruments are in a 12-foot-square, fenced-in plot. The sensors are waist-high to head-high above the grass. Their data are sent to Sterling hourly over telephone lines.

When the last Custom House data was transmitted at noon yesterday, it was 72 degrees downtown -- 5 degrees warmer than the airport. When the first Science Center data went out at 4 p.m., it was 74 degrees downtown -- 1 degree warmer than BWI.

But that asterisk will always be in the record books, with a new set of record highs and lows. Climatologists, weather buffs and weather-sensitive commercial interests will need to figure out how to adjust new data to fit the old.

Perugini said such station changes have been occurring with increasing frequency. In Philadelphia, for example, airport construction recently turned a grassy field to concrete.

"Suddenly Philadelphia was having its hottest days on record," he said. "People blamed it on global warming, and really it was a slab of concrete next to the detector. Which is why we're going to have to treat the information coming in, and predictions of the end of the world, with a grain of salt, because we're doing things differently than we were."

Pub Date: 4/30/98

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