Logan Airport

An aerial view of Logan International Airport.

Credit: David Wilson via Flickr

Why Is Boston's Official Weather Measured at Logan Airport?

July 19, 2017

Everyday at Logan International Airport, thousands of workers ensure that thousands more people can come and go on hundreds of flights. That makes complete sense since, after all, it's an airport. But it's also where, every day, news personalities across the region turn to for the city of Boston’s official weather conditions. This struck a few of my colleagues here at WGBH as a little ... well, curious. The other day, they recounted a recent conversation they had for me.

Michelle: "I think David started it."
Allanah: "Yeah. you brought it up because [WGBH's Morning Edition host] Bob Seay always says on the weather in the morning, the weather at Logan is blah blah..."
David: "Right. Bob Seay and every other weather report I’ve ever heard it’s always at Logan Airport. Why is that the official temperature?"
Don: "Then we started arguing about how that came to be and we figured, Edgar would know."

Truth be told, I didn’t. But I did know where to go for answers: The National Weather Service home base in Taunton, where I met up with one of their meteorologists, Kimberly Buttrick.

"The reason being is that we have an automated sensor at the airport. It’s called an ASOS and that stands for an Automated Surface Observing System," explained Buttrick. 

The partnership between the Weather Service and airports is as old as flight itself, which makes sense. As nice as it is for you and me to know what the current temperature or wind speed is on any given day, that information is a bit more critical for pilots. 

"It seemed like a good marriage because, in the age of flight, airplanes rely on temperature, dew point, mean sea level pressure, wind direction, wind speed," said Buttrick.

And so when the ASOS system — which dynamically measures everything from temperature to wind speed, rain totals to sea level pressure — was rolled out in the 1990s, it was centered in airports large and small across the country — including around here.

"Providence, Worcester, Bradley, Beverly, Lawrence, Falmouth, Martha’s Vineyard, Nantucket, shall I go on?" said Buttrick, listing some of the region's airports equipped with an ASOS. 

An ASOS at Elko Regional Airport in Nevada.
Photo Credit: Famartin via Wikipedia https://creativecommons.org/licenses/by-sa/3.0/

Each ASOS automatically updates conditions hourly, 24 hours a day, seven days a week. The hourly data is immediately available online to everyone, including news readers. As for why the one from Logan gets referenced the most? For starters, it’s the city of Boston’s official ASOS. And at larger, busier airports, like Logan, the system is monitored by a person 24 hours a day for quality assurance. 

"But it’s also because [Boston is] the Hub," said Buttrick. "Like why do people say they’re from Boston when they’re not really from Boston? It’s the center of the universe for people up here in southern New England."

But there is a catch. It turns out that airports aren’t exactly the best place to get an accurate read on the weather. For example, Buttrick says Logan is consistently windier, cooler, and less rainy than other areas of the city.

"The Weather Service knew that when these systems were deployed that it would impact the climate [data]," she said. "But when you’re also flying and landing aircraft, with the safety of people, it’s better to have a more robust observing system located at the airports."

Notice that Buttrick said "climate." It’s not really that big a deal on any given day if Boston’s official high temperature is a few degrees cooler compared to what it was in, say, Jamaica Plain. But when it comes to the long-term climate record, that can get a little tricky. To combat this, the National Weather Service has a small army of citizen scientists across the region — volunteers who take methodical daily measurements on official equipment that help give a fuller picture of the weather across the city and the region. And then there is New England's ace in the hole — 635 feet above the city atop Great Blue Hill.

Looking toward Boston from the Great Blue Hill observation deck.
Photo Credit: Edgar B. Herwick III/WGBH News

"We have the longest climate study in the United States," said Kaitlin Geagan, an observer and educator at the Great Blue Hill Observatory in Milton. "We are studying weather the same way they did back in 1885."

The same way, in the same place, for the past 132 years: A circular deck atop a stone tower with a pretty sweet view. Here, they use the equipment of a bygone era to ensure the long-term continuity of their data. For example, sunlight is measured using an honest-to-God crystal ball.

"It concentrates the sun into a beam of light and that light physically burns a hole in a card stock," explained Geagan. "And along the day, if a cloud moves over then it stops burning so we know when we have overcast skies and we also know when we have full bright sunshine."

This is the third crystal ball used over the last 100+ years to measure sunlight.
Photo Credit: Edgar B. Herwick III/WGBH News

Wind speed, direction and gusts get recorded — analogue style — on huge reels of paper over 24-hour periods. And then there’s the mercury barometer that has far outlived its warranty.

"It was first read on January 1, 1888," said Geagan. "We read it every morning still at 7 a.m. and it’s our most accurate barometer still to this date."

Reading the barometer at 7 a.m. this time of year means they are actually reading it at what the rest of us would call 8 a.m. That's because not only do they observe the weather on 19th century equipment, they also do it on 19th century time.

"We do not observe daylight savings here. Daylight savings wasn’t observed until World War I," Geagan said.

But it’s not all vintage fare atop Blue Hill. As it turns out, there’s also a modern ASOS here. It's essentially the same system they have at Logan and it's hourly data is just as available. The biggest difference, at least according to the gang here, is that theirs is perhaps slightly more accurate. 

If there is something you have been itching to know more about, email The Curiosity Desk. We might just look into it for you.

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