Well-weathered radar gets a boost

Well-weathered radar gets a boost

Bronwyn Chester | When people first glimpse McGill's James Stewart Marshall Radar Observatory, they probably don't suspect that it's a vital tool for weather forecasting in the Montreal area. In fact, to those of us who envision a radar antenna as something resembling the ever-turning piece of curved metal atop Jacques Cousteau's famous boat, Calypso, the observatory looks more like a peculiar tourist attraction -- the world's biggest golf ball.

Professor Isztar Zawadzki PHOTO: Owen Egan

Inside the huge white geodesic dome perched high on its 30-metre tower, there is, in fact, a Calypso-like radar antenna, measuring nine metres in diameter. Its fibreglass cover offers protection from the elements and reduces interference from the wind.

Revolving six times per minute, while constantly altering its angle vis à vis the earth, the antenna emits microwaves into the atmosphere. These, in turn, bump into any precipitation and return to the antenna, where they are collected in a long metal pipe and funnelled into the observatory's transmitters and later, computers, in order to process the radar's message.

The message might be: Thunderstorm to hit Dorval in one hour or 20 centimetres of snow to fall on Montreal beginning in two hours. The radar might sound an alert to the Montreal Urban Community about the possibility of sewers flooding within the hour or a warning to drivers to cover their cars as a hailstorm is expected to reach the island of Montreal in 30 minutes.

Radar meteorology, both in Canada and internationally, has its beginnings at McGill, and the Canada Foundation for Innovation has seen fit to grant the observatory $800,000 to modernize the 32-year-old S-band (10 cm-long wavelength) radar, the radar under the dome. Given to McGill by the United States Army, the 1950s-built radar needs new transmitters, a new computer system and a "refurbishing so that it will last another 20 years," says the observatory director, atmospheric and oceanic sciences professor Isztar Zawadzki.

The money will also purchase 30 "ground stations," automatic surface observation stations to be planted in the ground within a 150-kilometre radius of the observatory. Each of these will measure standard meteorological parameters such as wind, temperature, pressure, humidity and precipitation.

Zawadzki's own goal is to refine and improve radar's forte in meteorology, the short-term (zero to four hours) forecast or "nowcast," as well as to further the understanding of the physics of clouds, wind and storms.

It's a task that weather physicists at McGill have been at ever since 1945, when the Stormy Weather Group, a team of researchers convened in 1943 by the Canadian Army to study radar's use in meteorology, moved to McGill. Radar -- radio detection and ranging -- was in its infancy. It had just got its operational debut in the Second World War, where it was used to spot enemy aircraft.

But radar did more than it was originally designed to. Not only did the radio waves emitted by the antennae detect aircraft, they also detected blobs of "echoes," created when the waves hit precipitation.

Led by James Stewart Marshall, the six members of Stormy Weather concentrated on documenting the radar's observations of weather and keeping statistics on the echoes. "It was the "first operational weather radar in the world," notes Zawadzki. "Marshall laid the foundation for radar meteorology."

Zawadzki arrived at McGill as a graduate student in 1965. His research, under Marshall's supervision, involved using radar to study the formation of hail in Alberta, where it does serious damage to crops. When it came time for the young Argentinian physicist to return home, stormy political weather in the form of a coup d'état and the imposition of a military regime left him stranded in Montreal.

So he made a life for himself in this city. After joining the academic ranks of the Université de Québec à Montréal for a period, Zawadski returned to McGill.

Sitting in his office on the eighth floor of Burnside Hall on this, by turns, rainy and snowy day, the greying director looks with envy at the web site photo of the Stormy Weather Group. "In the good old days of Stormy Weather, they were six," he notes.

"Those were the years when radar science was born. Today, we are only two profs at the observatory; we're too few. Now, I'm the old guy of the story," he laughs.

However, alongside Zawadski and his atmospheric and oceanic sciences colleague, Professor Frédéric Fabry, there are seven graduate students and three engineers and research associates at the observatory.

Furthermore, Zawadzki is now soliciting candidates for a newly created Industrial Chair in Significant Weather. It will be the first chair ever to involve funding from both from the Natural Sciences and Engineering Research Council and a group of insurance companies.

Why insurance companies? Because weather radar, with its ability to detect the sorts of local weather events that develop very quickly, such as tornadoes, thunderstorms, windstorms and hail, can help insurance companies determine responsibility for damage to a building or a food crop.

Aldo Bellon, a research associate at the observatory, for instance, used to be an occasional expert witness in such cases. (Now, Environment Canada sends the witnesses.) Because the S-band radar transmitter rotates non-stop, and the information received from the reflected microwaves is constantly being processed by the computer system, Bellon can simply punch in the date of the storm and see the movement and intensity of the weather at the particular time and place.

"I would write a report on the return period of a particular storm then leave it up to them to decide whether or not it was an act of God," says Bellon, explaining that the "return period" refers to how often such a storm will occur.

"July 14, 1987 [the rapid deluge that put cars on the Decarie Expressway under water], for instance, with a 1,000-year return period was a definite act of God," he continues. "Companies or municipalities could not be held responsible for the damage caused by the rain."

This constant recording of weather data, with equipment located both at the observatory and on the roof of Burnside Hall, is "unique to McGill," says Zawadzki. "The instruments are running all the time and used operationally; that's why we get the funding."

Zawadzki is referring to the observatory's arrangement with Environment Canada whereby the government's weather service funds 60 per cent of the observatory in exchange for the right to use and sell the data.

The data also goes to the Environment Canada weather office at Dorval Airport and to the Bureau des services météorologiques et environnementaux de Montréal -- the local weather office -- in Ville St. Laurent.

It is also available in real time to anyone on the Internet. In fact, when Zawadzki wants to know if he needs to take an umbrella to work, he opens up his computer. Here, in his office on the laptop computer, the constantly moving shades of green and blue colours across the island of Montreal indicate precipitation coming -- and from the northeast, which is unusual. Sure enough, rain, then wet snow, begins to fall outside the window. What's a weather nuisance to the individual, however, can spell disaster at the airport, making radar meteorology crucial. "Airports need to know the forecast for the next 30 minutes. Ten minutes is the time required for take-off and landing," explains Zawadzki. Sudden hail, freezing rain, windshifts or a sudden rain or thunderstorm can create dangerous situations.

Cities, too, need the short-term forecasting made possible by radar. The urban hydrology department of the Montreal Urban Community, for instance, needs to know 30 minutes to an hour before a heavy rainstorm is going to reach the city in order to divert sewer flow from one part of the network to another.

The MUC may one day also be able to benefit from radar reports on impending snowfalls to organize its snow removal crews to take quick action. However, given that the organization needs three hours' notice and the observatory can't yet make such long-term predictions, "this is at the research stage," says Zawadzki.

Farmers may also soon benefit from radar's ability to detect humidity in the air. Fabry has perfected a way of detecting humidity (defined as water dissolved in air) which will one day help farmers know whether or not they need to spray their crops in order to prevent a particular mould caused by humidity.

Zawadzki is optimistic about the possibilities offered by radar. "Our means of prediction and ability to respond to emergencies will improve... That's my forecast."