Uses of Radar Data

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Radar measures rainfall and the radial component of the wind over large areas in real-time. Furthermore, because it sees echo movement, it is also very useful for short term precipitation prediction. All the uses of radar data hence take advantage of one or several of these capabilities.
Besides the research work done at McGill and at other institutions in the Montreal area, radar is also used for:

Short-term public weather forecasts. One of the primary applications of radar data is short-term (0-4 hr) weather forecasting, also known as nowcasting. Data collected at McGill is sent in real-time to the Bureau des Services Météorologiques et Environnementaux (BSME) de Montréal (the local weather office). Since the range of the radar is limited to a few hundred kilometers and since weather

Sequence of radar images
generally moves at speeds averaging 50 km/hr (faster in winter, slower in summer), radar can only see precipitation a few hours ahead at most. It has hence limited applications for the usual longer term weather forecasts, but proves extremely useful to issue warnings when severe weather develops rapidly in the vicinity. In fact, if a severe thunderstorm warning is issued in your area, it is generally because it has been detected and tracked by radar.

Short-term forecasts for aviation. Another application of radar is to improve short-term weather forecasts around airports, also known as "terminal forecasts". Aircrafts, being large and heavy machines having pretensions to fly like birds, are very susceptible to severe weather. In summer, the danger takes the form of hail (damages the aircraft), very heavy rain (gets swallowed by the engine which it can extinguish), rapid wind shifts (complicates airport management and ruins approach routes), and downbursts (pushes the aircraft towards the ground quite spectacularly). In winter, icing (the formation of ice on wings) makes aircrafts heavier but also reduces lift by distorting the wings' precise shape. All these meteorological conditions can be detected at least to some extent by weather radars and therefore radar has an important role to help aircrafts stear out of dangerous areas.

Downburst on radar

River and sewer flow forecasting. Rivers take their water from rain (or snow). Radar measures rainfall and snowfall rates over large areas, and can also be used to make short term predictions of precipitation amounts. Therefore, radar can be used, in conjunction with appropriate models of river flow (hydrological models), to predict the flow and the level of the water in a river. Sewers can be viewed as a special kind of river; they are man-made, generally underground, and cover small areas, but in many ways they can viewed as rivers. And when they flood, they do as much if not more damage than the real ones. This is why the Montreal Urban Community tries to predict sewer levels using radar data provided by McGill. If sewers are predicted to overflow, special measures (like diverting water from one part of the network to the next) can be taken to prevent damage to property.

Legal issues concerning damage from weather. When the weather strikes and damage occurs, complex issues often arise about financial responsibility. Was the damage caused really caused by the weather? Shouldn't the structure have coped with the precipitation? Who should pay for the repair? As a result, researchers from the radar observatory are sometimes called to testify as expert witness and use the radar data to describe the event and quantify to what extent it was exceptional or ordinary.


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