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READING THE RADAR IMAGE |
Hour -by-hour view of nighttime migration
through Toronto.
Follow nighttime bird migration through Toronto For additional info, click here |
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Radar emits pulses of energy into the atmosphere at regular intervals. When this energy bumps into something, some of the energy is received back at the radar dish. The higher the energy value the larger the object i.e. large raindrops and hail produce higher values than drizzle. In general, energy values greater than 15 indicate areas where precipitation is reaching the ground. The radar operates in one of two modes.Clear airorPrecipitation. Generally speaking when there is no precipitation within the range of the radar site (230 km, or about 140 miles), the radar system is switched into clear airmode. In clear air mode the sensitivity of the radar is increased dramatically. |
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The radar can actually detect energy levels so small they are reported in terms of negative values ( i.e. -10 DBZ). In the clear air mode the echoes of the image are simply indicating variations in the atmospheric conditions such as migrating birds. The animated gif above illustrates a series of radar images from a night of heavy bird migration. The chart on the left shows how to read the colour patterns in the radar image. |
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