PRIMUSr 880 Digital Weather Radar System
The following are some truths about weather and flying, as shown in figure 5- 26.
DTurbulence results when two air masses at different temperatures and/or pressures meet.
DThis meeting can form a thunderstorm.
DThe thunderstorm produces rain.
DThe radar displays rain (thus revealing the turbulence).
DIn the thunderstorm’s cumulus stage, echoes appear on the display and grow progressively larger and sharper. The antenna can be tilted up and down in small increments to maximize the echo pattern.
DIn the thunderstorm’s mature stage, radar echoes are sharp and clear; hail occurs most frequently early in this stage.
DIn the thunderstorm’s dissipating stage, the rain area is largest and shows best with a slight downward antenna tilt.
Radar can be used to look inside the precipitation area to spot zones of present and developing turbulence. Some knowledge of meteorology is required to identify these areas as being turbulent. The most important fact is that the areas of maximum turbulence occur where the most abrupt changes from light or no rain to heavy rain occur. The term applied to this change in rate is rain gradient. The greater the change in rainfall rate, the steeper the rain gradient. The steeper the rain gradient, the greater the accompanying turbulence. More important, however, is another fact: Storm cells are not static or stable, but are in a constant state of change. While a single thunderstorm seldom lasts more than an hour, a squall line, shown in figure 5- 27 can contain many such storm cells developing and decaying over a much longer period. A single cell can start as a cumulus cloud only 1 mile in diameter, rise to 15,000 ft, grow within 10 minutes to 5 miles in diameter and tower to an altitude of 60,000 feet or more. Therefore, weather radar should not be used to take flash pictures of weather, but to keep weather under continuous surveillance.
Radar Facts | A28- 1146- 102- 00 |
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