Research Aircraft are used to obtain detailed information about the atmosphere. They carry very sophisticated radar and laser equipment that records a three-dimensional picture of clouds at various levels in the atmosphere. Some planes are dedicated to monitoring hurricanes, often flying into the centre of the storm itself. The information collected by aircraft is much more detailed than that collected by weather balloons.
A recent example of unexpected utility is the meteorological application of transponders developed for air-traffic management. Accurate wind information for the upper atmosphere is a key requirement for weather prediction. Currently, most wind data comes from weather balloons, wind profilers, Doppler radars and satellites. Mode-S EHS, a novel source of wind data from aircraft flight levels, is helping us to make more accurate weather forecasts.
Under European regulations, all large aircraft must carry Mode-S EHS- enhanced surveillance navigation apparatus. Aircraft equipped with EHS transponders are interrogated every four seconds by ground-based radar and, in response, send information on position, flight level, magnetic heading, air speed and ground speed. Air-traffic control monitors this data to ensure efficient and safe operations.
Suppose a plane is heading eastwards at 200m per second. Its position is known accurately by the satellite-based global positioning system or GPS. Four seconds later, it should be 800m east of its initial position. But suppose there is a wind of 50m per second from the southeast. This will slow the plane and cause it to drift to the north.
The GPS location shows precisely where the plane has gone in four seconds and determines the ground speed. Since ground speed (G) is the vector sum of air speed (A) and wind speed (W), a simple vector calculation gives us the wind. What a delightfully simple application of vectors; what a shame that vectors have been dropped from Leaving Cert maths.
Picture Credit : Google