Windshear is the local variation of the wind vector. Shear may be produced by different meteorological causes, such as fronts, low-level jets, mountain waves etc.
Vertical windshear together with marked ground inversion may in unhappy situations be the determining factor to an aircraft accident.
This paper is treating one method of measuring the shear and the temperature gradient by using data from a height, 350 feet above the aerodrome level.
Some situations with SODAR-measurements are also discussed.
The problems with shear in connection with aircraft take-off and landning are also treated in this report.