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Wind gradient
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A wind gradient - spatial change of speed and direction of wind.
Even though gradient is a three dimensional field in meteorological applications wind gradient is often referred to a particular direction, usually perpendicular to Earth's surface. In most conditions there is a wind gradient just above the ground.
The wind at the surface may be 270 degrees at 15 kts, while at 1000 feet above the ground it is 280 degrees at 25 kts, and at 2000 feet above the ground it is 290 degrees at 35 kts. In this example, the wind gradient is 10 kts per 1000 feet. Wind gradient and wind shear differ semantically in that wind shear is more abrupt, and often involves a change in wind azimuth of greater than 30 degrees and or more than 15 knots over a very short vertical distance (less than 1000 feet)in the atmosphere. Wind gradient is a normal everyday occurrence based on coriolis force and surface friction. Wind shear can occur due to gust fronts associated with thunderstorms, frontal passage, microbursts, and temperature inversion layers.