The vertical geostrophic wind shear for a given layer of the atmosphere, i.e. the vector that defines the difference between the geostrophic winds at the bottom and at the top of the layer. It is parallel to the mean isotherms (thickness contours) and blows with cold air (low thickness) on the left in the northern hemisphere and on the right in the southern hemisphere. Its name refers to the fact that it is driven by temperature gradients.
Subjects: Earth Sciences and Geography.