The geostrophic wind is a fundamental concept in dynamic meteorology. It represents the wind resulting from perfect balance between the pressure gradient force (pushing air from high to low pressure) and the Coriolis force (deflecting it due to Earth's rotation).
Practical application
In the real atmosphere, the geostrophic wind is a good approximation above 1,000–1,500 metres, where surface friction is negligible. Below that, friction slows the wind and it turns toward low pressure. Synoptic charts allow estimation of geostrophic speed: the closer the isobars, the stronger the wind.