Air

What they are

Winds are more or less rapid horizontal displacements of air masses caused by differences in the pressure distribution. Due to the fact that pressure variations are mainly caused by temperature variations, it follows that the wind’s main motor is the divergence in solar radiation in the different regions of the world.
Wind direction
Each wind is characterized by the direction in which it moves and by its speed. Normally, when one talks about wind direction, one means the direction the wind comes from: westerly winds, for example, are winds that blow from the West to the East.
Air masses would tend to move perpendicularly to the isobars, following the pressure gradient, i.e. the difference in pressure that brings about the displacement of masses of air, but the Coriolis effect modifies their course. In ideal conditions in which there is no friction, and in which the pressure gradient force and the Coriolis effect are equal and opposite, winds move parallel to the isobar lines, leaving the high pressure areas to their right in the Northern Hemisphere and to their left in the Southern Hemisphere: these are the so-called geostrophic winds (vedi grafico16: I venti geostrofici), winds that are ‘ideal’ so to speak.
Generally, at ground level, friction with the Earth’s surface causes deviations in the wind’s direction and only winds at an altitude  greater than 1,500 m are very similar to geostrophic winds.