4.3.4. Frictional Force

It lessens the speed of the wind. It is greatest at the surface and its influence generally extends upto an elevation of 1 - 3 km. Over the sea surface the friction is minimal. By reducing speed of wind, it weakens the Coriolis force. This allows the pressure gradient to assert its greater strength by causing the air to flow more towards low pressure. Thus, the usual situation is that surface winds flow at a slight angle to the isobars (figure 16(b)).