How do convection currents cause wind?

Convection occurs when the Earth is heated unevenly. The air over the Earth will heat according to how fast the Earth under it heats. That part is the atmosphere will heat faster and therefore expand. As volume increases, pressure drops. The warmer air has a drop in pressure and therefore lower pressure than the air that surrounds it. This difference in pressure is called a pressure gradient and this creates a force called the pressure gradient force (the air just wants to move from an area of high pressure to an area of lower pressure - a bit like diffusion does with particles). This force is the driving force behind the wind. The air heats, expands and the pressure drop causes air to rise. Over the water, the air is cooler and the air doesn’t expand. Pressure is higher here so Air over water moves so it is on land. In summary: Convection lowers surface pressure which creates a pressure gradient that tries to correct itself by having Air move from higher pressure to the lower pressure area created by the rising air. This correction in pressure is what we call wind.