Wind on planet Earth is caused by the heat of the sun (the source of most of the energy and movement on the planet). The sun's rays strike the Earth and heat up the air. It is a well known fact that hot air tends to rise (because it is an expanding gas). This is why a hot air balloon will rise. It is why when you open an oven a gush of air seems to come forth. It is why flames from a fire tend to go straight up.