Heat transfer in liquids and gases; this sounds familiar! Birds are very aware of convection currents in the air because with them it's possible to go upwards without efforts. The same for light planes or whatever object without too much weight.
But convection plays one of the greatest roles in atmospheric events as the differences in temperature permit very pronounced convection currents that lead to wind of any proportion. The Sun heats differently the ocean, the beach or fields with predominant dark colors that don't reflect the light. If a very dark field is surrounded by another ones with a bright appearance, almost sure in this place a great convection current will appear.
The air changes its density going upwards, and of course another air current appears to fill the void. A principle that also works under water, or in liquids generally speaking. Convection currents are a very interesting source of complexities but it can be understood and modeled at a global scale, at least accounting a percentage of all factors involved.