Answer: the air above a wildfire
Step-by-step explanation:
First part of question is: The diagram shows currents that form as water is heated.
When water is being heated from below, convection currents are used. This happens when the molecules at the bottom are heated thus giving them energy and enabling them rise to the surface. The colder water at the surface will therefore sink to the bottom where is is heated making it rise as well and the process is repeated.
When a wildfire is ignited, the concept is the same. The air above the wildfire is the water in this scenario. It is heated at the bottom and rises thereby forcing the air above to come down and be heated as well. Both situations uses convectional currents.