The term subaerial is mainly used in geology

Geology

Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...

 to describe events or structures that are located at the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's surface. This is to be contrasted with submarine events or structures — those located under the sea, or subglacial ones — those located beneath glacial ice

Glacier

A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

, such as ice sheet

Ice sheet

An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² , thus also known as continental glacier...

s.
A subaerial eruption

Subaerial eruption

A subaerial eruption is a volcanic eruption that has occurred on the surface. They generally produce pyroclastic flows, lava fountains, and lava flows, which are commonly classified in different subearial eruption types, including Plinian, Peléan, and Hawaiian eruptions. Subaerial eruptions...

 of a volcano

Volcano

2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 is one that ejects material into the air. Subaerial weathering

Weathering

Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

is weathering by rain, frost, rivers etc. Subaerial materials are materials at the surface of the planet exposed to the air. The term may exclude those processes occurring in caves.