Pertaining to zones of great depth in the oceans or lakes into which light does not penetrate; occasionally restricted to depths below 2,000 meters but more usually used for depths between 4,000 and 6,000 meters.
A process in which heat does not enter or leave a system. In the atmospheric sciences, adiabatic processes are often used to model internal energy changes in rising and descending parcels of air in the atmosphere. When a parcel of air rises in expands because of a reduction in pressure. If no other non-adiabatic processes occur (like condensation, evaporation and radiation), expansion causes the parcel of air to cool at a set rate of 0.98° per 100 meters. The opposite occurs when a parcel of air descends in the atmosphere. The air in a descending parcel becomes compressed. Compression causes the temperature within the parcel to increase at a rate of 0.98° per 100 meters.
The slope (usually equatorward, or southward in the Northern Hemisphere) of a mountain that faces into the sun. The term is originally and most often used in referring to mountains in the Alps. Tilted toward the sun, an adret is characterized by higher temperatures, a longer growing season, less snow cover and a shorter duration of snow cover, and a higher timber line and snow line than the shaded side (the ubac).