Advection is the transfer of heat, mass, or other physical properties by the movement of a fluid. In other words, it refers to the horizontal and vertical movement of a substance within a fluid, such as water or air.
Advection is a major process in atmospheric science, where it is important in the transfer of heat and moisture from one place to another. For example, warm air can be advected from the tropics to the poles, helping to distribute heat around the planet. Advection is also an important process in oceanography, where it is responsible for the transport of heat, salt, and other properties in the ocean.
Advection can occur in a variety of fluid systems, including the atmosphere, oceans, and rivers. It is a fundamental process in fluid dynamics and is often modeled using mathematical equations that describe the fluid velocity and its effect on the movement of physical properties within the fluid.
Advection can be distinguished from other processes such as diffusion, which is the transfer of heat or mass due to the random motion of particles, and conduction, which is the transfer of heat through a material by direct molecular contact. Understanding the relative importance of advection, diffusion, and conduction is important for understanding the behavior of fluid systems and for predicting their future states.