Atmospheric Transport Pathways for the Arctic

Dispersion of a gravitationally neutral tracer in the lower 50 km of the atmosphere is generally governed by the macroscopic motion of the air itself. Molecular diffusion can be disregarded except for laminar layers of air with thickness on the order of a few centimetres close to rigid surfaces. The macroscopic perception of fluid flows are based on the concept that fluid parcels can be regarded as thermodynamically homogeneous. The total mass of each parcel is assumed to be constant; i.e. no molecular diffusion of total mass is permitted, and a unique velocity of the air-parcels can be defined as the derivative of parcel positions with respect to time.