Convection includes both advection (fluid motion) and diffusion (conduction). Atangana and Kilicman extended the fractional advection dispersion equation to a variable order equation. Two basic mechanisms are responsible for fluid mixing&colon; diffusion and advection. This equation also generalizes the advection equation. The heat from the lower crust moves via conduction and groundwater advection. CIN is strengthened by low altitude dry air advection and surface air cooling. The convection term formula 43 can be written as , where is the advection operator. AD module&colon; an advection dispersion module. They are cooled by advection, and are radiatively ineffective. It can also form due to the lifting of advection fog during breezy conditions. Bulk motion, or bulk flow, is the characteristic of advection. As previously mentioned, derechos favor environments of low-level warm advection and significant low-level moisture. Similar analysis shows that a FTCS scheme for linear advection is unconditionally unstable. The extent of inland advection is limited by southern California's coastal mountain ranges. This phenomenon is called chaotic advection.