Subsidence is the large-scale downward motion of air, opposite to convection. It occurs at the centre of anticyclones, in the descending branch of the Hadley cell, and behind upper-level ridges.
Effects
As air descends, it compresses adiabatically and warms, reducing its relative humidity. This creates temperature inversions that prevent convective cloud formation, producing clear skies and dry weather. In urban areas, subsidence traps pollutants below the inversion, worsening air quality.