Planetary Boundary Layer (PBL) is the lowest part of the atmosphere which is directly influenced by the Earthâs surface. The top of the PBL often acts like a cap to trap air in the layers below thus having a major influence on atmospheric phenomenon like dispersion and concentration of pollutants (air quality), trade winds, cloud formation and, extreme weather to name a few. The thickness of the planetary boundary layer, commonly referred to as the Planetary Boundary Layer Height (PBLH) is strongly influenced by the topography, ground cover, temperature and winds. Consequently, PBLH exhibits strong temporal variations (changing with time of the day and seasons) and spatial variations (changing from one place to another). Some feature that can be observed are: Deeper PBLH over dry subtropical land on summer days due to rising thermals and convective mixing; Deeper PBLH during the day than during nights; Fluctuations in PBLH are more pronounced over land than over oceans.
