Comprehensive observational evidence for the effect of clouds in the diurnal evolution of atmospheric boundary layer

Atmospheric boundary layer (ABL) is the lower part of the troposphere which directly responds to the instantaneous changes in surface forcing within a typical time scale of less than an hour. The turbulent eddies provides a major pathway for the vertical mixing of aerosols, water vapour and pollutants in the ABL and vertical flux of energy and momentum which make ABL distinct from the other atmospheric layers. ABL is characterized by the remarkable strong diurnal variation of its vertical extent, turbulent intensity and meteorological parameters which is mainly driven by surface energy balance arising from incoming solar flux, emitted thermal radiation, heat transfer and the ground energy flux. The diurnal evolution of ABL is also significantly modulated by the background meteorological conditions and geography of the region. The boundary layer height (BLH) is a key parameter that determines the vertical extent of mixing and dispersal of atmospheric constituents. Even though various techniques exist for measuring BLH, they are not sufficient to study the diurnal evolution of BLH (due to the rapid development of convective boundary layer) under all-weather conditions (due to cloud cover). Microwave Remote sensing serves as the best method for studying diurnal cycle of BLH under clear and cloudy conditions since microwaves are capable of penetrating clouds.