Dual polarization micropulse lidar observations of the diurnal evolution of atmospheric boundary layer over a tropical coastal station

Abstract

High-resolution dual polarized micropulse lidar (MPL) observations have been used to investigate the diurnal evolution of atmospheric boundary layer (ABL) during winter (2008–2011) over Thiruvananthapuram (8.5°N, 77°E), a tropical coastal station located at southwest Peninsular India, adjoining the Arabian Sea. The lidar observations are compared with the boundary layer characteristics derived from concurrent balloon-borne radiosonde observations. This study shows that the mixed layer height over this coastal station generally increases from <300 m in the morning to ∼1500 m by the afternoon. Growth rate of the mixed layer height is rapid (∼350 m/hr) during 09–11 IST and slows down with time to <150 m/hr during 11–14 IST and <90 m/hr during 14–16 IST. Thermal internal boundary layer during the afternoon, caused by sea breeze circulation, extends up to ∼500 m altitude and is characterized by highly spherical aerosols, while a distinctly non-spherical aerosol layer appear above this altitude, in the return flow arising from the landmass.