Investigation of Atmospheric Boundary Layer characteristics using Ceilometer Lidar, COSMIC GPS RO satellite, Radiosonde and ERA-5 reanalysis dataset over Western Indian Region

Abstract

Atmospheric Boundary Layer (ABL) characteristics are investigated using a Ceilometer Lidar over Ahmedabad, a semi-arid region in western India. Strong diurnal variations of ABL are observed during 2019, the observation period. There is a stark winter-summer difference in ABL, with summer Boundary Layer Height (BLH) exceeding winter BLH by 1–1.5 km. ABL usually collapses during monsoon and is equivocal due to the presence of thick clouds on top of ABL. The ABL is thicker during the onset of monsoon in contrast to active monsoon, rises again during the withdrawal of monsoon. Lidar observed ABL has been compared with satellite, radiosonde, and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5) dataset. ERA5 shows good agreement with differences within 500 m; radiosonde observations have under-estimated ground-based measurements, especially during summer. Satellite observations highly overestimated BLH. This comparative study reveals the importance of ground-based lidars in continuous monitoring of ABL at high resolution because radiosonde, satellite, and reanalysis datasets have coarser resolutions and sparse observations. Such quantitative evaluation of ABL is formerly unavailable over this region, which can now be used to improve the representation in numerical models and thereby estimates of radiative and climate effects due to ABL.