Abstract

Global Positioning System (GPS) Radio Occultation (RO) remote sensing with its high vertical resolution and sensitivity to moisture gradients is an efficient method for monitoring Atmospheric Boundary Layer (ABL)depth, particularly over the ocean. In previous studies by different authors the ABL ... Show moreGlobal Positioning System (GPS) Radio Occultation (RO) remote sensing with its high vertical resolution and sensitivity to moisture gradients is an efficient method for monitoring Atmospheric Boundary Layer (ABL)depth, particularly over the ocean. In previous studies by different authors the ABL top was determined mainly from vertical gradients of scalars retrieved from the GPS RO signals, such as bending angle, refractivity, moisture, etc. In this study we apply the approach based on the bending angle for analysis of the spatial and temporal variability of the ABL depth over the subtropical oceanic regions west of the coasts of North America, South America and South Africa. These regions are characterized by a relatively shallow stratocumulus-topped ABL with a strong capping inversion. The study is based on 3 years of COSMIC data. We found very clear seasonal variation with magnitude ~200-300m and weaker diurnal variation with magnitude ~20-100m. The diurnal variation over the oceans shows afternoon minimum which is somewhat opposite to the variation over land (with the afternoon maximum). Show less