Vertical Profiling of the Planetary Boundary Layer from GNSS Radio Occultations

GNSS radio occultations (RO) measurements have been used to estimate the height of the planetary boundary layer (PBL) due to their sensitivity to the strong vertical gradient of refractivity in the transition between the PBL and free troposphere. The limb-viewing, microwave L-band, coherent RO observations provide high vertical resolution profiles that penetrate through clouds and precipitation that are often present above and within the PBL, over both land and ocean surfaces. While the PBL height is a key parameter characterizing the PBL, GNSS-RO can in fact provide valuable information on the vertical distribution of moisture within the PBL. In this presentation, we will highlight our recent work in these areas, focusing on the “decoupling” of the subtropical PBL. We will describe new algorithms developed to improve the refractivity/humidity retrievals within the PBL, definition of the decoupling parameter, validation with radiosondes, and comparison with GCM outputs. Current limitations and future outlooks from GNSS-RO will be discussed.