Characterizing the Vertical Stratification of the Planetary Boundary Layer from Space with GNSS Radio Occultation

GNSS radio occultation (RO) from COSMIC and other missions has demonstrated strong potential in sensing the Planetary Boundary Layer (PBL) from space. In particular, multiple studies have shown that GNSS-RO profiles can be used to infer PBL heights over the globe. The algorithms used to estimate the PBL heights are based on the strong vertical change in variables such as specific humidity, temperature, refractivity, or bending angles in the transition from the PBL to the free troposphere. These methods are especially effective over the subtropics where the transitions can be very sharp.

In this study, we investigate the vertical structure within the PBL retrieved from GNSS-RO. We define a decoupling parameter that characterizes the change in specific humidity within the PBL. The decoupling parameter obtained from GNSS-RO is validated with radiosonde soundings from the MAGIC campaign over the Northeast Pacific Ocean. We then present climatologies of the decoupling parameter over different ocean basins and compare the GNSS-RO results with those obtained from ECMWF analysis and climate models. Limitations of the GNSS-RO observations in sensing the PBL vertical structure will be discussed, and our recent works in addressing these limitations will be summarized. Finally, we will discuss the potential benefits for PBL remote sensing from the recently launched COSMIC-2 GNSS-RO mission.