Monitoring the Atmospheric Boundary Layer by Radio Occultation Signals Recorded by COSMIC Satellites

The Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) uses radio occultation (RO) observations of the Global Positioning System (GPS) satellites to retrieve vertical profiles of the bending angle and refractivity in the atmosphere. Unlike previous RO missions utilizing the phase-locked loop (PLL) signal tracking technique, COSMIC receivers record L1 GPS signals in open-loop (OL) mode in the lowest 10 km of the troposphere by allowing penetration of the retrieved profiles down to the ocean surface. This provides an opportunity for monitoring the atmospheric boundary layer (ABL) with high vertical resolution (50-100 m), not available from other satellite data and not generally possible with PLL RO data from previous RO missions due to insufficient penetration and tracking errors. The optimal way of utilizing information about the ABL from RO observations is direct assimilation of the inverted bending angle and refractivity profiles into atmospheric models with sufficiently high vertical resolution in the lower troposphere. Alternatively, estimates of the depth of the ABL, which is an important parameter for meteorology and climatology, can be extracted from the structure of RO signals and inverted profiles. Such methods and results of their application to COSMIC RO data will be discussed.