Use of radio occultation for long-term tropopause studies: uncertainties, biases, and instabilities.

Research suggests that changes in tropopause structure can both indicate and impact changes in the global climate system. The Global Positioning System radio occultation (RO) technique shows tremendous potential for monitoring the global tropopause due to its precision, temporal consistency, and global measurement density. This study examines the capability of RO to monitor the global tropopause by addressing three specific objectives: (1) quantify sources of error in individual RO tropopause measurements, (2) examine absolute bias and long-term stability of RO tropopause parameters with respect to those obtained from radiosondes, and (3) distinguish between errors due to processing and RO instrument differences by comparing tropopause parameters from different RO products. In this study, we make use of data from four different RO missions, including the recent COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate).