An Analysis of the Temporal and Spatial Variations of the Global Tropopause with COSMIC Radio Occultation Bending Angles

Abstract

As the transition layer between the troposphere and the stratosphere, the structure of the tropopause is closely related to the weather and climate of the near-surface layer. The variation of the tropopause parameters including the height, the temperature and the pressure of the tropopause are sensitive indicators of climate variability and global change. Characterized by the advantages of high vertical resolution, low-cost, global coverage, and all-weather capability, the Global Positioning System (GPS) radio occultation (RO) technology provides rich observation data for the study of the global tropopause structure. The precise identification of the tropopause height is the prerequisite for the accurate determination of the tropopause temperature and pressure. The tropopause height identified from GPS RO temperature profile will be affected by the errors brought out by the assumptions and the prior atmosphere background applied in the inversion process of the temperature profile. To determine the tropopause height directly from RO bending angle profile is an effective way to avoid such errors. In this paper, the natural logarithm objective covariance transform method is used to identify the tropopause height from GPS RO bending angle profiles. With the GPS RO data from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) mission, the spatial and temporal variations of the global tropopause parameters included height, temperature and pressure are analyzed. It is found that the latitudinal distribution characteristics of the tropopause parameters are distinct and the seasonal variation trends of the tropopause structure are significant. It is also found that the temporal and spatial distributions of the tropopause parameters are asymmetric over the northern and the southern hemispheres.