Tropical tropopause in Tibet: Insights from ground‐based global navigation satellite system and space‐based radio occultation observations

Abstract

Abstract Changes in the tropopause can explain regional and global weather and climate. In Tibet, there are few radiosonde stations, and the detection height is not high enough. Radio occultation (RO) data are insufficient because of the small regional scale, which is not conducive to the analysis of tropopause change. Moreover, in some middle and high latitudes, it was more difficult to identify the tropopause height from the temperature profile. In this study, an improved method has been developed for the inversion of the tropical tropopause based on a ground‐based global navigation satellite system (GNSS) network combined with reanalysis data. Using zenith tropospheric delay data from 49 GNSS reference stations in Tibet from January 2017 to December 2019, combined with ERA5 reanalysis, the tropical tropopause (TPH) was successfully inversed, its temporal and spatial distribution is analysed, and compared with ERA5‐derived TPH obtained by the temperature profile of the interpolated co‐site points. In more than 90% of cases, the difference between the two is <2 km. The root mean square of the tropopause difference detected by GNSS‐derived TPH and RO‐derived TPH was ±1.25 km; the accuracies were at the same level. By combining the tropopause obtained from ground‐based GNSS and that from space‐based RO, temporal and spatial changes in the tropopause were analysed. The tropopause in Tibet has a latitude‐zoning distribution with obvious unimodal seasonal changes. Monthly changes excluding seasonal variation indicate a slight downward trend from 2017 to 2019. At the same time, changes in the tropopause are closely related to those in weather and climate. The results of this study confirm that the combination of ground‐based GNSS and space‐based RO can realize long‐term, continuous, and full coverage monitoring of the regional tropopause. This expands the application possibilities of ground‐based GNSS.

Keywords

• global navigation satellite system
• Qinghai–Tibet Plateau
• radio occultation
• tropopause
• zenith tropospheric delay