Characteristics of the Trends in the Global Tropopause Estimated From COSMIC Radio Occultation Data

This paper discusses the variabilities and trends in the global tropopause based on the gridded monthly mean Global Positioning System radio occultation data from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission during July 2006–February 2014. We find that the tropopause height can reflect El Nino–Southern Oscillation (ENSO) events. The correlation coefficient between global tropopause height anomalies and the Nino 3.4 sea surface temperature index is 0.53, with a maximum correlation coefficient of 0.8 at a lag of three months. We present first the detailed investigations about the spatial distribution of trends in tropopause parameters in each 10° $\times$ 5° longitude–latitude grid cell over the globe and find that the rates of change in the tropopause parameters during this time period are high in some particular regions such as the Southern Indian Ocean, Antarctica, Western Europe, North Pacific, and the east coast of North America. An analysis of global monthly means of the tropopause parameters indicates a global tropopause height increase of 0.03 $\pm$ 2.36 m/year during 2006–2014, with a corresponding temperature increase of 0.020 $\pm$ 0.008 °C/year, and a pressure increase of 0.11 $\pm$ 0.059 hPa/year. The upward trend of tropopause height is significantly weaker than that in the past years, which might be attributed to the expected stratospheric ozone recovery associated with the Montreal Protocol, the global warming slowdown, and the abnormal global climate change in recent years. The trends of the tropopause parameters are the most significant over the Southern Indian Ocean and Antarctica during September/October/November, which could be due to the stratospheric ozone recovery.