Trends in the global tropopause thickness revealed by radiosondes

The first global trends in the thickness of the tropopause layer (TL) are analyzed based on radiosonde data in the Integrated Global Radiosonde Archive (IGRA) for the period of 1965-2004. It reveals that TL has been thickening for the entire globe with positive trends of 0.16±0.12km/decade during this period. Statistically significant thickening is observed in the tropics, North Hemisphere (NH) extratropics, and NH poles. Accompanied by overall cooling of -0.58±0.40K/decade in TL's top, remarkable rising trends of 0.35±0.29km/decade are observed in the correspoding height. However, the anti-correlation of the trends in the tropopause temperature and the corresponding height is not observed in its lower boundary, namely the first lapse rate tropopause (LRT), for all the latitude bands as suggested by the previous studies. The results imply that the temperature of the TL is primarily couple with the height of its upper boundary as the thickness of the TL is more correlated with the temperature of the lower stratosphere than with the tempeature of the upper troposphere. Long-term changes in TL may in turn carry more information how tropopause change in response to climate change than in the sharp "tropopause surface" only.