Trends in the global tropopause estimated from GPS radio occultation data

T. SCHMIDT1, A. DE LA TORRE2, P. ALEXANDER2, C. ARRAS1, G. BEYERLE1, S. HEISE1, P. LLAMEDO2, J. WICKERT1, AND M. ROTHACHER1

Bologna, Italia

Congreso; SPARC; 2008

We examine global tropopause variability on the basis of zonal monthly means using GPS radio occultation (RO) data from 2001-2008. The RO technique uses GPS signals received aboard low Earth orbiting satellites for atmospheric limb sounding. Atmospheric temperature profiles are derived with high vertical resolution. Due to its long-term stability, all-weather capability and global coverage the GPS RO technique offers the possibility for global monitoring of the tropopause and for detection of changes in tropopause parameters. The German CHAMP mission delivers RO data continuously since May 2001, thus generating the first long-term GPS RO data set. In our study we found a global increase of the tropopause height between 26-44 m during the observation period depending on the binning method (5 deg or 10 deg latitude bands) and the used tropopause detection algorithm. The corresponding trend errors vary between 18-21 m. The inclusion of the QBO in the regression model leads to a global increase of the LRT height up to 5 m (10%) during the time period depending on the binning. The global tropopause height variations are positively correlated with upper tropospheric (500-100 hPa) and anti-correlated with lower stratospheric (100-30 hPa) temperature variations.