(a) Top Deseasonalized anomalies of tropical (20°S–20°N) tropopause temperatures from the GPS-RO (blue) and MERRA data (red). The black line indicates the influence of stratospheric aerosols estimated by linear regression (see details in “Data and Methods”). Bottom Tropical tropopause anomalies from MERRA data (red) where the influences of stratospheric aerosols has been removed according to the aerosol regression on top. The thick black line represents low-pass filtered (6 years) data. (b) Power spectrum of tropical tropopause temperatures from MERRA data without influences of stratospheric aerosol for the period 1979–2014. The thick black line indicates the best fit based on a first-order autoregressive model, whereas the dashed black line indicates the 95% confidence level. Dashed lines in the vertical indicate time periods of 9 and 13 years.