NASA - National Aeronautics and Space Administration

Cold point tropopause temperature is a key regulator of cirrus clouds and stratospheric water vapor, which have significant impacts on the Earth’s radiation budget and climate. Using tropical radiosonde observations, we show that waves in the tropical tropopause layer lower cold point temperature by 1.6 K on average relative to the seasonal mean. Furthermore, wave activity in the tropical tropopause layer has not been constant over the last 2.5 decades, altering the magnitude of the wave impacts on cold point temperature at a decadal scale. The change in the direct wave impact is partially (~20–30%) responsible for the sudden decrease in cold point temperature and stratospheric water vapor at the end of 2000, which has not been fully explained by changes in the Brewer-Dobson circulation. We further show that these wave impacts are not well represented in reanalysis data.