Temperature, Humidity, and Wind at the Global Tropopause

Abstract

This study presents global statistics of tropopause parameters for a 15-yr period (1979?93). The parameters are height, temperature, potential temperature, mixing ratio of water vapor, and zonal, meridional and vertical wind. The global tropopause is derived from ECMWF reanalysis data by applying the thermal and dynamical definitions of the tropopause. The tropopause climatology evaluated from the ECMWF reanalysis data is compared with those provided by radiosonde and satellite data. The meridional and zonal variations in the mean tropopause height and temperature reflect the global jet stream structure. The seasonal variation of tropical tropopause temperatures is characterized by a minimum during Northern Hemispheric summer and a corresponding winter maximum. The tropopause mixing ratio of water vapor attains a minimum in the Tropics that increases gradually poleward. The maximum of the relative humidity occurs in the Tropics above the Pacific and Indian Oceans. There are no global trends in the height and temperature of the tropopause but a decrease of about 10% per decade is evaluated for the mixing ratio of water vapor. The negative trend is particularly strong above both polar regions.