Upwelling across the tropical tropopause diagnosed from ozone observations and meteorological re-analyses

Upwelling across the tropical tropopause as a measure of the strength of the stratospheric Brewer-Dobson circulation is estimated from ozone observations and from meteorological re-analyses of the European Centre for Medium Range Weather Forecast (ECMWF). Upwelling from ozone observations is estimated by using the observed vertical ozone gradient and calculated chemical ozone production and loss terms. We calculate upwelling from the ECMWF reanalyses in three ways: (a) directly through the transformed Eulerian mean approach, (b) from momentum balance and the principle of downward control and (c) through diabatic heating rates. Upwelling estimated from ozone observations of the Halogen Occultation Experiment (HALOE) over the period 1992-2005 agrees well with upwelling from the ERA-Interim re-analysis. A clear QBO signal is visible in the tropical upwelling at altitudes above ~70hPa, while much of the variability seen in upwelling across the tropical tropopause can be related to changes in tropical sea surface temperatures and the ENSO index.