Seasonal and interannual variability of the stratosphere diagnosed from UKMO TOVS analyses

UK Meteorological Office (UKMO) TOVS analyses are used to show that the record of satellite radiance measurements is now long enough to capture the vast majority of year-to-year variability in the stratosphere. Given this, a climatology of the stratosphere is constructed and used to identify robust hut detailed features of the seasonal evolution in the northern and southern hemispheres. Interannual variability is also investigated. In the northern winter stratosphere, the interannual variability in geopotential height increases monotonically towards the pole. In contrast, in the southern hemisphere the largest interannual variability occurs in a collar of high values surrounding a low-variability region over the pole. For the Tropics, we show that quasi-biennial and semiannual oscillations in the tropical zonal wind can be derived from the geopotential-height analyses. However, comparisons of tropical winds from three different methods of analysis show that the current meridional resolution of the analysis limits the accuracy of the stratospheric winds over the equator. Finally, the satellite radiance data are used to derive updated temperature trends for the stratosphere. These show a cooling trend throughout most of the stratosphere that increases with height above the tropopause and exceeds 2 K per decade at the stratopause.