All wind and temperature observations use ERA-I (1989-2008).

Observational uncertainty for wind fields comes from the UKMO analysis (1992-2001) and for temperature fields comes from MERRA (1989-2008).

Water vapour observations use MERRA (1989-2008), with observational uncertainty from ERA-I (1989-2008).

Age of air observations are from

Andrews, A. E., and Coauthors, 2001: Mean ages of stratospheric air derived from in situ observations of CO2, CH4, and N2O. J. Geophys. Res., 106 (D23), 32295-32314.

Engel, A., and Coauthors, 2009: Age of stratospheric air unchanged within uncertainties over the past 30 years. Nat. Geosci., 2, 28-31, doi:10.1038/NGEO388.

The polar night jet and easterly jet strengths measure how realistic the zonal wind climatology is in the stratosphere.  Extratropical T(50hPa) is important for polar stratospheric cloud formation (in wind/spring).  The QBO is a good measure of tropical variability in the stratosphere.  The cold point (100hPa) temperature is an important factor in determining the stratospheric water vapour concentrations at entry point (70hPa, 10S-10N), and this in turn is important for the simulation of stratospheric chemistry, and for the correct radiative balance.  Age of air diagnoses how well the stratospheric meridional mass circulation is simulated.
