Interannual-to-decadal Variability of Stratospheric Chemistry and Climate during the 20th century

Stratospheric interannual-to-decadal variability is dominated to a large degree by external forcings, such as variability of the sun, volcanic eruptions, as well as by internal factors like El Niño Southern Oscillation (ENSO) variability and the quasi-biennial oscillation (QBO). The current data records as well as model simulations addressing stratospheric chemical climate variability mostly cover the past few decades only, which often is not sufficient to address interannual-to-decadal variability.

Here we present results of transient simulations with the chemistry-climate model (CCM) SOCOL, spanning the whole 20th century. SOCOL is a combination of the middle atmosphere version of ECHAM4 (MPI, Hamburg) and the chemistry-transport model MEZON (PMOD/WRC, Davos). The simulations are carried out in ensemble-mode (9 members) prescribing sea surface temperature, sea ice distribution, volcanic aerosols, solar variability, greenhouse gases, ozone depleting substances, land surface changes, and QBO.

We will present an extensive validation of model results against various observational and (prior to 1957) reconstructed upper-air datasets as well as several long total ozone series (Oxford starting in 1924, Arosa in 1926, Tromso in 1935, and Spitsbergen in 1950). Furthermore we will also show results of process-oriented validation methods in the framework of the CCMval.

Results on the effect of solar and volcanic forcings as well as on the effect of ENSO on the stratosphere will be presented.