Whilst flowing across the area between the two columns that cold air does not warm up by compression despite falling in height because it remains in contact with stratospheric air with which it can freely exchange energy by conduction and mixing. (newclimatemodel.com)
Studies using SF6 to estimate the mean age of stratospheric air have assumed the influence of mesospheric photochemical destruction is negligible. (pubs.giss.nasa.gov)
Cold air at the top of ascending columns is forced to one side by warmer air continuing to flow up from beneath but it is blocked by the warmer stratospheric air above and so flows laterally and downward to the top of descending columns, following the undulating slope of the tropopause. (newclimatemodel.com)