The Tropopause in the Polar Regions

Abstract

Abstract The polar and subpolar tropopause in both hemispheres is investigated using the ECMWF Reanalysis (ERA) data from 1979 to 1993 and radiosonde data from 1989 to 1993. Both the thermal and the dynamical criteria are applied to each dataset. The tropopauses derived from the radiosonde data are used to validate the ERA-derived tropopauses and to investigate the sharpness of the tropopause. The validation reveals that the ERA data are well suited for the determination of the tropopause. A comparison between the thermal and the dynamical tropopause shows a very good agreement except for polar winter, and there is clear evidence that the dynamical criterion is more appropriate in winter. The results show that the annual cycle of the polar tropopause can be classified into three different patterns. A single wave with a tropopause pressure maximum in winter and a minimum in summer is typical for the subpolar parts of eastern Siberia and North America. A double wave with pressure maxima in spring and autumn...