A climatology of multiple tropopauses derived from GPS radio occultations with CHAMP and SAC-C

A global climatology of multiple tropopauses (MT) is discussed based on Global Positioning System (GPS) radio occultation (RO) data from the German CHAMP (CHAllenging Minisatellite Payload) and the US-Argentinian SAC-C (Satelite de Aplicaciones Cientificas-C) satellite mission for the period May 2001 - April 2005. In this study we present first detailed investigations about the geographical and temporal distribution of MT during different seasons. The thickness of the layer between the lowest (first) and highest (last) tropopause has a strong annual cycle. In the vicinity of the subtropical jet (STJ) stream region values vary between 4 - 5 km during winter and 2 - 3 km during summer, respectively, whereas higher differences were found on the northern hemisphere. It is shown that the occurrence distribution of MT is in good agreement with the mean climatological location of the STJ (30 degrees-40 degrees) on both hemispheres, in particular during winter time.