Observing the upper troposphere and lower stratosphere with GPS radio occultation data: Results from CHAMP, GRACE and COSMIC

SCHMIDT, T.; WICKERT, J.; HASER, A.; DE LA TORRE A.; ALEXANDER, P.; S. HEISE; G. BEYERLE

Workshop; 4th Cosmic Data users Workshop; 2009

The radio occultation (RO) technique uses GPS signals received aboard low Earthorbiting satellites for atmospheric limb sounding. Atmospheric temperature profilesare derived with high vertical resolution. Due to its long-term stability, all-weathercapability and global coverage the GPS RO technique offers the possibility for globalmonitoring of the tropopause and temperature structure in the upper troposphere andlower stratosphere (UTLS) region. The German CHAMP (2001-2008), theUS/German GRACE (since 2006), the Taiwan/US FORMOSAT-3/COSMIC (since2006), and the German TerraSAR-X (since 2007) missions provide about 2500occultation measurements daily. An overview of recent results from RO data is given with respect to• tropopause and temperature trends in the UTLS region: A global increase ofthe tropopause height is observed combined with a global upper troposphericwarming of about 0.1 K/year and a cooling of 0.1–0.2 K/year above thetropopause for the time interval 2001-2009.• global gravity wave (GW) activity in the UTLS: The specific potential energy asa measure of GW activity is deduced from the temperature profile for eachoccultation event up to 35-40 km. To separate the GWs from the backgrounda band-pass filter associated to different vertical wave lengths is applied to themeasured temperature profiles. Seasonal changes of GW activity will bediscussed and results from COSMIC with the higher spatial density comparedwith the other single RO missions will be highlighted.