Title: Characteristics of tropopause parameters as observed with GPS radio occultation
Abstract: Abstract. Characteristics of the lapse rate tropopause are analyzed globally for tropopause altitude and temperature using Global Positioning System (GPS) Radio Occultation (RO) data from late 2001 to 2012. RO profiles feature high vertical resolution and excellent quality in the upper troposphere and lower stratosphere, which are key factors for tropopause determination, including multiple ones. Furthermore, global coverage is reached on a monthly basis, allowing to examine both temporal and spatial characteristics thoroughly. To investigate latitudinal and longitudinal tropopause characteristics, the mean annual cycle, and inter-annual variability, we use tropopauses from individual profiles as well as their monthly mean and median for 10° zonal bands. The latitudinal structure of first tropopauses shows the well-known distribution with high (cold) tropical tropopauses and low (warm) extratropical tropopauses. In the transition zones (20° N/S to 40° N/S), individual profiles reveal varying tropopause altitudes from 7 km to 17 km due to the influence of the subtropical jets. In this region, we also find multiple tropopauses throughout the year. Longitudinal variability is strongest at northern hemispheric mid latitudes and in the Asian monsoon region. The mean annual cycle features changes in amplitude and phase depending on latitude. This is caused by different underlying physical processes (such as the Brewer-Dobson Circulation) and atmospheric dynamics (such as the very strong polar vortex in southern hemispheric winter). Inter-annual anomalies of tropopause parameters show signatures of El Niño–Southern Oscillation, the Quasi-Biennial Oscillation, and the varying strength of the polar vortex, including sudden stratospheric warming events.