Stratosphere stratosphere 12 Temperature 8 Upper atmosphere 8 MSU 6 Principal component analysis 6 Southern Hemisphere 6 Troposphere 6 Atmospheric temperature 4 Climate change 4 Climatology 4 Double tropopause 4 Extratropical tropopause layer 4 Gravity waves 4 Meteorology 4 Radiosondes 4 Rawinsonde 4 Single tropopause 4 South America 4 Thermal effects 4 Tropopause climatology 4 Variability 4 Zonal waves 4 climatology 4 extratropical environment 4 jet stream 4 microwave radiometer 4 spatiotemporal analysis 4 subtropical region 4 temperature anomaly 4