Observations of variability in the polar upper troposphere and stratosphere using GPS radio occultation data

The recent availability of Global Positioning System (GPS) radio occultation data sets has provided an unprecedented high vertical resolution view of the polar regions of the upper troposphere and stratosphere that are poorly sampled by ground-based radiosonde data sets. In this study, GPS profiles from the CHAMP and COSMIC satellite missions are used 1) to establish the high vertical resolution climatology of the Arctic and Antarctic upper troposphere and stratosphere and 2) to investigate the variability about this climatology. One particular focus of the project is the tropopause inversion layer (TIL), a sharp temperature inversion in a narrow layer above the extratropical tropopause. During the summer months, the polar TIL is stronger and more clearly defined than during the winter months. However, preliminary research suggests that the strength of the Northern Hemisphere wintertime TIL can be modulated by intraseasonal dynamic variability in the stratosphere. The strengthening of the polar TIL following a sudden stratospheric warming event may be relevant to the communication of stratospheric circulation anomalies to tropospheric levels that is often observed during the same period.