Thermal Variability of the Tropical Tropopause Region Derived From GPS/MET Observations

Randel, W. J. and Wu, F. and Rios, W. R. (2002) Thermal Variability of the Tropical Tropopause Region Derived From GPS/MET Observations. Submitted to Journal Geophysical Research.

Abstract

Structure and variability of temperatures in the tropical upper troposphere and lower stratosphere (~10-30 km) and studied based on Global Positioning System Meteorology (GPS/MET) observations during April 1995-February 1997. Comparisons with several hundred co-located radiosondes demonstrates the high accuracy of GPS/MET retrievals in the tropics. Mean structure and variability of the tropical cold point tropopause is examined, and much of the sub-seasonal variability in cold point temperature and height appears to be related to wave-like fluctuations (such as gravity waves or Kevin waves). Significant correlations are found between the GPS/MET temperatures and daily, gridded outgoing longwave radiation data (a proxy for tropical deep convection), providing independent confirmation of the GPS/MET temperature fluctuations. These correlations quantify the large-scale tropical temperature response to transient convection, showing coherent wave-like variations over ~12-18 km which span a hemisphere in longitude. The GPS/MET data also show clear evidence of the stratospheric quasi-biennial oscillation (QBO) in temperatures over altitudes ~16-40 km.