Seasonal, Interannual, and Zonal Temperature Variability of the Tropical Stratosphere Based on TOVS Satellite Data: 1987–91

Abstract

A 4½-yr monthly stratospheric temperature record derived from TIROS-N Operational Vertical Sounder satellite observations has been used to study the global variability of the stratosphere in the Tropics. A comparison with an independent set of temperatures (Free University of Berlin) is first discussed. Among the different parameters that influence the tropical stratosphere, 1) the regular seasonal cycle, 2) the quasi-biennal oscillation (QBO), and 3) the El Niño?Southern Oscillation (ENSO) effects are studied in detail. A transition level has been found at about 30 hPa. Below this level, the standard stratospheric seasonal cycle in the temperatures is modulated by ENSO and the QBO, while above, ENSO has no discernible influence. In addition, longitudinal variations of monthly mean temperatures show minima during northern winter months from the tropopause up to 50 hPa over some areas, in relation to convection. Results presented here are also discussed in the view of recently published studies based on either radiosonde reports or microwave satellite measurements. While there is a fair agreement with radiosonde-based studies, more finescale details on the horizontal are obtained due to a much better sampling. Differences with other satellite-based studies are due to a better description of the temperature behavior along the vertical.