Atmospheric Temperatures near the Tropical Tropopause: Temporal Variations, Zonal Asymmetry and Implications for Stratospheric Water Vapor

Abstract

Analysis of temperature measurements obtained over an eight-year period in the vicinity of the low-latitude tropopause confirms the existence of longitude regions which are consistently colder by approximately 2?3 K than elsewhere in the tropics. These temperature differences, however, are confined to a layer of thickness 3?5 km centered on the tropopause. The lowest monthly mean temperatures observed at the colder stations yield saturation mixing ratios that are consistent with the range of measured stratospheric water vapor. Examination of the daily variations in temperature at a given station reveals a more complex pattern than indicated by the monthly averages. On many days temperatures at the colder longitudes correspond to water vapor abundances that are less than observed in the stratosphere despite the favorable comparison of the monthly means. The results point to the need for a series of water vapor soundings at selected longitudes and times in order to define the extent to which the tropical tropopause controls the stratospheric water vapor abundance.