New Characteristics of the Tropical Tropopause Revealed by CHAMP/GPS Measurements

抄録

Structure and variability of the tropical tropopause are presented using radio occultation measurements by CHAMP/GPS (CHAllenging Mini satellite Payload/Global Positioning System) from May 2001 to December 2004 (with a total of 175,149 occultations). The tropopause heights defined by both lapse rate and cold point generally show large-scale, off-equatorial maxima (tropopause increase at 20°N or S than at equator), and sometimes even a high tropopause for about 0.3 to 0.65 km (on an average) at 20°N and S simultaneously than at the equator along a particular meridian, in contrast to our previous knowledge. Although this feature has already been reported partially during the summer monsoon season, the present study shows the seasonal and geographical distributions of the tropical tropopause comprehensively using a new promising observational technique. In addition, the vertical shape of the tropopause is found to be sharp in the equatorial region and broad in the subtropics especially in northern winter. Possible mechanisms are discussed in light of dynamical and radiative processes.