Colloquium: 2 Dec 2008, EN6060, NOTE: 10 am

Abstract:
In the global tropospheric-stratospheric mass exchange pattern, air enters the stratosphere mainly through the tropical tropopause. Size resolved aerosol concentration profiles have been obtained using in situ balloon-borne measurements in the tropics. Two profiles were obtained during the monsoon seasons in Niamey, Niger (130 N) (July-August 2006) and one profile from Darwin, Australia (130S) during November 2005. These measurements show large particles (> 1 um) in the lower stratosphere in one of the Niger profiles (31 July) and also in Australia. Such large particles have not been observed in mid-latitude balloon-borne measurements, Satellite data analyses have also been carried out to look for any evidence of such tropospheric air intrusion into the stratosphere in the tropics. The SAGE II 1 um extinction data were analyzed over 15 years to look for the frequency of tropospheric air intrusion into the stratosphere. AURA MLS data have been used to look for evidence of tropospheric air in the stratosphere near the time of the measurements in Niger and Australia.