Seminar

Abstract

Stratospheric aerosols are an important and variable term in Earth's energy budget. Due to the lifetime of these particles being ~ 100 times that of tropospheric aerosols, the small sources of these particles are disproportionally significant for climate. Since the discovery of the Junge Layer in the 1960s the sources of sulfur that maintain these particles has been debated, with carbonyl sulfide (COS) and sulfur dioxide (SO₂) transported from the troposphere being suggested as the most-likely important precursor gases. The stratospheric SO₂ source during volcanically quiescent periods is highly uncertain because until recently, SO₂ had never been measured in-situ at the tropical tropopause where this gas would primarily enter the stratosphere.

To help address this issue we have developed a new laser-induced fluorescence based instrument with a detection limit for SO₂ in the single-ppt range and deployed it on the NASA WB-57F to acquire measurements at and above the tropical tropopause during October 2015 on a mission called VIRGAS. In this talk I will describe the new instrument and it's capabilities, and will present comparisons of the VIRGAS measurements with the MIPAS and ACE-FTS satellite instrument retrievals, and with simulations from the WACCM and GEOS-5 global models. The implications for the importance of SO₂ transport into the stratosphere as a source of background aerosols will be discussed.