The LIF-SO2 instrument detects sulfur dioxide at the single-part per trillion (ppt) level using red-shifted laser-induced fluorescence. It has operated on the WB-57 and Global Hawk aircraft in the UT/LS, as well as on the DC-8. Sulfur Dioxide is an important precursor for aerosols including nucleation of new particles globally and can be greatly enhanced in the stratosphere following explosive volcanic eruptions. An important implication of the Asian Monsoon is transport of aerosol precursors including SO2 into the lower stratosphere.