Infrared heating rates in the stratosphere due to volcanic sulphur dioxide

A narrow-band radiative-transfer model is used to assess potential infrared cooling rates due to SO2 injected into the stratosphere by volcanic eruptions. In addition to SO2 profiles representing the eruptions of El Chichon and Pinatubo, two hypothetical SO2 profiles following a massive volcanic eruption are used. The net radiative impact of the SO2 depends on the vertical distribution as well as the altitude and magnitude of its injection. For broader distributions the magnitudes of the infrared heating rates are comparable with those due to heating caused by the absorption of solar ultraviolet by SO2 tending to enhance the hearing of the lower stratosphere and reduce it in the upper stratosphere. These results are explained in terms of the relative strengths of the SO2 bands and of those of H2O and O-3 overlapping in the same spectral regions.