The 1991 Pinatubo volcanic clouds from a satellite remote sensing perspective

In this study, ultraviolet TOMS (Total Ozone Mapping Spectrometer) satellite data for SO₂ are re-evaluated for the first 15 days following the June 15, 1991 Pinatubo eruption to reflect new data retrieval and reduction methods. Infrared satellite SO₂ data from the TOVS/HIRS/2 (TIROS Optical Vertical Sounder/High Resolution Infrared Radiation Sounder/2) sensor are also analyzed for the first time for-Pinatubo. Extrapolation of SO ₂ masses calculated from TOMS and TOVS satellite measurements 19–118 hours after the eruption suggest initial SO₂ releases of 15 ± 5 Mt for TOMS and 19 ± 4 Mt for TOVS, including SO₂ sequestered by ice in the early Pinatubo cloud. To estimate the total S released we must also include SO₂ which was rapidly converted to sulfate aerosol during eruption, about 3 ± 3 Mt. Thus the total S release by Pinatubo, calculated as SO₂, is 18 ± 7 Mt based on TOMS and 22 ± 5 Mt based on TOVS. The SO₂ removal from the volcanic cloud during 19–374 hours of atmospheric residence follows overall e-folding times of 25 ± 8 days for TOMS and 23 ± 5 days for TOVS. These removal rates are higher in the first 118 hours after eruption, reflecting rapid fallout of ice and ash, which can catalyze SO₂ conversion.; Pinatubo's June 15, 1991 eruption was Earth's largest of the last 25 years and it formed a substantial volcanic cloud. We present results of analysis of satellite-based infrared remote sensing using AVHRR (Advanced Very High Resolution Radiometer) and TOVS'HIRS/2 sensors during the first few days of atmospheric residence of the Pinatubo volcanic cloud, as it drifted from the Philippines toward Africa. An SO₂-rich upper (25km) portion drifted westward slightly faster than an ash-rich lower (22km) part, though uncertainty exists due to the difficulty in precisely locating the ash cloud.; The Pinatubo clouds contained particles of ice, ash, and sulfate which could be sensed with infrared satellite data. Multispectral IR data from HIRS/2 were most useful for sensing the Pinatubo clouds because of the subequal amounts of ice and ash present. Ice and ash particles had peak masses of about 80 Mt and 50 Mt, respectively, within the first day of atmospheric residence and declined very rapidly to values that were <10 Mt within 3 days. Ice and ash declined at a similar rate and it seems likely that ice and ash formed mixed aggregates which enhanced fallout.; Sulfate particles were detected in the volcanic cloud by IR satellites very soon after eruption and their masses increased systematically at a rate consistent with their formation from SO₂, which was slowly decreasing in mass during the same period. The initially detected sulfate mass was 3.3 Mt and then after 5 days was 12–16 Mt.