Observing Popocatepetl’s Volcanic Clouds Using MODIS Infrared data M. Alexandra Matiella 1(mamatiel@mtu.edu) Hugo Delgado-Granados 2 (hugo@tonatiuh.igeofcu.unam.mx) William I. Rose 1 (raman@mtu.edu) I. Matthew Watson 1 (watson@mtu.edu) 1Dept. of Geological Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931-1295, USA 2Instituto de Geofisica, Universidad Nacional Autonoma de Mexico (UNAM), Mexico

Abstract

Popocatepetl Volcano, Mexico, is a tropical volcano with significant and persistent emissions of SO2 and ash. These emissions pose significant hazards to the large population in close proximity to the volcano and are an important indicator of eruptive activity (Love et al., 1998, Nature 396: 563-566). Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery provides us with a synoptic perspective of volcanic emissions and atmospheric interactions, information unavailable from ground-based or aircraft studies, which can be useful for hazard mitigation. We report on MODIS data during December 2000 and January 2001 coincident with abundant emissions based on COSPEC data. SO₂ masses are retrieved using the 7.3 µm and 8.6 µm absorption features of SO₂ (7.3 µm method after Prata et al, in press, AGU Volcanism Atmospheric Monograph; 8.6 µm method after Realmuto et al, 1997, J. Geophys Res 102: 15057-15072). Ash masses are retrieved using silicate absorption features at 11 µm and 12 µm (Wen & Rose, 1994, J Geophys Res 99: 5421-5431). Furthermore, this data set tests the accuracy of the algorithms and the conditions under which the algorithms work best, and can be compared to COSPEC measurements taken by Popocatepetl’s monitoring team. We found that MODIS data often showed more than one volcanic cloud. For example, one MODIS image collected January 23rd, 2001, at 0450 UT, shows four large eruptions that have dispersed volcanic clouds over an extensive area of Mexico. Using upper air data and monitoring records, the movements of the 4 ash clouds are fit with eruption times and winds, and using retrieval data for SO₂ and ash we can derive a time based SO₂ and fine ash emission record. The results of these retrievals compliment ground-based measurements which cannot measure large scale eruptions.