HR: 1400h
AN: V43A-07 [Abstracts]
TI: Photometric Observations of Aerosol Plumes From Lascar Volcano, Chile
AU: * Rodriguez, L A
EM: larodrig@mtu.edu
AF: Geological and Mining Engineering & Sciences, Michigan Technological University, 1400
Townsend Drive, Houghton, MI 49931, United States
AU: * Rodriguez, L A
EM: larodrig@mtu.edu
AF: Department of Geology, University of Puerto Rico - Mayaguez Campus, PO Box 9017,
Mayaguez, PR 00681, Puerto Rico
AU: Watson, I
EM: Matt.Watson@bristol.ac.uk
AF: Geological and Mining Engineering & Sciences, Michigan Technological University, 1400
Townsend Drive, Houghton, MI 49931, United States
AU: Watson, I
EM: Matt.Watson@bristol.ac.uk
AF: Earth Sciences, University of Bristol, Queen's Road, Bristol, BS8 1RJ, United Kingdom
AU: Viramonte, J G
EM: viramont@unsa.edu.ar
AF: Instituto GEONORTE, Facultad de Ciencias Naturales, Universidad Nacional de Salta,
Buenos Aires 177, Salta, Argentina
AU: Poodts, M
EM: marpoodts@yahoo.com.ar
AF: Instituto GEONORTE, Facultad de Ciencias Naturales, Universidad Nacional de Salta,
Buenos Aires 177, Salta, Argentina
AU: Cabrera, A
EM: agustincabrera@yahoo.com
AF: School of Geosciences, Monash University, Victoria 3800, Australia
AU: Amigo, A
EM: Alvaro.Amigo@bristol.ac.uk
AF: Earth Sciences, University of Bristol, Queen's Road, Bristol, BS8 1RJ, United Kingdom
AU: Rose, W I
EM: raman@mtu.edu
AF: Geological and Mining Engineering & Sciences, Michigan Technological University, 1400
Townsend Drive, Houghton, MI 49931, United States
AU: Oppenheimer, C M
EM: co2000@com.ac.uk
AF: Department of Geography, Cambridge University, Downing Place, Cambridge, CB2 3EN,
United Kingdom
AU: Bluth, G J
EM: gbluth@mtu.edu
AF: Geological and Mining Engineering & Sciences, Michigan Technological University, 1400
Townsend Drive, Houghton, MI 49931, United States
AB:
Lascar volcano, Chile, is the most active volcano in the Central Andes region. We conducted field campaigns at
Lascar during October-November 2002 and December 2004, using a visible to near infrared Microtops II sun-
photometer to measure spectral optical depths in order to infer particle size distributions of volcanic aerosols in
the volcanic plume. Through this method we hope to increase the understanding of emission and conversion
processes of tropospheric volcanic aerosols, specifically on atmospheric conditions similar to those at Lascar (a
high volcano in a dry atmosphere). Data were collected on October 26, 28 to 31 (2002), November 5, 10, and 12
(2002), and December 2, 3, 4, and 8 (2004). We conducted Langley calibrations of the instruments during both
campaigns, on 28 October 2002 and 3 December 2004. The optical properties of tropospheric volcanic aerosols
were retrieved after the removal of the background optical depth. The plume optical depths for most of the 2002
data were extremely low (generally below 0.1), which is probably caused by the extreme dry conditions of the
region (RH<15%). This result also shows that the plumes were very optically thin. Through the application of
the Ångstrom equation and a King-type inversion, the Ångstrom coefficients (alpha and beta), the particle
size distribution, and the effective radius were determined. Alpha averaged 1.5 to 1.9 for the 2002 data, which are
large positive values, indicating that the particle distribution is dominated in number by small particles. The
particle distribution spectra indicate bimodal distributions. The smallest radius mode is believed to be a
nucleation mode consisting of particles generated by gas and aqueous phase oxidation of SO2 to
H2SO4. The largest radius mode probably consists of large water droplets and/or ice. Variation in the
relative size of the modes is a function of emissions and/or meteorological conditions. Preliminary results for the
2004 data show optically thin plumes, with lower plume optical depths than those of 2002.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 8408 Volcano/climate interactions (1605, 3309)
DE: 8409 Atmospheric effects (0370)
DE: 8485 Remote sensing of volcanoes
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly