HR: 16:45h
AN: V24A-04    [Abstracts]
TI: Refinement of Effusion Rate Calculations from Handheld Infrared Imagery
AU: * Dehn, J
EM: jdehn@gi.alaska.edu
AF: Alaska Volcano Observatory, Geophysical Institute University of Alaska Fairbanks, Fairbanks, AK 99775 United States
AU: Harris, A
EM: harris@higp.hawaii.edu
AF: HIGP/SOEST, University of Hawaii 1680 East-West Road, Honolulu, HI 96822 United States
AB: Effusion rates have been calculated for active lavas using handheld infrared data at Stromboli and Etna volcanoes. The model, developed for satellite sensors, assumes that a certain volume of lava at a given temperature radiates a given amount of heat, based on its physical properties (e.g. latent heat of fusion, crystal content, density, temperature). The application of this model is more difficult, since the effects of mixed pixels (those with an unknown area of lava less than the pixel area) and the heterogeneous nature of the lava surface are quite large. In the past, an empirical equation was developed for each case, where a threshold pixel temperature was determined as a function of distance to the target (and thus pixel size). This equation had to regularly tested under different atmospheric and eruptive conditions to ensure accurate effusion rate calculations. Rather than an empirical equation dependent on the conditions at each eruption, a relationship has been developed which will work for each case. This has the advantage of saving the time an expense needed to determine the empirical equation. Like the original effusion rate relationship, a threshold temperature for pixels is calculated based on the physical properties of the lava and environmental conditions. A given pixel percentage is chosen (>50% works well), and based on the lava's expected temperature range and ambient conditions (distance to target, viewing angle, atmospheric transmissivity), the threshold temperature at that range can be determined. This refinement agrees well with past measurements, matching the empirical relationships determined for Stromboli. The new method also allows past data sets to be analyzed for effusion rates where no empirical equation was determined during the eruption.
DE: 8411 Thermodynamics (0766, 1011, 3611)
DE: 8414 Eruption mechanisms and flow emplacement
DE: 8419 Volcano monitoring (7280)
DE: 8429 Lava rheology and morphology
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005