Improved remote sensing estimates of lava flow cooling: A case study of the 1991–1993 Mount Etna eruption

Abstract

Abstract. Infrared radiance data acquired by the Landsat thematic mapper (TM) provide information regarding the thermal state of active lavas, which can be used to estimate flow surface temperatures and thus lava cooling. Saturation of one or both of TM's short-wave infrared (SWIR) wavebands has meant, however, that previous studies of lava flow cooling have approximated what is almost certainly an n thermal component flow surface temperature distribution (where n > 1), with a single pixel-integrated temperature (PIT). We show that the high sensitivity of TM's SWIR wavebands to the small amount of high-temperature (e.g., ~ 1000øC) material exposed in hot fractures within the flows cooler (e.g., ~200øC) surface crust results in the calculation of PITs that are higher than the temperature of this crust, which is usually the dominant radiative component. This causes heat loss from such pixels to be overestimated. We present adaptations that allow more realistic heat loss estimates to be produced using TM data by assuming that a second hightemperature component contributes to the radiance measured from saturated pixels and by defining an appropriate range for the temperature of the lava crust. By analyzing a suite of five TM images acquired during the 1991-1993 eruption of Mount Etna we present more realistic estimates of how this flow cooled, as well as results that show how the flow regime of the lava evolved over time. The methods we present will continue to be of use as, although the next generation of high spatial resolution sensors such as the Landsat 7 enhanced thematic mapper plus (ETM+) and the Terra advanced space-borne thermal emission and reflection radiometer (ASTER) will be less susceptible to saturation than TM, the problem will still persist.

Satellite and Ground Based Thermal Observation of the 2014 Effusive Eruption at Stromboli Volcano

“…Assuming that we know the temperature of one component, this method estimates the temperature of the second component and the partial area of both components. The assumption that merely two components cover the pixel is often unrealistic [45][46][47][48][49][50]. A better solution is the method proposed by Oppenheimer which assumes three components in a pixel [45].…”

“…This deviation will be addressed in the future, as TET-1 data will be available for several volcanoes. In the past, the dual band method has been criticized for yielding unrealistic results [45][46][47][48][49]. Compared to older satellite instruments (for instance MODIS), TET-1 has an improved spatial resolution.…”

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“…A method for calculating the fractional area and temperature of sub-pixel thermal components using concurrent multispectral measurements was first described by Dozier (1981), who used a "dual-band" method to unmix sub-pixel thermal components. Several studies have further developed this method (Rothery et al, 1988;Crisp and Baloga, 1990;Pieri et al, 1990;Oppenheimer et al, 1993;Wooster and Rothery, 1997;Harris et al, 1999;Wright et al, 2000;Lombardo and Buongiorno, 2003;Pieri and Abrams, 2005).…”

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“…For example, although the 1991-1993 eruption of Mount Etna lasted for 473 days, only five cloud-free TM acquisitions were possible (Wright, Rothery, Blake, & Pieri, 2000). As a result, volcanologists have looked to low-spatial-but high-temporal-resolution data from sensors such as the advanced very high resolution radiometer (AVHRR), geostationary operational environmental satellite series (GOES), and the along-track scanning radiometer (ATSR) to satisfy the need for an operational volcano monitoring capability.…”