Exploring the effect of steep, rough topography on satellite based estimates of radiative heat flux measurements of active volcanoes
Zusammenfassung der Projektergebnisse
Using thermal remote sensing is possible to detect thermal anomalies originating from a volcano by comparing signals in mid and thermal infrared spectra. The detected thermal anomalies can be characterized by the temperature, area, radiant power and discharge rate. The most robust parameter is radiant power, thus, it is suitable to monitor volcanic unrest. The derivation of the radiant power depends on atmosphere, satellite viewing angle and sensor characteristics. Some of these influences are easy to correct using standard remote sensing pre-processing techniques, but some noise still remains in data. Here we show how to estimate the uncertainty of the radiant power as the function of pixel area, cloud coverage and instruments radiometric characteristics. The measurements together with corresponding uncertainties are then subject to Kalman filtering. Using the Kalman filter we identified the outliers and reduced the noise of the radiant power time series. An important result of the study of uncertainties is also the influence of topography. This is especially important because it may significantly influence the area of a satellite pixel containing a volcanic thermal anomaly. To isolate these geometric effects from the various other influences, e.g. atmospheric attenuation and up-welling radiance, an indoor analog experiment was developed. Therein, the volcanic feature is simulated by an electrical heating alloy of 0.5 mm diameter, installed on a tiltable plywood panel. Two thermographic cameras, Infratec VarioCam high resolution and Infratec ImageIR 8300, recorded images of the artificial heat source in different spectral wavebands, comparable to those available in satellite data. These range from the short-wave IR over the middle IR to the thermal IR. Besides testing the influence of slope on the satellite observations, the developed lava simulator made possible to estimate the accuracy of the dual band method. The findings of the lab experiment were supposed to be tested with TET-1 data. However, because of the delayed start of the satellite, the field expedition was carried out almost in the end of the project. Thus the focus in the last months of the project was to optimize the TET-1 processing. Using TET-1, we retrieved the first long term satellite monitoring of an active lava flow on Stromboli volcano (August–November 2014) at high spatial resolution (160 m) and relatively high temporal resolution (~3 days). In the combination with MODIS instrument, we estimated the total erupted volume to be 7.4 × 10^6 m3. In the following months, we plan to apply the topographic correction to TET-1 and MODIS data as well.
Projektbezogene Publikationen (Auswahl)
- 2013. Constraining the uncertainties of volcano thermal anomaly monitoring using a Kalman filter technique. In: Pyle, D. M., Mather, T. A., Biggs, J. (eds). Remote sensing of volcanoes and volcanic processes: integrating observation and modelling, Geological Society, London, Special Publications, 380, 137-160
K. Zakšek, M. Shirzaei, & M. Hort
(Siehe online unter https://doi.org/10.1144/SP380.5) - Conclusion: recommendations and findings of the RED-SEED working group. In: Harris, A. J. L., De Groeve, T., Garel, F. & Carn, S. A. (eds) Detecting, Modelling and Responding to Effusive Eruptions. Geological Society, London, Special Publications, 426
J. L. Harris, S. Carn, J. Dehn, C. Del Negro, M. T. Guðmundsson, B. Cordonnier, T. Barnie, E. Chahi, S. Calvari, T. Catry, T. De Groeve, D. Coppola, A. Davies, M. Favalli, F. Ferrucci, E. Fujita, G. Ganci, F. Garel, M. T. Gudmundsson, P. Huet, J. Kauahikaua, K. Kelfoun, V. Lombardo, G. Macedonio, J. Pacheco, M. Patrick, N. Pergola, M. Ramsey, R. Rongo, F. Sahy, K. Smith, S. Tarquini, T. Thordarson, N. Villeneuve, P. Webley, R. Wright & K. Zakšek
(Siehe online unter https://doi.org/10.1144/SP426.11) - 2015. Satellite and Ground Based Thermal Observation of the 2014 Effusive Eruption at Stromboli Volcano. Remote Sensing, 7/12, 17190-17211
K. Zakšek, M. Hort, E. Lorenz
(Siehe online unter https://doi.org/10.3390/rs71215876) - Thermal monitoring of volcanic effusive activity: the uncertainties and outlier detection In: Harris, A. J. L., De Groeve, T., Garel, F. & Carn, S. A. (eds) Detecting, Modelling and Responding to Effusive Eruptions. Geological Society, London, Special Publications, 426. 2015
K. Zakšek, L. Pick, M. Shirzaei, & M. Hort
(Siehe online unter https://doi.org/10.1144/SP426.2)
