| 1. |
- De Schutter, Ann, et al.
(författare)
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Ash fall impact on vegetation: a remote sensing approach of the Oldoinyo Lengai2007–08 eruption
- 2015
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Ingår i: Journal of Applied Volcanology. - : Springer Science and Business Media LLC. - 2191-5040. ; 4:15
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Tidskriftsartikel (refereegranskat)abstract
- Impacts from ash fallout on the environment can be widespread and long lasting, even from moderate-sizeeruptions. Assessing ash impact on vegetation and the indirect impacts for people is often difficult in the field. Hereit is assessed how satellite data can help to map vegetation affected by ash and how temporal analysis enablescharacterization of vegetation recovery rate. The 2007–08 eruption of Oldoinyo Lengai, north Tanzania, is here usedas a case study. An 8 year-long (2005–2012) time series of half-monthly average of the Normalized DifferentialVegetation Index (NDVI) is constructed at 250 m spatial resolution from the Moderate Resolution ImageSpectro-radiometer (MODIS) sensor. Interpolated rainfall data is used to isolate NDVI values departing from the normalseasonal cycles. Month-to-month NDVI comparison, linear temporal trend analysis and Principal Component Analysisenable to identify a 11 × 4 km area over which ash fallout significantly affected the state of the vegetation. After theeruption’s end, time series of various recovery indices highlight a circumferential pattern in vegetation recovery. Theestimated recovery time varies from more than 5 years to less than 6 months with increasing distance from thevolcano. A non-linear moderate, but statistically significant, relationship is found between the recovery indices and thespatial variation of ash thicknesses measured in the field. Combining field and remote sensing constraints enable tore-assess the volume of the eruption to ~2 × 107 m3. The spatial pattern of the ash-affected area matches with thespatial contrast in the impact experienced by the local communities. The method applied here opens the scope todocument impact and intensity of ash fallout in areas where systematic field work is not possible and to supportrecovery plans for populations affected by ash fallout.
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| 2. |
- Harris, A. J L, et al.
(författare)
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Effusive crises at Piton de la Fournaise 2014–2015: a review of a multi-national response model
- 2017
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Ingår i: Journal of Applied Volcanology. - : Springer Science and Business Media LLC. - 2191-5040. ; 6:1
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Forskningsöversikt (refereegranskat)abstract
- Many active European volcanoes and volcano observatories are island-based and located far from their administrative “mainland”. Consequently, Governments have developed multisite approaches, in which monitoring is performed by a network of individuals distributed across several national research centers. At a transnational level, multinational networks are also progressively emerging. Piton de la Fournaise (La Réunion Island, France) is one such example. Piton de la Fournaise is one of the most active volcanoes of the World, and is located at the greatest distance from its “mainland” than any other vulnerable “overseas” site, the observatory being 9365 km from its governing body in Paris. Effusive risk is high, so that a well-coordinated and rapid response involving near-real time delivery of trusted, validated and operational product for hazard assessment is critical. Here we review how near-real time assessments of lava flow propagation were developed using rapid provision, and update, of key source terms through a dynamic and open integration of near-real time remote sensing, modeling and measurement capabilities on both the national and international level. The multi-national system evolved during the five effusive crises of 2014–2015, and is now mature for Piton de la Fournaise. This review allows us to identify strong and weak points in an extended observatory system, and demonstrates that enhanced multi-national integration can have fundamental implications in scientific hazard assessment and response during an on-going effusive crisis.
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