ABSTRACT. The 2008 Chaitén Volcano eruption began on 2 May 2008 with an explosive phase that injected large amounts of tephra into the atmosphere. During the first week of the eruption, volcanic ash clouds were transported for hundreds of kilometres over Argentina by the prevailing westerly winds. Tephra deposition extended to the Atlantic Ocean and severely affected the Argentinean Patagonia. Impacts included air and water quality degradation, disruption of ground transportation systems and cancellation of flights at airports more than 1,500 km apart. We use the FALL3D tephra transport model coupled with the Weather Research and Forecasting-Advanced Research Weather (WRF-ARW) meteorological model to simulate tephra fall from the 2-9 May 2008 eruptive period. Our hindcast results are in good agreement with satellite imagery and reproduce ground deposit observations. Key aspects of our analysis, not considered during syn-eruptive forecasts, are the re-initialization of each simulation with actualized meteorological forecast cycles and better constrained model inputs including column heights (inferred from reanalysis of GOES-10 imagery and nearby atmospheric soundings) and granulometric data obtained from field campaigns. This study shows the potential of coupling WRF/ARW and FALL3D models for short-term forecast of volcanic ash clouds. Our results highlight that, in order to improve forecasting of ash cloud dispersion and tephra deposition, it is essential to implement an operational observation system to measure temporal variations of column height and granulometric characteristics of tephra particles in nearly real-time, at proximal as well as distal locations. Keywords: Chaitén eruption, FALL3D model, Ash dispersion, Ground deposition, Granulometry, Risk management.263 Osores et al. / Andean Geology 40 (2): 262-276, 2013 RESUMEN. Validación del modelo FALL3D para la erupción del Chaitén en 2008 usando datos satelitales y de campo. La erupción del volcán Chaitén se inició el 2 de Mayo de 2008 con una fase explosiva que inyectó grandes cantidades de tefra a la atmósfera. Durante la primera semana de erupción, se dispersaron nubes volcánicas por cientos de kilómetros sobre Argentina, siguiendo los vientos dominantes del oeste. El depósito de tefra se extendió hasta el océano Atlántico y afectó severamente a la Patagonia. Los impactos incluyen degradación de la calidad del aire y el agua, interrupción del sistema de transporte terrestre y la cancelación de vuelos incluso en aeropuertos a 1.500 km del volcán. Aquí se usó el modelo FALL3D de transporte y depósito de tefra con el modelo meteorológico Weather Research and Forecasting-Advanced Research Weather (WRF-ARW) para simular el período eruptivo del 2 al 9 de mayo de 2008. Los resultados obtenidos del pronóstico retrospectivo tienen una buena concordancia con las imágenes satelitales y reprodujeron las observaciones de depósito en superficie. Los aspectos claves de este análisis, no considerado durante los pronósticos contemporáneos, son la reinicialización d...
Abstract. Variation in vegetation in extra‐Andean Patagonia (Argentina) was analyzed using spectral data derived from AVHRR/NOAA satellite. The study of seasonal dynamics of the Normalized Difference Vegetation Index (NDVI, i.e. a combined index of the reflection in the red and infrared bands) highlighted similarities in functional aspects between regional vegetation units which are dissimilar in a geographical, physiognomical and/or floristical way, and also suggested that gross primary production is correlated with mean annual rainfall. The first axis in a Principal Component Analysis of NDVI data was correlated (r2 = 0.90) with NDVI as integrated for the study period. The second axis was correlated (r2 = 0.50) with the differences in NDVI during the growing season, reflecting seasonality. Mean annual rainfall accounted for 60% of integrated NDVI variability among vegetation units. Much of the residual variance (62%) was accounted for by the inverse of the distance to the Atlantic Ocean, which is interpreted as an ocean effect on vegetation functioning in the extra‐Andean Patagonia.
On 14 December 2013, the Cooperative Institute for Meteorological Satellite Studies (United States) reported a volcanic ash cloud apparently emitted by the Puyehue Cordón Caulle Volcanic Complex (Chile) and indicated its cause was probably resuspension. The distinction of volcanic ash resuspension from volcanic eruptions is important because both processes pose different scenarios for civil protection authorities and besides, there is a special need of specific schemes for detecting and monitoring resuspension of volcanic ash. To this end, we intended to identify the cause of this event by using remote sensing technology. Remote sensing based volcanic ash products enabled us to confirm the presence of volcanic ash and observations on the Moderate Resolution Imaging Spectroradiometer (MODIS)-based cloud-integrated water path provided evidence in favour of a small and short-lived eruption. Thus, a volcanic eruption would constitute a plausible explanation for the cloud of 14 December 2013, but we were unable to discard resuspension. On the other hand, we found out that the water path product could constitute useful ancillary data to identify the origin of this kind of processes. The set of observations presented constitutes a good initial point towards the identification and subsequent development of decision support tools for the mitigation of the hazards posed by volcanic ash resulting from volcanic eruptions and resuspension.
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