Ground-based measurements of the 2014-2015 Holuhraun volcanic cloud
Artikel i vetenskaplig tidskrift, 2018
The 2014-2015 Bárðarbunga fissure eruption at Holuhraun was distinguished by high emission of gases, in total 9.6 Mt SO2, with almost no tephra. This work presents the ground-based measurements of this extraordinary eruption cloud made under particularly challenging conditions: remote location, optically dense plume with high SO2 column amounts, low UV intensity, frequent clouds and precipitation, an extensive and hot lava field, and developing ramparts which prevented a clear line of site to the main vent. Three scanning DOASes provided semi-continuous measurements that were augmented by car-mounted traverses along the ring-road and along the lava. The ratios of other gases/SO2 were measured by OP-FTIR, MultiGAS and Filterpacks. SO2/HCl = 30 – 110 and SO2/HF = 30 – 130 ratios show a halogen-poor eruption cloud. Scientists on-site reported extremely minor tephra production during the start of the eruption. OPC and filter packs showed low particle concentrations similar to non-eruption cloud conditions. Three weather radars detected a droplet-rich eruption cloud. Top of eruption cloud heights of 0.3 – 5.5 km agl were measured with ground- and aircraft-based visual observations, web camera and NICAIR2 infrared images, triangulation of scanning DOASes, and the location of SO2 peaks measured by DOAS traverses in conjunction with modeled winds. Plume height and emission rate measurements were critical for initializing gas dispersal simulations for hazard forecasting.