Gas flux monitoring
- San Cristobal Volcano in Nicaragua (photo by Thor Hansteen, 2005)
- Scheme of Mini-DOAS operation
Gas flux monitoring
With the development of the Scanning Mini-DOAS (Dual-beam miniature – Differential Optical Absorption Spectrometer), remote sensing of volcanic gas emissions has taken a significant leap forward. The instrument developed for use within the EU-project NOVAC will be used to measure both areal SO2 concentrations and SO2 and BrO flux. The high time-resolution of the data enables correlations with geophysical data, e.g. seismic data, thus significantly extending the information available for real-time risk assessment and research at the volcano. High SO2 fluxes remain a reliable indicator of the presence of magma during new episodes of unrest.
Mini-DOAS operation
Direct measurement of plume speed neccesary for flux calculations using the Dual-beam Mini-DOAS. Plume speed can be calculated when the plume height is known, and the fluctuating SO2 concentrations in the plume is continuously measured downwind in two slightly offset viewing directions (separated by the angle phi), identifying the time used by the plume to cover the known distance (X) between the two points of observation.