| The ash cloud of the Eyjafjallajökull volcano on Iceland caused closure of large parts of
European airspace in April and May 2010. For the validation and improvement of the
European volcanic ash forecast models several research flights were performed. Also the
CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an
Instrument Container) flying laboratory, which routinely measures at cruise altitude (11
km) performed three dedicated measurements flights through sections of the ash
plume. Although the focus of these flights was on the detection and quantification of
the volcanic ash, we report here on sulphur dioxide (SO2) and bromine monoxide
(BrO) measurements with the CARIBIC DOAS (Differential Optical Absorption
Spectroscopy) instrument during the second of these special flights on 16 May
2010. As the BrO and the SO2 observations coincide, we assume the BrO to have
been formed inside the volcanic plume. Both SO2 and BrO observations agree
well with simultaneous satellite (GOME-2) observations. SO2 column densities
retrieved from satellite observations are often used as an indicator for volcanic ash. For
SO2 some additional information on the local distribution can be derived from a
comparison of forward and back scan GOME-2 data. More details on the local
plume size and position are retrieved by combining CARIBIC and GOME-2 data. |