Air-traffic response to future incidents akin to the volcanic eruption in Iceland will be more effective if an automated instrument can be developed for continuous, near real-time monitoring of ash fallout from eruption plumes.

Ash from the Eyjafjallajökull eruption was carried towards Europe by prevailing winds. The height of the plume was used as the main indicator of mass transfer, a crucial input parameter in atmospheric models to define no-fly zones.

Although wind patterns are well understood, confusion over the ash load in volcanic plumes causes uncertainties in setting no-fly zone boundaries. The grain size and mass of ash fall per area can be used to reconstruct volcanic plumes. But this data would be more useful if operational in near real time.

Gravimetric measurements of the fallout weight could be used, for example, and a laser-dispersion instrument might measure particle concentration and size in the air. For prolonged explosive eruptions such as the recent Icelandic one, an array of these instruments could be located under plume trails.

These observations would provide timely 'ground-truth' to calibrate and complement remote-sensing techniques that rely on radar, lidar (light detection and ranging) and satellite data.

Governments, airlines and aviation authorities should help to develop and test such instruments.