On the 19th of September, 2021 an eruption began in the Cumbre Vieja volcanic ridge on the island of La Palma in the Canary Islands. This eruption lasted until the 13th of December. The 85-day eruption is the longest known eruption of a volcano in this location. This region had also been dormant for more than 50 years. Towns were damaged, people were evacuated, and the disruption resulted in millions of euros of losses.

Air Traffic Management Magazine had the opportunity to discuss this disaster with Reijo Roininen, Product Manager, Vaisala and David Suárez, AEMET (State Meteorological Agency) Delegate in the Canary Islands. We began with a recap of the impact to air traffic during this time. The impact on air traffic occurred mainly at La Palma airport (and occasionally at Tenerife airports). The following summary was provided by AENA via a news story. During the three months of volcano activity, 2,130 operations of the 2,889 operations planned were carried out. This translates to a 74% success rate. Of the flights that could not operate, 34% were cancelled as a result of operational closure of the airport due to the deposition of volcanic ash, while the other remaining 66% corresponds to the cessation of air activity by the airlines because they detected volcanic ash in the airspace.

The island of La Palma already used several legacy ceilometers near the airport and the nearby town of El Paso, but deployment the Vaisala CL61 opened the possibility of using depolarisation for a greater understanding than was possible before. Depolarisation allows for straightforward identification of several weather phenomena, such as liquid vs. solid precipitation, cloud phases, and melting layers. This level of differentiation is difficult or impossible using legacy equipment.

In our case,” says the AMET representative, Africa Barreto, “we can now see the volcano’s ash and many different types of aerosols. Ash is the thing that’s relevant and dangerous for aviation, not the sulfates. Sometimes you have both, and without the CL61’s depolarization ability we can’t distinguish between them adequately.”  

Vaisala’s CL61 was installed in El Paso, which lies in the caldera of La Palma and is 10 miles from the airport. The ceilometer’s small form factor and ease of setup meant that the AEMET team could locate it where it was most scientifically valuable. It easily integrated with the existing sensor network, and it began providing data to Barreto and her team quickly, while the volcano was still active.

Looking ahead, what might the lessons learned from this event be for ANSPs. This has been an emergency where from the aeronautical point of view, the need for collaboration between different actors (ENAIRE, AENA, AEMET, VAAC and airlines) has been highlighted to provide the best possible information on the phenomenon. In addition, AEMET has verified that, at least from a qualitative point of view, the pollutant dispersion model executed by AEMET (MOCAGE) in accident mode has been of great help for decision-making due to the good forecasts made with a range up to H+72. Of special impact on these models is the inclusion of the correct altitude of the volcanic plume from ground-based sensors.