Data assimilation for volcanic ash plumes using a satellite observational operator

Data assimilation for volcanic ash plumes using a satellite observational operator: A case study on the 2010 Eyjafjallajokull volcanic eruption

Fu, Guangliang (TU Delft Mathematical Physics)
Prata, Fred (Nicarnica Aviation AS)
Lin, H.X. (TU Delft Mathematical Physics)
Heemink, A.W. (TU Delft Mathematical Physics)
Segers, AJ (TNO)
Lu, S. (TU Delft Mathematical Physics)

2017-01-25

Using data assimilation (DA) to improve model forecast accuracy is a powerful approach that requires available observations. Infrared satellite measurements of volcanic ash mass loadings are often used as input observations for the assimilation scheme. However, because these primary satellite-retrieved data are often two-dimensional (2-D) and the ash plume is usually vertically located in a narrow band, directly assimilating the 2-D ash mass loadings in a three-dimensional (3-D) volcanic ash model (with an integral observational operator) can usually introduce large artificial/spurious vertical correlations.

In this study, we look at an approach to avoid the artificial vertical correlations by not involving the integral operator. By integrating available data of ash mass loadings and cloud top heights, as well as data-based assumptions on thickness, we propose a satellite observational operator (SOO) that translates satellite-retrieved 2-D volcanic ash mass loadings to 3-D concentrations. The 3-D SOO makes the analysis step of assimilation comparable in the 3-D model space.

Ensemble-based DA is used to assimilate the extracted measurements of ash concentrations. The results show that satellite DA with SOO can improve the estimate of volcanic ash state and the forecast. Comparison with both satellite-retrieved data and aircraft in situ measurements shows that the effective duration of the improved volcanic ash forecasts for the distal part of the Eyjafjallajökull volcano is about 6 h.

Satellite data
data assimilation
Ensemble Kalman filter
ensemble square root filter
aircraft data
satellite observational operator
OA-Fund TU Delft

http://resolver.tudelft.nl/uuid:74f8b276-179b-4f2f-b675-e621e054b125

https://doi.org/10.5194/acp-17-1187-2017

1680-7316

Atmospheric Chemistry and Physics (online), 17 (2), 1187-1205

Institutional Repository

journal article

© 2017 Guangliang Fu, Fred Prata, H.X. Lin, A.W. Heemink, AJ Segers, S. Lu