Marie Boichu (1), Laurent Menut (1), Dmitry Khvorostyanov (1), Lieven Clarisse (2), Cathy Clerbaux (2,3), Solène Turquety (1)

Transcription

1 Inverting for high temporal resolution SO 2 flux using satellite imagery and chemistry-transport modelling: application to the 2010 Eyjafjallajökull eruption Marie Boichu (1), Laurent Menut (1), Dmitry Khvorostyanov (1), Lieven Clarisse (2), Cathy Clerbaux (2,3), Solène Turquety (1) (1) IPSL, Laboratoire de Météorologie Dynamique, École Polytechnique (2) Université Libre de Bruxelles, (3) IPSL, LATMOS

2 Volcanic source Knowledge of the volcanic source is crucial: 1) for volcanologists (SO 2 = indicator of volcanic activity) 2) for atmospheric scientists (simulation & forecast of volcanic plume transport/dispersion) Usually for plume simulations: Ash: empirical relationships are used (linking ash mass rate with emission height) SO 2 : a constant source term is assumed (but difficult when long-lasting eruption!) => New approach here: Inverse modelling (Boichu et al., in prep. for ACP)

3 Inverse modelling Satellite images (IASI here) Chemistry-transport model (CHIMERE here) Inversion scheme: least squares inversion + nonnegativity of solution + no a-priori on source One tracer is released at source every hour (1hlong emission) Which superposition of tracers matches the best satellite observations?

4 CHIMERE: Regional chemistry-transport model Eulerian model Grid: 25 km horizontal resolution 18 vertical layers up to 200 hpa (~ 10 km) (~ 1km vert. resol. above 5 km) Forced with WRF meteorological field IASI (Infrared Atmospheric Sounding Interferometer) Abord the polar-orbiting MetOp-A Infrared (645 cm 1 to 2760 cm 1 ) 2 overpasses per day (9h30; 21h30 LT) Spatial resolution : (12 km x 12 km) pixel at nadir Retrieval of SO2 CA assuming a 7 km high plume. (Clerbaux et al. 09)

5 Focus on SO 2 Why SO 2? Good proxy for ash Often easier satellite retrieval Less input model parameters Crucial to monitor the volcanic activity 2010 Eyjafjallajökull eruption Sustained SO 2 -rich emissions in May 2010 Persistent long-lasting tropospheric SO 2 plume Up to 6 day old plume detected by IASI! Many observations available SO 2 source term in chemistry-transport models: Flux at source Emission height above the vent (fixed to 7 km) Emission profile (Gaussian profile chosen here)

6 Observations/Simulations

7 Reconstruction of the source

8 Reconstruction of the source

9 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

10 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

11 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

12 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

13 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

14 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

15 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

16 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

17 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

18 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

19 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

20 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC

21 Retrospective analysis (1 => 13 May 2010) IASI Simulation Map: h => h UTC Obs.

22 Methodological results improving plume simulation/forecast Use of time-series of satellite images: to improve time-resolution of the source and accuracy of its intensity. Specific data decimation before inversion Dealing with old plume parts

23 Specific random sampling of zero pixels before inversion

24 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation

25 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation

26 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation CAREFUL: note that the colorbar is changing!

27 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation CAREFUL: note that the colorbar is changing!

28 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation CAREFUL: note that the colorbar is changing!

29 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation CAREFUL: note that the colorbar is changing!

30 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation CAREFUL: note that the colorbar is changing!

31 Plume forecast Map: h UTC => h UTC IASI Forecast Simulation Source for forecast Source for simulation CAREFUL: note that the colorbar is changing!

32 Comparison with other available observations of the volcanic source Ground DOAS (Allard, pers. comm.): 9 May 2010, 6000 t/d Ash flux time-series: SO 2 [This study] Ash [Stohl et al. 2011]

33 Can the emission height be also estimated by inverse modelling? It depends on: The variability of the plume altitude If wind shear exists on that range of altitudes

34 Perspectives Refine the model description of the SO 2 chemical conversion Interpretation of the reconstructed SO 2 flux time-series in terms of volcanic activity & magma dynamics How couldthismethodbeusedduringan eruptive crisis as a forecasting tool? Adapt the same method for ash

35 Merci pour votre écoute

36 Emission height (Arason et al.) SO 2 (This study) (Stohl Ash et al. 2011)