Incorporating Volcanic Eruptions into Near Real time Aerosol Forecasts

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Loraine Daisy Weaver
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1 Incorporating Volcanic Eruptions into Near Real time Aerosol Forecasts Eric Hughes 1 Nick Krotkov 2 Arlindo Da Silva 2 Peter Colarco 2 (1) University of MD Department of Atmospheric and Oceanic Sciences (2) Goddard Space Flight Center NASA

2 Aerosols from Volcanic Eruptions Volcanic eruptions produce aerosols in the form of: Volcanic Ash. Lifetime of few days. SO 2 > SO 4 (sulfate aerosols) Lifetime of days to weeks (troposphere) Vanuatu (Ambrym) Small effusive/degassing volcanoes: Emits SO 2 and aerosols from summit Low concentrations. Frequent, daily. Explosive Eruptions Emits SO 2 and Ash high into atmosphere Higher concentrations Sporadic, less frequent. Dec 4th 2013 Modis Terra (RGB)

Volcanic Eruptions in Aerosol Forecast models Challenges with Volcanic Eruptions: Sporadic Events Eruption Parameters often unknown (time/duration, altitude, mass loading) Without knowledge of

3 Volcanic Eruptions in Aerosol Forecast models Challenges with Volcanic Eruptions: Sporadic Events Eruption Parameters often unknown (time/duration, altitude, mass loading) Without knowledge of volcanic eruptions, an aerosol forecast tends to assimilate observed volcanic aerosols incorrectly (into other aerosols). Assimilated Elevated Sea Salt Aerosols as a results of Eyjafjallajokull eruption. ECMWF Tech Memo 653

4 Overview: Modeling and Data Assimilation Initial Volcano Report Observations Cloud Location & Tonnage Under Development Parameter Estimation Estimate of Source Terms Output Analysis Evaluate source term estimates. Compare simulation to observations. Model Simulation Reconstruct Observations & Generate Forecast Output Forecast

5 Parameter Estimation: Parameters necessary for the simulation? Total amount: Can be computed directly from satellite observations Total Tonnage SO 2 ~ 19.7 Kt Emission Time and Altitude: Can be estimated from back trajectories from observations Trajectory Altitude: 2.5 km Trajectory Altitude: 7.3 km Satellite Observations

6 Parameter Estimation: Deriving Emission Probability Distribution Functions (PDFs) The Trajectory Transport Test: A trajectory has successfully described the transport of an SO 2 measurement if it arrives within a minimum distance of the volcano. The Distance of Closest Approach r*(,t*) the theta height of that trajectory t* is the time of closest approach P(t*) [Dec 2 nd ] P( t*) *) *)

7 Eruption of Sangeang Api on May 30 th 2014 SO 2 Emission Height Time PDF AIRS observation of initial eruptive event (image from Observed SO 2 tonnage ~ 130 kt (about a medium size eruption)

8 OMPS Observation May 31 st More trajectories are added from new observations SO 2 Emission Height Time PDF SO 2 Column Amount [DU]

9 OMPS Observation June 1 st Eventually, more trajectories don t add more information to the emission PDF SO 2 Column Amount [DU] SO 2 Emission Height Time PDF 0 1 2

10 SO 2 Emission Height Time PDF GEOS 5/GOCART May 31 SO 2 kg/m 2 June 1 Use emission PDFs and observed SO 2 tonnages to simulate in aerosol forecast June 2 SO 2 > SO 4 in Aerosol Forecasts

11 SO 2 only observed until June 2 nd Sulfate Cloud 9 Days After Eruption (June 7 th ) June 7 SO 4 Column Mass kg/m 2 Volcanic sulfate aerosols extend far beyond region of volcano

12 Verification SO 4 of Altitude CALIPSO Total Attenuated Backscatter (TAB) 532nm CALIPSO observations show a coincident weak scattering layer between 15 18km.

13 Sulfate Cloud From Volcano vs. Background SO4 including Volcano SO4 without Volcano Difference (Volcanic contribution) SO4 Column Mass kg/m2 Volcanic sulfate aerosols 9 days post eruption of comparable magnitude to pollution sulfated from Eastern Asia

14 Contribution of volcanic SO4 to AOT AOT including Volcano AOT without Volcano Difference (Volcanic contribution) Volcanic sulfate aerosols 9 days post eruption contribute less to AOT, but still relatively significant AOT (sulfates only)

15 Putting it all together into a near real time framework Part of a Natural Hazards project to improve volcanic cloud monitoring and forecasting

16 Overview of Current System Setup

17 Use information provided by VAACs as eruption first guess Overview of Proposed System Setup

18 In Summary Back trajectory methods can be used to make a first guess at eruption parameters Subsequent observations help refine the first guess Sulfate aerosols from volcanic eruptions can contribute to AOT calculations in aerosol forecast models (can last many days after an eruption) Currently working to develop for near real time application Currently working on a volcanic ash component to model for similar analysis

19 Thank You!

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