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Tianfeng Chai, Roland Draxler, and Ariel Stein
NOAA Air Resources Laboratory College Park, Maryland, USA
ObjecCve
24/09/15 Air Resources Laboratory 2 Day
Cs-137Em
issionrate(Bq/hr)
03/13 03/18 03/23 03/28 04/021011
1012
1013
1014
Katata et al. (2015) HYSPLIT (Hybrid Single-‐ParCcle Lagrangian Integrated Trajectory)
EsCmaCon of radionuclide releases from the Fukushima nuclear accident
Methodology
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• Transfer coefficient matrix (TCM) is used to capture source-‐receptor relaConship (N=99, M=1296)
• Best release esCmate minimizes the cost funcCon
Twin experiments � In twin experiments, pseudo-‐observaCons are generated with known sources (Katata et al. 2015 )
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Where
� They are used to address the following issues: 1. How to measure the concentraCon/release differences? 2. How does the cost funcCon approach compare to SVD? 3. Will the results be sensiCve to measurement errors? 4. Will the results be sensiCve to the first guess?
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Control and metric variables
MAE: mean absolute error; RMSE: root-‐mean-‐square error; MRE: mean relaCve error; R: linear correlaCon coefficient. Units of MAE and RMSE: mBq/m3 for concentraCons, Bq/h for releases.
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Day
Cs-137Em
issionrate(Bq/hr)
03/12 03/19 03/26 04/021011
1012
1013
1014KatataT01T02T03T04SVD
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Twin experiments: Control and metric variables
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ObservaConal error & SVD
MAE: mean absolute error; RMSE: root-‐mean-‐square error; MRE: mean relaCve error; R: linear correlaCon coefficient. Units of MAE and RMSE: mBq/m3 for concentraCons, Bq/h for releases.
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First guess
MAE: mean absolute error; RMSE: root-‐mean-‐square error; MRE: mean relaCve error; R: linear correlaCon coefficient. Units of MAE and RMSE: mBq/m3 for concentraCons, Bq/h for releases.
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Day
Cs-137Em
issionrate(Bq/hr)
03/12 03/19 03/26 04/021011
1012
1013
1014KatataR01+
Real observaCons: without smoothness (R01)
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Cs-137Em
issionrate(Bq/hr)
03/12 03/19 03/26 04/021011
1012
1013
1014
KatataR02R03
Smoothness penalty term R02: Csm = 1.0 R03: Csm = 0.1
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Cs-137Em
issionrate(Bq/hr)
03/12 03/19 03/26 04/021011
1012
1013
1014
Katata-6hrKatata-24hrKatata-96hrR02R03
Compared to running-‐average
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Limited observaCon
Csm = 1.0
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Day
G131,P131,TotalI131
03/12 03/19 03/26 04/02
1012
1013
1014
1015
G131P131Total I131G131P131Total I131
Half life: Cs-‐137=30.17 years , I-‐131= 8.02 days
I-‐131 test cases
Summary � Emission inversion has been built based on HYSPLIT model, its TCM, and a cost funcCon;
� Cs-‐137/I-‐131 releases from Fukushima accident were recovered using global air concentraCons;
� Using ln(c) differences in the cost funcCon is bejer than using concentraCons themselves;
� Inversion is not sensiCve to observaConal errors or different first guesses;
� A temporal smoothness penalty is capable of removing arCficial variability from the results.
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Thank you!
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Acknowledgement: This study was supported by NOAA grant NA09NES4400006 (CooperaCve InsCtute for Climate and Satellites-‐CICS) at the Resources Laboratory in collaboraCon with the University of Maryland. AddiConal funding for this study was provided by the U.S. Department of State.
Reference: Source term esCmaCon using air concentraCon measurements and a Lagrangian dispersion model–Experiments with pseudo and real cesium-‐137 observaCons from the Fukushima nuclear accident, T Chai, R Draxler, A Stein Atmos. Environ. 106, 241-‐251, 2015
