Dispersion Simulations of Radionuclides in the Ocean1. Model results for regional dispersion off...
Transcript of Dispersion Simulations of Radionuclides in the Ocean1. Model results for regional dispersion off...
Dispersion Simulations of Radionuclides in the Ocean
Yukio Masumoto(The University of Tokyo ; JAMSTEC)
+ Contributors to the model intercomparison
Why do we need dispersion simulations?
- Models can show detailed distribution in a large area and can interpolate/extrapolate sparse observed distributions
- Models can be used for predictions of radionuclide dispersions
- Model results may suggest important processes responsible for the dispersion
(Bq/m3)
- Models show their own worlds, with a certain degree of uncertainty
Model (a)
Model (b)Observation
1. Model results for regional dispersion off Tohoku area
2. Model results for basin-scale dispersion in the North Pacific
• Regional model intercomparison
- Originally started as one of the activities of “the Earthquake Disaster Response Working Group” under the Oceanographic Society of Japan. Now continuing under a working group of the Science Council of Japan.
- To understand similarities and discrepancies among model results and to identify important oceanic processes responsible for the radionuclide dispersion.
- Only a few models have been used for the basin-scale dispersion simulation
Regional Model Intercomparison
11 models are participating in the intercomparison (6 from Japan, 5 from abroad)
Note: Domain, resolution, discharge scenario, and atmospheric depositions are all different among the models.
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Model Domains
Surface distribution of 137Cs (Apr.21-30)
Observation
• Anticyclonic meso-scale eddy off Ibaraki prevents radionuclides to spread southward
• Currents along the coast determine the direction of initial dispersion
• Location of the Kuroshio axis differs significantly among the models
137Cs activity (Surface) in June, 2011
(1.58) (1.33) (4.15)
(3.06)(3.52)(1.78)
(4.52)(4.01)(1.57)
(4.17)
Inventory : 1.9 ~ 2.1 PBq
R/V Ka’imikai-o-Kanaloa(Buesseler et al., 2012)
Observed reference:
Inventory Summary
(PBq)
Inset value for each panel shows the Inventory in
each model
Apr., 2012
Jan.-Mar./Feb.15, 2012
Observations : Aoyama et al. (2013)Simulation : Tsumune et al., (2013)
Simulation : Rossi et al., (2013)
Two model results for basin-scale Cs distributions (Bq/m )137 3
• Rossi et al. adopted the direct discharge of 22 PBq, with no atmospheric deposition
• Tsumune et al. employed 3.6 PBq of the direct discharge, together with 3.0 PBq of the atmospheric deposition
Summary
• Dispersion simulation of radionuclides is a useful tool to understand how the radionuclides are transported and distributed over time
• Each model shows reasonable agreement with observations, but significant discrepancy exists among the models, due to the different model settings and source scenarios
• Need to be aware of model uncertainty when describing the model results