JMA's Regional ATM Calculations for the WMO Technical Task Team on Meteorological Analyses for Fukushima Daiichi Nuclear Power Plant Accident

Title:

JMA's Regional ATM Calculations for the WMO Technical Task Team on Meteorological Analyses for Fukushima Daiichi Nuclear Power Plant Accident.

Authors:

Kazuo Saito, Meteorological Research Institute, Ibaraki, Japan, ksaito@mri-jma.go.jp

Toshiki Shimbori, Meteorological Research Institute, Ibaraki, Japan, shimbori@mri-jma.go.jp

Abstract:

The World Meteorological Organization (WMO) convened a small technical task team of experts to produce a set of meteorological analyses that would be used to drive atmospheric transport, dispersion and deposition models (ATMs) of the UN Committee on the Effects of Atomic Radiation (UNSCEAR) for the Fukushima Daiichi Nuclear Power Plant accident. The primary aim of the group is to examine how the use of meteorological analyses could improve the ATM calculations. The task team's detailed activities have been reported by Draxler et al. (2013).

  A regional ATM for radionuclides has been developed at the Meteorological Research Institute (MRI), based on the Japan Meteorological Agency (JMA) mesoscale tracer transport Lagrangian model (Seino, 2004; Takano, 2007; Shimbori, 2010) for prediction of volcanic ash and oxidant concentration. This transport model shares its horizontal and vertical grid configurations with the JMA operational nonhydrostatic mesoscale model (Saito, 2012) and the mesoscale analysis. With reference to the JMA's global environmental emergency response model, dry deposition, wet scavenging, and gravitational sedimentation for light particles have been revised.

Preliminary calculations of the JMA's regional ATM were conducted according to the task team's agreed standard with a horizontal resolution of 5 km using a unit source emission rate. The simulations are conducted for the period 11 through 31 March 2011. The 4D-VAR mesoscale analysis data of JMA (3-hourly, 5-km horizontal, and 50-hybrid level vertical resolution) were used to drive the ATM, while the JMA's Radar/Rain Gauge analyzed precipitation data (every 30 min at 1-km resolution) were employed to evaluate the wet scavenging. The number of Lagrangian particles was 300,000 per three hours. Vertical advection was calculated using spatially averaged (9-grid cells) vertical winds of the mesoscale analysis. These values were also assumed to be terrain-following at the lowest model level of ATM (40 m). In the presentation, results of ATM calculation will be shown with comparison to the observed Cs-137 deposition pattern and the time series of Cs-137 and I-131 air concentrations.

References:

Daxler, R., P. Chen, M. Hort, A. Malo, K. Saito, and G. Wotawa, 2013: World Meteorological Organization's evaluation of the radionuclide dispersion and deposition from the Fukushima Daiichi Nuclear Power Plant accident. Proceeding, Special Symposium on the Transport and Diffusion of Contaminants from the Fukushima Dai-Ichi Nuclear Power Plant: Present Status and Future Directions. (this volume)

Saito, K., 2012: The Japan Meteorological Agency nonhydrostatic model and its application to operation and research. InTech, Atmospheric Model Applications, 85-110. doi: 10.5772/35368.

Seino, N., H. Sasaki, J. Sato, and M. Chiba, 2004: High-resolution simulation of volcanic sulfur dioxide dispersion over the Miyake Island. Atmospheric Environment, 38, 7073-7081.

Shimbori, T., Y. Aikawa, K. Fukui, A. Hashimoto, N. Seino, and H. Yamasato, 2010: Quantitative tephra fall prediction with the JMA mesoscale tracer transport model for volcanic ash: A case study of the eruption at Asama volcano in 2009. Pap. Met Geophys., 61, 13-29. (in Japanese with English abstract and figure captions)

Takano, I., Y. Aikawa, and S. Gotoh, 2007: Improvement of photochemical oxidant information by applying transport model to oxidant forecast, CAS/JSC WGNE Res. Act. Atmos. Ocea. Model., 37, 5.35-5.36.