Akiko Furuno

A new trajectory analysis method for migratory planthoppers, Sogatella furcifera (Horváth) (Homoptera: Delphacidae) and Nilaparvata lugens (Stål), using an advanced weather forecast model

Abstract 1 A new method of backward trajectory analysis for planthopper migration is presented. The method consists of two components: an advanced weather forecast model, MM5, for weather simulation, and a migration model for trajectory calculation. The weather forecast model simulates wind fields in which trajectories are calculated by the migration model.

A migration analysis of the rice planthopper Nilaparvata lugens from the Philippines to East Asia with three-dimensional computer simulations

Migrations of the rice planthopper Nilaparvata lugens (Stål) (Delphacidae) from the Philippines to Taiwan, southern China, and southern Japan were analyzed using three-dimensional migration simulations. The results strongly suggested that the Southeast Asian population of N. lugens mixes with the East Asian population. This highlighted the possibility that planthoppers from the Southeast Asian population, which have properties different from those in the East Asian population such as feeding of resistant rice varieties and wing polymorphism, could migrate to Japan via southern China and Taiwan. This study, therefore, emphasizes the special care that should be taken to monitor the properties of immigrants to Japan.

Improvement of Worldwide version of System for Prediction of Environmental Emergency Dose Information (WSPEEDI), (I) new combination of models, atmospheric dynamic model MM5 and particle random walk model GEARN-new

The new version of WSPEEDI (Worldwide version of System for Prediction of Environmental Emergency Dose Information) is developed by introducing the combination of models, the atmospheric dynamic model MM5 and the Lagrangian particle dispersion model GEARN-new to improve the prediction capability of atmospheric dispersion of radionuclides discharged during nuclear emergency. The major improvements are (1) the forecasts of meteorological conditions with high resolution in time and space, (2) the simultaneous calculations for local and regional areas and (3) the consideration of detailed physical processes (e.g. wet deposition, vertical diffusion in atmospheric boundary layer). The performance of new models is evaluated by air sampling data on 137Cs over Europe during the Chernobyl accident. The calculated surface air concentrations showed good agreement with measurements.

A migration analysis of Sogatella furcifera (Horváth) (Homoptera: Delphacidae) using hourly catches and a three-dimensional simulation model

Abstract  1 Migrations of Sogatella furcifera captured in Japan in the 2003 season were analysed using hourly catches and a simulation model. 2 The catch data showed several clear migration peaks, with average durations of 4 h. The peaks were separated from each other by approximately 12 h, corresponding to the observed fact that planthoppers take off at dusk or dawn. 3 The simulation model comprised two components: a numerical weather forecast submodel, MM5, and a particle dispersion submodel, GEARN. The simulation model used three‐dimensional meteorological data and calculated the relative aerial density of migrating planthoppers to allow analysis of the timing and area of migrations in Japan. 4 The simulation model, together with the hourly catches, enabled an estimation of migration source regions. 5 Possible migration sources during our hourly observation period were located in the coastal area of Fujian province in China, as well as Taiwan.

Evaluation of a long-range Lagrangian dispersion model with ETEX

Performance of a Lagrangian dispersion model was examined in connection with its dependency on the boundary layer modelling and the input data resolution. The European Tracer Experiment (ETEX) data were used as reference. According to the sensitivity analysis of the model performance, the long-range dispersion model with the sparse input data was not noticeably different from that with the finer resolution data. The assumption of the prescribed constant mixing depth did not largely degrade the prediction results as compared with the simulation results with the temporally changing boundary layer. It is, therefore, concluded that the model is practical, considering the limited input data in the operational mode. However, it was also pointed out that the parameterization for the horizontal and vertical diffusion processes used in the present model enhanced the growth of plume. The improvement of input data resolution in time and space caused further dispersion of tracer deterministically. These resulted in the underestimation of the maximum concentration and the unfocussed concentration distribution map although the mean concentration was predicted fairly well.

Submesoscale Mixing on Initial Dilution of Radionuclides Released From the Fukushima Daiichi Nuclear Power Plant

This study developed a submesoscale eddy-resolving oceanic dispersal modeling system comprising a double-nested oceanic downscaling model and an offline oceanic radionuclide dispersion model. This was used to investigate the influences of submesoscale coherent structures (SCSs) and associated ageostrophic secondary circulations (ASCs) on the three-dimensional (3-D) dispersal of dissolved cesium137 (Cs) released from the Fukushima Daiichi Nuclear Power Plant (FNPP1). Extensive model-data comparison demonstrated that the innermost high-resolution model, with a lateral grid resolution of 1 km, could successfully reproduce transient mesoscale oceanic structures, the Kuroshio path and stratification, and spatiotemporal variations of Cs concentrations. Using an accompanying mesoscale eddy-resolving model (grid resolution: 10 km) as a guide, we showed that submesoscale dynamics are important for improved representation of both the eddy field and the resultant 3-D dispersal of Cs, with the temporal variability of surface Cs near the FNPP1 being equivalent to that in the coarse-resolution model. According to energy conversion and spectral analyses, SCSs and ASCs occur most intensively on the submesoscale, primarily because of shear instability. However, baroclinic instability serves as a secondary mechanism. SCSs have prominent seasonality, reflected by intensification in the colder months, which is when the FNPP1 accident occurred. Analysis of the vertical flux of Cs was performed by decomposition of the variables into eddy, mesoscale, and submesoscale components using frequency and wave number filters. It revealed that 42.7% of the FNPP1-derived Cs was transported downward below the mixed layer by eddies with the major contribution being from ASCs induced by submesoscale eddies.