Development of the Eulerian atmospheric transport model GEARN-FDM; Validation against the European tracer experiment

Kadowaki, Masanao   ; Katata, Genki; Terada, Hiroaki   ; Nagai, Haruyasu  

We developed a dispersion model based on the finite difference method, GEARN-FDM, for long-range dispersion, which solves the advection-diffusion equation using numerical schemes with low artificial diffusion. The advection and diffusion terms are modeled using a fully mass conservative scheme and the Crank-Nicolson method, respectively. GEARN-FDM was validated using the dataset from the European Tracer Experiment. In the entire domain throughout the simulation period of the observed dataset, GEARN-FDM showed high performance with factors of 2 and 5 of 39% and 78%, respectively. While testing the sensitivity of the horizontal diffusivity with this model, the simulated horizontal diffusivity was distributed heterogeneously in the model domain. High diffusivity was primarily seen over the coastal and mountainous regions. Therefore, for the long-range simulations of radionuclides, we need to consider to the transport caused by horizontal diffusion.