TRACER TRANSPORT MODEL AT JAPAN-METEOROLOGICAL-AGENCY AND ITS APPLICATION TO THE ETEX DATA

This paper describes the JMA tracer transport model and its sensitivit y to model physics and initial conditions by using the ETEX data. Comp ared with observations, the model overestimates ground-level concentra tion in the early stage within about one day from the emission, possib ly due to underestimation of vertical diffusion. In the early stage, t he enhanced vertical diffusion effectively transports the tracer upwar d and decreases the ground-level concentration, while in the later sta ge, it enhances downward transports from the upper layer and increases the ground-level concentration. A conceptual model is given for under standing the vertical transport due to vertical diffusion. The horizon tal diffusion introduced to the model has preferable impacts on foreca sts especially in the early stage. Finally, we discuss the predictabil ity of this model based on sensitivity to initial conditions of emissi on time and height. (C) 1998 Elsevier Science Ltd. All rights reserved .