Use of the CAPTEX data for evaluations of a long-range transport numerical model with a four-dimensional data assimilation technique

Abstract

The assimilated wind fields and model-produced turbulence fields during a period of 2.25 days are used to simulate plume trajectories and surface concentrations through a random-particle statistical method. Two tracer releases in the CAPTEX are investigated: one was in a light-wind fair weather condition and produced a widely spread puff distribution; the other was associated with a surface cold front resulting in a rather narrow puff distribution. The observed winds are successfully assimilated in both cases except in the period of the cold front passage, suggesting that a finer temporal resolution of the rawinsonde observations is desirable in dealing with special weather conditions. The general patterns of the puff distributions are also well simulated. Quantitatitively, 57% of the modeled concentrations are within a factor of 4 in comparison with the observed concentrations in the light-wind case. -from Authors