The Use of high resolution numerical meteorological fields for regulatory dispersion modelling: An analysis of RAMS and MC2 fields over Kamloops, B.C

Numerical met fields have been used in regulatory dispersion modelling in B.C. during the last several years. The mesoscale fields are typically used in conjuction with surface observations in the CALMET meteorological model, which in turn is used to drive the CALPUFF dispersion model. Although the use of numerical data to represent upper-air flow is commonly considered a superior methodology to the extrapolation of twice-daily radiosonde data, there is little validation to support the claim. With the latest CALMET version, the option of modelling without any surface or upper-air observations is possible. It has been well documented that mesoscale models can have difficulty simulating the Boundary Layer in regions of complex terrain. Because of this, full use of the simulated data has the potential to significantly influence the determination of dispersion parameters in a model like CALPUFF. However, higher resolution numerical simulations may improve representation of Boundary Layer wind and other parameters.

A 1 km horizontal resolution RAMS simulation, and a 2 km MC2 simulation of the atmosphere over Kamloops, B.C. were used to conduct two-week CALMET simulations during a calm, episodic period in January, 2003. The CALMET simulations were compared to a benchmark simulation using 5 surface and one nearby upper-air observation stations. The comparison highlights the strengths and weaknesses of using the numerical fields both as a complete dataset and in combination with surface observations.