Sensitivity of the DERMA long-range Gaussian dispersion model to meteorological input and diffusion parameters

Abstract The Danish Emergency Response Model of the Atmosphere (DERMA) is described and applied to the first ETEX experiment. By using analysed low-resolution numerical weather-prediction data from the global model of the European Centre for Medium-range Weather Forecast (ECMWF) as well as higher-resolution data from two versions of the High Resolution Limited Area Model (HIRLAM), which are operational at the Danish Meteorological Institute (DMI), the sensitivity of DERMA to the resolution of meteorological data is analysed by comparing DERMA results with concentration measurements. Furthermore, the sensitivity to boundary-layer height and diffusion parameters is studied. These parameters include the critical bulk Richardson number, which is used to estimate the atmospheric boundary-layer height, the horizontal eddy diffusivity and the Lagrangian turbulence time scale. The parameters, which provide the best performance of DERMA, are 0.25 for the critical bulk Richardson number, 6×103 m2 s-1 for the horizontal eddy diffusivity, and 3 h for the Lagrangian time scale. DERMA is much more sensitive to boundary-layer parameters when using high-resolution DMI-HIRLAM data than when using data of lower resolution from the ECMWF. Finally, the bulk Richardson number method of boundary-layer height calculation applied to DMI-HIRLAM data is verified directly against routine radiosondes released under the tracer gas plume. The boundary-layer height estimates based on analysed NWP model data agree well with observations, and the agreement deteriorates as a function of forecast length.

[1]  A. Arakawa.  Computational design for long-term numerical integration of the equations of fluid motion: two-dimen , 1997 .

[2]  Erik Lyck,et al.  Mesoscale influence on long-range transport — evidence from ETEX modelling and observations , 1998 .

[3]  F. B. Smith.  Conditioned particle motion in a homogeneous turbulent field , 1968 .

[4]  Paolo Zannetti,et al.  Air pollution modeling , 1990 .

[5]  D. Williams,et al.  Measurements of relative σy up to 1800 km from a single source , 1988 .

[6]  J. T. Lee,et al.  The use of eulerian initial conditions in a Lagrangian model of turbulent diffusion , 1983 .

[7]  Jerzy Bartnicki,et al.  A real time dispersion model for severe nuclear accidents, tested in the European tracer experiment , 1996 .

[8]  A. Rasmussen,et al.  Forecast of atmospheric boundary-layer height utilised for ETEX real-time dispersion modelling , 1996 .

[9]  Albert A. M. Holtslag,et al.  Eddy Diffusivity and Countergradient Transport in the Convective Atmospheric Boundary Layer , 1991 .

[10]  L. Mahrt,et al.  The Nocturnal Surface Inversion and Influence of Clear-Air Radiative Cooling , 1982 .

[11]  K Nodop.  ETEX symposium on long-range atmospheric transport, model verification and emergency response 13-16 May 1997, Vienna(Austria) : proceedings , 1997 .

[12]  I. Troen,et al.  A simple model of the atmospheric boundary layer; sensitivity to surface evaporation , 1986 .

[13]  A. Simmons,et al.  An Energy and Angular-Momentum Conserving Vertical Finite-Difference Scheme and Hybrid Vertical Coordinates , 1981 .

[14]  S. Barr,et al.  The random force theory applied to regional scale tropospheric diffusion , 1987 .

[15]  R. H. Maryon,et al.  The U.K. nuclear accident model , 1991 .

[16]  F. A. Gifford,et al.  Horizontal diffusion in the atmosphere: A Lagrangian-dynamical theory , 1982 .

[17]  Geoffrey Ingram Taylor,et al.  Diffusion by Continuous Movements , 1922 .

[18]  J. T. Lee,et al.  Eulerian—Lagrangian relationships in monte carlo simulations of turbulent diffusion , 1983 .

[19]  A. Holtslag,et al.  Evaluation and model impacts of alternative boundary-layer height formulations , 1996 .

[20]  F. A. Gifford,et al.  The random force theory: Application to meso- and large-scale atmospheric diffusion , 1984 .

[21]  P. Zannetti.  Air Pollution Meteorology , 1990 .