Lagrangian particle dispersion modeling for the high Alpine site Jungfraujoch

This study investigates the performance of a regional‐scale, time‐reversed Lagrangian particle dispersion model (LPDM) to model the atmospheric transport of inert trace gases to the Swiss high Alpine measurement station Jungfraujoch on a routine basis. The model is based on the operational dispersion model of the Swiss and German weather services (MeteoSwiss and DWD) and runs on analyzed meteorological fields from the weather prediction model Consortium for Small‐Scale Modeling (COSMO) of MeteoSwiss. On the basis of a sensitivity analysis, parameter values are derived which result in a reasonable compromise between accuracy and computational costs. The uncertainty associated with the choice of parameter values is estimated to be approximately 40% for modeled total times during which the air had ground contact before reaching Jungfraujoch and approximately 50% for modeled CO mixing ratios at Jungfraujoch. The release height of the particles has the most significant impact. Comparison of modeled CO mixing ratios with measured data over a 4‐month period from July to October 2004 reveals best agreement for a release height of 80 m above model ground. The correlation between 3‐hour averages of measured and modeled data results is r = 0.4. For daily mean values we find r = 0.5. Correlations are higher in autumn than in summer. Absolute values of modeled mixing ratios tend to be rather low but still within the range of measured data.