Status and evaluation of Enviro-HIRLAM: Differences between online and offline models

Abstract

Online coupled model systems in which a meteorological model contains emissions, transport, dispersion, deposition, chemistry and aerosol physics of pollutants have recently received much attention, mainly due to the prospects of including feedbacks between pollutants and meteorological fields and quantifying indirect effects. There are, however, several other important differences between online and offline coupled models and in this context it is important to investigate when online models are useful. This study presents the current status of Enviro-HIRLAM, an online coupled model developed at the Danish Meteorological Institute, and investigates the importance of increased availability of meteorological information to transport and dispersion. Enviro-HIRLAM is shown to perform satisfactory during tests of transport, dispersion and deposition, using data from the first European Tracer Experiment (ETEX-1) and measurements of deposited Cesium-137 made after the Chernobyl accident. Offline and online simulations of the ETEX-1 release are compared and it is shown that the offline coupling interval plays an important role in constraining the influence of meso-scale disturbances on (long range) plume development. © 2011 Springer Berlin Heidelberg.