The relation of the planetary boundary layer height to the vertical aerosol distribution in chemistry transport models


Simulated meteorological fields, ground values of aerosol concentrations (PM2.5) and aerosol concentration profiles, all calculated within the Air Quality Model Evaluation International Initiative (AQMEII) for the year 2006 for Europe are used to investigate the relation of the height of the planetary boundary layer (PBL) to the modelled aerosol concentrations. It was found that in many cases simulated PBL heights match the observed values at Lindenberg, Germany, quite well at noon and under convective conditions. On the other hand, in winter and at night time, when the atmosphere is more frequently stably stratified, the modelled values underestimate the observed PBL height quite significantly. A strong relationship between the simulated PBL height and the aerosol concentrations at ground was found. While those models which showed good agreement with the observed PBL height typically underestimate PM2.5, too low PBL heights were connected with higher aerosol concentrations close to ground and therefore lower bias. Model biases in PBL height and in PM2.5 concentration at ground were found to be highly anti-correlated.
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