Measurements of aerosol fluxes to speulder forest using a micrometeorological technique

It has often been stated that micrometeorological and throughfall measurements of dry deposition differ by an order of magnitude with the results being highly variable and difficult to interpret or reconcile. We present measurements by the eddy correlation method of sub-micron aerosol deposition to a forest and show that they are large, typically 1 cm s−1 or more. We compare the measurements with literature values obtained by throughfall and related techniques. The results, rather than being irreconcilable, show a clear and consistent behaviour in deposition velocity across the aerosol size spectrum, despite the very different techniques involved. There would appear to be a contradiction with previously assumed model predictions of aerosol deposition velocity to forests and rough vegetated surfaces particularly for particles in the size range 0.1–1.0 μm where collection efficiencies appear to be significantly underestimated. A simple deposition velocity parameterisation as a function of stability and size is presented.