Comment on: “Corrections to the Mathematical Formulation of a Backwards Lagrangian Particle Dispersion Model” by Gibson and Sailor (2012: Boundary-Layer Meteorology 145, 399 - 406)

Summary, in English

We discuss the results of Gibson and Sailor (Boundary-Layer Meteorol 145:399–
406, 2012)who suggest several corrections to themathematical formulation of the Lagrangian
particle dispersion model of Rotach et al. (Q J R Meteorol Soc 122:367–389, 1996). While
most of the suggested corrections had already been implemented in the 1990s, one suggested
correction raises a valid point, but results in a violation of the well-mixed criterion. Here we
improve their idea and test the impact on model results using a well-mixed test and a comparison
with wind-tunnel experimental data. The new approach results in similar dispersion
patterns as the original approach, while the approach suggested by Gibson and Sailor leads
to erroneously reduced concentrations near the ground in convective and especially forced
convective conditions.