Source-receptor matrix calculation with a Lagrangian particle dispersion model in backward mode

[摘要] The possibility to calculate linear-source receptorrelationships for the transport of atmospheric trace substances with a Lagrangian particle dispersion model (LPDM) running in backward modeis shown and presented with many tests and examples. This mode requires only minor modifications of the forward LPDM. The derivationincludes the action of sources and of any first-order processes (transformation with prescribed rates, dry and wet deposition,radioactive decay, etc.). The backward mode is computationally advantageous if the number of receptors is less than the number of sourcesconsidered. The combination of an LPDM with the backward (adjoint) methodology is especially attractivefor the application to pointmeasurements, which can be handled without artificial numerical diffusion. Practical hints are provided for source-receptor calculationswith different settings, both in forward and backward mode.The equivalence of forward and backward calculations is shown in simpletests for release and sampling of particles,pure wet deposition, pure convective redistribution and realistic transport over a shortdistance.Furthermore, an application example explaining measurements of Cs-137 in Stockholm as transport from areas contaminated heavily inthe Chernobyl disaster is included.

[学科分类] 大气科学