Extended back-trajectories by means of adjoint equations

Type: Report
Series: RMK 105
Author: Robertson, Lennart


Back-trajectory models are examples of the most simple adjoint models used for tracing of important source regions attributed to measured tracers. These models do, however, suffer from oversimplification of the transport-diffusion processes in the atmosphere. By utilizing adjoint equations in a 3D transport-diffusion model several advantages could be achieved, all transport mechanisms are included and the response at receptor points could more properly mimic the sampled time-period of the measurements. In this paper the concept of adjoint equations is described, the similarity between back-trajectories and the adjoint technique is demonstrated, and options of using the ad joint technique for guidance of emission sources are explored. To illustrate the possibilities four different events are examined, the Chernobyl accident, the ETEX I exercise, the Algeciras accident and an event with heavy smoke noticed in Scandinavia. Finally, a suggestion for an operational setup is discussed.