Almost there!
Here are the final suggestions from Referee #1 that you may wish to consider:
I would like to thank the authors for addressing the comments. I have two follow-up comments that I suggest to address before publication.

1/ I agree that the source profile is a more accurate representation of the situation than two point sources, but does it affect the results downwind, for instance in EXP2, after 50 km transport?

2/ If Gaussian turbulence is used, I wonder its validity within the boundary layer in unstable situations (even with the TKE approach). Note that Flexpart v10.4 can handle skewed turbulence (see the work of Cassiani et al 2015; or Fig 1 in Pisso et al 2019, where concentrations are 30 % higher due to skewed turbulence.) I suggest to add a brief mentioning / discussion on this. On the other hand, perhaps the uncertainty added from the Gaussian turbulence assumption is small compared to the benefits from the online TKE approach.

References

Pisso, I., Sollum, E., Grythe, H., Kristiansen, N. I., Cassiani, M., Eckhardt, S., ... & Stohl, A. (2019). The Lagrangian particle dispersion model FLEXPART version 10.4. Geoscientific Model Development, 12(12), 4955-4997.

Cassiani, M., Stohl, A., & Brioude, J. (2015). Lagrangian stochastic modelling of dispersion in the convective boundary layer with skewed turbulence conditions and a vertical density gradient: Formulation and implementation in the FLEXPART model. Boundary-Layer Meteorology, 154(3), 367-390.