The authors study troposphere-to-stratosphere (TST) transport during landfall of typhoon Molave over the Philippines. Specifically, they quantify TST using a particle dispersion model embedded in a high-resolution simulation of the typhoon. Their results suggest that orographically enhanced convection as well as the associated gravity wave activity play an important role in TST in this particular case.

 

The study contains interesting new insights and inferences into the complex dynamics and transport contributions of tropical cyclones. The results should be of interest to the readership of ACP. I recommend publication after taking into account the comments below. One of the more general comments (3) may require major revisions, which is why I selected "major revision", although I'm not sure.

 

General comments:

 

1)

The authors use the instantaneous local tropopause levels (lapse-rate tropopause, LRT, for bottom of TTL; cold-point tropopause, CPT, for bottom of stratosphere) to determine whether parcels enter the TTL or stratosphere. At such a local, instantaneous level it is not completely clear whether this tropopause really acts as a transport barrier. Conceptually, one would need some sort of background tropopause from the surrounding area and/or time period to characterize it as a transport barrier. I appreciate that this would be complicated to implement and would result in additional uncertainties. But I'd like to see some discussion of this potential issue.

 

2)

The above potential issue is also related to the question of the fate of those air parcels that locally overshoot/enter stratosphere further downstream. In lines 194-196 the authors allude to the fact that many parcels in fact do not stay above the tropopause until the end of the simulation, which suggests that they did not conclusively cross the transport barrier. What does this mean for the actual net impact by the tropical cyclone on the composition of stratospheric air? Again, I'd like to see more discussion of this potential issue.

 

3)

Yet another related, and more technical question is to what extend parcels fluctuate above/below the tropopause due to fluctuations in the parcel position itself or fluctuations in the tropopause level? This could be quantified and would provide a feeling for the transient nature of the local tropopause itself and its potential role in the studied transport pathways.

 

4)

Importance of tropical cyclones for overall TST across the entire tropical tropopause is debatable - I'm not aware of evidence that this component of TST is substantial (measured relative to TST by other transport pathways, such as planetary-scale overturning circulations, equatorial waves, "regular" deep convection). From that perspective one might question the importance of orographically enhanced TST via the associated gravity waves, which may represent a small portion of all tropical cyclones. So the motivation in the context of tropics-mean TST seems questionable. Do the authors agree? Or do you see stronger motivation? In either case it'd be nice to spell this out more explicitly.

 

 

Minor comments:

 

line 11 (last sentence of abstract): this seems like a strong overstatement to me (see general comment above); I recommend to instead add a sentence about potential implications for TST in other tropical cyclones

 

Introduction: I'm missing some motivation as to why you chose to provide another study of Molave (beyond Huang et al., who already studied STE associated with gravity wave activity for this particular typhoon). To be sure, I'm not saying that there aren't sufficiently novel insights here, but given the broader question of importance of the findings (see general comment above) it seems desirable to provide more/different motivation.

 

line 63: please add information whether this is a one-moment or two-moment scheme?

 

line 90: please state here which configuration you actually did include (passive?)

 

line 124: please clarify in which way you need/use the two time steps

 

line 127: how do you define the top of PBL?

 

line 158: please include more detail in which way the wave may become unstable and how you infer this from the plots

 

Fig. 4: it'd be helpful to have axes on the zoomed panels (e.g., upper left looks like it has longitude on x and latitude on y - correct?)

 

line 196: missing "." at end of sentence after "simulation"

 

Fig. 5: it'd be helpful to label the panels in some way (e.g., "entering TTL, single intrusion" etc.)

 

line 204: I don't understand how the remark in parenthesis fits the preceding statement "mostly affected by first intrusions" (btw, you could delete "(Table 2)" in this line - should be clear from previous sentence)

 

Fig. 7: I can't quite follow some of the plotting choices - why is there no shaded indication of convection for the "orographically enhanced updrafts"? What is the difference between the "overshooting updrafts" as part of the typhoon and the "overshooting convection" (gray) next to it? In what way should I be able to infer the interaction of the typhoon with orography (the surface winds look confusing to me - shouldn't they converge into the typhoon instead of flowing out)?