Review of “A long pathway of high water vapor from the Asian summer

monsoon into the stratosphere” by Konopka et al.

This is an important paper, and it provides good evidence that ‘convective moistening of the stratosphere’ over monsoons is far more complicated than some of the earlier proponents have envisioned.  Previous discussions of the convective moistening process have assumed that

Convection reaching above the tropopause simply resets the relative humidity to saturation.  In this study, it is evident that the air parcels may continue to dehydrate due to the elevated cold points as they move around in the Asian monsoon anticyclone.  In my own mind, the higher the convection, the colder the air due to adiabatic expansion and the more complete the dehydration.  This paper shows that parcels launched at the top of other convective events, can transit through colder air undergoing later dehydration. 

I found the abstract quite descriptive and useful.  I recommend that a longer version of the abstract be repeated in the summary section which could be expanded.

In general, the figures are hard to read, and the captions are too long. The author might consider breaking up the figures into smaller groups and edit the captions.

I would delete Fig. 5, not very helpful.

Specific comments:

I would reference Brewer (1949) as the originator of the CP regulation of water vapor theory.

The introduction is too brief to cover this complex and important scientific field.  For example, you might also expand on some of the previous publications mentioned. The Randel & Park (2019) paper is a particularly important prelude to these conclusions.  Additionally, there are additional trajectory model simulations by Ueyama & Schoeberl and collaborators are relevant – these papers also used convection and ice formation models.  The Avery paper focusses on El Nino, not the monsoon. Lumping the regular monsoon convection system with El Nino seems like a stretch to me.

Table 1 is confusing. 10.08 flights? Is this the date? Why is this relevant? I would put a comment in the Table on the difference between Type A and Type B.  Perhaps a comment line ‘recent convective influence’ and ‘aged convective influence’ for A and B -  something that the reader can immediately grasp.

I would put the references to the instruments in Figure 1 caption into the text. All the references make the caption difficult to read. “time distance?” you mean time since encountering an LDP.

The exact LDP is a little uncertain since gravity waves could create an LDP even after the temperature along the path has warmed up a little.  I assume you observed temperature fluctuation measurements as part of the aircraft flights. You could translate this into an uncertainty in the LDP time using Delta-T and the temperature along the path. These fluctuations could be important.  It wasn’t clear from the text that Podglajen et al. (2016) gravity wave parameterization is included, or if it is included, does it match observations over mountainous Himalayas?

You might add some additional references on CO photolysis beyond von Hobe (2021).  CO is measured by MLS.  Minschwaner et al., (2010) is the classic paper on CO lifetime, also see Liang et al. (2023) and references therein.

Clearly type B is ‘aged air’ with higher ozone, lower CO whereas type A is ‘younger air’. So it was a little surprising to see the LDP age for type A all over the map (Fig.1 C).  This confusing point was straightened out in Fig. 1d so maybe 1c could be eliminated or make the symbols smaller.

FIG. 2 – it might be useful to locate where the Part b Lagrangian dry point is located on the map shown in Part a.  I would have shown the type A trajectory in 2c – makes your point better – and put the Type A label inside 2d.  Remove the not-needed information from caption of Fig. 2

Line 80.  CALIPSO does not detect ice mixing ratios. It detects particles and then using a model the ice mixing ratios are inferred… maybe ‘..which can be used to infer ice mixing ratios (Avery et al., 2012).

Fig. 4 caption, although way too long, was actually readable.

How does the aircraft temperatures compare with ERA5. The type B trajectories will encounter ERA5 temperatures, if these temperatures are too warm and you are downstream from the coldest temperature, then you might see a bias.  Can you validate these temperatures against GNSS-RO?

How do you account for the vertical averaging kernel in the MLS measurements?

Line 100 Schoeberl and Dessler used forward trajectories.

I think some explanation on what is done with full trajectories is needed.  Does the full start at the measurement point and go backward X days, or – like Ueyama et al. (2023) does it terminate at convection?

Line 111 ‘highest ice concentration found mainly at southern edge.’  Where the temperatures are coldest according to Fig. 4.. might want to point that out.

Line 117  … vertical sampling resolution than CALIPSO

Line 124  ‘ are not able to freeze out the excess water’  … assuming the temperatures from ERA5 are correct and there are no gravity waves. How much colder would the temperatures have to be to get the right water vapor?  I suspect only a couple degrees…

Line 126.. I am confused about the backward trajectories.  Presumably you start with the aircraft measurement of water and you go backward in time to get a temperature field.

Then starting with a saturated parcel at the furthest back time where it has encountered convection, you dehydrate and arrive at the predicted measurement. Do the two values of water agree?  I am wondering if the instrument measured air might be wet biased. Do they agree with MLS?  I think that this weird Type B bias needs more discussion as to possible sources of error. 

I would delete Fig. 5. I found it confusing and not helpful.

1^st review of “A long pathway of high water vapor from the Asian summer monsoon into the stratosphere” submitted by Konopuka et al. to EGUsphere.

This manuscript describes that the variation of water vapor content in the Asian summer monsoon region and its effect on water vapor distribution in the lower stratosphere on the large-scale through backward/forward trajectory analysis that considers the microphysical processes of ice clouds while referring to in-situ observation data from aircraft, StratoClim Geophysica campaign. In-situ observation data from the campaign are extremely valuable, and unique research is expected in that the simultaneous observation of water vapor, ice clouds, and water vapor isotopes, actually it is valuable that those data set specified the history of the air from fresh convective air as Type A. This reviewer likes this research subject and prefer to publish if the responses to the reviewer's major comments are satisfactory. The followings are my major and minor comments for your reference.

Major comments:

• Title/Abstract

In the title and abstract, the discussion of high-concentration water vapor content appears, but the main text is more about the relationship between the formation of low-concentration water vapor content above the CPT and ice clouds. It would be better to change the title/abstract along the main subject or vice versa. If you want to investigate the behavior of high-concentration water vapor above the CPT, why not analyze cases where water vapor is more than 7ppmv shown in Fig.1a? It is also not clear the reason why Type B and M were used for analysis. Please describe the reason to select those cases.

• Structure of manuscript

Many explanations and interpretations (and it is important!) of the figures were written on the appendix, and it was very difficult to read. Implying that it may be a difficult task to summarize in a short report. For example, “fresh convection signature” in Figure 1 was explained in the caption of Figure A1 of Appendix A, and the explanation of the trajectory analysis and the definition of CPT were in Appendix A those are important matter for this study.

• Representativeness of selected data

Regarding the effect on water vapor in the lower stratosphere, which is the purpose, there is a gap because the trajectory analysis is performed with only a limited number of observations (Type A,B and M). Further, related with my major comment (1), it is unclear whether the selected cases are actually representative ones. It is recommended that you add the reason for the selection and add an evaluation of its validity.

• Quality of trajectory model

The trajectory model used for the analysis may be the latest, but what is the guarantee of the reliability of the expression of supersaturation and vertical flow (here, diabatic heating is substituted), which exist in many cases? Shouldn't those differences (between observation and simulation) also be included in the discussion section?

Minor comments:

Line numbers in odd pare are missing from page 3.

p.2, l.26: How scales of “the large-scale moisture budget” for temporal and horizontal? How scales of “the large-scale moisture budget” for temporal and horizontal?

p.2, l.28: the subtitle should be changed, for example in situ and behavior of selected data etc..

p.2, l.30 : need the explanation of definition of “the local CPT” here and the “local” means unclear.

p.3, l.1: as a function of “vertical” distance to the CPT. Let me confirm that this distance was defined in either direction (up/down or above/below).

p.3, l.4 with Figure 1c: “fresh convection signatures” In the case of "fresh", the CO concentration is likely to be high due to the air from troposphere, but this is inconsistent with the fact that the CO concentration has a range from 30 to 100 ppb. How can this be explained? In relation to this, does the distribution of LDP age from 60 days before in Fig1c mean that it has been present in the lower stratosphere since 60 days before? If so, can you say "fresh"? This reviewer confuses this point.

p.3, Fig1: To understand the positional relationship in the vertical direction, it is useful to have the potential temperature distribution.

p.4, l.48: Considering supersaturation, should it be removed?

p.4, l.63-64; “where …” Is it not fully represented by FDM, or does it look like it has not been removed because the fluctuation of FDM is small?

p.4, last paragraph : On Type A, the temperatures are rising in the first three days (Fig 2c), but there is a lot of ice (Fig2d). In Fig 3, is it due to the sedimentation of the ice that the decrease in water vapor is remarkable after 7 hours and 2 days?

p.5, bottom of Fig 2c:  It is better that the y-axis direction is opposite. It is easy to understand to express that the temperature is low at the top, that is, the altitude is high.

p.5, l.2 in caption of Fig 2. : in Figure 1 (a). Three representative … (need comma)

p.5, l.5 in caption of Fig 2. : replace to slash, 60/43/54

p.6, last sentence of caption in Fig3.: back (grey) and forward (black)

p.7, l.9 in caption of Fig 4:  light grey -> white?

In general, the 2-3PV is defined as dynamical tropopause. The value of 5.8 – 6.2 PVU is higher than general.

p.8, l.88: on “spread” for Type B; Can't you visualize how much the trajectory is “spread”? Is it possible to add an example of spreading to Fig2a?

p.8, l.112: Is it correct (good correlation) to focus only on the south side of ASM in the case of Type B?

p.9, l.121: Figure 5(c) -> Figure 4(c)

p.9, Fig5: The horizontal and vertical lines for supplementation in the figure are too thin to be seen.