Impact of Increased Vertical Resolution in WACCM on the Climatology of Major Sudden Stratospheric Warmings

Round 1

Reviewer 1 Report

Dear Editor,

The authors have all my concerns. The revision have improved the manuscript.  I only have a couple of minor suggestions (below), almost all of which are grammatical.

The line numbers correspond to the manuscript with highlighted corrections.

L37 : space between 'displacement' and 'or'
L52 : Perhaps this phrase can be rephrased a bit? "For example, as shown by other studies [27,28], dynamical cores can underestimate the occerences of SSWs"
L65 : My guess is that GW represents Gravity Waves - but this short form has not been introduced in the text before this point. 

Figure 3 caption : significativity -> significance

L351 : I do not fully agree with the explanation. Are the authors suggesting that the planetary waves generated by land-sea contrast or orography are affected by the non orographic gravity waves generated exclusively through parameterizations? I am almost certain that this is not the case.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

This is a resubmission of the manuscript that I reviewed last year. This manuscript performed three kinds of comparisons: WACCM3.5 vs. WACCM4.0, standard vs. high vertical resolution, and coupled vs. non-coupled ocean, concerning the SSW frequency and the SSW_D/SSW_S ratio. Although the primary focus of this manuscript is the impact of increases vertical resolution, how it affects the SSW frequency and the SSW_D/SSW_S ratio is not discussed sufficiently. Further analysis for this purpose is required as mentioned below. Thus I recommend major revision of this manuscript before acceptance.

Major comments:

• Although the authors concluded that the SSW frequency was improved in WACCM4.0 compared to WACCM3.5, it is not statistically significant. So they should say that the SSW frequency was not improved in a statistical sense.
• The SSW_D/SSW_S ratio is closer to the reanalysis in the standard than in the high vertical resolution, and in the coupled than in the non-coupled ocean. The former can change the momentum deposit due to gravity waves and zonal wind distribution, so that it would alter the planetary wave propagation. The latter would change the planetary wave generation through the change of land-ocean heat contrast. In order to clarify what affects the SSW_D/SSW_S ratio, E-P flux due to zonal wavenumber 1 and 2 needs to be evaluated separately. However, this analysis is not performed in this manuscript, so that the discussion on this problem is very poor.
• L.258-271
  This part discusses the effect of high vertical resolution on the GWD and planetary wave propagation. However, if the GWD alters the propagation of planetary waves with zonal wavenumber 1 and 2 in a similar fashion, it cannot explain the change of SSW_D/SSW_S ratio. In addition, the effect of coupled or non-coupled ocean is not discussed at all. As mentioned above, the E-P flux with zonal wavenumber 1 and 2 needs to be examined separately.

Minor comments:

• L.61-63
  Please show adequate references.
• L.170
  The authors should mention that mesoscale GWs are parameterized.
• L.200-202
  Why can the authors say that the high vertical resolution favors the occurrence of SSWs despite the different feature between REFC1 and REFC2?
• Figs. 6 and 7
  Please show contour intervals.
• L.307-313
  I cannot find where the authors showed ", with the exception of the period prior to -15 days relative to the central date during SSW_S,."

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

My overall impression of this paper is pretty positive.

This manuscript is well written and a worth-well study, and the results of this paper undoubtedly are interesting.

I recommend the publication of the manuscript.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors adequately answered to my previous comments, so that my concern was resolved. I agree with the publication of this manuscript in current form.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Dear Editor and Authors,

PFA a PDF with my comments

Comments for author File: Comments.pdf

Reviewer 2 Report

See attached file

Comments for author File: Comments.pdf

Reviewer 3 Report

General comments:

This manuscript examines effects of model vertical resolution on the SSW behavior in WACCM based on 4 kinds of ensemble simulations with/without high vertical resolution and coupled ocean. Although the result itself is interesting, how the authors interpret the result is not discussed well. In addition, there are some mistakes in their figure(s) and table which can change the conclusion. Thus, I recommend rejection of this manuscript and resubmission after the revision.

Major comments:

-Section 2

The authors should describe the GWD parameterization used in WACCM. Especially whether both of orographic and non-orographic schemes are implemented or not is crucial and affects the subsequent discussion.

-Fig.3

A sum of SSW monthly frequency for JRA55 is about 0.55, which is not consistent with 0.65 given in Table. 1. If the seasonal variation of SSW frequency is wrong, the discussion in L.195-201 must be changed.

-Fig.4 and L.148-158

I cannot understand why this part is included in this manuscript.

-SSW_S/SSW_D ratio

The authors mentioned that the coupled ocean improved the SSW_S/SSW_D ratio, but no discussion is performed in the manuscript. If the specified SST is monthly mean, it would suppress the planetary wave generation due to heat contrast. If the authors show how much the ratio between wavenumber 1 and 2 E-P flux changes between REFC1 and REFC2, it will help us interpret the difference of SSW_S/SSW_D ratio. The authors should mention these possibilities.

Minor comments:

-L.64

“CCMVAL2” -> “CCMVal2”

-L.101

“1.3” -> “1.25”

-L.119

“flow” -> “flux”

-Table.1

Is SSW_D/SSW_S in JRA55 really 0.68? The value between 1958-2002 shown in Charlton and Polvani (2007) is 16/15(=1.07), which is much higher than 0.68.

-L.144

“0.5-0.2” -> “0.05-0.2”

“December” -> “November”

-L.178

Is “20 days” really true? It seems a few days to me.

-L.179-180

I cannot catch this feature in Fig. 5.

-Fig.6

“DIC” -> “DEC”

-L.191-192

The values should be positive.

-L.192-195

I cannot catch this feature in Fig. 6.

-Sec.6

“Gravity Wave Drag” should be “Parameterized Gravity Wave Drag”, because the E-P flux must include resolved gravity waves.

-Fig.7

I think “p > 0.05” is stippled.

The E-P flux divergence shows a stepwise feature in the vertical around 20-40 km over the NH polar region, which looks artificial. Please check the calculation.

It is better to add a climatological tropopause in the figures.

-L.207-217

The content partially overlaps with the next paragraph. This paragraph should focus on that the differences between high and standard resolutions are concentrated in NH polar USLM and extratropical/polar UTLS, and the differences between REFC1 and REFC2 appear only in the extratropical UTLS.

-L.223-226

It seems that positive and negative are opposite.

-L.232

Please explain what the seeming contradiction is.

-L.233

The UTLS region is not drawn in Fig. 8.

-L.236-237

Why can you conclude that the non-orographic GWD is dominant from the figure of GWD/EPFD?

-L.243

The authors mentioned in the abstract that the frequency of occurrence of SSWs is improved. Was it improved or close to the previous one?

-L.248

“< 1.85” -> “> 1.85”

-L.252-256

No discussion specific to SSW_S was performed in this manuscript.