Orographic and convective gravity waves above the Alps and Andes Mountains during GPS radio occultation events – a case study

Hierro, Rodrigo; Steiner, Andrea K.; de la Torre, Alejandro; Alexander, Peter; Llamedo, Pablo; Cremades, Pablo

doi:https://doi.org/10.5194/amt-11-3523-2018

Articles | Volume 11, issue 6

https://doi.org/10.5194/amt-11-3523-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Observing Atmosphere and Climate with Occultation Techniques...

https://doi.org/10.5194/amt-11-3523-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 11, issue 6

Research article

|

19 Jun 2018

Research article |

| 19 Jun 2018

Orographic and convective gravity waves above the Alps and Andes Mountains during GPS radio occultation events – a case study

Rodrigo Hierro, Andrea K. Steiner, Alejandro de la Torre, Peter Alexander, Pablo Llamedo, and Pablo Cremades

Download

Final revised paper (published on 19 Jun 2018)
Preprint (discussion started on 24 Oct 2017)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

- Printer-friendly version

- Supplement

RC1: 'reviewer comment', Anonymous Referee #1, 14 Nov 2017
- AC1: 'Orographic and convective gravity waves above the Alps and Andes mountains during GPS radio occultation events – a case study', Rodrigo Hierro, 19 Feb 2018
RC2: 'Review for Hierro et al.', Anonymous Referee #2, 14 Jan 2018
- AC2: 'Orographic and convective gravity waves above the Alps and Andes mountains during GPS radio occultation events – a case study', Rodrigo Hierro, 19 Feb 2018

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Rodrigo Hierro on behalf of the Authors (19 Feb 2018) Manuscript

ED: Referee Nomination & Report Request started (05 Mar 2018) by Jens Wickert

RR by Anonymous Referee #1 (14 Mar 2018)

Suggestions for revision or reasons for rejection

Review of the revised manuscript "Orographic and convective gravity waves above the Alps and Andes mountains during GPS radio occultation events – a case study" by Hierro et al.

The authors did a great job in addressing my major comments - congratulations!
The following revisions were made:
(I) The amplitude attenuation factor has been considered for the case studies discussed.
(II) It has been considered that WRF simulations will not always be sufficient to describe the waves seen in RO soundings.
(III) ERA Interim data were analyzed for the case in which WRF simulations were not sufficient to explain the RO soundings. For matching the RO soundings now also temperature fluctuations are considered, in addition to fluctuations of vertical wind
(IV) Discussion of wavelength biases was moved into an appendix.

Overall, the manuscript is much improved now and can be recommended for publication in AMT after addressing a couple of remaining minor, but important comments.

My main comments are:
* it is difficult to generally rule out the co-existence of jet-generated GWs in the subtropics, even for selected cases
* the text should be screened for consistency and some additional information added, some points are listed in my Minor Comments

In the following, line numbers refer to the manuscript version with changes NOT highlighted.

Minor comments:

(1) The existence of jet-generated GWs cannot be generally ruled out because your work focuses on the subtropics, and there the subtropical jets are more or less omnipresent. This is confirmed for your Alps and Andes cases in Figs. 5 and 9 where wind speeds of well above 20m/s are evidently seen in the troposphere.

Therefore my questions, concerning l.193, but also elsewhere:
What is the criterion you are using to make sure that GWs generated by jets or fronts are absent?

Are you sure that this criterion will always work?
The wave seen in ERA Interim (Fig.7) that could not be simulated by WRF could be a jet-generated GW.

(2) l.318:
The MW should be considerably attenuated below AND ABOVE the tropopause, and therefore be invisible for RO soundings.
This is also what you discuss in Sect. 3.1.3.

(3) l.329:
It should be mentioned that ERA Interim will give some information about longer horizontal wavelength GWs, but has a relatively coarse resolution and will strongly underestimate wave amplitudes. Accordingly, amplitudes in Fig. 7 are quite low. If this wave is seen in RO soundings, it would have a much larger amplitude.
Of course, higher resolution ECMWF data would have been better suited, however, they are probably difficult to obtain. Therefore I really appreciate the authors' efforts based on ERA Interim.

(4) After l.339: caption of Table 1
Please mention that line 1 in the table refers to the wave seen in ERA-Interim, while lines 2-4 in this table refer to the WRF simulations.

(5) l.391-395: I guess, erroneously a wrong word was used in l.391!
Mountain waves cannot produce circular wave patterns! MWs usually have wave fronts that are aligned parallel to the mountain range, or, in case of isolated mountains, MWs can display ship-wave patterns.
Circular wave patterns are usually found above convective GW sources.

Suggestion: just change "orographic" in l.391 to "non-orographic"

(6) l.442: It should be mentioned that attenuation factors close to 1 have to be taken with some caution because "ideal" wave patterns are assumed for this calculation.

(7) l.499: below the tropopause -> below and above the tropopause

(8) l.500: delete "in the troposphere" and refer to the GWs simulated with WRF
suggestion:

attenuation factor in the troposphere confirms that the GW
->
attenuation factor confirms that these GW

(9) l.505: same problem as in l.391-395
orographic -> non-orographic

Other comments:

(1) l.28 In this last case -> In the Andes case

(2) l.43 less than -> better than

(3) l.90 determined -> showed

(4) l.104 intrinsic period -> intrinsic frequency

(5) l.110 anomay -> anomaly

(6) l.114/115
to Alps and Andes ranges.
->
to the Alps and Andes mountain ranges.

(7) l.185 inner one. -> inner ones.

(8) Fig.5: color scales for dw and dT are missing
In the figure caption it should be better clarified that in (a) dw is shown, while in (b) and (c) dT is shown. The wording "...dw and dT..." with dw and dT so close together is somehow misleading.

(9) l.323:
presence of GW with scale long enough is not able to be
->
presence of large scale GWs that are not able to be

(10) l.325: are observed. -> are analyzed.

(11) l.325: a defined -> a well defined

(12) l.327: in 0.90. -> to 0.90 (first line in Table 1).

(13) l.371 respectedly, -> respectively,

(14) l.376: "The TP altitudes." not a complete sentence!

(15) Caption of Fig.9, same problem with dw and dT as for Fig.5

(16) Text after l.415: These sentences are somehow twisted, please rewrite!
Suggestion:

Next, the wavelike structure of the RO T profile, retrieved at the Andes region. This profile is shown in the central panels of Fig 3b. Its horizontally projected LTP is seen in Fig. 8, is analyzed.
->
Next, the wavelike structure of the RO T profile retrieved at the Andes region is analyzed. This profile is shown in the central panels of Fig 3b, and its horizontally projected LTP is seen in Fig. 8.

(17) After l.420 in the revised manuscript, there is a dashed line. Possibly, a file conversion error. Please check!

(18) After l.450 in the revised manuscript:
Please check! It looks like an equation should have been deleted, but wasn't.

(19) l.475: orographic forcing and -> orographically forced or

(20) l.512: decreasing Lz. -> at the same time Lz decreases.

(21) l.518
A partial attenuation reveals
->
An evaluation of the partial attenuation coefficient reveals

(22) l.533:
Apendix -> Appendix

(23) l.542: This sentence is somehow twisted, suggestion:
It is defined the distortion as the ratio:
->
We define the distortion as the ratio:

(24) l.586: wasinitiated -> was initiated

(25) l.589: wassupported -> was supported

Hide

ED: Publish subject to minor revisions (review by editor) (14 May 2018) by Jens Wickert

AR by Rodrigo Hierro on behalf of the Authors (25 May 2018) Author's response Manuscript

ED: Publish as is (04 Jun 2018) by Jens Wickert

AR by Rodrigo Hierro on behalf of the Authors (05 Jun 2018)

Short summary

This paper analyzed the collocated GPS radio occultation profiles near the convective systems identified from ISCCP over two orographic regions of the Alps and Andes. Gravity wave (GW) analysis over both selected regions was also carried out. The gravity wave signature from the two case studies were investigated using mesoscale WRF simulations, ERA-Interim reanalysis data, and measured RO temperature profiles. The absence of fronts or jets during both case studies reveals similar relevant GWs.