Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

Pramitha, M.; Venkat Ratnam, M.; Taori, A.; Krishna Murthy, B. V.; Pallamraju, D.; Vijaya Bhaskar Rao, S.

doi:https://doi.org/10.5194/acp-15-2709-2015

Articles | Volume 15, issue 5

https://doi.org/10.5194/acp-15-2709-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-15-2709-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 15, issue 5

Research article

|

10 Mar 2015

Research article |

| 10 Mar 2015

Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

M. Pramitha, M. Venkat Ratnam, A. Taori, B. V. Krishna Murthy, D. Pallamraju, and S. Vijaya Bhaskar Rao

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Final revised paper (published on 10 Mar 2015)
Preprint (discussion started on 29 Jul 2014)

Interactive discussion

Status: closed

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

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- Supplement

RC C6175: 'Review comment', Anonymous Referee #1, 25 Aug 2014
- AC C8630: 'Replies to Reviewer #1 Comments/suggestions', M. Venkat Ratnam, 30 Oct 2014
RC C8015: 'Interactive comment', Anonymous Referee #2, 14 Oct 2014
- AC C8638: 'Replies to Reviewer #2 Comments/suggestions', M. Venkat Ratnam, 30 Oct 2014

Peer-review completion

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

AR by M. Venkat Ratnam on behalf of the Authors (30 Oct 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Nov 2014) by William Ward

RR by Anonymous Referee #1 (23 Nov 2014)

Suggestions for revision or reasons for rejection

The paper presents an interesting study to infer GW sources by reverse ray-tracing. The paper is well structured and the evidence shown is convincing. The English should be improved with the help of the copy-editing service of Copernicus. A few minor comments which should be taken into account and a few suggestions for better readability are given below.

Minor comments:

L495 For "likely" there is too sparse evidence presented in the paper. The wave also may reach a critical level from below and a different kind of source (asociated or non-associated with a postential wave from below) generates the new wave reaching the MLT.
A potential explanation is that the waves ...

L314 Background wind ... this condition is already contained in 4). You should not need to use an additional condition

A few suggestions for the abstract (and please don't use successful, for the technical part it is straight forward!)

Sources and propagation characteristics of high frequency gravity waves observed in the mesosphere using airglow emissions from Gadanki (13.5oN, 79.2oE) and
Hyderabad (17.5oN, 78.5oE) are investigated using reverse ray tracing. Wave amplitudes are also traced back including both radiative and diffusive damping.
The ray tracing is performed using background temperature and wind data obtained from MSISE-90 and HWM-07 models, respectively. For the Gadanki region the suitability of
these models is tested. Further, a climatological model of the background atmosphere for the Gadanki
region has been developed using nearly 30 years of observations available from a variety of ground-based
(MST radar, radiosonde, MF radar), rocket-, and satellite-borne measurements. ERA-Interim products are utilized for constructing
background parameters of the individual meteorological condition of the observations.
By the reverse ray tracing method, the source locations for nine wave events could be identified
to be in the upper troposphere, whereas, for five other events the waves got terminated in the
mesosphere itself. Uncertainty in locating the terminal points in the horizontal direction is
estimated to be within 50-100 km and 150-300 km for Gadanki and Hyderabad wave events,
respectively. This uncertainty arises mainly due to non-consideration of the day-to-day
variability in tidal amplitudes. Conditions
prevailing at the terminal points for each of the 14 events are provided.
As no convection in-and-around the terminal points is noticed, convection
is unlikely to be the source. Interestingly, large (~9 m/s/km) vertical shears in the horizontal
wind are noted near the ray terminal points (at 10-12 km altitude) and are thus identified to be the
source for generating the observed high phase speed, high frequency gravity waves.

real-time or near real-time is used to express that a data set can be processed in a very limited time:
http://en.wikipedia.org/wiki/Real-time_computing

L57 confined to low ground-based frequencies and phase speeds

L72 omit indirectly

L105 the ray path including radiative and turbulent damping in order to identify the sources for the observed waves.

L115 with a 24 mm Mamiya fish eye lens

L141 Coriolis was a person and the frequency / parameter named after him => Capital
http://en.wikipedia.org/wiki/Gaspard-Gustave_Coriolis

L171 All wave events obseved at Gadanki and Hyderabad correspond to high frequency high phase speed gravity waves as seen from their large vertical wavelengths, small periods and high phase speeds listed in Table 1.

L189 a grid extent of 5°X5° is considered to be adequate. ?

L227 frequently in the troposphere

L310 I find the combination 1) m^2 slightly confusing:
... ray 1) when m^2 becomes ... 2) when the intrinsic ...
4) when the vertical wave number $m$ becomes

L413 As expected, This is one of your main findings that you can exclude convection in a radius wider than that indicated by the backward trajectories. You shouldn't devaluate your conclusion by saying it is expected, in particular when it is not really that clear.

L431 From figure 11 it can

L454 this wave event also could propagate down to ~16 km in the reverse ray tracing.

L470 please omit successfully : You apply this on a theoretical basis and whether this is successful in terms of describing the reality is not shown.

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ED: Reconsider after minor revisions (Editor review) (04 Feb 2015) by William Ward

AR by M. Venkat Ratnam on behalf of the Authors (12 Feb 2015) Author's response Manuscript

ED: Publish as is (14 Feb 2015) by William Ward

AR by M. Venkat Ratnam on behalf of the Authors (16 Feb 2015)

Short summary

Sources and propagation characteristics of high-frequency gravity waves observed in the mesosphere using airglow emissions from Gadanki and Hyderabad, India, are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. Interestingly, large vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12km altitude) and are thus identified to be the source for generating the observed gravity waves.