the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Full-scale spectra of 15-year time series of near-surface horizontal wind speed on the north slope of Mt. Everest
Abstract. Wind speed spectra analysis is of great importance for understanding boundary layer turbulence characteristics, atmospheric numerical model development, and wind energy assessment. 15-year time series of near-surface horizontal wind data from the national Observation and Research Station for Qomolongma Special Atmospheric Processes and Environmental Changes (QOMS) on the north slope of Mt. Everest has been used to investigate the full-scale wind spectrum in the frequency range from about 10 yr-1 to 5 Hz. The annual average wind speed showed almost no detectable trend from 2006 to 2018 at the QOMS station. Three peaks were identified in the full-scale spectra at the frequencies of 1 yr-1, 1 day-1, and 12 hr-1, respectively. The 12 hr-1 peak is rarely observed at an offshore, coastal, or terrestrial site, and indicates the unique local circulations at the QOMS station. The spectral density was the highest on the low-frequency side of the diurnal peak and in the microscale frequency range (f ≥ 1×10-3 Hz) in winter, indicating frequent synoptic weather events and vigorous turbulent intensity generated by shear due to strong wind during winter. An obvious spectral gap around the frequency of 4.5×10-4 Hz was observed in the composite seasonal and daily spectrum in winter, while the spectral gap disappeared in summer. The linear composition of microscale and mesoscale wind spectra also held, and the gap region of the horizontal wind spectrum was modeled very well at the QOMS site.
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RC1: 'Comment on egusphere-2024-1963', Anonymous Referee #1, 05 Sep 2024
Comments on Full-scale spectra of 15-year time series of near-surface horizontal wind speed on the north slope of Mt. Everest
In this article, a 15-year wind time series of near-surface horizontal winds from the National Observation and Research station called QOMS is analyzed. The research station is located on the north slope of Mt. Everest. The authors have also examined horizontal winds' spectral characteristics during different seasons. The wind data comprises 10-min data from 2005 to 2019 at four heights: 1.5, 2, 4, 10, and 20m. High-frequency 10 Hz data from 2015 and 2016 are also studied for information about microscale turbulence.
Overall, the study is quite interesting and provides many insights about wind climatology in the area. I believe the study can be further improved by addressing the following queries:
- The wind roses in Figures 2 and 3 show higher wind speeds from the south, but no explanation is given for this phenomenon. Do katabatic winds play a role in this speed-up as the cold, dense air flows down from the top and becomes less dense as it heats up in the valley, Especially during the winter season? Please comment on this.
- In Section 2.3, it is mentioned that “linear detrending is applied to the wind speed data time series”. Sometimes, this can significantly reduce the low-frequency part of the power spectrum. It would be interesting to know whether linear detrending the time series affects the results in this article considerably or not.
- The article focuses on horizontal winds, but it would be interesting to also look at the vertical wind spectrum obtained from sonic anemometer. This would explain the flow circulation in the valley and high-altitude mountains in the south. Plus, you could see the distinction between microscale 3D turbulence and mesoscale 2D turbulence on the frequency scale.
- In Figures 7 and 8, while the low-frequency part of the spectra follows the f-2/3 scaling, the high-frequency part does not follow the same scaling. What could be the reason behind this? According to studies such as Larsén et al., 2016 and Kaimal and Finnigan 1994, you should observe the same scaling in the high-frequency part. Similarly, the Kaimal spectrum (blue dots) can be extended for frequencies higher than 4x10-3 Hz.
Citation: https://doi.org/10.5194/egusphere-2024-1963-RC1 -
AC1: 'Reply on RC1', Cunbo Han, 27 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1963/egusphere-2024-1963-AC1-supplement.pdf
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RC2: 'Comment on egusphere-2024-1963', Anonymous Referee #2, 04 Oct 2024
Publisher’s note: a supplement was added to this comment on 11 October 2024.
There are major flaws in this paper which I have tried to summarize, along with how to fix them. Even so, I'm not sure the results are that novel, other than the fact that they are collected in the Himalayas.
However, if others deem the results sufficiently interesting, I am willing to review the paper again, seeing if the authors have addressed my significant concerns.
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AC2: 'Reply on RC2', Cunbo Han, 27 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1963/egusphere-2024-1963-AC2-supplement.pdf
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AC2: 'Reply on RC2', Cunbo Han, 27 Oct 2024
Status: closed
-
RC1: 'Comment on egusphere-2024-1963', Anonymous Referee #1, 05 Sep 2024
Comments on Full-scale spectra of 15-year time series of near-surface horizontal wind speed on the north slope of Mt. Everest
In this article, a 15-year wind time series of near-surface horizontal winds from the National Observation and Research station called QOMS is analyzed. The research station is located on the north slope of Mt. Everest. The authors have also examined horizontal winds' spectral characteristics during different seasons. The wind data comprises 10-min data from 2005 to 2019 at four heights: 1.5, 2, 4, 10, and 20m. High-frequency 10 Hz data from 2015 and 2016 are also studied for information about microscale turbulence.
Overall, the study is quite interesting and provides many insights about wind climatology in the area. I believe the study can be further improved by addressing the following queries:
- The wind roses in Figures 2 and 3 show higher wind speeds from the south, but no explanation is given for this phenomenon. Do katabatic winds play a role in this speed-up as the cold, dense air flows down from the top and becomes less dense as it heats up in the valley, Especially during the winter season? Please comment on this.
- In Section 2.3, it is mentioned that “linear detrending is applied to the wind speed data time series”. Sometimes, this can significantly reduce the low-frequency part of the power spectrum. It would be interesting to know whether linear detrending the time series affects the results in this article considerably or not.
- The article focuses on horizontal winds, but it would be interesting to also look at the vertical wind spectrum obtained from sonic anemometer. This would explain the flow circulation in the valley and high-altitude mountains in the south. Plus, you could see the distinction between microscale 3D turbulence and mesoscale 2D turbulence on the frequency scale.
- In Figures 7 and 8, while the low-frequency part of the spectra follows the f-2/3 scaling, the high-frequency part does not follow the same scaling. What could be the reason behind this? According to studies such as Larsén et al., 2016 and Kaimal and Finnigan 1994, you should observe the same scaling in the high-frequency part. Similarly, the Kaimal spectrum (blue dots) can be extended for frequencies higher than 4x10-3 Hz.
Citation: https://doi.org/10.5194/egusphere-2024-1963-RC1 -
AC1: 'Reply on RC1', Cunbo Han, 27 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1963/egusphere-2024-1963-AC1-supplement.pdf
-
RC2: 'Comment on egusphere-2024-1963', Anonymous Referee #2, 04 Oct 2024
Publisher’s note: a supplement was added to this comment on 11 October 2024.
There are major flaws in this paper which I have tried to summarize, along with how to fix them. Even so, I'm not sure the results are that novel, other than the fact that they are collected in the Himalayas.
However, if others deem the results sufficiently interesting, I am willing to review the paper again, seeing if the authors have addressed my significant concerns.
-
AC2: 'Reply on RC2', Cunbo Han, 27 Oct 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1963/egusphere-2024-1963-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Cunbo Han, 27 Oct 2024
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