Preprints
https://doi.org/10.5194/egusphere-2023-1563
https://doi.org/10.5194/egusphere-2023-1563
20 Jul 2023
 | 20 Jul 2023

Investigation of Gravity Waves using Measurements from a Sodium Temperature/Wind Lidar Operated in Multi-Direction Mode

Bing Cao and Alan Z. Liu

Abstract. A narrow-band sodium lidar provides high temporal and vertical resolution observations of sodium density, atmospheric temperature, and wind that facilitate the investigation of atmospheric waves in the mesosphere and lower thermosphere (80–105 km). In order to retrieve full vector winds, such a lidar is usually configured in a multi-direction observing mode, with laser beams pointing to the zenith and several off-zenith directions. Gravity wave events were observed by such a lidar system from 06:30 to 11:00 UTC on 14 January 2002 at Maui, Hawaii (20.7° N, 156.3° W). A novel method based on cross-spectrum was proposed to derive the horizontal wave information from the phase shifts among measurements in different directions. At least two wave packets were identified using this method, one with a period of ~1.6 hr and a horizontal wavelength of ~438 km and propagating toward the southwest, the other one with a ~3.2 hr period and ~975 km wavelength and propagating toward the northwest. The background atmosphere states were also fully measured, and all intrinsic wave properties of the wave packets were derived. Dispersion and polarization relations were used to diagnose wave propagation and dissipation. It was revealed that both wave packets propagate through multiple thin evanescent layers and are partially reflected but still get a good portion of energy to penetrate higher altitudes. A sensitivity study demonstrates the capability of this method in detecting medium-scale and medium-frequency gravity waves. With continuous and high-quality measurements from similar lidar systems worldwide, this method can be utilized to detect and study the characteristics of gravity waves of specific spatio-temporal scales.

Bing Cao and Alan Z. Liu

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1563', Anonymous Referee #1, 25 Aug 2023
    • AC1: 'Reply on RC1', Bing Cao, 19 Dec 2023
  • CC1: 'Comment on egusphere-2023-1563', Lidar Scientist, 07 Sep 2023
    • AC3: 'Reply on CC1', Bing Cao, 19 Dec 2023
  • RC2: 'Comment on egusphere-2023-1563', Anonymous Referee #2, 08 Nov 2023
    • AC2: 'Reply on RC2', Bing Cao, 19 Dec 2023

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1563', Anonymous Referee #1, 25 Aug 2023
    • AC1: 'Reply on RC1', Bing Cao, 19 Dec 2023
  • CC1: 'Comment on egusphere-2023-1563', Lidar Scientist, 07 Sep 2023
    • AC3: 'Reply on CC1', Bing Cao, 19 Dec 2023
  • RC2: 'Comment on egusphere-2023-1563', Anonymous Referee #2, 08 Nov 2023
    • AC2: 'Reply on RC2', Bing Cao, 19 Dec 2023
Bing Cao and Alan Z. Liu
Bing Cao and Alan Z. Liu

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Short summary
A narrow-band sodium lidar measures atmospheric waves but focuses on vertical variations. By analyzing phase shifts among laser beams in different directions, horizontal wave information can be derived. With this method, two wave packets were identified, propagating in different directions. These waves interacted with thin evanescent layers, reflecting partially but transmitting energy to higher altitudes. The method can be used to detect more gravity waves from similar lidar systems worldwide.