Modulation of upper mesospheric temperature inversions due to tidal-gravity Wave interactions

Abstract. A mesospheric bore event was observed using an OH all-sky airglow imager (ASAI) at Xinglong (40.2° N, 117.4° E), in northern China, on the night of 8–9 January 2011. Simultaneous observations by a Doppler meteor radar, a broadband sodium lidar, and TIMED/SABER OH intensity and temperature measurements are used to investigate the characteristics and environment of the bore propagation and the possible relations with the Na density perturbations. The bore propagated from northeast to southwest and divided the sky into bright and dark halves. The calculations show that the bore has an average phase velocity of 68 m s−1. The crests following the bore have a horizontal wavelength of ~ 22 km. These parameters are consistent with the hydraulic jump theory proposed by Dewan and Picard, as well as the previous bore reports. Simultaneous wind measurements from the Doppler meteor radar at Shisanling (40.3° N, 116.2° E) and temperature data from SABER on board the TIMED satellite are used to characterize the propagating environment of the bore. The result shows that a thermal-Doppler duct exists near the OH layer that supports the horizontal propagation of the bore. Simultaneous Na lidar observations at Yanqing (40.4° N, 116.0° E) suggest that there is a downward displacement of Na density during the passage of the mesospheric bore event.

Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Investigation of a mesospheric bore event over northern China

Yue

et al. 2013

“…Thayaparan et al (1995) observed positive (negative) correlation between diurnal tidal amplitude and gravity wave variance in winter (summer) and observed no correlation between semidiurnal tidal amplitude and gravity wave variance. Sica et al (2002) found positive correlation between semidiurnal tide and gravity wave variance. These observations suggest that gravity wave tidal interaction occurred.…”

Section: Discussionmentioning

confidence: 85%

“…Using coincident measurements with the MF radar and lidar at Western Ontario (42.9 • N, 81.4 • W), Sica et al (2002) observed that there are two type of inversions. The first type, which persists for many hours, is associated with increased gravity wave variance, as the magnitude of westward tide decreases.…”

Section: Introductionmentioning

confidence: 99%

Influence of gravity waves and tides on mesospheric temperature inversion layers: simultaneous Rayleigh lidar and MF radar observations

Sridharan

Sathishkumar²,

Gurubaran³

2008

Abstract. Three nights of simultaneous Rayleigh lidar temperature measurements over Gadanki (13.5 • N, 79.2 • E) and medium frequency (MF) radar wind measurements over Tirunelveli (8.7 • N, 77.8 • E) have been analyzed to illustrate the possible effects due to tidal-gravity wave interactions on upper mesospheric inversion layers. The occurrence of tidal gravity wave interaction is investigated using MF radar wind measurements in the altitude region 86-90 km. Of the three nights, it is found that tidal gravity wave interaction occurred in two nights. In the third night, diurnal tidal amplitude is found to be significantly larger. As suggested in Sica et al. (2007), mesospheric temperature inversion seems to be a signature of wave saturation in the mesosphere, since the temperature inversion occurs at heights, when the lapse rate is less than half the dry adiabatic lapse rate.

“…The large variability of the gravity-wave energy density could be due to modulation of wave breaking due to longer period waves such as tides or larger-scale gravity waves. Such interaction between tides and gravity waves has been shown for PCL measurements of mesospheric inversion layers (MILs) by Sica et al (2002). Furthermore, Sica et al (2007) have presented a theory for MILs based on the effects of large-scale waves modifying the temperature structure in which the smaller-scale waves propagate.…”

Section: Discussionmentioning

confidence: 90%

Seasonal and nightly variations of gravity-wave energy density in the middle atmosphere measured by the Purple Crow Lidar

Sica

Argall

2007

Abstract.The Purple Crow Lidar (PCL) is a large power-aperture product monostatic Rayleigh-RamanSodium-resonance-fluorescence lidar, which has been in operation at the Delaware Observatory (42.9 • N, 81.4 • W, 237 m elevation) near the campus of The University of Western Ontario since 1992. Kinetic-energy density has been calculated from the Rayleigh-scatter system measurements of density fluctuations at temporal-spatial scales relevant for gravity waves, e.g. soundings at 288 m height resolution and 9 min temporal resolution in the upper stratosphere and mesosphere. The seasonal averages from 10 years of measurements show in all seasons some loss of gravity-wave energy in the upper stratosphere. During the equinox periods and summer the measurements are consistent with gravity waves growing in height with little saturation, in agreement with the classic picture of the variations in the height at which gravity waves break given by Lindzen (1981). The mean values compare favourably to previous measurements when computed as nightly averages, but the high temporal-spatial resolution measurements show considerable day-to-day variability. The variability over a night is often extremely large, with typical RMS fluctuations of 50 to 100% at all heights and seasons common. These measurements imply that using a daily or nightly-averaged gravity-wave energy density in numerical models may be highly unrealistic.