Sodium lidar‐observed gravity wave breaking followed by an upward propagation of sporadic sodium layer over Hefei, China

Abstract

The University of Science and Technology of China sodium temperature/wind lidar observed a strong zonal wind shear (~60 m/s/km) near 98 km between 1315 and 1330 UT on 29 July 2013 and a cooling near 96–100 km (above a warming near 90–95 km) between 1330 and 1430 UT. This suggests a possible gravity wave (GW) breaking event. Comparison of the lidar results with observations from a nearby meteor radar and with satellite results indicated that the GW likely broke down over a large horizontal area. In addition, the sodium number density suddenly increased 10–12 times (∼13, 000atm/cm3) near 95 km at 1400 UT, immediately following the GW breaking. This sporadic sodium layer (SSL), which is different from most previously observed SSL events (which propagate downward), tended to propagate upward and also appeared ~2 min earlier in the west channel than in the east channel. The horizontal propagation direction of the SSL was aligned with the horizontal wind direction, which was likely due to the propagation of a high‐density sodium layer from the northwest of the lidar site, and was possibly related to the earlier GW breaking event.

Large‐Scale Horizontally Enhanced Sodium Layers Coobserved in the Midlatitude Region of China

“…The SSLs of the three cases above all had time delays between Hefei and Wuhan, which indicates the existence of a long‐distance horizontal transport process. Wind transport may be the reason for the long‐distance horizontal transport process (Ban et al, ; Tsuda, Nozawa, et al, ). Unfortunately, we do not have enough data to verify the above conjecture.…”

“…Most SSLs they observed had a horizontal extent of less than 300 km. Using ground‐based observations, Ban et al () observed an upwardly propagating SSL through different beams of one lidar site and found that the SSL in the western beam was 2 min earlier than that of the eastern beam, and the SSL propagation direction was consistent with the horizontal wind direction. Tsuda et al () analyzed an SSL observed by a five‐directional lidar and compared it with the background wind velocity from the collocated meteor radar and electron density and electric field form European Incoherent Scatter radar.…”

The Enhancement of Neutral Metal Na Layer Above Thunderstorms

“…Fluctuations in the metal layer can be produced by GWs (Hickey & Plane, ; Li et al, ; Plane & Rollason, ). The GWs can be associated with the E s layer (Van Eyken et al, ) and the sporadic Na layer can appear following the GW breaking (Ban et al, ). There is a dominant response 19 h after lightning.…”

Lidar observations of the upper atmospheric nickel layer at Beijing (40∘N,116∘EWu1, Zheng2, Yang3 et al. 2021Journal of Quantitative Spectroscopy and Radiative Transfer81110View full textAdd to dashboardCite

“…The ablation of cosmic dust particles entering the Earth's atmosphere produces layers of metal atoms in the mesosphere and lower thermosphere region (MLT from 80 to 110 km [1]. The metal layers are very useful tracers of atmospheric dynamics (e.g., gravity waves and tides [2][3][4], and also of coupling between the neutral atmosphere and ionosphere [5][6][7]. The resonance lidar is a powerful tool for detecting the metal layers with excellent spatial and temporal resolution (Na at 589 nm, K at 770 nm, Fe at 372 nm, and Ca at 423 nm [8][9][10]; Due to the large resonance scattering cross section and relatively high concentration of Na atoms, the sodium lidar was the first resonance lidar to be developed [11].…”