Comparison of atmospheric gravity wave event statistics between Dandong and Lhasa

Using a recognition model of atmospheric gravity waves (AGWs), we identified 519 AGW events from the OH airglow images observed at the Dandong and Lhasa stations from 2015 to 2017. The 317 AGW events detected at the Dandong station have wavelengths ranging from 30 to 60 km, periods from 14 to 20 min, horizontal speeds from 30 to 60 m/s, and relative intensities from 0.4% to 0.6%, respectively. The parameters of 202 events recorded at the Lhasa station mainly vary within 15–35 km in horizontal wavelength, 4–6 min in period, 40–100 m/s in horizontal velocity, and 0.1%–0.3% in relative intensity. The occurrence rate peaks in winter and summer at Dandong and the peak in summer are absent at Lhasa because of the lack of convective weather. The seasonal propagation directions of the waves are influenced by both the wind field-filtering effect and the distribution of wave sources. In spring, because of the southeastward background wind field, fewer southeastward events are observed at the Dandong station. The situation at the Lhasa station is similar. In summer, both the Lhasa and Dandong stations are dominated by northeastward AGWs, which can be attributed to the southwestward wind. In autumn, ray-tracing results show that the events at Dandong mainly originate from wind shear, whereas the events at the Lhasa station are triggered by convective weather. The location of the wave sources determines the trend of the propagation directions at the Dandong and Lhasa stations in autumn. In winter, because of the eastward wind, more events are propagating to the southwest at the Dandong station.