Comparison of Atmospheric Gravity Wave Event Statistics between Dandong and Lhasa

Based on recognition model of atmospheric gravity waves (AGWs), we identified 519 AGWs events from the OH airglow images observed at Dandong and Lhasa stations during 2015-2017. The 317 AGW events detected at Dandong station have wavelengths ranging from 30 to 60 km, periods from 14 to 20 minutes, 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 Lhasa station mainly vary within 15-35 km in horizontal wavelength, 4-6 minutes 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 is absent at Lhasa due to lack of convective weather. The seasonal propagation directions of the waves are influenced by both wind field filtering effect and the distribution of wave sources. In spring, due to the southeastward background wind field, there are fewer southeastward events at the Dandong station. The situation at the Lhasa station is similar. In summer, both 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, while 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, due to the eastward wind, there are more events propagating to the southwest at the Dandong station.