Observational study of quasi-monochromatic gravity waves characteristics in mesopause region with sodium fluorescence Doppler lidar

The quasi-monochromatic gravity waves （QM GWs)parameters in the mesopause region over Langfang (39.4N, 116.6E) were studied based on the 60 h sodium fluorescence Doppler lidar data during 2011-2013 year. A total of 85 QM GWs were extracted from the simultaneously measured temperature and wind profiles between 85 km and 95 km using hodograph method. The result shows that vertical wavelengths (horizontal wavelengths) and observed periods are mainly distributed from 6 km to 9 km (200 km to 800 km) and 2 h to 7 h, with the mean values 6.6 km (727.8 km) and 7.4 h respectively. GWs propagating upward in the vertical direction are with an occurrence of 75.29%. The intrinsic periods are mainly distributed from 3 h to 9 h with a mean value 7.76 h. There is no dominant horizontal propagation direction. The probability of the horizontal background wind component along the horizontal propagate direction Up0 is about 50% for upward GWs, but for downward GWs the probability of Up0 is about 66.66%, which is about 2 times of the probability of Up0 (33.33%)，which suggests that the observed downward GWs are mainly propagating horizontally along the wind.