Inertial gravity waves observed by a Doppler wind LiDAR and their possible sources

In this paper, we use wind observations by a Doppler wind LiDAR near Delingha (37.4 degrees N, 97.4 degrees E), Qinghai, Northwestern China to study the characteristics of inertial gravity waves in the stratosphere. We focus on 10-12 December 2013, a particularly interesting case study. Most of the time, the inertial gravity waves extracted from the LiDAR measurements were stationary with vertical wavelengths of about 9-11 km and horizontal wavelengths of about 800-1000 km. However, for parts of the observational period in this case study, a hodograph analysis indicates that different inertial gravity wave propagation features were present at lower and upper altitudes. In the middle and upper stratosphere (similar to 30-50 km), the waves propagated downward, especially during a period of stronger winds, and to the northwest-southeast. In the lower stratosphere and upper troposphere (similar to 10-20 km), however, waves with upward propagation and northeast-southwest orientation were dominant. By taking into account reanalysis data and satellite observations, we have confirmed the presence of different wave patterns in the lower and upper stratosphere during this part of the observational period. The combined data sets suggest that the different wave patterns at lower and upper height levels are likely to have been associated with the presence of lower and upper stratospheric jet streams.