On the evaluation of the phase relation between temperature and
wind tides based on ground-based measurements and reanalysis
data in the middle atmosphere
Abstract. The variability of the middle atmosphere is driven by a variety of waves covering different spatial and temporal scales. We are diagnosing the variability of the thermal tides due to changes in the background wind by an adaptive spectral filter, which takes the intermittency of tides into account. We apply this diagnostic to temperature observations from a daylight-capable lidar at mid-latitudes (54° N, 12° E) as well as to reanalysis data of horizontal winds from MERRA-2. These reanalysis data provide additional wind information in the altitude range between 30 and 70 km at the location of the lidar as well as on a global perspective. Using the global data gives information of the tidal modes seen at one location. A comparison of the temperature and wind information affirms whether there is a fixed phase relation of the tidal waves in the temperature and the wind data. We found that in general the local tidal signatures are dominated by migrating tidal modes and the signature is weaker in temperatures than in winds. While the meridional wind tide is leading the zonal wind tide by 90°, the phase relation between the temperature and the wind tide is more complex. At certain altitudes the temperature tide follows the zonal wind tide. This knowledge helps to improve the interpretation of the seasonal variation of tides from different observables especially when only data from single locations are used. The findings provide additional information about the phase stability of tidal waves and the results clearly show the importance of a measurement acquisition on a routine basis with high temporal and spatial resolution.