Lidar Observations of Seasonal Variability of Gravity-Waves

In order to understand the generation, propagation and climatology of gravity waves (GWs)observations with high temporal and vertical resolution are required. The observation of gravity waves is important to understand the vertical coupling in the atmosphere.

Recent developments in lidar technology give us new possibilities to study GWs experimentally on a more or less regular basis and resolve spatial sales of 150 meters in the vertical and temporal scales of about 10 minutes. In particular, the capability to operate the lidar during daytime allows for long duration GW observations. The Doppler Rayleigh Iodine Spectrometer (DoRIS) in additionto the established hydrostatic temperature measurement technique yields simultaneous and common volume measurements of winds.

At the ALOMAR observatory in northern Norway (69°N, 16°E) the gravity wave potential energy density (GWPED) in the stratosphere is shown to have a large seasonal variation with a maximum in winter and a minimum in summer.

In this work we use the phase relation between both zonal and meridional wind components and temperature. We study gravity waves sorted for up- and downward propagating waves under summer and winter conditions to investigate different wave propagation and generation scenarios. We discuss the winter/summer difference not only in terms of total GWPED, but in terms of wave characteristics obtained from our extended analysis technique. We demonstrate, for example, that amount of downward propagating waves is larger in winter than in summer. Also, other wave characteristics like phase speed and mean intrinsic period will be discussed.