Gravity wave morphology examined by lidar at 54°N

Scope

Since summer 2002 the temperature measurements taken at Kühlungsborn with two different lidars yield a data set covering the whole altitude range between the troposphere and the lower thermosphere (1-105 km). Measurements from more than 230 nights were collected. Temperature fluctuations caused by waves are always observed but they have different amplitudes and vertical characteristics. Apart from the calculation of mean temperatures from the troposphere up to the lower thermosphere the wave activity is determined depending on time and altitude. It is used to derive e.g. amplitudes and vertical wavelengths. To extract information about the waves the average profile is subtracted and only the temperature deviations are examined. In the Figure the temperature deviations between 25 and 27 February 2003 are shown. The potassium lidar measurements are carried out the whole time but the calculation of temperatures is only possible at altitudes around 90 km. However, around noon the solar background is too large to determine temperatures with statistical uncertainties smaller than 10 K. Temperature values with more than 10 K uncertainty are discarded. Rayleigh and rotational Raman temperatures can only be calculated at night. In both nights the downward propagating phases of upward propagating waves are clearly visible. Also dominating vertical wavelengths between 10 and 20 km are determined depending on time and altitude. The goals of the investigations are to characterise the amplitudes, vertical wavelengths and phase velocities of waves with periods between 20 min and 8 h by means of lidar measurements.

Temperature deviations

Temperature deviations from nightly mean between the 25th and 27th February 2003.