Articles | Volume 15, issue 4
Research article
27 Feb 2015
Research article |  | 27 Feb 2015

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

A. Schneider, M. Gerding, and F.-J. Lübken

Abstract. Stratospheric turbulence is important for the mixing of trace species and the energy balance, but direct measurements are sparse due to the required resolution and accuracy. Recently, turbulence parameters such as the energy dissipation rate ε were inferred from standard radiosonde data by means of a Thorpe analysis. To this end, layers with vertically decreasing potential temperature are analysed, which is expected to indicate turbulence. Such an application assumes a proportionality between the Thorpe length LT and the Ozmidov scale LO. While this relation is accepted for the ocean, experimental evidence for such proportionality in the stratosphere is sparse. We have developed a high-resolution (8 kHz) turbulence measurement system called LITOS (Leibniz Institute Turbulence Observations in the Stratosphere), which for the first time resolves the inner scale of turbulence in the stratosphere. Therewith the energy dissipation rate ε can be determined by spectral analysis. This independent value for ε enables us to check the relation LOLT. In our measurements no such proportionality can be seen, although the mean of the ratio LO/LT is close to what is assumed in radiosonde analyses. Dissipation rates for individual layers obtained from radiosondes deviate up to a factor of ~3000 from those obtained by spectral analysis. Some turbulent layers measured by LITOS are not observed by the radiosonde at all, and vice versa. However, statements about the statistical mean seem to be possible by Thorpe analysis.

Short summary
Stratospheric turbulence is essential for the atmospheric energy budget. We compare in situ observations with our LITOS method based on spectral analysis of mm-scale wind fluctuations with the Thorpe method applied to standard radiosondes. Energy dissipations rates from both methods differ by up to 3 orders of magnitude. Nevertheless, mean values are in good agreement. We present case studies on both methods and examine the applicability of the Thorpe method for calculation of dissipation rates.
Final-revised paper