2011, Theuerkauf, A., Gerding, M., Lübken, F.-J.

We have developed a new compact balloon payload called LITOS (Leibniz-Institute Turbulence Observations in the Stratosphere) for high resolution wind turbulence soundings in the stratosphere up to 35 km altitude. The wind measurements are performed using a constant temperature anemometer (CTA) with a vertical resolution of ∼2.5 mm, i.e. 2 kHz sampling rate at 5 m/s ascent speed. Thereby, for the first time, it is possible to study the entire turbulence spectrum down to the viscous subrange in the stratosphere. Including telemetry, housekeeping, batteries and recovery unit, the payload weighs less than 5 kg and can be launched from any radiosonde station. Since autumn 2007, LITOS has been successfully launched several times from the Leibniz-Institute of Atmospheric Physics (IAP) in Kühlungsborn, Germany (54° N, 12° E). Two additional soundings were carried out in 2008 and 2009 in Kiruna, Sweden (67° N, 21° E) as part of the BEXUS program (Balloon-borne EXperiments for University Students). We describe here the basic principle of CTA measurements and prove the validity of this method in the stratosphere. A first case study allows a clear distinction between non-turbulent regions and a turbulent layer with a thickness of some tens of meters. Since our measurements cover the transition between the inertial and viscous subrange, energy dissipation rates can be calculated with high reliability.

2008, Sica, R.J., Izawa, M.R.M., Walker, K.A., Boone, C., Petelina, S.V., Argall, P.S., Bernath, P., Burns, G.B., Catoire, V., Collins, R.L., Daffer, W.H., De Clercq, C., Fan, Z.Y., Firanski, B.J., French, W.J.R., Gerard, P., Gerding, M., Granville, J., Innis, J.L., Keckhut, P., Kerzenmacher, T., Klekociuk, A.R., Kyrö, E., Lambert, J.C., Llewellyn, E.J., Manney, G.L., McDermid, I.S., Mizutani, K., Murayama, Y., Piccolo, C., Raspollini, P., Ridolfi, M., Robert, C., Steinbrecht, W., Strawbridge, K.B., Strong, K., Stübi, R., Thurairajah, B.

An ensemble of space-borne and ground-based instruments has been used to evaluate the quality of the version 2.2 temperature retrievals from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The agreement of ACE-FTS temperatures with other sensors is typically better than 2 K in the stratosphere and upper troposphere and 5 K in the lower mesosphere. There is evidence of a systematic high bias (roughly 3–6 K) in the ACE-FTS temperatures in the mesosphere, and a possible systematic low bias (roughly 2 K) in ACE-FTS temperatures near 23 km. Some ACE-FTS temperature profiles exhibit unphysical oscillations, a problem fixed in preliminary comparisons with temperatures derived using the next version of the ACE-FTS retrieval software. Though these relatively large oscillations in temperature can be on the order of 10 K in the mesosphere, retrieved volume mixing ratio profiles typically vary by less than a percent or so. Statistical comparisons suggest these oscillations occur in about 10% of the retrieved profiles. Analysis from a set of coincident lidar measurements suggests that the random error in ACE-FTS version 2.2 temperatures has a lower limit of about ±2 K.

2015, Schneider, A., Gerding, M., Lübken, F.-J.

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 LO ∝ LT. 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.