LITOS – a new balloon-borne instrument for fine-scale turbulence soundings in the stratosphere

Abstract

Abstract.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 LeibnizInstitute of Atmospheric Physics (IAP) in Kühlungsborn, Germany (54 • N, 12 • E). Two additional soundings were carried out in 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.

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

“…where ν is the kinematic viscosity (derived from the radiosonde measurement of temperature and pressure on the same gondola), and c = 5.7 (Theuerkauf et al, 2011;Haack et al, 2014). For the example in Fig Example of raw data (left) and associated power spectrum (right) computed for the shaded area in the raw data plot.…”

“…As described in Theuerkauf et al (2011), LITOS is a balloonborne instrument which measures winds with high vertical resolution of millimetres. The wind sensor is a constant temperature anemometer (CTA), which facilitates the cooling effect on a heated wire of 5 µm diameter.…”

“…But for the atmosphere there are only few examinations of the proportionality (e. g. Gavrilov et al, 2005;Kantha and Hocking, 2011;Wilson et al, 2014). With our new high-resolved instrument LITOS (Leibniz Institute Turbulence Observations in the Stratosphere) (Theuerkauf et al, 2011), the energy dissipation rate ε is obtained independent of L T by means of spectral analysis of wind fluctuations. Thus it is possible to check the relation L O ∝ L T .…”

“…As in the stratosphere turbulent dissipation occurs on small scales of centimetres and below, measurements are technically challenging and therefore sparse (e.g. Barat, 1982;Theuerkauf et al, 2011).…”

Gravity Waves excited during a Minor Sudden Stratospheric Warming

“…At high latitudes, only few of these radiosondes reach altitudes higher than 30 km in winter as the conventional 300 … 500 g rubber balloons burst in the cold stratosphere. During the METROSI 1 campaign in Northern Scandinavia, 3000 g rubber balloons were used by the LITOS group (Theuerkauf et al, 2011, Haack et al, 2014, 10 Schneider et al, 2017) studying fine-scale turbulence in the upper troposphere/lower stratosphere (UTLS) mainly from Andøya, Norway (69°N, 15.7°E). A common deployment phase of their turbulence sensor took place in Kiruna, Sweden (68°N, 20°E) during GW-LCYCLE 2 2 .…”