Comparing turbulent parameters obtained from LITOS and radiosonde measurements

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 drive 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, 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 &propto; LT. It turns out that no proportionality can be seen in our measurements. Furthermore, dissipation rates obtained from radiosondes deviate up to a factor of ~ 3000 to those obtained by spectral analysis. Some turbulent layers measured by LITOS are not observed by the radiosonde at all, and vice versa.

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Comparing turbulent parameters obtained from LITOS and radiosonde measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-2159-2015 ◽

2015 ◽

Vol 15 (4) ◽

pp. 2159-2166 ◽

Cited By ~ 19

Author(s):

A. Schneider ◽

M. Gerding ◽

F.-J. Lübken

Keyword(s):

Spectral Analysis ◽

Energy Dissipation ◽

Dissipation Rate ◽

Potential Temperature ◽

Energy Dissipation Rate ◽

Radiosonde Data ◽

Turbulence Measurement ◽

Trace Species ◽

Ozmidov Scale ◽

Inner Scale

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 LO &propto; 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.

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Estimation of Small-Scale Vertical Diffusivity for CO2 Injected in the Deep Ocean

Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization, Parts A and B ◽

10.1115/omae2009-79973 ◽

2009 ◽

Author(s):

Shinichiro Hirabayashi ◽

Toru Sato

Keyword(s):

Spectral Analysis ◽

Energy Dissipation ◽

Dissipation Rate ◽

Spatial Information ◽

Measurement Data ◽

Deep Ocean ◽

Energy Dissipation Rate ◽

Small Scale ◽

Computational Domain ◽

Vertical Diffusivity

In this study, vertical diffusivity, the scale of which was O (10 m), at a particular site in the deep ocean was estimated by using numerical simulations with forcing low-wavenumber components, which had been reproduced from measurement data. Spatial information of velocity field was reproduced by spectral analysis of 4 sets of time-series measured simultaneously at different places in the real ocean. In order to estimate finer-scale structures, which are necessary to obtain statistical quantities such as energy dissipation rate, large eddy simulations were carried out with forcing low-wavenumber components of velocity reproduced in the spectral analysis. The low-wavenumber components generated by the nonlinear interaction of forced components and resolved components were successfully removed from the computational domain by introducing a partial spectral filter in place of the conventional FFT filter. Vertical diffusivity was estimated by using the energy dissipation rate of the reproduced flow field, which was 3.3×10−5 m2s−1 on the time average.

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