Case study of wave breaking with high-resolution turbulence measurements with LITOS and WRF simulations
Measurements of turbulent energy dissipation rates obtained from wind fluctuations observed with the balloon-borne instrument LITOS (Leibniz-Institute Turbulence Observations in the Stratosphere) are combined with simulations with the Weather Research and Forecasting (WRF) model to study the bre...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/7941/2017/acp-17-7941-2017.pdf |
| Summary: | Measurements of turbulent energy dissipation rates obtained from wind
fluctuations observed with the balloon-borne instrument LITOS
(Leibniz-Institute Turbulence Observations in the Stratosphere) are combined
with simulations with the Weather Research and Forecasting (WRF) model to
study the breakdown of waves into turbulence. One flight from Kiruna
(68° N, 21° E) and two flights from Kühlungsborn
(54° N, 12° E) are analysed. Dissipation rates are of the
order of 0. 1 mW kg<sup>−1</sup> (∼ 0.01 K d<sup>−1</sup>) in the
troposphere and in the stratosphere below 15 km, increasing in
distinct layers by about 2 orders of magnitude. For one flight covering the
stratosphere up to ∼ 28 km, the measurement shows nearly no
turbulence at all above 15 km. Another flight features a patch with
highly increased dissipation directly below the tropopause, collocated with
strong wind shear and wave filtering conditions. In general, small or even
negative Richardson numbers are affirmed to be a sufficient condition for
increased dissipation. Conversely, significant turbulence has also been
observed in the lower stratosphere under stable conditions. Observed energy
dissipation rates are related to wave patterns visible in the modelled
vertical winds. In particular, the drop in turbulent fraction at
15 km mentioned above coincides with a drop in amplitude in the wave
patterns visible in the WRF. This indicates wave saturation being visible in
the LITOS turbulence data. |
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| ISSN: | 1680-7316 1680-7324 |