Strong Mixing Events Observed near the Tropopause with the MU Radar and High-Resolution Balloon Techniques

Luce, Hubert; Fukao, S.; Dalaudier, Francis; Crochet, M.

doi:10.1175/1520-0469(2002)059<2885:smeont>2.0.co;2

Cited by 71 publications

(59 citation statements)

References 25 publications

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“…Note that Love and Geller (2012) call 1 Hz (5 m) high resolution, while we call it low resolution (compared to LITOS with 8 kHz). In principle, the Thorpe analysis can also be performed on data with higher resolution, as done, e.g., by Luce et al (2002) for temperature data with a 50 Hz sampling rate; however, these data are rarely available compared to those of standard radiosonde. Furthermore, a kind of spectral analysis can be used to determine dissipation rates from low-resolution wind data (Barat, 1982), but this method depends on the absolute value of the wind velocity, which is not available for our measurements (see next section).…”

Section: A Schneider Et Al: Turbulence Soundings By Litos and Radiomentioning

confidence: 99%

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

2015

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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 L T and the Ozmidov scale L O . 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 L O ∝ L T . In our measurements no such proportionality can be seen, although the mean of the ratio L O /L T 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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Section: A Schneider Et Al: Turbulence Soundings By Litos and Radiomentioning

confidence: 99%

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

2015

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“…The HR profiles were acquired with a sampling frequency of 25 Hz for the SFT flights and 50 Hz for the MUTSI flights. The reader can find more details about the HR measurements in Luce et al (2002) and Gavrilov et al (2005). The HR and LR sensors were on the same gondola, and the data were acquired simultaneously.…”

Section: The Datasetsmentioning

confidence: 99%

“…Luce et al (2002) reported observations of strong and isotropic radar echoes (suggesting the presence of turbulence) probably related to several unstable or nearly neutralized layers which were detected by high-resolution balloon measurements. These observations support the hypothesis of turbulent events related to overturns in the potential temperature profile.…”

Section: Introductionmentioning

confidence: 96%

“…Thorpe, 1977;Galbraith and Kelley, 1996;Ferron et al, 1998;Alford and Pinkel, 2000) or pressure-temperature (PT) in the atmosphere (Luce et al, 2002;Gavrilov et al, 2005;Clayson and Kantha, 2008;Wilson et al, 2010). It has been recently proposed by Clayson and Kantha (2008) to apply Thorpe analyses to the huge data-base of meteorological radiosondes (hereafter noted RS), in order to infer the space-time variability of atmospheric turbulence in the free atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Can one detect small-scale turbulence from standard meteorological radiosondes?

2011

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Abstract. It has been recently proposed by Clayson and Kantha (2008) to evaluate the climatology of atmospheric turbulence through the detection of overturns in the free atmosphere by applying a Thorpe analysis on relatively low vertical resolution (LR) profiles collected from standard radiosoundings. Since then, several studies based on this idea have been published. However, the impact of instrumental noise on the detection of turbulent layers was completely ignored in these works. The present study aims to evaluate the feasibility of overturns detection from radiosoundings. For this purpose, we analyzed data of two field campaigns during which high-resolution (HR) soundings (10-20 cm) were performed simultaneously with standard LR soundings. We used the raw data of standard meteorological radiosondes, the vertical resolution ranging from 5 to 9 m.A Thorpe analysis was applied to both LR and HR potential temperature profiles. A denoising procedure was first applied in order to reduce the probability of occurrence of artificial overturns, i.e. potential temperature inversions due to instrumental noise only. We then compared the empirical probability density functions (pdf) of the sizes of the selected overturns from LR and HR profiles.From HR profiles measured in the troposphere, the sizes of the detected overturns range from 4 to ∼1000 m. The shape of the size pdf of overturns is found to sharply decrease with increasing scales. From LR profiles, the smallest size of detected overturns is ∼32 m, a similar decrease in the shape of the pdf of sizes being observed. These results suggestCorrespondence to: R. Wilson (richard.wilson@upmc.fr) that overturns, resulting either from small-scale turbulence or from instabilities, can indeed be detected from meteorological radiosonde measurements in the troposphere and in the stratosphere as well. However they are rather rare as they belong to the tail of the size distribution of overturns: they only represent the 7 % largest events in the troposphere, and 4 % in the stratosphere.

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“…Other work has compared the backscatter echo received by radar (at 50 m resolution and corrected for range attenuation effects) with the square of the mean vertical gradient of the generalized potential refractive index (obtained from high-resolution radiosonde balloons) (Luce et al, 2002(Luce et al, , 2007, and references therein). These have produced excellent correspondence under particular atmospheric conditions with persistent horizontal structure, where the large (many km) separation between an advected balloon and the radar beam are inconsequential.…”

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confidence: 99%

Simultaneous observations of structure function parameter of refractive index using a high-resolution radar and the DataHawk small airborne measurement system

et al. 2016

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Abstract. The SOUSY (SOUnding SYstem) radar was relocated to the Jicamarca Radio Observatory (JRO) near Lima, Peru, in 2000, where the radar controller and acquisition system were upgraded with state-of-the-art parts to take full advantage of its potential for high-resolution atmospheric sounding. Due to its broad bandwidth (4 MHz), it is able to characterize clear-air backscattering with high range resolution (37.5 m).A campaign conducted at JRO in July 2014 aimed to characterize the lower troposphere with a high temporal resolution (8.1 Hz) using the DataHawk (DH) small unmanned aircraft system, which provides in situ atmospheric measurements at scales as small as 1 m in the lower troposphere and can be GPS-guided to obtain measurements within the beam of the radar. This was a unique opportunity to make coincident observations by both systems and to directly compare their in situ and remotely sensed parameters.Because SOUSY only points vertically, it is only possible to retrieve vertical radar profiles caused by changes in the refractive index within the resolution volume. Turbulent variations due to scattering are described by the structure function parameter of refractive index C 2 n . Profiles of C 2 n from the DH are obtained by combining pressure, temperature, and relative humidity measurements along the helical trajectory and integrated at the same scale as the radar range resolution. Excellent agreement is observed between the C 2 n estimates obtained from the DH and SOUSY in the overlapping measurement regime from 1200 m up to 4200 m above sea level, and this correspondence provides the first accurate calibration of the SOUSY radar for measuring C 2 n .

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Strong Mixing Events Observed near the Tropopause with the MU Radar and High-Resolution Balloon Techniques

Cited by 71 publications

References 25 publications

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

Comparing turbulent parameters obtained from LITOS and radiosonde measurements

Can one detect small-scale turbulence from standard meteorological radiosondes?

Simultaneous observations of structure function parameter of refractive index using a high-resolution radar and the DataHawk small airborne measurement system

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