Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons
<p>This article deals with the detection of small-scale turbulence from in situ meteorological measurements performed under superpressure balloons (SPBs). These balloons allow long-duration flights (several months) at a prerequisite height level. The data set is gathered from the Strateole-2 p...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/16/311/2023/amt-16-311-2023.pdf |
| _version_ | 1797946557744545792 |
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| author | R. Wilson C. Pitois A. Podglajen A. Hertzog M. Corcos R. Plougonven |
| author_facet | R. Wilson C. Pitois A. Podglajen A. Hertzog M. Corcos R. Plougonven |
| author_sort | R. Wilson |
| collection | DOAJ |
| description | <p>This article deals with the detection of small-scale turbulence from in situ meteorological measurements performed under
superpressure balloons (SPBs). These balloons allow long-duration flights (several months) at a prerequisite height level. The data set is gathered from the Strateole-2 probationary campaign during which eights SPBs flew in the tropical tropopause layer at altitudes of around 19 and 20.5 km from November 2019 to March 2020.</p>
<p>Turbulence is not directly measured by the instrument set onboard the SPBs.
Nonetheless, there is the potential to derive information about the occurrence of turbulence from the temporally well-resolved measurements of pressure, temperature, and position. It constitutes a challenge to extract the aforementioned information from a measurement set that was not designed for quantifying turbulence, and the paper explains the methodology developed to overcome this difficulty.</p>
<p>It is observed that SPBs oscillate quasi-periodically around their equilibrium positions. The oscillation periods, which are 220 s on average with a range of 130 to 500 s, are close to but noticeably smaller than the Brunt–Väisälä period (<span class="inline-formula">∼300</span> s). The amplitude of these vertical motions is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mo>±</mo><mn mathvariant="normal">15</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="19ce794aa253fe705dbc0a72e5751e03"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-311-2023-ie00001.svg" width="32pt" height="10pt" src="amt-16-311-2023-ie00001.png"/></svg:svg></span></span> m, inducing large fluctuations in all quantities,
whether measured (e.g., pressure, temperature and position) or inferred (e.g., density and potential temperature). The relationships between the changes in these quantities and the vertical displacements of the balloons are used to infer properties of the flow in which the SPBs drift.</p>
<p>In the case of active turbulence, the vertical stratification as well as the wind shear are likely to be reduced by mixing. Hence, the increments of potential temperature, <span class="inline-formula"><i>δ</i><i>θ</i></span>, and of the vertical displacements of the balloon, <span class="inline-formula"><i>δ</i><i>z</i><sub>B</sub></span>, are expected to be uncorrelated because <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∂</mo><mi mathvariant="italic">θ</mi><mo>/</mo><mo>∂</mo><mi>z</mi><mo>→</mo><mn mathvariant="normal">0</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7c0132bb1bf339b0fcf49a8d337abfc2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-311-2023-ie00002.svg" width="58pt" height="14pt" src="amt-16-311-2023-ie00002.png"/></svg:svg></span></span>. Moreover, the local vertical gradients of measured quantities, temperature (<span class="inline-formula"><i>T</i></span>) and horizontal velocities (<span class="inline-formula"><i>u</i></span> and <span class="inline-formula"><i>v</i></span>),
are estimated from the covariance of the increments of the considered quantity with <span class="inline-formula"><i>δ</i><i>z</i><sub>B</sub></span>. The Richardson number of the flow is deduced.</p>
<p>Several binary indexes (true or false) to describe the state of the flow,
laminar or turbulent, are evaluated. These turbulence indexes, based either on correlations between <span class="inline-formula"><i>δ</i><i>θ</i></span> and <span class="inline-formula"><i>δ</i><i>z</i><sub>B</sub></span> or on estimates of the local Richardson number, are found to be consistent, as they differ in less than 3 % of cases. The flow is observed to be turbulent for about 5 % of the time, with strong inhomogeneities along the longitude.</p> |
| first_indexed | 2024-04-10T21:12:56Z |
| format | Article |
| id | doaj.art-3a362fa7fd5a42abbca994bf2756f23d |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-10T21:12:56Z |
| publishDate | 2023-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-3a362fa7fd5a42abbca994bf2756f23d2023-01-20T14:55:11ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482023-01-011631133010.5194/amt-16-311-2023Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloonsR. Wilson0C. Pitois1A. Podglajen2A. Hertzog3M. Corcos4R. Plougonven5LATMOS-IPSL, Sorbonne Université, Paris, FranceLATMOS-IPSL, Sorbonne Université, Paris, FranceLMD-IPSL, École polytechnique, Palaiseau, FranceLMD-IPSL, École polytechnique, Palaiseau, FranceLMD-IPSL, École polytechnique, Palaiseau, FranceLMD-IPSL, École polytechnique, Palaiseau, France<p>This article deals with the detection of small-scale turbulence from in situ meteorological measurements performed under superpressure balloons (SPBs). These balloons allow long-duration flights (several months) at a prerequisite height level. The data set is gathered from the Strateole-2 probationary campaign during which eights SPBs flew in the tropical tropopause layer at altitudes of around 19 and 20.5 km from November 2019 to March 2020.</p> <p>Turbulence is not directly measured by the instrument set onboard the SPBs. Nonetheless, there is the potential to derive information about the occurrence of turbulence from the temporally well-resolved measurements of pressure, temperature, and position. It constitutes a challenge to extract the aforementioned information from a measurement set that was not designed for quantifying turbulence, and the paper explains the methodology developed to overcome this difficulty.</p> <p>It is observed that SPBs oscillate quasi-periodically around their equilibrium positions. The oscillation periods, which are 220 s on average with a range of 130 to 500 s, are close to but noticeably smaller than the Brunt–Väisälä period (<span class="inline-formula">∼300</span> s). The amplitude of these vertical motions is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∼</mo><mo>±</mo><mn mathvariant="normal">15</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="32pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="19ce794aa253fe705dbc0a72e5751e03"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-311-2023-ie00001.svg" width="32pt" height="10pt" src="amt-16-311-2023-ie00001.png"/></svg:svg></span></span> m, inducing large fluctuations in all quantities, whether measured (e.g., pressure, temperature and position) or inferred (e.g., density and potential temperature). The relationships between the changes in these quantities and the vertical displacements of the balloons are used to infer properties of the flow in which the SPBs drift.</p> <p>In the case of active turbulence, the vertical stratification as well as the wind shear are likely to be reduced by mixing. Hence, the increments of potential temperature, <span class="inline-formula"><i>δ</i><i>θ</i></span>, and of the vertical displacements of the balloon, <span class="inline-formula"><i>δ</i><i>z</i><sub>B</sub></span>, are expected to be uncorrelated because <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>∂</mo><mi mathvariant="italic">θ</mi><mo>/</mo><mo>∂</mo><mi>z</mi><mo>→</mo><mn mathvariant="normal">0</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="58pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7c0132bb1bf339b0fcf49a8d337abfc2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-311-2023-ie00002.svg" width="58pt" height="14pt" src="amt-16-311-2023-ie00002.png"/></svg:svg></span></span>. Moreover, the local vertical gradients of measured quantities, temperature (<span class="inline-formula"><i>T</i></span>) and horizontal velocities (<span class="inline-formula"><i>u</i></span> and <span class="inline-formula"><i>v</i></span>), are estimated from the covariance of the increments of the considered quantity with <span class="inline-formula"><i>δ</i><i>z</i><sub>B</sub></span>. The Richardson number of the flow is deduced.</p> <p>Several binary indexes (true or false) to describe the state of the flow, laminar or turbulent, are evaluated. These turbulence indexes, based either on correlations between <span class="inline-formula"><i>δ</i><i>θ</i></span> and <span class="inline-formula"><i>δ</i><i>z</i><sub>B</sub></span> or on estimates of the local Richardson number, are found to be consistent, as they differ in less than 3 % of cases. The flow is observed to be turbulent for about 5 % of the time, with strong inhomogeneities along the longitude.</p>https://amt.copernicus.org/articles/16/311/2023/amt-16-311-2023.pdf |
| spellingShingle | R. Wilson C. Pitois A. Podglajen A. Hertzog M. Corcos R. Plougonven Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons Atmospheric Measurement Techniques |
| title | Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons |
| title_full | Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons |
| title_fullStr | Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons |
| title_full_unstemmed | Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons |
| title_short | Detection of turbulence occurrences from temperature, pressure, and position measurements under superpressure balloons |
| title_sort | detection of turbulence occurrences from temperature pressure and position measurements under superpressure balloons |
| url | https://amt.copernicus.org/articles/16/311/2023/amt-16-311-2023.pdf |
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