Improved Lyman‐alpha hygrometer for small‐scale atmospheric turbulence measurements. Part I: Miniaturizing the sampling volume

1986 ◽  
Vol 57 (1) ◽  
pp. 20-25 ◽  
Author(s):  
Patrice Mestayer ◽  
Claude Rebattet ◽  
Florence Goutail
Keyword(s):  
Atmospheric Turbulence ◽  
Small Scale ◽  
Turbulence Measurements ◽  
Lyman Alpha ◽  
Sampling Volume

scholarly journals Fabrication of freestanding Pt nanowires for use as thermal anemometry probes in turbulence measurements

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Hai Le-The ◽  
Christian Küchler ◽  
Albert van den Berg ◽  
Eberhard Bodenschatz ◽  
Detlef Lohse ◽  
...  
Keyword(s):  
Room Temperature ◽  
Fluid Velocity ◽  
Current Mode ◽  
Constant Current ◽  
Small Scale ◽  
Turbulence Measurements ◽  
High Dynamic ◽  
Scale Turbulence ◽  
Constant Current Mode ◽  
Pt Nanowires

AbstractWe report a robust fabrication method for patterning freestanding Pt nanowires for use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 µm length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining wet etching processes with dry etching processes, these Pt nanowires were successfully released, rendering them freestanding between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed gentle release of the device without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires, while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in constant-current mode. A robust calibration between the output voltage and the fluid velocity was established over the velocity range from 0.5 to 5 m s−1 in a SF6 atmosphere at a pressure of 2 bar and a temperature of 21 °C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires can withstand high dynamic pressures by testing them in air at room temperature for velocities up to 55 m s−1.

scholarly journals On the Structure of the Small-Scale Atmospheric Turbulence Near the Ground

1959 ◽  
Vol 37 (5) ◽  
pp. 160-163 ◽  
Author(s):  
J. Sakagami ◽  
M. Mochizuki ◽  
M. Ishige ◽  
S. Nakagawa
Keyword(s):  
Atmospheric Turbulence ◽  
Small Scale

222Rn as indicator of atmospheric turbulence: measurements at Lake Maggiore and on the pre-Alps

2006 ◽  
Vol 86 (2) ◽  
pp. 271-288 ◽  
Author(s):  
Lucia Sesana ◽  
Barbara Ottobrini ◽  
Giancarla Polla ◽  
Ugo Facchini
Keyword(s):  
Atmospheric Turbulence ◽  
Turbulence Measurements ◽  
Lake Maggiore

scholarly journals Estimation of the Turbulent Fraction in the Free Atmosphere from MST Radar Measurements

2005 ◽  
Vol 22 (9) ◽  
pp. 1326-1339 ◽  
Author(s):  
Richard Wilson ◽  
Francis Dalaudier ◽  
Francois Bertin
Keyword(s):  
Dissipation Rate ◽  
Spectral Width ◽  
Unbiased Estimation ◽  
Small Scale ◽  
Doppler Width ◽  
Free Atmosphere ◽  
Dissipation Rates ◽  
Sampling Volume ◽  
Radar Measurements ◽  
Width Measurements

Abstract Small-scale turbulence in the free atmosphere is known to be intermittent in space and time. The turbulence fraction of the atmosphere is a key parameter in order to evaluate the transport properties of small-scale motions and to interpret clear-air radar measurements as well. Mesosphere–stratosphere–troposphere (MST)/stratosphere–troposphere (ST) radars provide two independent methods for the estimation of energetic parameters of turbulence. First, the Doppler spectral width σ2 is related to the dissipation rate of kinetic energy εk. Second, the radar reflectivity, or C2n, relates to the dissipation rate of available potential energy εp. However, these two measures yield estimates that differ with respect to an important point. The Doppler width measurements, and related εk, are reflectivity-weighted averages. On the other hand, the reflectivity estimate is a volume-averaged quantity. The values of εp depend on both the turbulence intensity and the turbulent fraction within the radar sampling volume. Now, the two dissipation rates εp and εk are related quantities as shown by various measurements within stratified fluids (atmosphere, ocean, lakes, or laboratory). Therefore, by assuming a “canonical” value for the ratio of dissipation rates, an indirect method is proposed to infer the turbulent fraction from simultaneous radar measurements of reflectivity and Doppler broadening within a sampling volume. This method is checked by using very high resolution radar measurements (30 m and 51 s), obtained by the PROUST radar during a field campaign. The method is found to provide an unbiased estimation of the turbulent fraction, within a factor of 2 or less.

scholarly journals Modulation of Small-Scale Turbulence by Ducted Gravity Waves in the Nocturnal Boundary Layer

2008 ◽  
Vol 65 (4) ◽  
pp. 1414-1427 ◽  
Author(s):  
Y. P. Meillier ◽  
R. G. Frehlich ◽  
R. M. Jones ◽  
B. B. Balsley
Keyword(s):  
Boundary Layer ◽  
Gravity Waves ◽  
Richardson Number ◽  
Potential Temperature ◽  
Nocturnal Boundary Layer ◽  
Small Scale ◽  
Temperature Structure ◽  
Turbulence Measurements ◽  
Gradient Richardson Number ◽  
Scale Turbulence

Abstract Constant altitude measurements of temperature and velocity in the residual layer of the nocturnal boundary layer, collected by the Cooperative Institute for Research in Environmental Sciences (CIRES) Tethered Lifting System (TLS), exhibit fluctuations identified by previous work (Fritts et al.) as the signature of ducted gravity waves. The concurrent high-resolution TLS turbulence measurements (temperature structure constant C2T and turbulent kinetic energy dissipation rate ɛ) reveal the presence of patches of enhanced turbulence activity that are roughly synchronized with the troughs of the temperature and velocity fluctuations. To investigate the potentially dominant role ducted gravity waves might play on the modulation of atmospheric stability and therefore, on turbulence, time series of the wave-modulated gradient Richardson number (Ri) and of the vertical gradient of potential temperature ∂θ/∂z(t) are computed numerically and compared to the TLS small-scale turbulence measurements. The results of this study agree with the predictions of previous theoretical studies (i.e., wave-generated fluctuations of temperature and velocity modulate the gradient Richardson number), resulting in periodic enhancements of turbulence at Ri minima. The patches of turbulence observed in the TLS dataset are subsequently identified as convective instabilities generated locally within the unstable phase of the wave.

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