scholarly journals The Structure of Thermals in Cumulus from Airborne Dual-Doppler Radar Observations

2006 ◽  
Vol 63 (5) ◽  
pp. 1432-1450 ◽  
Author(s):  
Rick Damiani ◽  
Gabor Vali ◽  
Samuel Haimov
Keyword(s):  
Doppler Radar ◽  
Ambient Air ◽  
Velocity Fields ◽  
Vertical Shear ◽  
Vortex Rings ◽  
Interface Instability ◽  
Cloud Radar ◽  
Free Air ◽  
Ring Core

Abstract A newly developed technique for airborne dual-Doppler observations with the Wyoming Cloud Radar is used to characterize the velocity fields in vertical planes across cumulus turrets. The clouds sampled were continental in nature, with high bases (near 0°C) and with depths of 2–3 km. Clear evidence was found that the clouds evolved through sequences of bubbles, or thermals, with well-defined toroidal circulations, or vortex rings. The ring core and tube diameters were about 200–600 m, leading to turret sizes of 1–2 km in the horizontal. The largest updraft speeds were observed in the ring centers, but regions of turbulent, ascending air extended behind the thermals to distances comparable with the toroid sizes. Vertical shear of ambient winds, when present, led to a tilting of the updrafts and toroids. Patterns in the reflectivity and velocity fields indicated regions of major intrusions into the thermals, accompanied by entrainment of ambient air, or recycling of larger hydrometeors, depending on their location. In addition, at the upper cloud/environment interface, instability nodes contributed to further entrapment of cloud-free air. The observations presented in this paper constitute clear demonstrations and quantitative characterization of vortical circulations in growing cumulus turrets; they should provide a more reliable basis for the assessment of simulations and of model parameterizations.

An Air Curtain Along a Wall With High Inlet Turbulence

2004 ◽  
Vol 126 (3) ◽  
pp. 391-398 ◽  
Author(s):  
Brandon S. Field ◽  
Eric Loth
Keyword(s):  
Ambient Air ◽  
Reynolds Numbers ◽  
Velocity Fields ◽  
Air Curtain ◽  
Image Velocimetry ◽  
Number Variation ◽  
Inflow Turbulence ◽  
High Turbulence ◽  
Isothermal Wall ◽  
Eddy Dynamics

A downward blowing isothermal wall jet at moderate Reynolds numbers (1,500 to 8,500) with significant inflow turbulence (ca. 6%) was investigated. The flow configuration is an idealization of the air curtains of refrigerated display cases. Flow visualization using particle seeding was employed to identify the flow field eddy dynamics. Particle Image Velocimetry was used to examine the velocity fields in terms of mean and fluctuating values. These diagnostics showed that the air curtain entrainment was dominated by a large variety of eddies that engulfed ambient air into the air curtain. The velocity fields generally showed linear spreading, significant deceleration and high turbulence levels (ca. 25%). It was observed that the air curtain dynamics, velocity fields and growth were not significantly sensitive to Reynolds number variation between Re=3,800 and Re=8,500. However, at low air velocities (Re=1,500), the curtain was found to detach, leading to a large air curtain thickness and high curtain entrainment.

A Variational Method for Filling in Missing Data in Doppler Velocity Fields

2021 ◽  
Author(s):  
VINCENT T. WOOD ◽  
ROBERT P. DAVIES-JONES ◽  
ALAN SHAPIRO
Keyword(s):  
Missing Data ◽  
Doppler Radar ◽  
Signal To Noise Ratio ◽  
Original Data ◽  
Radar Data ◽  
Velocity Fields ◽  
Doppler Velocity ◽  
Doppler Radar Data ◽  
Ground Clutter ◽  
Tornado Warnings

AbstractSingle-Doppler radar data are often missing in important regions of a severe storm due to low return power, low signal-to-noise ratio, ground clutter associated with normal and anomalous propagation, and missing radials associated with partial or total beam blockage. Missing data impact the ability of WSR-88D algorithms to detect severe weather. To aid the algorithms, we develop a variational technique that fills in Doppler velocity data voids smoothly by minimizing Doppler velocity gradients while not modifying good data. This method provides estimates of the analysed variable in data voids without creating extrema.Actual single-Doppler radar data of four tornadoes are used to demonstrate the variational algorithm. In two cases, data are missing in the original data, and in the other two, data are voided artificially. The filled-in data match the voided data well in smoothly varying Doppler velocity fields. Near singularities such as tornadic vortex signatures, the match is poor as anticipated. The algorithm does not create any velocity peaks in the former data voids, thus preventing false triggering of tornado warnings. Doppler circulation is used herein as a far-field tornado detection and advance-warning parameter. In almost all cases, the measured circulation is quite insensitive to the data that have been voided and then filled. The tornado threat is still apparent.

Mode-Dependent Characterization of Rayleigh Backscattering in Ring-Core Fibers

2021 ◽  
Author(s):  
Cong Huang ◽  
Junyi Liu ◽  
Zhenrui Lin ◽  
Jie Liu ◽  
Jiangbo Zhu ◽  
...  
Keyword(s):  
Rayleigh Backscattering ◽  
Ring Core

Pulsed Vulcanian explosions: A characterization of eruption dynamics using Doppler radar

Geology ◽  
2015 ◽  
Vol 43 (11) ◽  
pp. 995-998 ◽  
Author(s):  
Lea Scharff ◽  
Matthias Hort ◽  
Nick R. Varley
Keyword(s):  
Doppler Radar ◽  
Eruption Dynamics ◽  
Vulcanian Explosions

scholarly journals Characterization of a free air ionization chamber for low energy X-rays

2016 ◽  
Vol 733 ◽  
pp. 012090
Author(s):  
N F Silva ◽  
M Xavier ◽  
V Vivolo ◽  
L V E Caldas
Keyword(s):  
Ionization Chamber ◽  
Low Energy ◽  
X Rays ◽  
Free Air ◽  
Air Ionization

of storage as short as possible, only; 24 h should not be ex­ ceeded. Table III comprises the most important criteria for valid static and dynamic sampling. It seems that both the guide of Warren Springs, U.K. and the VDI-Guideline might be a useful base to describe commonly accepted sampling procedures aiming at a standardization of sampling which might be a first step for a harmonization of olfactometric measurements in the different laboratories and countri es. REFERENCES (1) BULLEY, N.R. and D. PHILLIPS (1980). Sensory evaluation of agricul­ tural odours: A critical review. Can. Agric. Eng. 22, 107 - 112. (2) HENRY, J.G. and R. GEHR (1980). Odour control: An operator's guide. Journal WPCF 52, 2523 - 2537. (3) ROOS, C., J.A. DON and J. SCHAEFER (1984). Characterization of odour-polluted air. In: Proc.Int.Symp., Soc. Beige de Filtr. (eds.), 25-27 April 1984, Louvain-La-Neuve, Belgium, pp. 3 - 22. (4) BAKER, A.R. and R.C. DOERR (1959). Methods of sampling and storage of air containing vapors and gases. Int.J.Air Poll. 2, 142 - 158. (5) SCHUETTE, F.J. (1967). Plastic bags for collection of gas samples. Atmosph.Environm. 1, 515 - 519. (6) SCHODDER, F. (1977T. Messen von Geruchsstoffkonzentrationen, Erfassen von Geruch. Grundl. Landtechnik 27, 73 - 82. (7) CORMACK, D., T.A. DORLING and B.W7J. LYNCH (1974). Comparison of tech­ niques for organoleptic odour-intensity assessment. Chem.Ind. (Lon­ don) no. 2, 857 - 861. (8) SCHUETZLE, D., T.J. PRATER and S. RUDDELL (1975). Sampling and anal­ ysis of emissions from stationary sources. I. Odour and total hydro­ carbons. APCA Journal 25, 925 - 932. (9) WAUTERS, E., E. WALRAVENS, E. MUYLLE and G. VERDUYN (1983). An evalu­ ation of a fast sampling procedure for the trace analysis of volatile organic compounds in ambient air. Environm.Monitor.Assessm. 3, 151-160. (10) LACHENMAYER, U. and H. KOHLER (1984). Untersuchungen zur Neuentwick-lung eines Olfaktometers. Staub - Reinhalt. Luft 44, 359 - 362. (11) BERNARD, F. (1984). Simplified methods of odour measurement: Indus­ trial application and interest for administrative control. Proc. Int. Symp., Soc. Beige de Filtr. (eds.), 25 - 27 April 1984, Louvain-La-Neuve, Belgium, pp. 139 - 150. (12) GILLARD, F. (1984). Measurement of odours by dynamic olfactometry. Application to the steel and carbonization industries. Proc.Int.Symp., Soc. Beige de Filtr. (eds.), 25 - 27 April 1984, Louvain-La-Neuve, Belgium, pp. 53 - 86. (13) MANNEBECK, H. (1975). Tragbare Olfaktometer. VDI-Bericht 226, 103-105. (14) BEDBOROUGH, D.R. (1980). Sensory measurement of odours. In: Odour Control - a concise guide, F.H.H. Valentin and A.A. North (eds.), Warren Springs Laboratories, Stevenage, Hertfordshire, U.K., pp. 17-30. (15) THIELE, V. (1984). Olfaktometrie an einer Emissionsquelle - Ergebnis-se des VDI-Ringvergleichs. Staub - Reinhalt. Luft 44, 342 - 351. (16) DUFFEE, R.A., J.P. WAHL, W. MARRONE and J.S. NADERT1973). Defining and measuring objectionable odors. Internat. Pollution Eng. Congress, Philadelphia, paper no 25a, pp. 192 - 201.

1986 ◽  
pp. 62-62
Keyword(s):  
Ambient Air ◽  
Sampling Procedure ◽  
Plastic Bags ◽  
Volatile Organic ◽  
Odour Control ◽  
Sampling Procedures ◽  
Dynamic Sampling ◽  
Concise Guide ◽  
And Storage

scholarly journals Characterization of PM1-Bound Metallic Elements in the Ambient Air at a High Mountain Site in Northern China

2018 ◽  
Vol 18 (12) ◽  
pp. 2967-2981
Author(s):  
Jun-Jie Yue ◽  
Roberta Palmiero ◽  
Yang-Yang Han ◽  
Yan Wang ◽  
Qian-Qian Li ◽  
...  
Keyword(s):  
Northern China ◽  
Ambient Air ◽  
High Mountain ◽  
Metallic Elements ◽  
Mountain Site

scholarly journals Characterization and Applications of Diamond-like Nanocomposites: A Brief Review

2018 ◽  
Author(s):  
Kalyan Adhikary ◽  
Sayan Das ◽  
Debasish De ◽  
Anup Mondal ◽  
Utpal Gangopadhyay ◽  
...  
Keyword(s):  
Silicon Oxide ◽  
High Ratio ◽  
Atomic Scale ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Marine Energy ◽  
Deposition Parameters ◽  
Free Air ◽  
Wide Range ◽  
Scale Network

Diamond-like Nanocomposites (DLN) is a newly member in amorphous carbon (a:C) family. It consists of two or more interpenetrated atomic scale network structure. The amorphous silicon oxide (a:SiO) is incorporated within diamond-like carbon (DLC) matrix i.e. a:CH and both the network is interpenetrated by Si-C bond. Hence, the internal stress of deposited DLN film decreases remarkably compare to DLC. The diamond like properties has come due to deform tetrahedral carbon with sp3 configuration and high ratio of sp3 to sp2 bond. The DLN has excellent mechanical, electrical, optical and tribological properties. Those the properties of DLN could be varied over a wide range by changing deposition parameters, precursor and even post deposition treatment also. The range of properties are : Resistivity 10-4 to 1014 Ωcm, hardness 10–22 GPa, coefficient of friction 0.03-0.2, wear factor 0.2-0.4 10-7mm3/Nm, transmission Vis-far IR, modulus of elasticity 150-200 GPa, residual stress 200-300 Mpa, Dielectric constant 3-9 and maximum operating temperature 6000C in oxygen environment and 12000C in O2 free air. Generally, the PECVD method is used to synthesis the DLN film. The most common procedures used for investigation of structure and composition of DLN films are Raman spectroscopy, Fourier transformed infrared spectroscopy (FTIR), HRTEM, FESEM and X-ray photo electron spectroscopy (XPS). Interest in the coating technology has been expressed by nearly every industrial segment including automotive, aerospace, chemical processing, marine, energy, personal care, office equipment, electronics, biomedical and tool and die or in a single line from data to beer in all segment of life. In this review paper, characterization of Diamond-like Nanocomposites is discussed and subsequently different application areas are also elaborated.

OAM Mode Transmission Characterization of Hollow Ring-core POF Related to Geometric Tolerance

2020 ◽  
Vol 49 (6) ◽  
pp. 606002-606002
Author(s):  
袁苑 Yuan YUAN ◽  
孔德鹏 De-peng KONG ◽  
贺正权 Zheng-quan HE ◽  
王丽莉 Li-li WANG
Keyword(s):  
Geometric Tolerance ◽  
Ring Core
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