scholarly journals On the estimation of vertical air velocity and detection of atmospheric turbulence from the ascent rate of balloon soundings

2019 ◽  
Author(s):  
Hubert Luce ◽  
Hiroyuki Hashiguchi
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Atmospheric Turbulence ◽  
Radar Data ◽  
Weak Turbulence ◽  
Air Velocity ◽  
Convective Boundary ◽  
Ascent Rate ◽  
Mu Radar ◽  
Turbulence Effects ◽  
The Cost

Abstract. Vertical ascent rate VB of meteorological balloons is sometimes used for retrieving vertical air velocity W, an important parameter for meteorological applications, but at the cost of crude hypotheses on atmospheric turbulence and without the possibility of formally validating the models from concurrent measurements. From simultaneous radar and Unmanned Aerial Vehicles (UAV) measurements of turbulent kinetic energy dissipation rates ϵ, we show that VB can be strongly affected by turbulence, even above the convective boundary layer. For “weak” turbulence (here ϵ ≲ 10−4 m2 s-3), the fluctuations of VB were found to be fully consistent with W fluctuations measured from MU radar, indicating that an estimate of W can indeed be retrieved from VB if the free balloon lift is determined. In contrast, stronger turbulence intensity systematically implies an increase of VB, not associated with an increase of W according to radar data, very likely due to the decrease of the turbulence drag coefficient of the balloon. From the statistical analysis of data gathered from 376 balloons launched every 3 hours at Bengkulu (Indonesia), positive VB disturbances, mainly observed in the troposphere, were found to be clearly associated with Ri ≲ 0.25, usually indicative of turbulence, confirming the case studies. The analysis also revealed the superimposition of additional positive and negative disturbances for Ri ≲ 0.25 likely due to Kelvin-Helmholtz waves in the vicinity of the turbulent layers. From these experimental evidences, we conclude that the ascent rate of meteorological balloons, with the current performance of radiosondes in terms of altitude accuracy, can potentially be used for the detection of turbulence. The presence of turbulence makes impossible the estimation of W and misinterpretations of VB fluctuations can be made if localized turbulence effects are ignored.

scholarly journals On the estimation of vertical air velocity and detection of atmospheric turbulence from the ascent rate of balloon soundings

2020 ◽  
Vol 13 (4) ◽  
pp. 1989-1999
Author(s):  
Hubert Luce ◽  
Hiroyuki Hashiguchi
Keyword(s):  
Atmospheric Turbulence ◽  
Large Scale ◽  
Radar Data ◽  
Air Velocity ◽  
Convective Boundary ◽  
Ascent Rate ◽  
Mu Radar ◽  
Turbulence Effects ◽  
Aerial Vehicle ◽  
The Cost

Abstract. Vertical ascent rate VB of meteorological balloons is sometimes used for retrieving vertical air velocity W, an important parameter for meteorological applications, but at the cost of crude hypotheses on atmospheric turbulence and without the possibility of formally validating the models from concurrent measurements. From simultaneous radar and unmanned aerial vehicle (UAV) measurements of turbulent kinetic energy dissipation rates ε, we show that VB can be strongly affected by turbulence, even above the convective boundary layer. For “weak” turbulence (here ε≲10−4 m2 s−3), the fluctuations of VB were found to be fully consistent with W fluctuations measured by middle and upper atmosphere (MU) radar, indicating that an estimate of W can indeed be retrieved from VB if the free balloon lift is determined. In contrast, stronger turbulence intensity systematically implies an increase in VB, not associated with an increase in W according to radar data, very likely due to the decrease in the turbulence drag coefficient of the balloon. From the statistical analysis of data gathered from 376 balloons launched every 3 h at Bengkulu (Indonesia), positive VB disturbances, mainly observed in the troposphere, were found to be clearly associated with Ri≲0.25, usually indicative of turbulence, confirming the case studies. The analysis also revealed the superimposition of additional positive and negative disturbances for Ri≲0.25 likely due to Kelvin–Helmholtz waves and large-scale billows. From this experimental evidence, we conclude that the ascent rate of meteorological balloons, with the current performance of radiosondes in terms of altitude accuracy, can potentially be used for the detection of turbulence. The presence of turbulence complicates the estimation of W, and misinterpretations of VB fluctuations can be made if localized turbulence effects are ignored.

Analysis of non-Kolmogorov weak turbulence effects on infrared imaging by atmospheric turbulence MTF

2013 ◽  
Vol 300 ◽  
pp. 114-118 ◽  
Author(s):  
Bindang Xue ◽  
Lei Cao ◽  
Linyan Cui ◽  
Xiangzhi Bai ◽  
Xiaoguang Cao ◽  
...  
Keyword(s):  
Atmospheric Turbulence ◽  
Infrared Imaging ◽  
Weak Turbulence ◽  
Turbulence Effects

scholarly journals MU Radar and Lidar Observations of Clear-Air Turbulence underneath Cirrus

2010 ◽  
Vol 138 (2) ◽  
pp. 438-452 ◽  
Author(s):  
Hubert Luce ◽  
Takuji Nakamura ◽  
Masayuki K. Yamamoto ◽  
Mamoru Yamamoto ◽  
Shoichiro Fukao
Keyword(s):  
Convective Instability ◽  
Radar Data ◽  
Ice Crystals ◽  
Shear Instability ◽  
Cloud Base ◽  
Doppler Spectrum ◽  
Cirrus Cloud ◽  
Air Turbulence ◽  
Mu Radar ◽  
Generation Mechanisms

Abstract Turbulence generation mechanisms prevalent in the atmosphere are mainly shear instabilities, breaking of internal buoyancy waves, and convective instabilities such as thermal convection due to heating of the ground. In the present work, clear-air turbulence underneath a cirrus cloud base is described owing to coincident observations from the VHF (46.5 MHz) middle and upper atmosphere (MU) radar, a Rayleigh–Mie–Raman (RMR) lidar, and a balloon radiosonde on 7–8 June 2006 (at Shigaraki, Japan; 34.85°N, 136.10°E). Time–height cross section of lidar backscatter ratio obtained at 2206 LT 7 June 2006 showed the presence of a cirrus layer between 8.0 and 12.5 km MSL. Downward-penetrating structures of ice crystals with horizontal and vertical extents of 1.0–4.0 km and 200–800 m, respectively, have been detected at the cirrus cloud base for about 35 min. At the same time, the MU radar data revealed clear-air turbulence layers developing downward from the cloud base in the environment of the protuberances detected by the RMR lidar. Their maximum depth was about 2.0 km for about 1.5 h. They were associated with oscillatory vertical wind perturbations of up to ±1.5 m s−1 and variances of Doppler spectrum of 0.2–1.5 m−2 s−2. Analysis of the data suggests that the turbulence and the downward penetration of cloudy air were possibly the consequence of a convective instability (rather than a dynamical shear instability) that was likely due to sublimation of ice crystals in the subcloud region. Downward clear-air motions measured by the MU radar were associated with the descending protuberances, and updrafts were observed between them. These observations suggest that the cloudy air might have been pushed down by the downdrafts of the convective instability and pushed up by the updrafts to form the observed protuberances at the cloud base. These structures may be virga or perhaps more likely mamma as reported by recent observations of cirrus mamma with similar instruments and by numerical simulations.

scholarly journals Removing Atmospheric Turbulence Effects in Unified Complex Steerable Pyramid Framework

IEEE Access ◽  
2018 ◽  
Vol 6 ◽  
pp. 75855-75867 ◽  
Author(s):  
Chao Zhang ◽  
Bindang Xue ◽  
Fugen Zhou ◽  
Wei Xiong
Keyword(s):  
Atmospheric Turbulence ◽  
Turbulence Effects ◽  
Atmospheric Turbulence Effects ◽  
Steerable Pyramid

Investigation of Ash-Related Issues During Combustion of Maize Straw and Wood Biomass Blends in Lab-Scale Bubbling Fluidized Bed Reactor

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Krzysztof Głód ◽  
Janusz Lasek ◽  
Krzysztof Słowik ◽  
Jarosław Zuwała ◽  
Daniel Nabagło ◽  
...  
Keyword(s):  
Fluidized Bed ◽  
Air Velocity ◽  
Interesting Phenomenon ◽  
Simultaneous Application ◽  
Agglomeration Process ◽  
Bubbling Fluidized Bed ◽  
Bed Agglomeration ◽  
The Cost ◽  
The Impact ◽  
Combustion Of Solid Fuels

Abstract During the combustion of solid fuels, the undesired effects of ash transformation include bed agglomeration, slagging, and fouling processes. In particular, a problematic consequence of bed agglomeration is the defluidization process, resulting from the disappearance of gaseous bubbles that are created behind air distributors. Different solutions can be applied against the agglomeration process. One possible method is to apply some additives that influence the ash behavior, thus inhibiting the agglomeration process. This paper presents the results of investigations into ash-related issues in a laboratory-scale bubbling fluidized bed (BFB) reactor. In particular, the impact of additives (kaolin, halloysite, fly ash, and the residuals from wet desulfurization system (IMOS)) on bed agglomeration was investigated. It was found that the addition of these compounds increased the defluidization time from ∼109 min (without additive) to ∼285 min in the BFB (with the addition of 0.1 g/min of kaolin). The morphology of additive (kaolin and halloysite) transformation after their addition into the combustion chamber was discussed. Another interesting phenomenon is that residuals from the IMOS exhibited the ability to be an additive against the agglomeration process. The defluidization time can be also significantly increased by the simultaneous application of the additive and the control of fluidization air velocity. The procedure of periodical bed moving by impulse primary air feeding against defluidization (PADM) is suggested and discussed. The PADM procedure resulted in a 36% reduction of additive, thus reducing the cost of measures against ash-related issues.

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