air turbulence
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Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1691
Author(s):  
Jianli Ma ◽  
Li Luo ◽  
Mingxuan Chen ◽  
Siteng Li

The echo of weather radar is seriously disturbed by clear-air turbulence echo (CAT) which needs identifying and eliminating to improve the data quality of weather radar. Using the data observed with the five X-band dual polarimetric radars in Changping, Fangshan, Miyun, Shunyi, and Tongzhou, Beijing in 2018, the probability density distribution (PDD) of the horizontal texture of four radar moments reflectively factor (ZH), differential reflectivity (ZDR), correlation coefficient (ρHV), differential propagation phase shift (ΦDP), and then the CAT is identified and removed using Bayesian method. The results show that the radar data can be effectively improved after the CAT has been eliminated, which include: (1) the removal rate of CAT is more than 98.2% in the analyzed cases. (2) In the area with high-frequency distribution of CAT, the CAT can be effectively suppressed; in the area with low-frequency distribution, some weather echo in the edge with SNR < 15 dB may be mistakenly identified as CAT, but the proportion of meteorological echoes to the total echoes is more than 85%, which indicate that the error rate is very low and does not affect the radar operation.


2021 ◽  
Author(s):  
Xindi Huang

The article deals with the application of the Gaussian distribution for calculating the concen-tration of pollutants. When using the principle of superposition, we have the opportunity to obtain models for calculating the concentration of impurities from a point source of continuous action, in-stantaneous areal and instantaneous volumetric sources. The obtained standard deviations make it possible to assess the effect of air turbulence on the dispersion of pollutants. The first Gaussian model allows one to obtain a diffusion model of a local small-scale space and make predictions, then, based on the Gaussian model of the study, a modified model is obtained for other reliefs and weather conditions. Therefore, the modeling accuracy and applicable conditions are difficult to cope with the needs of large-scale complex meteorological conditions of air quality models.


2021 ◽  
pp. 1-13
Author(s):  
G. B. Gratton ◽  
P. D. Williams ◽  
A. Padhra ◽  
S. Rapsomanikis

Abstract Climatechange is increasing global-mean tropospheric temperatures, but the localised trends are uneven, including cooling the lower stratosphere and lifting the tropopause. The wind speeds are also being modified, both at the surface and aloft. A further effect, additional to wind and temperature alone, is of increasing fluctuations and severity of extreme weather. These are impacting air transport, and this will continue. The effects are known to include increased take-off distances where excess runway lengths exist and reduced payloads where they do not, increased en-route flight times, increased frequency and severity of encounters with clear air turbulence in some regions, changed patterns of wildlife — particularly bird — activity in some regions (potentially also for other anthropogenic reasons) are shifting locations of flight safety hazards, and increased burdens upon airport and associated infrastructure. There is increasing understanding and acknowledgment by companies and authorities of these effects and the importance of mitigating them, although this is not universal and there are as yet no universally understood best practices for air transport climate change mitigation.


2021 ◽  
Vol 2021 (2) ◽  
pp. 56-63
Author(s):  
Alexander Nikolaevich Rukavitsyn ◽  
Leon Andreas Santiago Martinez

The paper considers approaches to creating a new type of unmanned aircrafts - quadcopters. It is stated that the efficiency of a quadcopter directly depends on its frame design and the structural materials used. The approaches to designing the aircraft frame using computer-aided design tools (SolidWorks package) are described. The stress maps obtained during the strength study for the frame beam made of carbon fiber allow asserting a large margin of structural strength. The strength calculation carried out predetermined the need to take into account the influence of additional factors (the air flow created by the traction screws). The existing restrictions on the maximum size of the rotating propellers predetermined the design of the quadcopter frame taking into account the maximum number of possible aerodynamic effects that determine the stability of flight characteristics by minimizing interference from air turbulence, as well as from possible natural phenomena. The designed quadcopter frame has special aerodynamic surfaces that allow for a stable flight path in a volatile air environment. The generated torque is determined by the characteristics of the traction screw motors. The influence of the isosurface air flow on the design of the quadcopter was evaluated.


2021 ◽  
Vol 15 ◽  
Author(s):  
Harrison Tuckman ◽  
Mainak Patel ◽  
Hong Lei

Air turbulence ensures that in a natural environment insects tend to encounter odor stimuli in a pulsatile fashion. The frequency and duration of odor pulses varies with distance from the source, and hence successful mid-flight odor tracking requires resolution of spatiotemporal pulse dynamics. This requires both olfactory and mechanosensory input (from wind speed), a form of sensory integration observed within the antennal lobe (AL). In this work, we employ a model of the moth AL to study the effect of mechanosensory input on AL responses to pulsatile stimuli; in particular, we examine the ability of model neurons to: (1) encode the temporal length of a stimulus pulse; (2) resolve the temporal dynamics of a high frequency train of brief stimulus pulses. We find that AL glomeruli receiving olfactory input are adept at encoding the temporal length of a stimulus pulse but less effective at tracking the temporal dynamics of a pulse train, while glomeruli receiving mechanosensory input but little olfactory input can efficiently track the temporal dynamics of high frequency pulse delivery but poorly encode the duration of an individual pulse. Furthermore, we show that stronger intrinsic small-conductance calcium-dependent potassium (SK) currents tend to skew cells toward being better trackers of pulse frequency, while weaker SK currents tend to entail better encoding of the temporal length of individual pulses. We speculate a possible functional division of labor within the AL, wherein, for a particular odor, glomeruli receiving strong olfactory input exhibit prolonged spiking responses that facilitate detailed discrimination of odor features, while glomeruli receiving mechanosensory input (but little olfactory input) serve to resolve the temporal dynamics of brief, pulsatile odor encounters. Finally, we discuss how this hypothesis extends to explaining the functional significance of intraglomerular variability in observed phase II response patterns of AL neurons.


Electronics ◽  
2021 ◽  
Vol 10 (18) ◽  
pp. 2277
Author(s):  
Chiman Kwan ◽  
Bence Budavari

Although many algorithms have been proposed to mitigate air turbulence in optical videos, there do not seem to be consistent blind video quality assessment metrics that can reliably assess different approaches. Blind video quality assessment metrics are necessary because many videos containing air turbulence do not have ground truth. In this paper, a simple and intuitive blind video quality assessment metric is proposed. This metric can reliably and consistently assess various turbulent mitigation algorithms for optical videos. Experimental results using more than 10 videos in the literature show that the proposed metrics correlate well with human subjective evaluations. Compared with an existing blind video metric and two other blind image quality metrics, the proposed metrics performed consistently better.


Photonics ◽  
2021 ◽  
Vol 8 (9) ◽  
pp. 394
Author(s):  
Chiman Kwan ◽  
Jude Larkin

Detection of small moving objects in long range infrared (IR) videos is challenging due to background clutter, air turbulence, and small target size. In this paper, we present two unsupervised, modular, and flexible frameworks to detect small moving targets. The key idea was inspired by change detection (CD) algorithms where frame differences can help detect motions. Our frameworks consist of change detection, small target detection, and some post-processing algorithms such as image denoising and dilation. Extensive experiments using actual long range mid-wave infrared (MWIR) videos with target distances beyond 3500 m from the camera demonstrated that one approach, using Local Intensity Gradient (LIG) only once in the workflow, performed better than the other, which used LIG in two places, in a 3500 m video, but slightly worse in 4000 m and 5000 m videos. Moreover, we also investigated the use of synthetic bands for target detection and observed promising results for 4000 m and 5000 m videos. Finally, a comparative study with two conventional methods demonstrated that our proposed scheme has comparable performance.


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