scholarly journals Observations of Turbulence in Free Atmosphere by Balloon-Borne Sensors

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3273
Author(s):  
Lesong Zhou ◽  
Zheng Sheng ◽  
Qixiang Liao
Keyword(s):  
Large Scale ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Sensor Data ◽  
Free Atmosphere ◽  
Height Range ◽  
High Latitude Region ◽  
Thorpe Scale ◽  
Scale Turbulence ◽  
Turbulence Parameters

In recent years, Thorpe analysis has been used to retrieve the characteristics of turbulence in free atmosphere from balloon-borne sensor data. However, previous studies have mainly focused on the mid-high latitude region, and this method is still rarely applied at heights above 30 km, especially above 35 km. Therefore, seven sets of upper air (>35 km) sounding data from the Changsha Sounding Station (28°12′ N, 113°05′ E), China are analyzed with Thorpe analysis in this article. It is noted that, in the troposphere, Thorpe analysis can better retrieve the turbulence distribution and the corresponding turbulence parameters. Also, because of the thicker troposphere at low latitudes, the values of the Thorpe scale L T and turbulent energy dissipation rate ε remain greater in a larger height range. In the stratosphere below the height of 35 km, the obtained ε is higher, and Thorpe analysis can only be used to analyze the characteristics of large-scale turbulence. In the stratosphere at a height of 35–40 km, because of the interference of sensor noise, Thorpe analysis can only help to retrieve the rough distribution position of large-scale turbulence, while it can hardly help with the calculation of the turbulence parameters.

scholarly journals Measurements of Boundary Layer Profiles with In Situ Sensors and Doppler Lidar

2008 ◽  
Vol 25 (8) ◽  
pp. 1328-1340 ◽  
Author(s):  
Rod Frehlich ◽  
Yannick Meillier ◽  
Michael L. Jensen
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Energy Dissipation Rate ◽  
High Rate ◽  
Doppler Lidar ◽  
Stratified Turbulence ◽  
In Situ Sensors ◽  
The Impact ◽  
Turbulence Parameters

Abstract A new in situ measurement system and lidar processing algorithms were developed for improved measurements of boundary layer profiles. The first comparisons of simultaneous Doppler lidar–derived profiles of the key turbulence statistics of the two orthogonal horizontal velocity components (longitudinal and transverse) are presented. The instrument requirements for accurate observations of stably stratified turbulence were determined. A region of stably stratified low turbulence with constant gradients of temperature and velocity was observed above the nocturnal boundary layer using high-rate sensors. The important turbulence parameters were estimated, and turbulence spectra were consistent with new theoretical descriptions of stratified turbulence. The impact of removing the larger-scale velocity features in Doppler lidar estimates of turbulent velocity variance and length scales was investigated. The Doppler lidar–derived estimates of energy dissipation rate ε were found to be insensitive to spatial filtering of the large-scale atmospheric processes. The in situ and lidar-derived profiles were compared for the stable boundary layer in a suburban environment.

scholarly journals Role of large-scale advection and small-scale turbulence on vertical migration of gyrotactic swimmers

2019 ◽  
Vol 4 (12) ◽  
Author(s):  
C. Marchioli ◽  
H. Bhatia ◽  
G. Sardina ◽  
L. Brandt ◽  
A. Soldati
Keyword(s):  
Vertical Migration ◽  
Large Scale ◽  
Small Scale ◽  
Scale Turbulence

scholarly journals Multi-task learning based Encoder-Decoder: A comprehensive detection and diagnosis system for multi-sensor data

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110131
Author(s):  
Junfeng Wu ◽  
Li Yao ◽  
Bin Liu ◽  
Zheyuan Ding ◽  
Lei Zhang
Keyword(s):  
Anomaly Detection ◽  
Event Detection ◽  
Large Scale ◽  
Multivariate Time Series ◽  
Sensor Data ◽  
Unified Framework ◽  
Diagnosis System ◽  
Learning Framework ◽  
Task Learning ◽  
Detection And Diagnosis

As more and more sensor data have been collected, automated detection, and diagnosis systems are urgently needed to lessen the increasing monitoring burden and reduce the risk of system faults. A plethora of researches have been done on anomaly detection, event detection, anomaly diagnosis respectively. However, none of current approaches can explore all these respects in one unified framework. In this work, a Multi-Task Learning based Encoder-Decoder (MTLED) which can simultaneously detect anomalies, diagnose anomalies, and detect events is proposed. In MTLED, feature matrix is introduced so that features are extracted for each time point and point-wise anomaly detection can be realized in an end-to-end way. Anomaly diagnosis and event detection share the same feature matrix with anomaly detection in the multi-task learning framework and also provide important information for system monitoring. To train such a comprehensive detection and diagnosis system, a large-scale multivariate time series dataset which contains anomalies of multiple types is generated with simulation tools. Extensive experiments on the synthetic dataset verify the effectiveness of MTLED and its multi-task learning framework, and the evaluation on a real-world dataset demonstrates that MTLED can be used in other application scenarios through transfer learning.

Holes and Entrainment in Stratocumulus

2005 ◽  
Vol 62 (2) ◽  
pp. 443-459 ◽  
Author(s):  
H. Gerber ◽  
G. Frick ◽  
S. P. Malinowski ◽  
J-L. Brenguier ◽  
F. Burnet
Keyword(s):  
High Speed ◽  
Large Scale ◽  
Evaporative Cooling ◽  
Length Distribution ◽  
Relative Length ◽  
Minimal Amount ◽  
Entrainment Rate ◽  
Conditional Sampling ◽  
Free Atmosphere ◽  
Average Width

Abstract Aircraft flights through stratocumulus clouds (Sc) during the Dynamics and Chemistry of Marine Stratocumulus II (DYCOMS-II) study off the California coast found narrow in-cloud regions with less liquid water content (LWC) and cooler temperatures than average background values. The regions are named cloud holes and are assumed to be a result of water evaporated by the entrainment of dryer air from above the Sc. While such features have been noted previously, this study provided a unique opportunity to investigate in much greater detail the nature of the holes, as well as their relationship to the entrainment rate, because high-speed temperature and LWC probes with maximum spatial resolution of 10 cm were flown together for the first time. Nine long-duration flights were made through mostly unbroken Sc for which conditional sampling was used to identify the location and size of the holes. The holes are concentrated near cloud top, their average width near cloud top is about 5 m, their relative length distribution is nearly constant for all flights, and they can penetrate hundreds of meters deep into the Sc before being lost by mixing. Entrainment velocities at cloud top are estimated from measurements of fluxes of reduced LWC and vapor mixing ratios in holes, the fraction of cloud area covered by holes, and the total water jump between cloud top and the free atmosphere. Rates as large as 10 mm s−1 are found for nocturnal flights, and these rates are about 3 times larger than for daytime flight segments. The rates correlate best with the size of the buoyancy jump above the Sc; the present conditional-sampling approach for measuring the rates gives larger rates than the “flux jump” rates determined by others for the same flights by a factor of about 2. The stability criterion for all Sc predicts thinning and breakup of the Sc, which does not occur. The minimal amount of cloud-top evaporative cooling caused by entrainment contributes little to the top-down convection dominated by radiative cooling during nocturnal flights; however, evaporative cooling caused by the mixing of holes as they subduct with the large-scale eddy circulation in the Sc may contribute, but with an as-of-yet unknown amount.

scholarly journals Spectral characteristics of spring arctic mesosphere dynamics

1998 ◽  
Vol 16 (12) ◽  
pp. 1607-1618 ◽  
Author(s):  
C. M. Hall ◽  
A. H. Manson ◽  
C. E. Meek
Keyword(s):  
Energy Dissipation ◽  
Middle Atmosphere ◽  
Spectral Characteristics ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Spectral Signature ◽  
Upper Limits ◽  
Waves And Tides ◽  
Signal Fading ◽  
Mf Radar

Abstract. The spring of 1997 has represented a stable period of operation for the joint University of Tromsø / University of Saskatchewan MF radar, being between refurbishment and upgrades. We examine the horizontal winds from the February to June inclusive and also include estimates of energy dissipation rates derived from signal fading times and presented as upper limits on the turbulent energy dissipation rate, ε. Here we address the periodicity in the dynamics of the upper mesosphere for time scales from hours to one month. Thus, we are able to examine the changes in the spectral signature of the mesospheric dynamics during the transition from winter to summer states.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides).

scholarly journals Using autonomous video to estimate the bottom-contact area of longline trap gear and presence–absence of sensitive benthic habitat

2018 ◽  
Vol 75 (5) ◽  
pp. 797-812 ◽  
Author(s):  
Beau Doherty ◽  
Samuel D.N. Johnson ◽  
Sean P. Cox
Keyword(s):  
Contact Area ◽  
Large Scale ◽  
Marine Protected Area ◽  
Cold Water ◽  
Sensor Data ◽  
Benthic Habitat ◽  
Commercial Fishing ◽  
Depth Sensor ◽  
Quality Of Data ◽  
Bottom Contact

Bottom longline hook and trap fishing gear can potentially damage sensitive benthic areas (SBAs) in the ocean; however, the large-scale risks to these habitats are poorly understood because of the difficulties in mapping SBAs and in measuring the bottom-contact area of longline gear. In this paper, we describe a collaborative academic–industry–government approach to obtaining direct presence–absence data for SBAs and to measuring gear interactions with seafloor habitats via a novel deepwater trap camera and motion-sensing systems on commercial longline traps for sablefish (Anoplopoma fimbria) within SGaan Kinghlas – Bowie Seamount Marine Protected Area. We obtained direct presence–absence observations of cold-water corals (Alcyonacea, Antipatharia, Pennatulacea, Stylasteridae) and sponges (Hexactinellida, Demospongiae) at 92 locations over three commercial fishing trips. Video, accelerometer, and depth sensor data were used to estimate a mean bottom footprint of 53 m2 for a standard sablefish trap, which translates to 3200 m2 (95% CI = 2400–3900 m2) for a 60-trap commercial sablefish longline set. Our successful collaboration demonstrates how research partnerships with commercial fisheries have potential for massive improvements in the quantity and quality of data needed for conducting SBA risk assessments over large spatial and temporal scales.

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