scholarly journals Spatio-temporal evolution of snow depth observed by time-lapse laser scanning in the Alps and in Antarctica

2016 ◽  
Author(s):  
Ghislain Picard ◽  
Laurent Arnaud ◽  
Jean-Michel Panel ◽  
Samuel Morin
Keyword(s):  
Spatial Variability ◽  
Snow Depth ◽  
Laser Scanning ◽  
Single Point ◽  
Measurement Techniques ◽  
Strong Wind ◽  
Slow Increase ◽  
Automatic Instrument ◽  
Spatio Temporal ◽  
Wind Events

Abstract. Although both the temporal and spatial variations of the snow depth are usually of interest for numerous applications, available measurement techniques are either space-oriented (e.g. terrestrial laserscans) or time-oriented (e.g. ultrasonic ranging probe). Because of snow heterogeneity, measuring depth in a single point is insufficient to provide accurate and representative estimates. We present a cost-effective automatic instrument to acquire spatio-temporal variations of snow depth. The device comprises a lasermeter mounted on a two-axis stage and can scan ≈ 200,000 points over an area of 100–200 m2 in 4 hours. Two copies, installed in Antarctica and in the French Alps, have been operating daily, unattended over 2015 with a success rate of 65 % and 90 % respectively. The precision of single point measurements and long-term stability were evaluated to be about 1 cm and the accuracy to be 5 cm or better. The spatial variability in the scanned area reached 7–10 cm (root mean square) at both sites, which means that the number of measurements is sufficient to average out the spatial variability and yield precise mean snow depth. With such high precision, it was possible for the first time at Dome C 1) to observe a 3-month period of regular and slow increase of snow depth disconnected from snowfalls and 2) to highlight that most of the annual accumulation stems from a single event although several snowfall and strong wind events were predicted by the ERA-Interim reanalysis. At last the paper discusses the benefit of the RLS solution compared to multiplying single-point sensors in the context of monitoring snow depth.

scholarly journals Design of a scanning laser meter for monitoring the spatio-temporal evolution of snow depth and its application in the Alps and in Antarctica

2016 ◽  
Vol 10 (4) ◽  
pp. 1495-1511 ◽  
Author(s):  
Ghislain Picard ◽  
Laurent Arnaud ◽  
Jean-Michel Panel ◽  
Samuel Morin
Keyword(s):  
Spatial Variability ◽  
Snow Depth ◽  
Laser Scanning ◽  
Single Point ◽  
Measurement Techniques ◽  
Strong Wind ◽  
Slow Increase ◽  
Automatic Instrument ◽  
Spatio Temporal ◽  
Wind Events

Abstract. Although both the temporal and spatial variations of the snow depth are usually of interest for numerous applications, available measurement techniques are either space-oriented (e.g. terrestrial laser scans) or time-oriented (e.g. ultrasonic ranging probe). Because of snow heterogeneity, measuring depth in a single point is insufficient to provide accurate and representative estimates. We present a cost-effective automatic instrument to acquire spatio-temporal variations of snow depth. The device comprises a laser meter mounted on a 2-axis stage and can scan  ≈  200 000 points over an area of 100–200 m2 in 4 h. Two instruments, installed in Antarctica (Dome C) and the French Alps (Col de Porte), have been operating continuously and unattended over 2015 with a success rate of 65 and 90 % respectively. The precision of single point measurements and long-term stability were evaluated to be about 1 cm and the accuracy to be 5 cm or better. The spatial variability in the scanned area reached 7–10 cm (root mean square) at both sites, which means that the number of measurements is sufficient to average out the spatial variability and yield precise mean snow depth. With such high precision, it was possible for the first time at Dome C to (1) observe a 3-month period of regular and slow increase of snow depth without apparent link to snowfalls and (2) highlight that most of the annual accumulation stems from a single event although several snowfall and strong wind events were predicted by the ERA-Interim reanalysis. Finally the paper discusses the benefit of laser scanning compared to multiplying single-point sensors in the context of monitoring snow depth.

scholarly journals Multiscale spatial variability of lidar-derived and modeled snow depth on Hardangervidda, Norway

2013 ◽  
Vol 54 (62) ◽  
pp. 273-281 ◽  
Author(s):  
Kjetil Melvold ◽  
Thomas Skaugen
Keyword(s):  
Spatial Variability ◽  
Snow Depth ◽  
Laser Scanning ◽  
Regional Scale ◽  
Local Scale ◽  
Snow Accumulation ◽  
Large Variability ◽  
Airborne Laser ◽  
Snow Distribution ◽  
Snow Model

AbstractThis study presents results from an Airborne Laser Scanning (ALS) mapping survey of snow depth on the mountain plateau Hardangervidda, Norway, in 2008 and 2009 at the approximate time of maximum snow accumulation during the winter. The spatial extent of the survey area is >240 km2. Large variability is found for snow depth at a local scale (2 m2), and similar spatial patterns in accumulation are found between 2008 and 2009. The local snow-depth measurements were aggregated by averaging to produce new datasets at 10, 50, 100, 250 and 500 m2 and 1 km2 resolution. The measured values at 1 km2 were compared with simulated snow depth from the seNorge snow model (www.senorge.no), which is run on a 1 km2 grid resolution. Results show that the spatial variability decreases as the scale increases. At a scale of about 500 m2 to 1 km2 the variability of snow depth is somewhat larger than that modeled by seNorge. This analysis shows that (1) the regional-scale spatial pattern of snow distribution is well captured by the seNorge model and (2) relatively large differences in snow depth between the measured and modeled values are present.

scholarly journals Spatio-Temporal Variation Characteristics of Snow Depth and Snow Cover Days over the Tibetan Plateau

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 307
Author(s):  
Chi Zhang ◽  
Naixia Mou ◽  
Jiqiang Niu ◽  
Lingxian Zhang ◽  
Feng Liu
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Snow Depth ◽  
Feedback Effect ◽  
Effect Of Temperature ◽  
The Tibetan Plateau ◽  
Reanalysis Dataset ◽  
Spatio Temporal ◽  
The Impact ◽  
Main Factor

Changes in snow cover over the Tibetan Plateau (TP) have a significant impact on agriculture, hydrology, and ecological environment of surrounding areas. This study investigates the spatio-temporal pattern of snow depth (SD) and snow cover days (SCD), as well as the impact of temperature and precipitation on snow cover over TP from 1979 to 2018 by using the ERA5 reanalysis dataset, and uses the Mann–Kendall test for significance. The results indicate that (1) the average annual SD and SCD in the southern and western edge areas of TP are relatively high, reaching 10 cm and 120 d or more, respectively. (2) In the past 40 years, SD (s = 0.04 cm decade−1, p = 0.81) and SCD (s = −2.3 d decade−1, p = 0.10) over TP did not change significantly. (3) The positive feedback effect of precipitation is the main factor affecting SD, while the negative feedback effect of temperature is the main factor affecting SCD. This study improves the understanding of snow cover change and is conducive to the further study of climate change on TP.

scholarly journals Spatio-Temporal Change Monitoring of Outside Manure Piles Using Unmanned Aerial Vehicle Images

Drones ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
Geonung Park ◽  
Kyunghun Park ◽  
Bonggeun Song
Keyword(s):  
Point Source ◽  
Laser Scanning ◽  
Image Data ◽  
Surface Model ◽  
Point Source Pollution ◽  
Efficient Management ◽  
Aerial Vehicle ◽  
Spatio Temporal ◽  
Agricultural Areas ◽  
Water Quality Deterioration

Water quality deterioration due to outdoor loading of livestock manure requires efficient management of outside manure piles (OMPs). This study was designed to investigate OMPs using unmanned aerial vehicles (UAVs) for efficient management of non-point source pollution in agricultural areas. A UAV was used to acquire image data, and the distribution and cover installation status of OMPs were identified through ortho-images; the volumes of OMP were calculated using digital surface model (DSM). UAV- and terrestrial laser scanning (TLS)-derived DSMs were compared for identifying the accuracy of calculated volumes. The average volume accuracy was 92.45%. From April to October, excluding July, the monthly average volumes of OMPs in the study site ranged from 64.89 m3 to 149.69 m3. Among the 28 OMPs investigated, 18 were located near streams or agricultural waterways. Establishing priority management areas among the OMP sites distributed in a basin is possible using spatial analysis, and it is expected that the application of UAV technology will contribute to the efficient management of OMPs and other non-point source pollutants.

scholarly journals The intensity of slope and fluvial processes after a catastrophic windthrow event in small catchments in the Tatra Mountains

2021 ◽  
Vol 18 (6) ◽  
pp. 1405-1423
Author(s):  
Dariusz Strzyżowski ◽  
Elżbieta Gorczyca ◽  
Kazimierz Krzemień ◽  
Mirosław Żelazny
Keyword(s):  
Environmental Changes ◽  
Bedload Transport ◽  
Strong Wind ◽  
Tatra Mountains ◽  
Salvage Logging ◽  
Fluvial Processes ◽  
Wind Events ◽  
And Control ◽  
The Tatra Mountains ◽  
The Impact

AbstractStrong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation.

scholarly journals A methodology to conduct wind damage field surveys for high-impact weather events of convective origin

2020 ◽  
Vol 20 (5) ◽  
pp. 1513-1531 ◽  
Author(s):  
Oriol Rodríguez ◽  
Joan Bech ◽  
Juan de Dios Soriano ◽  
Delia Gutiérrez ◽  
Salvador Castán
Keyword(s):  
Field Studies ◽  
High Impact ◽  
Strong Wind ◽  
Field Surveys ◽  
Weather Events ◽  
Straight Line ◽  
High Impact Weather ◽  
Strong Winds ◽  
Wind Events ◽  
The One

Abstract. Post-event damage assessments are of paramount importance to document the effects of high-impact weather-related events such as floods or strong wind events. Moreover, evaluating the damage and characterizing its extent and intensity can be essential for further analysis such as completing a diagnostic meteorological case study. This paper presents a methodology to perform field surveys of damage caused by strong winds of convective origin (i.e. tornado, downburst and straight-line winds). It is based on previous studies and also on 136 field studies performed by the authors in Spain between 2004 and 2018. The methodology includes the collection of pictures and records of damage to human-made structures and on vegetation during the in situ visit to the affected area, as well as of available automatic weather station data, witness reports and images of the phenomenon, such as funnel cloud pictures, taken by casual observers. To synthesize the gathered data, three final deliverables are proposed: (i) a standardized text report of the analysed event, (ii) a table consisting of detailed geolocated information about each damage point and other relevant data and (iii) a map or a KML (Keyhole Markup Language) file containing the previous information ready for graphical display and further analysis. This methodology has been applied by the authors in the past, sometimes only a few hours after the event occurrence and, on many occasions, when the type of convective phenomenon was uncertain. In those uncertain cases, the information resulting from this methodology contributed effectively to discern the phenomenon type thanks to the damage pattern analysis, particularly if no witness reports were available. The application of methodologies such as the one presented here is necessary in order to build homogeneous and robust databases of severe weather cases and high-impact weather events.

scholarly journals Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

2015 ◽  
Vol 778 ◽  
pp. 216-252 ◽  
Author(s):  
C. D. Pokora ◽  
J. J. McGuirk
Keyword(s):  
Fourth Order ◽  
Single Point ◽  
Aerodynamic Noise ◽  
Filter Method ◽  
Frequency Noise ◽  
Turbulent Structures ◽  
Validation Data ◽  
Piv Measurements ◽  
Temporal Correlations ◽  
Spatio Temporal

Stereoscopic three-component particle image velocimetry (3C-PIV) measurements have been made in a turbulent round jet to investigate the spatio-temporal correlations that are the origin of aerodynamic noise. Restricting attention to subsonic, isothermal jets, measurements were taken in a water flow experiment where, for the same Reynolds number and nozzle size, the shortest time scale of the dynamically important turbulent structures is more than an order of magnitude greater that in equivalent airflow experiments, greatly facilitating time-resolved PIV measurements. Results obtained (for a jet nozzle diameter and velocity of 40 mm and $1~\text{m}~\text{s}^{-1}$, giving $\mathit{Re}=4\times 10^{4}$) show that, on the basis of both single-point statistics and two-point quantities (correlation functions, integral length scales) the present incompressible flow data are in excellent agreement with published compressible, subsonic airflow measurements. The 3C-PIV data are first compared to higher-spatial-resolution 2C-PIV data and observed to be in good agreement, although some deterioration in quality for higher-order correlations caused by high-frequency noise in the 3C-PIV data is noted. A filter method to correct for this is proposed, based on proper orthogonal decomposition (POD) of the 3C-PIV data. The corrected data are then used to construct correlation maps at the second- and fourth-order level for all velocity components. The present data are in accordance with existing hot-wire measurements, but provide significantly more detailed information on correlation components than has previously been available. The measured relative magnitudes of various components of the two-point fourth-order turbulence correlation coefficient ($R_{ij,kl}$) – the fundamental building block for free shear flow aerodynamic noise sources – are presented and represent a valuable source of validation data for acoustic source modelling. The relationship between fourth-order and second-order velocity correlations is also examined, based on an assumption of a quasi-Gaussian nearly normal p.d.f. for the velocity fluctuations. The present results indicate that this approximation shows reasonable agreement for the measured relative magnitudes of several correlation components; however, areas of discrepancy are identified, indicating the need for work on alternative models such as the shell turbulence concept of Afsar (Eur. J. Mech. (B/Fluids), vol. 31, 2012, pp. 129–139).

Lessons learnt at the Met Office from the Great Storm of 1987 - a comparison with recent strong wind events

Weather ◽  
2012 ◽  
Vol 67 (10) ◽  
pp. 268-273 ◽  
Author(s):  
Alexander Fox ◽  
Rebekah Sherwin ◽  
Fraser Ralston
Keyword(s):  
Strong Wind ◽  
Lessons Learnt ◽  
Wind Events
Sign in / Sign up

Export Citation Format

Share Document