| 11. |
- Soja, Maciej, 1985, et al.
(författare)
-
Mapping Tree Height in Burkina Faso Parklands with TanDEM-X
- 2021
-
Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 13:14
-
Tidskriftsartikel (refereegranskat)abstract
- Mapping of tree height is of great importance for management, planning, and research related to agroforestry parklands in Africa. In this paper, we investigate the potential of spotlight-mode data from the interferometric synthetic aperture radar (InSAR) satellite system TanDEM-X (TDM) for mapping of tree height in Sapone, Burkina Faso, a test site characterised by a low average canopy cover (similar to 15%) and a mean tree height of 9.0 m. Seven TDM acquisitions from January-April 2018 are used jointly to create high-resolution (similar to 3 m) maps of interferometric phase height and mean canopy elevation, the latter derived using a new, model-based processing approach compensating for some effects of the side-looking geometry of SAR. Compared with phase height, mean canopy elevation provides a more accurate representation of tree height variations, a better tree positioning accuracy, and better tree height estimation performance when assessed using 915 trees inventoried in situ and representing 15 different species/genera. We observe and discuss two bias effects, and we use empirical models to compensate for these effects. The best-performing model using only TDM data provides tree height estimates with a standard error (SE) of 2.8 m (31% of the average height) and a correlation coefficient of 75%. The estimation performance is further improved when TDM height data are combined with in situ measurements; this is a promising result in view of future synergies with other remote sensing techniques or ground measurement-supported monitoring of well-known trees.
|
|
| 12. |
|
|
| 13. |
- Burlakovs, Juris, 1977-, et al.
(författare)
-
Magnetometry and electromagnetic screening of dumps - fast solution for geoenvironmental information aquisition
- 2021
-
Ingår i: 82nd EAGE Conference and Exhibition 2021. - : European Association of Geoscientists and Engineers, EAGE. - 9781713841449 ; , s. 3032-3036
-
Konferensbidrag (refereegranskat)abstract
- Dumps and landfills are the end place of unwanted material and disposed products. Burried resources may be landfill mined and environmental pollution diminished. The problem is lack of information on unknown dump sites of former times – there remote sensing and traditional geodesy, proximal sensing techniques could be used. Near surface geophysical methods are valuable for screening of areas where drilling is limited due to technological limitations and anthropogenic unhomogenousity of material. The aim of this study was to determine whether screening of magnetometry and geoelectrical methods may be useful for old burried dumps recognition. Protonmagnetometer was used in Eastern Latvia to detect burried dump in forest, already covered by soil and vegetation. Induced polarisation and electric resistivity research was done in Southern Sweden for the macro-content analysis of dump hills composed of glass industry residuals and construction waste mixture. Surveying helped to determine macroproperties such as geomorphology and physical type of material underneath the surface. Results allowed spatially characterize dumpsite masses (location and dimensions) and identify the internal structure of a these sites. This is valuable information in order to estimate the material recovery potential of landfills.
|
|
| 14. |
- Verheijen, Hendricus, et al.
(författare)
-
Magnitude and Origin of CO2 Evasion From High-Latitude Lakes
- 2022
-
Ingår i: Journal of Geophysical Research - Biogeosciences. - : John Wiley & Sons. - 2169-8953 .- 2169-8961. ; 127:6
-
Tidskriftsartikel (refereegranskat)abstract
- Lakes evade significant amounts of carbon dioxide (CO2) to the atmosphere; yet the magnitude and origin of the evasion are still poorly constrained. We quantified annual CO2 evasion and its origin (in-lake net ecosystem production vs. lateral inputs from terrestrial ecosystems) in 14 high-latitude lakes through high-frequency estimates of open water CO2 flux and ecosystem metabolism and inorganic carbon mass-balance before and after ice breakup. Annual CO2 evasion ranged from 1 to 25 g C m−2 yr−1 of which an average of 57% was evaded over a short period at ice-breakup. Annual internal CO2 production ranged from −6 to 21 g C m−2 yr−1, of which at least half was produced over winter. The contribution of internal versus external source contribution to annual CO2 evasion varied between lakes, ranging from fully internal to fully external with most lakes having over 75% of the evasion sustained through a single source. Overall, the study stresses the large variability in magnitude and control of CO2 evasion and suggests that environmental change impacts on CO2 evasion from high-latitude lakes are not uniform.
|
|
| 15. |
- Shao, Xinyuan, 1997, et al.
(författare)
-
Near-wall modeling of forests for atmosphere boundary layers using lattice Boltzmann method on GPU
- 2022
-
Ingår i: Engineering Applications of Computational Fluid Mechanics. - : Informa UK Limited. - 1994-2060 .- 1997-003X. ; 16:1, s. 2142-2155
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the simulation and modeling of the turbulent atmospheric boundary layers (ABLs) in the presence of forests are studied using a lattice Boltzmann method with large eddy simulation, which was implemented in the open-source program GASCANS with the use of Graphic Processing Units (GPU). A method of modeling forests in the form of body forces injected near the wall is revisited, while the effects of leaf area density (LAD) on the model accuracy is further addressed. Since a uniform cell size is applied throughout the computational domain, the wall-normal height of the near-wall cells is very large, theoretically requiring a wall function to model the boundary layer. However, the wall function is disregarded here when the forest is modeled. This approximation is validated based on the comparison with previous experimental and numerical data. It concludes that for the ABL conditions specified in this study as well as a large body of literature, the forest forces overwhelm the wall friction so that the modeling of the latter effect is trivial. Constant and varying LAD profiles across the forest zone are defined with the same total leaf area despite the varying one being studied previously. It is found that the two LAD profiles provide consistent predictions. The present forest modeling can therefore be simplified with the use of the constant LAD without degrading the model accuracy remarkably.
|
|
| 16. |
|
|
| 17. |
- Burlakovs, Juris, 1977-, et al.
(författare)
-
Geophysical aspects of abandoned landfill geomorphological and material properties macro-characterization
- 2020
-
Ingår i: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM. - : International Multidisciplinary Scientific Geoconference. - 9786197603057 ; , s. 551-558
-
Konferensbidrag (refereegranskat)abstract
- Landfills (dumps) are places where the end of the life cycle of products can be found - useful material is dumped away from the sight creating contaminant flows around. Another problem is huge unexplored potential of resources recycling - we have limited knowledge also on useful elements and materials that are buried. The solution to overcome the limitations that provide remote sensing and traditional geodesy, proximal sensing techniques could be used. “Near surface geophysics” with operation at or just below the soil surface, significantly may contribute to give answers that traditionally are solved only after excavation. Geophysical methods are various, those can be active (i.e. create its own signal) or passive (i.e. register an existing signal); invasive (by inserting devices into the soil) or non-destructive. Some of these methods are static (e.g. a sequence of inserted electrodes), others can be used in a mobile way (e.g. pulled by a quad-bike). In general, their depth of exploration can vary from a few decimetres to some tens of metres. Thus in range of wide geophysical methodology spectrum almost all methods might be of use for unknown dump exploration depending on circumstances. In this paper, the aim is to macro-characterize anthropogenic geomorphological forms for contouring of old buried dumps by use of magnetometry, and geoelectric research methods to provide knowledge on approximate content of the dump. Protonmagnetometer was used in Eastern Latvia to determine unseen on surface dumpsite, buried in forest; induced polarisation and electric resistivity research was done in Southern Sweden for the macro-content analysis of dump hills composed of glass industry residuals and construction waste mixture. Geophysical surveying was performed to support site investigation with respect to landfill-related environmental problems, to enhance the opportunity for contouring of location of material mass and initially evaluate its physical properties. Results have shown good potential of geophysical surveying to spatially characterize landfill masses (location and dimensions) and to identify the internal structure of a landfill site, which already provides valuable information to estimate the landfill mining (material recovery) potential of landfills.
|
|
| 18. |
- Gumbel, Jörg, et al.
(författare)
-
The MATS satellite mission - gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy
- 2020
-
Ingår i: Atmospheric Chemistry And Physics. - : COPERNICUS GESELLSCHAFT MBH. - 1680-7316 .- 1680-7324. ; 20:1, s. 431-455
-
Tidskriftsartikel (refereegranskat)abstract
- Global three-dimensional data are a key to understanding gravity waves in the mesosphere and lower thermosphere. MATS (Mesospheric Airglow/Aerosol Tomography and Spectroscopy) is a new Swedish satellite mission that addresses this need. It applies space-borne limb imaging in combination with tomographic and spectroscopic analysis to obtain gravity wave data on relevant spatial scales. Primary measurement targets are O-2 atmospheric band dayglow and nightglow in the near infrared, and sunlight scattered from noctilucent clouds in the ultraviolet. While tomography provides horizontally and vertically resolved data, spectroscopy allows analysis in terms of mesospheric temperature, composition, and cloud properties. Based on these dynamical tracers, MATS will produce a climatology on wave spectra during a 2-year mission. Major scientific objectives include a characterization of gravity waves and their interaction with larger-scale waves and mean flow in the mesosphere and lower thermosphere, as well as their relationship to dynamical conditions in the lower and upper atmosphere. MATS is currently being prepared to be ready for a launch in 2020. This paper provides an overview of scientific goals, measurement concepts, instruments, and analysis ideas.
|
|
| 19. |
|
|
| 20. |
- Sjöström, Jenny K., et al.
(författare)
-
Paleodust deposition and peat accumulation rates : bog size matters
- 2020
-
Ingår i: Chemical Geology. - : Elsevier. - 0009-2541 .- 1872-6836. ; 554
-
Tidskriftsartikel (refereegranskat)abstract
- We present a high-resolution peat paleodust and accumulation rate record spanning the last 8300 years from Draftinge Mosse (400 ha), southern Sweden (57 degrees 06'27.6 '' N 13 degrees 42'54.1 '' E). The record was analysed for peat accumulation rates (PAR), elemental concentrations, mineralogy, and plant macrofossil content. Five periods of increased mineral deposition were recorded. The first event occurred between similar to 6280 and similar to 5570 cal BP, during the fen to bog transition. This is followed by four atmospheric mineral dust events (DE) which were recorded in the ombrotrophic section of the sequence at (cal BP): similar to 2200; similar to 1385-1150; similar to 830-590, and from similar to 420 to the present. Statistical analysis and elemental ratios indicated that both the mineralogy and grain size shifted when the system transitioned from fen into bog, showing that the governing transport process shifted with the peat-land succession stages. This highlights the importance of identifying peatland succession stages within peat paleodust studies. Following all four DE, increases in PAR were observed, implying a coupling to dust deposition. Comparison of DE and PAR with a paleodust record from Store Mosse, a 20 times larger bog located ca 18 km away (Kylander et al. 2016), showed that both PAR and dust deposition are largely represented by single-core reconstructions, indicating that they are driven by a common climate forcing mechanism. However, higher PAR and dust deposition rates were observed in the more moderately sized Draftinge Mosse, suggesting that the size of the bog is important to consider in peat paleodust studies. Furthermore, the smaller bog responded more rapidly to hydrological changes, indicating that the size of the bog affects its' buffering capacity. Authigenic carbonates, observed here during episodes of rapid peat growth, coincide with changes in REE ratios, indicating that authigenic peat processes potentially cause REE fractionation.
|
|
