High-resolution snow depth prediction using Random Forest algorithm with topographic parameters and an ecosystem map: a case study in the Greiner Watershed, Nunavut

Increased surface temperatures (0.7℃ per decade) in the Arctic affects polar ecosystems by reducing the extent and duration of annual snow cover. Monitoring of these important ecosystems needs detailed information on snow cover properties (depth and density) at resolutions (< 100 m) that influence ecological habitats and permafrost thaw. As arctic snow is strongly influenced by vegetation, an ecotype map at 10 m resolution was added to a method with the Random Forest (RF) algorithm previously developed for alpine environments and applied here over an arctic landscape for the first time. The topographic parameters used in the RF algorithm were Topographic Position Index (TPI) and up-wind slope index (Sx), which were estimated from the freely available Arctic DEM at 2 m resolution. Ecotypes with taller vegetation with moister soils were found to have deeper snow because of the trapping effect. Using feature importance with RF, snow depth distributions were predicted from topographic and ecosystem parameters with a root mean square error = 8 cm (23%) (R² = 0.79) at 10 m resolution for an arctic watershed (1 500 km²) in western Nunavut, Canada.

Geoecological parameters indicate discrepancies between potential and actual forest area in the forest-steppe of Central Mongolia

Background Forest distribution in the forest-steppe of Mongolia depends on relief, permafrost, and climate, and is highly sensitive to climate change and anthropogenic disturbance. Forest fires and logging decreased the forest area in the forest-steppe of Mongolia. The intention of this study was to identify the geoecological parameters that control forest distribution and living-tree biomass in this semi-arid environment. Based on these parameters, we aimed to delineate the area that forest might potentially occupy and to analyse the spatial patterns of actual and potential tree biomass. Methods We used a combination of various geographic methods in conjunction with statistical analyses to identify the key parameters controlling forest distribution. In several field campaigns, we mapped tree biomass and ecological parameters in a study area within the Tarvagatai Nuruu National Park (central Mongolia). Forest areas, topographic parameters and vegetation indices were obtained from remote sensing data. Significant correlations between forest distribution and living-tree biomass on one hand, and topographic parameters, climate data, and environmental conditions on the other hand, were used to delineate the area of potential forest distribution and to estimate total living-tree biomass for this area. Results Presence of forest on slopes was controlled by the factors elevation, aspect, slope, mean annual precipitation, and mean growing-season temperature. Combining these factors allowed for estimation of potential forest area but was less suitable for tree-biomass delineation. No significant differences in mean living-tree biomass existed between sites exposed to different local conditions with respect to forest fire, exploitation, and soil properties. Tree biomass was reduced at forest edges (defined as 30 m wide belt), in small fragmented and in large forest stands. Tree biomass in the study area was 20 × 109 g (1,086 km2 forest area), whereas the potential tree biomass would reach up to 65 × 109 g (> 3168 km2). Conclusions The obtained projection suggests that the potential forest area and tree biomass under the present climatic and geoecological conditions is three times that of the present forest area and biomass. Forest fires, which mostly affected large forest stands in the upper mountains, destroyed 43% of the forest area and 45% of the living-tree biomass in the study area over the period 1986–2017.

Assessing the effect of topography on Cs-137 concentrations within forested soils due to the Fukushima Daiichi Nuclear Power Plant accident, Japan

Topographic effects on Cs-137 concentrations in a forested area were quantitatively examined using 58 soil core samples collected in a village in Fukushima, Japan, which was directly impacted by the radioactive plume emitted during the 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. In this study, five topographic parameters and two soil properties were evaluated as controls on the soil Cs-137 concentration using generalized additive models (GAMs), a flexible statistical method for evaluating the functional dependencies of multiple parameters. GAMs employing soil dry bulk density, mass water content, and elevation explained 54 % of the observed concentrations of Cs-137 within this landscape, whereas GAMs employing elevation, slope, and upslope distance explained 47 % of the observed concentrations, which provide strong evidence of topographic effects on Cs-137 concentrations in soils. The model fit analysis confirmed that the topographic effects are strongest when multiple topographic parameters and soil properties are included. The ability of each topographic feature to predict Cs-137 concentrations was influenced by the resolution of the digital elevation models. The movement of Cs-137 into the subsurface in this area near Fukushima was faster in comparison to regions affected by the Chernobyl Nuclear Power Plant accident. These results suggest that the effects of topographic parameters should be considered carefully in the use of anthropogenic radionuclides as environmental tracers and in the assessment of current and future environmental risks due to nuclear power plant accidents.

Changes in Corneal Parameters after DMEK Surgery: A Swept-Source Imaging Analysis at 12-Month Follow-Up Time

Purpose. To assess the time course changes in corneal topographic parameters during the one-year follow-up after Descemet membrane endothelial keratoplasty (DMEK) surgery. Materials and Methods. Twenty-one patients (24 eyes) who underwent DMEK surgery were evaluated. Best corrected visual acuity (BCVA), endothelial cell count (ECC), central corneal thickness (CCT), mean keratometry (MK), mean astigmatism (MA), astigmatism asymmetry (AA), and higher-order aberration (HOA) were assessed at baseline and 1, 3, 6 and 12 months after the surgery using CASIA2 anterior segment swept-source OCT (Tomey, Japan). Results. In patients who underwent DMEK surgery, BCVA improved gradually at the subsequent visits during the 12-month follow-up. A significant reduction in ECC and CCT at the 1st month was noted, which remained stable until the 6th month postoperatively. Anterior and total MK values remained unchanged, whereas changes in posterior keratometry were noticeable until the 6th month after surgery. A significant reduction in the anterior, posterior, and total astigmatism magnitude as well as astigmatism asymmetry was observed during the first 6 months after surgery. A gradual anterior, posterior, and total HOA decrease was documented until the 12th month after surgery. Negative correlations between baseline values of CCT, MK, MA, AA, and HOA and postoperative variations in those parameters at consecutive follow-up time points were observed. Accordingly, negative correlations between baseline CCT and postoperative changes in corneal topographic parameters after surgery were found. Conclusion. The stabilization of most corneal topographic parameters takes place within 6 months after the procedure, whereas HOA reduction and BCVA improvement gradually occur during the first year after surgery. Preoperative values of corneal topographic parameters strongly determine their changes detected after DMEK surgery, which may suggest that early therapeutic intervention results in better visual outcomes.

Diagnosis of Subclinical Keratoconus with a Combined Model of Biomechanical and Topographic Parameters

This study sought to develop a diagnostic model with aberrometry and biomechanical variables for subclinical keratoconus. The design was a cross-sectional study. The topographic data were obtained with a rotating Scheimpflug camera (Pentacam HR), and biomechanical data were obtained with Corvis ST. The study included 81 eyes distributed in 61 healthy corneas and 20 subclinical keratoconus (SCKC), defined as eyes with suspicious topographic findings, normal slit-lamp examination, and a manifestation of keratoconus. Analyses of the topographic and biomechanical data were performed, and a classifying model of SCKC was elaborated. The model for the diagnosis of SCKC includes posterior coma to 90°, Ambrósio’s Relational Thickness in the horizontal profile (ARTh), and velocity when the air pulse is off (A2 velocity). The sensitivity was 89.5%, specificity 96.7%, accuracy 94.9%, and precision 89.5%. The area under the curve (AUC) of the receiver operating characteristic (ROC) curve for the model was 0.951. Diagnosis of subclinical keratoconus depends on the aberrometry variable posterior coma to 90° and the biomechanical variables A2 velocity and ARTh.

TRIBOLOGY AND TOPOGRAPHY OF HARD MACHINED SURFACES

In machining automotive industrial parts by hard machining procedures, the topographic characteristics of high accuracy surfaces have high importance. In this paper 2D and 3D surface roughness features of gear bores machined by hard turning and grinding are demonstrated. The 3D roughness parameters, which are considered as more exact than the 2D parameters, were compared to the 2D ones, which are used more widely in industrial practice. The analyzed machining procedure versions were ranked based on the topographic parameters determining the tribological (wear and oil-retention capability) characteristics of the different surfaces.

Quantitative Assessment of Changes in Topography of Town Caused by Human Impact, Krakow City Centre, Southern Poland

For the area of historic centre of Krakow (area 9.29 km2), southern Poland, base maps were prepared showing hypsometry and distribution of landforms in historical variant (ca. 1000 AD) and current variant, based on published data mainly from archaeological and geoengineering research carried out for the last 60 years, and including geographic information system (GIS) tools. The aim of the work is to establish changes in undulation of the area studied within the landforms (Vistula riverbed, Holocene alluvial plain, Pleistocene terrace, limestone hills) over the last millennium. Topographic parameters calculated on the basis of the base maps (local relative height, mean slope, limit of areas without aspect and with N, E, S and W aspects) were considered. These changes were linked with dominating trends of the altitude increase due to the development of large area embankments and of convex landforms. The assessment of changes of land undulation includes four authorial methods of quantitative determination of topography changes. Until the beginning of the 19th century land flattening occurred in most of the area of the town centre. Then the increase of local relative heights started to predominate which resulted in changes of other topographic parameters. Differentiated changes, both positive and negative, in the area undulation with altitude increase were determined.

Evaluation of Corneal Endothelium in Middle-Aged Keratoconus Eyes

Purpose To investigate the corneal endothelial cell parameters and to evaluate the correlation with corneal topographic parameters in middle-aged non-treated keratoconus (KC) patients. Materials and Methods Thirty-six eyes of 21 KC patients in the middle decade (4th-5th) and age-gender matched 36 healthy eyes were included. Topographic parameters [(K1, K2 Sim K, central, thinnest pachymetry, anterior chamber depth (ACD)] were obtained with Galillei double scheimpflug analyzer. Patients were divided into stages according to mean keratometric values ​​(Mild < 45D,Moderate 45-52D, Severe > 52D, Advanced > 62 D). Endothelial cell density (ECD), coefficient of variation (CV) of cell areas and hexagonal cell percentage (HCP) obtained with specular microscopy were recorded.Corneal topography and specular microscopy parameters were compared between KC and healthy eyes. The correlation between topographic and specular microscopy parameters were analyzed. Results The mean age of the patients was 38.6 ± 6.0 and 37.8 ± 4.2 years in the KC and control group, respectively. Age and gender were statistically similar between the groups. ECD was 2772 ± 17 in the KC group and 2741 ± 30 cells / mm2 in the control group, and there was no statistical difference between the groups (p: 0.621). HCP was 63.5 ± 7.2, 67.4 ± 5.2 in KC and healthy eyes, respectively (p: 0.014); CV was 30.7 ± 5.2 and 28.6 ± 3.4, respectively (p: 0.058). Specular microscopy parameters were not statistically different according to KC stage. K1,K2,SimK, CCT, ACD did not correlate with ECD in patients. Conclusion Our results showed that endothelial cell morphology is significantly affected in middle-aged KC patients who have not been treated.