Appearance Of Snow Research Articles

Exploring Imaging Methods for In Situ Measurements of the Visual Appearance of Snow

We explored imaging methods to perform in situ field measurements of physical correlates of the visual appearance of snow. Measurements were performed at three locations in Norway between February and March 2023. We used a method to estimate the absorption and scattering coefficients of snow using only one measurement of reflectance captured by the Dia-Stron© TLS850 translucency meter. We also measured the sparkle indicators (contrast and density of sparkle spots) from digital images of snow. The contrast of sparkle spots can be defined as the median value of all the pixels identified as sparkle spots by an algorithm, and the density of sparkle spots is the number of sparkle spots in a selected area of the image. In the case of the sparkle of the snow surface, we found that there is a potential to use the sparkle indicators for classifying the grain types, but it requires a larger data set coupled with expert labelling to define the type of snow. For the absorption and scattering properties, the measurements confirm the fact that snow is a weakly absorptive and highly scattering material when modelling light interactions in the snow. No correlation between the optical properties and sparkle could be found in our data.

Rendering the Bluish Appearance of Snow: When Light Transmission Matters.

Material appearance is largely determined by complex light attenuation processes. The distinct bluish colorations that can be observed when light is transmitted through snow are among the most striking outcomes of these processes. In this article, we present a method for the predictive rendering of this phenomenon taking into account the variability of snow's physical and morphological characteristics. To achieve that, we employ an approach centered on the effective use of spectral transmittance data obtained using a first-principles light transport model for snow. The suitability of the proposed method to rendering applications is illustrated through the synthesis of images depicting the bluish appearance of snow under different illumination conditions.

Climate change and natural resources

Climate change is one of the greatest challenges of modern society. Combustion of fossil fuels, ie. anthropogenic emissions of carbon dioxide and other gases that cause the negative effect of the "greenhouse" are a key cause of global climate change. The global increase in air temperature was the trigger for changes in other climatic elements, and above all: evaporation, precipitation regime, the appearance of snow, stormy winds, long-lasting heat waves, etc. The last decade (2010‒2020) was the warmest in the instrumental period. The average annual temperature increased by 1 oC compared to the pre-industrial period. In addition to the increase in the average annual air temperature, there was also an increase in extreme temperatures, and changes in climate indices that are conditioned by the air temperature (frost, summer and tropical days). Such changes in air temperature and climate indices have led to increased evaporation and greater variability of the atmosphere. Climate change has caused a higher frequency and intensity of climate extremes, which have a very unfavorable impact on the environment and natural resources throughout the world. The area of Southeast Europe, ie. the Western Balkans, is one of the most endangered in the world in terms of floods, droughts, long-lasting heat waves and stormy winds. Climate change in the Republik of Srpska and Bosnia and Herzegovina has been particularly pronounced in the last three decades, when they have put increasing pressure on many natural resources, especially water, agricultural land, biodiversity and forest ecosystems. Climate models point to even more intense changes in the near future, which will require a planned approach in planning the resilience of the most vulnerable sectors to climate change on a scientific basis.

Climate Change in Bosnia and Herzegovina According to Climate Scenario RCP8.5 and Possible Impact on Fruit Production

This paper presents the results of research on possible climate change in Bosnia and Herzegovina according to the climate scenario RCP8.5 and its potential impact on fruit production. Climate change analyses are based on expected fluctuations in air temperature, precipitation and climate indices. The results indicate pronounced climate change, which refers to an increase in annual temperature to 5 °C, and a decrease in annual precipitation of up to 30% and in the summer season (June, July, and August) and up to 40% by the end of the XXI century. In addition, an increase in the number of summer days and a decrease in the number of days with the appearance of snow can be expected. Reducing the number of days with snow and snow cover can cause a decrease in underground aquifers with water during the winter and spring seasons. These changes can have a serious impact on the problem of drought and water deficit, which can have direct consequences for the agricultural sector in Bosnia and Herzegovina, especially for fruit production. These findings show that fundamental changes in agriculture and an approach to land treatment and water resources management, as well as fruit production planning in changed climatic conditions, are needed.

CLOUD DETECTION BASED ON DECISION TREE OVER TIBETAN PLATEAU WITH MODIS DATA

Abstract. Snow cover area is a very critical parameter for hydrologic cycle of the Earth. Furthermore, it will be a key factor for the effect of the climate change. An unbelievable situation in mapping snow cover is the existence of clouds. Clouds can easily be found in any image from satellite, because clouds are bright and white in the visible wavelengths. But it is not the case when there is snow or ice in the background. It is similar spectral appearance of snow and clouds. Many cloud decision methods are built on decision trees. The decision trees were designed based on empirical studies and simulations. In this paper a classification trees were used to build the decision tree. And then with a great deal repeating scenes coming from the same area the cloud pixel can be replaced by "its" real surface types, such as snow pixel or vegetation or water. The effect of the cloud can be distinguished in the short wave infrared. The results show that most cloud coverage being removed. A validation was carried out for all subsequent steps. It led to the removal of all remaining cloud cover. The results show that the decision tree method performed satisfied.

Selection of habitat and perches by the Great Grey Shrike Lanius excubitor and the effects of snow layer and prey type

Field observations on Great Grey Shrikes Lanius excubitor were performed in four study areas in SW Finland (60°N, 22°E). The relation between habitat use, perch selection, prey type and the presence of a snow layer was evaluated. The mean yearly (± SE) territory size was 144 ha ± 14.3. The habitat selection depended on if snow cover was present, reflecting the favouring of vegetation-scarce arable fields when hunting invertebrates and vegetation-rich habitats when mainly vertebrates were available. Consistent with theories on optimal perch height, the shrikes chose higher perches when mainly vertebrates were hunted and also increased the time/perch, probably reflecting that vertebrate prey occur less frequently than invertebrate prey. The selection of lower perches when hunting invertebrates was evident in mild winter periods but not in the autumn; the reasons for this is discussed. The appearance of snow increased the distance to mammalian prey but the average capture frequency of mammals remained unchanged. In accordance with optimal foraging theory the shrikes preferred to hunt invertebrates when these were available rather than to adopt a hunting strategy that would optimise the encounter rate with vertebrates. However, the average hunting rate of ground-living prey decreased as the snow depth increased whereas energetically costly types of hunting behaviour, like rate of movements, hovering and hunting of birds remained unchanged.

Use of Browse by White-Tailed Deer in an Enclosure in New Brunswick

Natural browse use by white-tailed deer (Odocoileusvirginianusborealis Miller) was measured in the fall of two consecutive years using captive animals in enclosures located in regenerative stands. Oven dry twig weight prediction equations were first established for each species in the area, and browse use measured weekly by counting the number of twigs removed. Average daily browse use amounted to 0.75 kg for fawns and to 0.80 kg for adults. Shadbush (Amelanchier spp.) and willow (Salix spp.) were highly preferred by the fawns; lambkill (Kalmiaangustifolia L.), red maple (Acerrubrum L.), and withe-rod (Viburnumcassinoides L.) were preferred by the adults. A shift towards use of conifers by fawns was observed in relation with the appearance of snow. No discernible lasting damage to regeneration of commercial species was noticed even at a browsing pressure evaluated at 2–3 times the normal level.

Ascent of Etna

IT was a bright sunny sky on the last day of April when we started, with Giuseppe Sedici as guide, from the Grand Hotel at Catania in a carriage and pair bound for Nicoloni, en route to the summit of Etna. A dusty drive of two and a half hours, and we were at the door of the inn in the centre of the village. Its appearance was somewhat forlorn, and its fare rather meagre, but the civility of mine host compensated for all other defects. Here we engaged two mules, a porter, and a driver, an operation which took more than two hours, and then set off again for the Casa del Bosco, which we reached in the middle of the afternoon after a ride of two and a quarter hours. A climb up a neighbouring hillock to see the sunset, dinner, and a few hours' rest filled up the time till 11 p.m., when we started off again and rode for about half an hour, till the appearance of snow made it necessary to dismount and continue the remainder of the journey on foot. Our guide was very slow, and on any attempt to force the pace stood still and ejaculated: “Fermo, Signore! Piano, Piano!” so that we did not arrive at the Casa Inglese till 5 a.m., and were obliged to content ourselves with seeing the sun rise from here instead of from the top, as we had intended. It did not much matter, as it was a cloudy morning, and the view was very poor, but still it was a disappointment. The Casa Inglese was covered with snow to the eaves of the roof, the observatory buried altogether, the Val del Booe a sea of white. After a short rest we trudged on again; so far it had been good walking up an easy ascent of crisp snow, but now it became a work of difficulty to pick one's way through deep drifts and treacherous-looking holes, which seemed to explain the guide's reluctance to undertake this part of the route by moonlight. Arrived however at the foot of the cone, the snow ceased, and a heavy climb up the frozen side under a biting wind began. Half way up matters were not improved by a severe attack of sickness; but at length the top was reached at 6.20 a.m. There was no distant view; within the crater the steam and smoke kept being blown hither and thither, and cleared off at times sufficiently to show parts of what looked like a bottomless pit. It was a curious and weird sight altogether, and well repaid the fatigues of the journey. During the descent the notes of the cuckoo and some very sweet violets found by chance under the snow reminded us that, notwithstanding the mountain's wintry mantle of white, it was really spring time, and that the morning sun had ushered in the merry month of May, a fact which we had well nigh forgotten but a few hours before, when our fingers were numb with cold and our ears threatened to become a thing of the past.