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[en] Daily snow depth (SD) and snow cover extent around 820 stations are used to analyse variations in snow cover characteristics in Northern Eurasia, a region that encompasses the Russian Federation. These analyses employ nearly five times more stations than in the previous studies and temporally span forty years. A representative judgement on the changes of snow depth over most of Russia is presented here for the first time. The number of days with greater than 50% of the near-station territory covered with snow, and the number of days with the snow depth greater than 1.0 cm, are used to characterize the duration of snow cover (SCD) season. Linear trends of the number of days and snow depth are calculated for each station from 1966 to 2007. This investigation reveals regional features in the change of snow cover characteristics. A decrease in the duration of snow cover is demonstrated in the northern regions of European Russia and in the mountainous regions of southern Siberia. An increase in SCD is found in Yakutia and in the Far East. In the western half of the Russian Federation, the winter-averaged SD is shown to increase, with the maximum trends being observed in Northern West Siberia. In contrast, in the mountainous regions of southern Siberia, the maximum SD decreases as the SCD decreases. While both snow cover characteristics (SCD and SD) play an important role in the hydrological cycle, ecosystems dynamics and societal wellbeing are quite different roles and the differences in their systematic changes (up to differences in the signs of changes) deserve further attention.
[en] This article presents an algorithm and a structured methodology to address the issue of the optimisation of resources when clearing snow from stretches of the manoeuvring area of an airport. This overall issue is how to best utilise limited resources to remove snow from taxiways and runways so as to leave surfaces in an acceptable state for aircraft operations. To achieve this the airfield is divided into subsets of significant stretches for the purpose of operations and target times are set at which these are to be open to aircraft traffic. The manoeuvring area is also divided into zones, with the condition that the subsets of significant stretches lie within just one of these zones. The mathematical model contains operating restrictions with regard to the fulfilment of partial operational targets applied to the subsets of significant stretches, and also concerning the snow-clearing machines. The problem is solved by an iterative optimisation process based on linear programming applied successively to the zones that make up the manoeuvring area during each iteration. The method is particularised for the case of the manoeuvring area of Adolfo Suarez Madrid - Barajas Airport. (Author)
[en] Up to now in the world literature of hydrology there has been only a few studies on the application of nuclear techniques to snow hydrology. For the first time in Turkey water equivalent of snow pack and runoff were determined by the absorbtion of gamma radiation passing through a snow pack and by the use of an environmental isotope respectively. By this research, the water equivalent of snow was determined by both the classical and the nuclear techniques. Snow cover depths versus the water equivalents of snow were plotted on a graph and linear regression equations were obtained for forcasting model by using the classical and the nuclear techniques. In addition, by using the flow hydrography and the environmental isotope contents of water samples, the subsurface flow hydrography and the surface flow hydrograph were found by the nuclear technique. Next, the flow hydrograph and the environmental isotope contents, which belong to these flows, were plotted on a graph. A good relationship between the flow hydrograph and the delta18 0 SMOW values was observed and long term forecasting model for the seasonal spring flood volume was developed. Finally, it was discovered that the nuclear techniques can be applied either together with the classical techniques or without them. (author)
[en] An analysis is made of changes in basal ice crust layer characteristics from snow cover surveys made at 958 Russian stations since 1966. The analysis revealed that substantial changes have occurred in response to two competing processes: an increase in thaws associated with strong regional warming and an increase in the duration of the basal ice layer presence on the ground, and a shortening of the snowmelt period associated with a decrease in basal ice layer event frequency and severity. The latter appears to be the more significant process over the past 40 years. Our findings support the notion that the entire spring snowmelt process has become shorter in duration and more intense when taking into account a concomitant trend toward increasing snow depths over large regions of Russia. A more intense spring melt period has important consequences for spring flood dynamics and deserves further study.
[en] Radioactive fallout measurements, generally performed to determine average snow accumulation rates, can also be used to determine other meteorological information. The following results were obtained from measurements on the Antarctic ice sheet: (1) A strasospheric residence time of 1.5 years for radioisotopes such as 90Sr and 137Cs. (2) A value of approximatively 1 of the ratio phi between the concentration measured in the air (g/m3 STP) and the concentration determined in the snow (g/g), with extreme values of 0.5 and 5. (3) The dry fallout represents between 15 and 25% of the total deposition in the coastal regions and as much as 40 to 60% in the central zones. (4) A precipitation increase of 30% occurred after 1965 when compared with the decade 1955-1965
[en] To calculate the wet deposition of aerosol-bound radionuclides on ground and vegetation, the scavenging coefficients must be well known. In case of rainfall there are, however, great differences between some of the experimental results published and theory. In the case of snowfall there is a large scatter in the experimental data published. Too little is known about the snow-out coefficient vs particle diameter as well as precipitation intensity. In the course of investigating snow-out, an outdoor experiment was set up to determine both the overall snow-out and wash-out coefficients (below cloud) of monodisperse test aerosols by natural hydrometeors. The collection efficiency of simple snowflake models was determined in laboratory experiments. The snow-out coefficient was calculated using empirical snowflake size spectra data. In the case of wash-out by rain, the results of the outdoor experiments are compared to results theoretically derived by an earlier study. In the case of snow-out, the results of the outdoor experiments are compared with those calculated from the collection efficiency data. The snow-out coefficients measured outdoors are about five times larger than the wash-out coefficients. (Author)
[en] This paper discusses the characteristics of the unique “Regional East Gale (REG) with Blowing Snow” natural disaster that occurs in Jeminay County, Xinjiang Uygur Autonomous Region, China. The damage caused by such REG events is described, followed by discussion on the possible prevention measures for this kind of disaster. This work provides a theoretical basis for continuing development of the service that forecasts REG disasters and thus helps with mitigating against their impacts.
[en] Washington State experienced widespread drought in 2015 and the largest burned area in the observational record, attributable in part to exceptionally low winter snow accumulation and high summer temperatures. We examine 2015 drought severity in the Cascade and Olympic mountains relative to the historical climatology (1950–present) and future climate projections (mid-21st century) for a mid-range global greenhouse gas emissions scenario. Although winter precipitation was near normal, the regional winter temperature anomaly was +2.1 °C (+2.0σ) in 2015, consistent with projections of a +2.3 °C (+2.2σ) temperature change and near normal precipitation in the future, relative to the climatology. April 1 snow water equivalent in 2015, −325 mm (−1.5σ), and the future, −252 mm (−1.1σ), were substantially lower than the climatology. Wildfire potential, as indicated by dead fuel moisture content, was higher in 2015 than mid-21st century mean projections. In contrast to most historical droughts, which have been driven by precipitation deficits, our results suggest that 2015 is a useful analog of typical conditions in the Pacific Northwest by the mid-21st century. (letter)