ABSTRACT. A grid-based surface energy-balance mass-balance model has been developed to simulate snow-and ice melt in mountainous regions with an hourly resolution. The model is applied to Storglaciären, a valley glacier in Sweden, using a 30 m resolution digital elevation model. Emphasis is directed towards computing the radiation components. These are modelled individually, considering the effects of slope angle, aspect and effective horizon. A new parameterization for snow albedo is suggested, modifying the albedo of the preceding hour as a function of time after snowfall, air temperature and cloudiness. The model is used to provide the meltwater input for discharge modelling and to assess the influence of the individual components on melt. Results are validated by means of observed melt rates, patterns of snow-line retreat and proglacial discharge. In general, simulations are in good agreement with observations. In particular, the diurnal and seasonal fluctuations of discharge are simulated remarkably well.
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AbstractThe effects of weather on the flight and flower-visiting activity of bumblebees and butterflies were studied at a subarctic-alpine site in northern Swedish Lapland. The study focused on the insects' role as potential pollinators and the effect of bumblebee flight and foraging activity on plant reproductive success. The activity rates of both bumblebees and butterflies were significantly correlated with ambient air temperature and solar radiation, and as a consequence, both bumblebees and butterflies exhibited a regular diurnal activity pattern. The butterflies' activity was more constrained by low temperature and solar radiation then the bumblebees' activity, and small worker bees were more affected by the weather than the larger queens.Only 1% of the butterflies observed were visiting flowers, as compared to 69% of the bumblebees. Thus, butterflies seem to be less important pollinators for the alpine plant community than bumblebees. Short-term micrometeorological impact on the reproduction of two bumblebee-pollinated plant species, Bartsia alpina and Diapensia lapponica, was also studied. In both species, reproductive success, measured as seed production, was significantly reduced during a spell of cold weather in comparison to a warmer period.
This report describes a new inherited disorder of myelination in the rat, named taiep, in which failure of normal myelination of the CNS and subsequent demyelination result in a progressive neurological disturbance. At two months of age, myelin is present throughout the spinal cord, but is immature in the fasciculus gracilis and corticospinal tracts despite the presence of abundant oligodendrocytes. By 12 months, myelin has largely been lost in these spinal cord tracts and also in more rostral parts of the CNS, such as the cerebellum and optic nerves. Other funiculi of the spinal cord show a more diffuse lack of myelin. Oligodendrocytes develop a unique cellular abnormality, most obviously in older rats, which is characterized by the accumulation of microtubules throughout their cytoplasm. As the mutant rats age, there is a continued protracted breakdown of myelin throughout the CNS, with evidence suggesting either persistent hypomyelination or attempts at remyelination of affected axons. It is proposed that the microtubular defect in oligodendrocytes results in a disruption of the normal myelination process in certain areas of the CNS of this mutant, and eventually leads to failure of maintenance of the myelin sheath.
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