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Analysis of main controls of runoff events in the Sumava Mts. caused by rain-on-snow
Šťovíček, Vít ; Jeníček, Michal (advisor) ; Juras, Roman (referee)
Rain-on-snow (ROS) events are hydrometeorological phenomena when a sufficient combination of rainfall and snowmelt can generate floods, snow avalanches or landslides. As average air temperature gradually increases, the trend of ROS events occurring earlier in spring and at higher altitudes can be expected to continue. Snowmelt during ROS events is controlled by the snowpack energy balance and is influenced by several factors, especially meteorological conditions, and initial conditions of the snowpack. The calculations were made using data from four automatic stations in the Šumava Mountains, namely the Vydra river basin. Based on these data and pre-defined threshold conditions, 105 ROS events were selected. Resulting components of the energy balance, climatic, snow and outflow characteristics were mutually correlated, and their influence on ROS events was determined. The analyses showed that during ROS events, the most important source of energy for melting were turbulent fluxes, i.e., latent, and especially sensible heats. According to the monthly averages, they accounted, at almost all observed stations, for at least 40% (and up to 60% in December), of the total energy available for snow melting. Another important energy flux was shortwave radiation, whose fraction increased with the progress of...
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Melt rates calculation with respect to meteorological conditions
Šťovíček, Vít ; Jeníček, Michal (advisor) ; Hotový, Ondřej (referee)
Meteorological conditions are an important factor affecting the speed of snowmelt. Their impacts have been changing accroding to physical-geographical factors such as elevation, slope of the terrain, slope orientation and vegetation, affecting energy balance of the snowpack. The calculations were made using data from four automatic stations in the Šumava Mountains, namely the Vydra river-basin. These stations measure individual meteorological aspect and snow properties. Based on these data and pre-defined conditions, 136 melting events were selected. The melt factors were calculated based on degree-day approach. Similarly, the melt rates were calculated from the snow water equivalent decrease and snowmelt event duration for each snowmelt event. The correlation and regression analyzes were used to determine the effect of each meteorological factor on the snowmelt speed. The analyses proved the highest dependence of the snowmelt speed on the precipitation amount (the value of the Spearman's rank correlation coefficient rs reached 0.54 for the melt factor and 0.68 for melt rate). There is more substantial difference in the effects of meteorological conditions if we compare the winter season from November to February and the spring snowmelt season from March to May, while the highest snowmelt...
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