This study presents an extended version of a single site daily weather generator after Richardson. The model is driven by daily precipitation series derived by a first-order two-state Markov chain and considers the an...This study presents an extended version of a single site daily weather generator after Richardson. The model is driven by daily precipitation series derived by a first-order two-state Markov chain and considers the annual cycle of each meteorological variable. The evaluation of its performance was done by deploying its synthetic time series into the physical based hydrological model BROOK90. The weather generator was applied and tested for data from the Anchor Station at the Tharandt Forest, Germany. Additionally its results were compared to the output of another weather generator with spell-length approach for the precipitation series (LARS-WG). The comparison was distinguished into a meteoro-logical and a hydrological part in terms of extremes, monthly and annual sums and averages. Extreme events could be preserved adequately by both models. Nevertheless a general underestimation of rare events was observed. Natural correlations between vapour pressure and minimum temperature could be conserved as well as annual cycles of the hydro-logical and meteorological regime. But the simulated spectrums of extremes, especially, of precipitation and temperature, are more limited than the observed spectrums. While LARS-WG already finds application in practice, the results show that the data derived from the presented weather generator is as useful and reliable as those from the established model for the simulation of the water balance.展开更多
Snow-melt runoff is an important factor in control of flooding and soil erosion in higher and cold regions of the world.In 1992-2008-2008,processes of snow accumulation and melting were monitored at two adjacent sites...Snow-melt runoff is an important factor in control of flooding and soil erosion in higher and cold regions of the world.In 1992-2008-2008,processes of snow accumulation and melting were monitored at two adjacent sites of the Paljakka environmental research centre(Finland).The forest stand of mature spruce(Picea abies)has been compared with adjacent,local,and open grassland.In the forest,snowpack duration fluctuated for 180-245 days,with a maximum depth of 78-152 cm and snow-water content of 167-406 mm,while in the open grassland this occurred for some 20 days less,with maximum depth 65-122 cm,and snow-water content 143-288 mm.The snow-water captured in the canopy reached a maximum 27%of that registered on the ground;the loss of intercepted snow by sublimation was approximately 26% of the annual snowfall.During the high melt period(April-May),the degree-day factor in the forest stand achieved 60%of values observed in the grassland(2.3-3.5 against 3.8-6.0 mm℃^(-1)day^(-1)).The hydrological model BROOK 90 was employed to analyse potential water resources recharge,and flood risk at Paljakka.Considering the normal climate season,snow-melt runoff from the forest exceeded the grassland by 22%(225 against 185 mm).In extreme situations,the maximum daily runoff from snow-melt in the grasslands(57 mm day^(-1))exceeded 2.6 times the values in spruce forest(22 mm day^(-1)).展开更多
基金supported by the German Academic Exchange Service(DAAD).
文摘This study presents an extended version of a single site daily weather generator after Richardson. The model is driven by daily precipitation series derived by a first-order two-state Markov chain and considers the annual cycle of each meteorological variable. The evaluation of its performance was done by deploying its synthetic time series into the physical based hydrological model BROOK90. The weather generator was applied and tested for data from the Anchor Station at the Tharandt Forest, Germany. Additionally its results were compared to the output of another weather generator with spell-length approach for the precipitation series (LARS-WG). The comparison was distinguished into a meteoro-logical and a hydrological part in terms of extremes, monthly and annual sums and averages. Extreme events could be preserved adequately by both models. Nevertheless a general underestimation of rare events was observed. Natural correlations between vapour pressure and minimum temperature could be conserved as well as annual cycles of the hydro-logical and meteorological regime. But the simulated spectrums of extremes, especially, of precipitation and temperature, are more limited than the observed spectrums. While LARS-WG already finds application in practice, the results show that the data derived from the presented weather generator is as useful and reliable as those from the established model for the simulation of the water balance.
基金supported by the Muhos Research Unit of the Finnish Forest Research Institute(Reijo Seppänen organized the field snow survey)the Oulu University(Pertti Vuolteenaho and Leo Koutaniemi developed the treeweighting equipment)by the Czech Technical University in Prague(SGS 14/128/OHK1/2T/11).
文摘Snow-melt runoff is an important factor in control of flooding and soil erosion in higher and cold regions of the world.In 1992-2008-2008,processes of snow accumulation and melting were monitored at two adjacent sites of the Paljakka environmental research centre(Finland).The forest stand of mature spruce(Picea abies)has been compared with adjacent,local,and open grassland.In the forest,snowpack duration fluctuated for 180-245 days,with a maximum depth of 78-152 cm and snow-water content of 167-406 mm,while in the open grassland this occurred for some 20 days less,with maximum depth 65-122 cm,and snow-water content 143-288 mm.The snow-water captured in the canopy reached a maximum 27%of that registered on the ground;the loss of intercepted snow by sublimation was approximately 26% of the annual snowfall.During the high melt period(April-May),the degree-day factor in the forest stand achieved 60%of values observed in the grassland(2.3-3.5 against 3.8-6.0 mm℃^(-1)day^(-1)).The hydrological model BROOK 90 was employed to analyse potential water resources recharge,and flood risk at Paljakka.Considering the normal climate season,snow-melt runoff from the forest exceeded the grassland by 22%(225 against 185 mm).In extreme situations,the maximum daily runoff from snow-melt in the grasslands(57 mm day^(-1))exceeded 2.6 times the values in spruce forest(22 mm day^(-1)).
