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Arman?GanjiEmail author Laxmi?Sushama Diana?Verseghy Richard?Harvey 《Theoretical and Applied Climatology》2017,127(1-2):45-59
Regional and global climate model simulated streamflows for high-latitude regions show systematic biases, particularly in the timing and magnitude of spring peak flows. Though these biases could be related to the snow water equivalent and spring temperature biases in models, a good part of these biases is due to the unaccounted effects of non-uniform infiltration capacity of the frozen ground and other related processes. In this paper, the treatment of frozen water in the Canadian Land Surface Scheme (CLASS), which is used in the Canadian regional and global climate models, is modified to include fractional permeable area, supercooled liquid water and a new formulation for hydraulic conductivity. The impact of these modifications on the regional hydrology, particularly streamflow, is assessed by comparing three simulations performed with the original and two modified versions of CLASS, driven by atmospheric forcing data from the European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis (ERA-Interim) for the 1990–2001 period over a northeast Canadian domain. The two modified versions of CLASS differ in the soil hydraulic conductivity and matric potential formulations, with one version being based on formulations from a previous study and the other one is newly proposed. Results suggest statistically significant decreases in infiltration and therefore soil moisture during the snowmelt season for the simulation with the new hydraulic conductivity and matric potential formulations and fractional permeable area concept compared to the original version of CLASS, which is also reflected in the increased spring surface runoff and streamflows in this simulation with modified CLASS over most of the study domain. The simulated spring peaks and their timing in this simulation are also in better agreement to those observed. This study thus demonstrates the importance of treatment of frozen water for realistic simulation of streamflows. 相似文献
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Ripu M. KUNWAR Laxmi MAHAT Lila N. SHARMA Keshab P. SHRESTHA Hiroo KOMINEE Rainer W. BUSSMANN 《山地科学学报》2012,9(5):589-600
Underutilized plant species help to alleviate common food insufficiencies by providing alternative food supply. They also complement primary health care, furnishing raw materials where the cultivation of staple cereal crops is least feasible and health care is pursued indigenously. Research and promotion of extraction, utilization, and conservation of underutilized species lead to exploration of new staple crops and motivate people to consume in a sustainable manner. The present study describes the current status, uses, and management of underutilized plant species in Far West Nepal. The relative importance of 49 underutilized plant species was computed employing a Relative Importance (RI) technique. The use-values assigned to the species fall into six use-categories: beverage, fodder, food & edible, medicinal, vegetable and veterinary. A total of 22 species appeared in multiple use-categories, while the rest were characterized by a single use-category. Based on relative importance and frequency, Ficus semicordata, Debregesia longifolia, Girardinea diversifolia, Hydrocotyle nepalensis, Garuga pinnata, Aloe vera and Pyrus pashia offer the most potential for future. Underutilized plants proved important to folk medicine and food. These species persist because they remain useful to local people as means of subsistence, production, and primary health care. The findings are important so far as they point up the role of underutilized plants in national food security policy and health care, spelling out their potentialities and cross cutting relationships. 相似文献
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The effects of future temperature and hence evapotranspiration increases on drought risk over North America, based on ten current (1970–1999) and ten corresponding future (2040–2069) Regional Climate Model (RCM) simulations from the North American Regional Climate Change Assessment Program, are presented in this study. The ten pairs of simulations considered in this study are based on six RCMs and four driving Atmosphere Ocean Coupled Global Climate Models. The effects of temperature and evapotranspiration on drought risks are assessed by comparing characteristics of drought events identified on the basis of Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspration Index (SPEI). The former index uses only precipitation, while the latter uses the difference (DIF) between precipitation and potential evapotranspiration (PET) as input variables. As short- and long-term droughts impact various sectors differently, multi-scale (ranging from 1- to 12-month) drought events are considered. The projected increase in mean temperature by more than 2 °C in the future period compared to the current period for most parts of North America results in large increases in PET and decreases in DIF for the future period, especially for low latitude regions of North America. These changes result in large increases in future drought risks for most parts of the USA and southern Canada. Though similar results are obtained with SPI, the projected increases in the drought characteristics such as severity and duration and the spatial extent of regions susceptible to drought risks in the future are considerably larger in the case of SPEI-based analysis. Both approaches suggest that long-term and extreme drought events are affected more by the future increases in temperature and PET than short-term and moderate drought events, particularly over the high drought risk regions of North America. 相似文献
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Laxmi Kant Kachhwal Ernest K. Yanful Colin D. Rennie 《Environmental Earth Sciences》2012,66(3):823-834
Wind-driven waves and currents exert shear stress on the bed of a tailings pond. A semi-empirical approach for estimating this bed shear stress is presented in this paper. For the first time in a mine tailings storage facility, the current-induced component of the bed shear stress was obtained using 1,200-kHz acoustic Doppler current profiler measurements of in situ currents and a log-law fit to the mean velocity profiles, while the wave-induced portion was calculated using empirical wave hindcasting equations. The total bed shear stress was obtained by non-linear addition of wave and current components using a wave–current interaction approach. The study was conducted in the middle cell of the Shebandowan tailings storage facility, northern Ontario, Canada. The measured currents facilitated the visualization of the complex near-bed circulatory flow pattern in the pond. The estimated combined wave–current bed shear stress varied from 0.0006 to 0.16 Pa with an average value of 0.028 Pa. The results also showed that linear addition of bed shear stresses due to waves and currents could underestimate the total bed shear stress. A comparison of the results of the present work to those of previous studies suggests that it is more reliable to obtain current-induced bed shear stress from field measurements than to estimate it from empirical equations. 相似文献