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21.
Jean-Denis Taupin Gaëlle Gaultier Guillaume Favreau Christian Leduc Christelle Marlin 《Comptes Rendus Geoscience》2002,334(1):43-50
The isotopic content of rainfall was measured in Niamey (Niger) over a period of eight years (1992–1999). Seasonal distribution of rainy events depends on the monsoon movement over the region. At the beginning and at the end of the rainy season, low rainfall, high temperatures and low relative humidity favour isotopic enrichment. In the middle of the rainy season, heavy rainfall, low temperatures and relative humidity close to saturation lead to isotopically depleted contents because of the mass effect; moreover, in the case of low rainfall, marked vertical convective development favours high altitude condensation. How far the Intertropical Front moves north, determines the quality of the rainy season and influences the isotopic contents. Thus the isotopic contents of rainfall are good climatic indicators. To cite this article: J.-D. Taupin et al., C. R. Geoscience 334 (2002) 43–50 相似文献
22.
This study examines runoff generated under simulated rainfall on Summerford bajada in the Jornada Basin, New Mexico, USA. Forty‐five simulation experiments were conducted on 1 m2 and 2 m2 runoff plots on grassland, degraded grassland, shrub and intershrub environments located in grassland and shrubland communities. Average hydrographs generated for each environment show that runoff originates earlier on the vegetated plots than on the unvegetated plots. This early generation of runoff is attributed to soil infiltration rates being overwhelmed by the rapid concentration of water at the base of plants by stemflow. Hydrographs from the degraded grassland and intershrub plots rise continuously throughout the 30 min simulation events indicating that these plots do not achieve equilibrium runoff. This continuously rising form is attributed to the progressive development of raindrop‐induced surface seals. Most grassland and shrub plots level out after the initial early rise indicating equilibrium runoff is achieved. Some shrub plots, however, display a decline in discharge after the early rise. The delayed infiltration of water into macropores beneath shrubs with vegetation in their understories is proposed to explain this declining form. Water yields predicted at the community level indicate that the shrubland sheds 150 per cent more water for a given storm event than the grassland. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
23.
SIMULATION OF HEAVY RAINFALL IN THE SUMMER OF 1998 OVER CHINA WITH REGIONAL CLIMATE MODEL 总被引:11,自引:0,他引:11
The heavy rainfall in the summer of 1998 over China has been simulated with the NCCRegional Climate Model(RegCM_NCC).It was successful for RegCM_NCC to reproduce thelocation and seasonal shift of the seasonal rain belt in the summer of 1998 over China.The rainyseason in the summer of 1998 over China can be divided into 7 episodes,including the pre-summerrainy season in South China.the Meiyu onset over the Yangtze-Huaihe River Basin,shortappearance of North China rain season and the retreat of seasonal rain belt,the second Meiyuseason over the Yangtze River Valley,the rainy period over the Yellow and Huaihe River Valleyand the seasonal retreat of rain belt over North China.The shortcoming of the RegCM_NCC isover-estimation of precipitation amounts.The regions with large latent heat flux,upper soilmoisture and total runoff are located in the rainy area and move with the simulated rain belt duringthe different episodes.On the contrary,the regions with small sensible heat flux are located in thesimulated rainy area and move with the simulated rain belt during the different episodes. 相似文献
24.
黄河中游降雨特性对泥沙粒径的影响 总被引:6,自引:3,他引:6
以黄河中游36个有泥沙粒径资料的水文测站流域为样本,在不同自然地理类型流域划分的基础上,建立了流域泥沙粒径特片与降雨特性的关系。结果表明,在不同类型流域,流域泥沙的粗细与降雨季节性变率和年际变率之间存在着相当好的线性正相关关系;而与年降雨量和降雨不均匀系数之间呈明显的非线性关系。流域地面物质、植被和地貌发育程序等下垫面环境因素对泥沙粒径特性与降雨特性之间关系起着十分重要的控制作用。不同类型流域曲线的斜率各不相同,在图中所处的位置也不相同。 相似文献
25.
26.
云南省金沙江流域土壤流失方程研究 总被引:17,自引:2,他引:17
云南金沙江流域是长江中上游水土流失最严重的区域。本项研究以“通用土壤流失方程”(USLE)为蓝本,运用小区实验等手段,综合分析了各个侵蚀因子,建立了云南金沙江流域土壤流失方程A=R·K·LS·c·P,并确定了方程中诸因子的求算方法和数值,以及该流域土壤允许流失量,为方程的应用提供了基本的技术数据。同时,还进行了方程的检验,方程计算值与小区实测值的相对误差在6.3%以下,表明该方程在实际应用中是可靠的。该方程的建立,可为云南金沙江流域预测预报土壤侵蚀,制定土地合理利用规划方案、水土保持措施和土地生态安全格局提供了一套可靠的科学方法和依据。 相似文献
27.
28.
Nozzle‐type rainfall simulators are commonly used in hydrologic and soil erosion research. Simulated rainfall intensity, originating from the nozzle, increases as the distance between the point of measurement and the source is decreased. Hence, rainfall measured using rain gauges would systematically overestimate the rainfall received at the ground level. A simple model was developed to adjust rainfall measured anywhere under the simulator to plot‐wide average rainfall at the ground level. Nozzle height, plot width, gauge diameter and height, and gauge location are required to compute this adjustment factor. Results from 15 runs at different rain intensities and durations, and with different rain gauge layouts, showed that a simple average of measured rain would overestimate the plot‐wide rain by about 20 per cent. Using the adjustment factor to convert measured rainfall for individual gauges before averaging improved the estimate of plot‐wide rainfall considerably. For the 15 runs considered, overall discrepancy between actual and measured rain is reduced to less than 1 per cent with a standard error of 0·97 mm. This model can be easily tested in the ?eld by comparing rainfall depths of different sized gauges. With the adjustment factor they should all give very similar values. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
29.
The Franz Josef Glacier, Westland, New Zealand, has a history of catastrophic sediment‐laden outburst ?oods associated with extreme rainfall events when the glacier toe is advanced over its own sediments. Consideration of these events and inspection of recent sediment deposits suggest that there are three distinct modes of outburst. The ?rst is associated with fans fed by over?ow along the glacier margin. As the glacier has advanced across its own fore?eld gravels, it is inferred that the primary drainage conduit has developed a reach of negative slope. In high ?ows massive boulders can block the conduit, trapping lesser clasts. The resulting backup of water causes over?ows through marginal moulins, producing the fan type of deposit. The second type of outburst deposits massive imbricated boulders at a greater or lesser distance from the glacier portal. In this case, pressure buildup drives the blockage out of the portal where the boulders deposit. Smaller materials are generally carried away. The third type consists of very shallow ?ows, and produces massive gravel deposits of uncertain provenance. In this condition, the excess pressure in the conduit results in slight uplift of the glacier and widespread discharge of water and sediment below the glacier snout; gravels and smaller sediments are laid down in a massive deposit across the fore?eld. The massive, boulder‐veneered deposit from the December 1995 outburst is interpreted in the light of the above mechanisms as a hyperconcentrated ?ow deposit from hydraulic jacking, overlain by boulders emplaced by a subsequent conduit outburst. A possible association of outbursts with the present advanced position of the glacier is suggested. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
30.
A. K. Mitra M. Das Gupta R. K. Paliwal S. V. Singh 《Journal of Earth System Science》2003,112(2):223-232
A daily rainfall dataset and the corresponding rainfall maps have been produced by objective analysis of rainfall data. The
satellite estimate of rainfall and the raingauge values are merged to form the final analysis. Associated with epochs of monsoon
these rainfall maps are able to show the rainfall activities over India and the Bay of Bengal region during the BOBMEX period.
The intra-seasonal variations of rainfall during BOBMEX are also seen using these data. This dataset over the oceanic region
compares well with other available popular datasets like GPCP and CMAP. Over land this dataset brings out the features of
monsoon in more detail due to the availability of more local raingauge stations. 相似文献