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971.
Watershed delineation is a required step when conducting any spatially distributed hydrological modelling. Automated approaches are often proposed to delineate a watershed based on a river network extracted from the digital elevation model (DEM) using the deterministic eight‐neighbour (D8) method. However, a realistic river network cannot be derived from conventional DEM processing methods for a large flat area with a complex network of rivers, lakes, reservoirs, and polders, referred to as a plain river network region (PRNR). In this study, a new approach, which uses both hydrographic features and DEM, has been developed to address the problems of watershed delineation in PRNR. It extracts the river nodes and determines the flow directions of the river network based on a vector‐based hydrographic feature data model. The river network, lakes, reservoirs, and polders are then used to modify the flow directions of grid cells determined by D8 approach. The watershed is eventually delineated into four types of catchments including lakes, reservoirs, polders, and overland catchments based on the flow direction matrix and the location of river nodes. Multiple flow directions of grid cells are represented using a multi‐direction encoding method, and multiple outflows of catchments are also reflected in the topology of catchments. The proposed approach is applied to the western Taihu watershed in China. Comparisons between the results obtained from the D8 approach, the ‘stream burning’ approach, and those from the proposed approach clearly demonstrate an improvement of the new approach over the conventional approaches. This approach will benefit the development of distributed hydrological models in PRNR for the consideration of different types and multiple inlets and outlets of catchments. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
972.
在宽频带数字地震观测技术领域,提出一种基于数字音频接口(S/PDIF接口)的数据采集电路板快速评估方法。该方法在数据采集电路设计过程中,在模拟/数字转换电路的输出端增加了一组S/PDIF数字音频接口,将模/数转换结果转换为符合音频传输标准的编码数据,并将此数据利用外置声卡同步传输到计算机,在计算机上进行数字抽取滤波、频谱分析等数据处理与解析,从而实现对地震数据采集电路板的快速评估。实验结果表明,该方法思路清晰,实现简便,结果有效可靠,能够解决常规测试评估方法中存在的问题,在高精度、高采样率数据采集技术研发和测试评估方面,具有比较强的实用性和应用前景。 相似文献
973.
以内蒙古锡林郭勒盟苏尼特右旗的察干淖尔盐湖为研究对象,利用OSL(Optically Stimulated Luminescence)测年技术和DEM(Digital Elevation Model)数字高程模型,重建湖面波动历史,探讨湖泊形成与环境变化过程.通过对察干淖尔盐湖周边大量的野外考察,发现湖泊周围存在海拔高程为1020、978和973 m的三级古湖岸阶地,其OSL测年结果分别为29.2±1.3、18.4±0.8及8.2 8.0 ka.通过湖岸阶地高程恢复的上述3个时期的古湖面积分别为3600、500和400 km~2.与现今的干旱盐湖景观迥然不同. 相似文献
974.
The Saharan dust event that occurred between the 22nd and 30th of June 2012 influenced the atmospheric radiative properties over North Africa, the Iberian Peninsula, the Western Mediterranean basin, extending its effects to France and Southern England. This event is well documented in satellite imagery, as well as on the air quality stations over the Iberian Peninsula and the AERONET NASA network. In order to assess the effect of the model vertical resolution on the extinction coefficient fields, as a proxy to the particulate matter concentrations in the atmosphere, the WRF-Chem model was applied during this period over a mother domain with a resolution of 18 km, covering Europe and North Africa. To this end five model setups differing in the number of vertical levels were tested. Model skills were evaluated by comparing the model results with CALIPSO and EARLINET LIDAR data. Results show that the model is able to simulate the higher level aerosol transport but it is susceptible to the vertical resolution used. This is due to the thickness of the transport layers which is, eventually, thinner than the vertical resolution of the model. When comparing model results to the observed vertical profiles, it becomes evident that the broad features of the extinction coefficient profile are generally reproduced in all model configurations, but finer details are captured only by the higher resolution simulations. 相似文献
975.
Small inland valley wetlands contribute substantially to the livelihoods of rural communities in East Africa. Their conversion into farmland is driven by water availability. We quantified spatial-temporal dynamics of water availability in a headwater wetland in the humid zone of Kenya. Climatic conditions, soil moisture contents, groundwater levels and discharge data were monitored. A land-use map and a digital elevation model of the valley bottom were created to relate variations in soil moisture to dominant land uses and valley morphology.Upland crops occupied about a third of the wetland area, while approximately a quarter of the wet, central part of the valley bottom was designated for flood-tolerant taro, grown either by itself or in association or in rotation with upland crops. Finally, natural vegetation was found in 3% of the mapped area, mainly in sections with nearpermanent soil saturation.The HBV rainfall-runoff model's overestimation of stream discharge during the long dry season of the hydrological year 2010/2011 can be explained by the strong seasonal impact of water abstraction on the wetland's water balance.Our study vividly demonstrates the necessity of multi-method approaches for assessing the impact of management practices on water availability in valley bottom wetlands in East Africa. 相似文献
976.
一直以来月球上都没有发现像地球上一样的全球板块构造现象,被认为是属于单板块构造的行星体并且是不活动的。随着月球地形探测精度的提高,人们逐渐发现了一些地质现象表明月球并不像之前想象的一样是不活动的。高精度的月形数据显示出了月球上除了存在众所周知的(撞击作用产生的)复杂的撞击构造外,仍然存在许多可能由内生作用产生的构造特征:如裂谷、山脊、火山群等。本文利用最新高精度月球激光高度数据(LOLA数据)建立了全月60m(相当于7秒网格)高精度月形图。由于数据量超大(TB级别),作者编写了基于并行架构的集群计算处理代码,其计算效率提高了近300倍。基于这些图件,作者在全球范围内找出许多重要的构造现象,并根据其构造及地质特征进行分类研究。研究结果表明并不像之前认识一样,月球上的确存在许多地质构造体是由月球的内生地质作用所产生,并建立对于月球结构和构造的新认识。此外,通过对比发现,像地球上全球尺度的线性山脉只是板块构造运动的结果;另一方面,在无板块构造的行星上,就像月球一样,会产生大面积的高地(月陆)和低地(月海地区),这种地质现象很有可能是行星地壳岩浆演化的直接结果。在文章最后,作者还将制作出的60m分辨率的全月月形系列图件附后并公开,以方便其他科研人员进一步开展相关研究;并以此敬献中国地质科学院60周年庆典。 相似文献
977.
During the construction process of Qingdao Jiaozhou Bay Undersea Tunnel, the faults and other unfavorable geological discontinuities were often encountered. To study the water inrush mechanism in the faults, both physical model test and numerical analysis were carried out. The results of crown displacement and hydraulic pressure of the monitoring sections in the physical model and numerical model were analyzed in this paper. It was found that the displacement and hydraulic pressure in the process of tunnel construction are often interacted as both cause and effect, and the lower of hydraulic pressure is often accompanied with the growth of its displacement. The changing of the excavation disturbed zone during the excavation in the undersea tunnel was also studied. The results show that the excavation disturbed zone in fault is larger than that in surrounding rock mass, and the excavation disturbance effects in the filling type fault are both transient and persistent. When the displacement and hydraulic pressure in the undersea tunnel change sharply during excavation, there are relatively slow and continuous change trend of the displacement and hydraulic pressure. For practical purposes, to prevent water inrush in the undersea tunnel, more attentions should also be paid to the undersea tunnel after excavation. 相似文献
978.
“德州市农业气象预报系统”是用VB 5．0和FoxPro 5.0和FoxPro 2.6两种语言开发的软件，并采用面向对象设计技术。通过简述该软件设计过程，阐明设计该软件的思路和方法。 相似文献
979.
利用中国国家级地面气象站逐时降水资料,采用地理加权回归(Geographically Weighted Regression,GWR)模型系统分析了中国中东部暖季降水与海拔高度的关系,并将二者关系作为一种客观标准,评估了ECMWF-IFS模式对2017年暖季降水的预报能力。主要结论如下:(1)总体来看,中国中东部降水频率(强度)随海拔高度升高而增加(减小),二者在不同地区的贡献程度不同导致降水量与海拔高度关系的区域差异显著。(2)通过对比午后短时和夜间长时降水事件与海拔高度关系的差异,发现午后短时降水事件的降水量主要随海拔高度升高而增加,且以降水频率与海拔高度关系的贡献为主。而夜间长时降水事件的降水量与海拔高度关系的区域一致性较差。相较于午后短时降水事件,夜间长时降水事件中有更多站点表现出降水量随海拔高度升高而减小的特征,在大地形周边陡峭地形处的站点所表现出的此种差异较东部孤立地形处更加显著。(3)根据ECMWF-IFS模式的评估结果,模式能够较好地刻画出中国中东部2017年暖季降水气候态的空间分布特征,且与观测具有较大的空间相关系数。但从降水与海拔高度关系来看,观测与模式的空间相关性偏弱。此外,模式能够表现出降水强度(频率)主要随海拔高度升高而减小(增加)的特征,但绝大多数站点在模式中的降水强度(频率)与海拔高度的负(正)回归关系要弱(强)于观测结果。 相似文献
980.
为提高大白菜等小粒径精密播种机的机械化水平,设计了一种小粒径气吸式排种器.首先利用JPS-12排种器性能检测试验台对排种器进行测试,得到不同参数组合下的性能指标与最优参数组合.然后使用计算流体力学方法（CFD）,借助FLUENT软件分析了吸种器内部流场的分布,得到了吸种器内部压力分布云图和吸种孔截面云图.最后基于离散元法（DEM）建立大白菜种子颗粒模型,对排种器仿真模型进行简化和网格划分,完成了小粒径气吸式排种器DEM-CFD耦合仿真实验.对比台架与仿真试验结果,得出如下的结论：当排种盘转速为20 r/min,真空度为2.2 kPa时,排种性能最佳. 相似文献