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21.
To accurately evaluate ecological risks trigged by groundwater exploitation, it must be clarified the relationship between vegetation and groundwater. Based on remote sensing data sets MOD13Q1, groundwater table depth (WTD) and total dissolved solids (TDS), the relationship between groundwater and natural vegetation was analyzed statistically in the main plain areas of Qaidam Basin. The results indicate that natural vegetation is groundwater-dependent in areas where WTD is less than 5.5 m and TDS is less than 7.5 g/L. Aquatic vegetation, hygrophytic vegetation and hygrophytic saline-alkali tolerant vegetation are mainly distributed in areas with WTD <1.1 m. Salt-tolerant and mesophytic vegetation mainly occur in areas with WTD of 1.4-3.5 m, while the xerophytic vegetation isprimarily present in areas where WTD ranges from 1.4 m to 5.5 m. Natural vegetation does not necessarily depend on groundwater in areas with WTD >5.5 m. For natural vegetation, the most suitable water TDS is less than 1.5 g/L, the moderately suitable TDS is 1.5-5.0 g/L, the basically suitable TDS is 5.0-7.5 g/L, and the unsuitable TDS is more than 7.5 g/L. 相似文献
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大同地震序列的震源机制解 总被引:1,自引:2,他引:1
使用CDSN长周期地震波形记录,利用Helmberger(1968)的广义地震射线理论得到的线性反演地震矩张量的方法,对1989年10月18日-1991年3月25日发生在大同的4个Ms>5.0的地震进行了反演,计算了这些地震矩张量和断层面解。 相似文献
24.
EFFECTS OF THE ENVELOPE DEGREE OF OROGRAPHY ON THE SIMULATED CLIMATE PROPERTIES 总被引:4,自引:0,他引:4 下载免费PDF全文
A primitive equation model with a zonal domain and a p-σ incorporated vertical coordinate systemis used to study the effects of the envelope degree of orography on the simulated properties of bothwinter and summer climates.Results show that the orography with a larger envelope degree can im-prove the simulations to certain extent,especially in winter.It is found that the simulated propertiesof climate are mainly determined by the co-effects of the land-sea and the orographic distributions,and the envelope degree of orography has a secondary effect.However it should be taken properly inorder to improve simulations:otherwise,it would be harmful.Different envelope degrees of orogra-phy can be adopted in different areas. 相似文献
25.
Wenxiang ZHANG Shilun YANG Jun ZHU Shiliang GONG Pingxing DING 《国际泥沙研究》2007,22(3):199-207
This paper reports the results of continuous monitoring of turbidity, water depth, salinity (using an Optical Backscatter Sensor (OBS)), and current velocity (using a Current meter (SLC9-2)) in the South Passage of the Changjiang Estuary over a spring–neap period in February 2003 (dry season). The turbidity measured via OBS was closely correlated with the suspended sediment concentration (SSC), which was highly variable. Over the study period, the SSC in the middle layer ranged from 110 to 1400 mg/l. The minimum SSC occurred during a late ebb tide, and the maximum SSC occurred during a late flood tide. On average, the SSC was 1.5 times higher during flood tide than during ebb tide. Vertically within the water column, SSC increased downward, with the ratio of SSC measured near the bed to that measured at the surface ranging from 1.90 to 18.3. The temporal variability in SSC is jointly governed by tides and wind-induced waves, whereas the vertical variability in SSC is attributed to the effect of gravity and vertical water circulation. 相似文献
26.
本文应用卫星云图与数值模拟结果对2000年6月2日发生的一次影响江苏的江淮气旋暴雨过程进行研究分析,阐述了这次暴雨过程表现的MCS基本特征。分析表明:MCS的形成可以由几个中β尺度对流云或对流带开始,在特定的环境场中汇合成合并;在其发展过程中必须维持湿度平流,低层到中层有暖平流,骨强偏南风急流伸向形成区,同时在其东北方向有一支高空西风急流相耦合;低层的辐合、整层凝结潜热的释放、垂直运动的增强、高层的辐散引起的正反馈机制是MCS发展的动因。 相似文献
27.
研究了西昌发射场特殊地形及地形梯度对其暴雨天气的影响。对比分析表明:2004年6月23日暴雨过程属于低涡切变型暴雨,6月27日暴雨过程属于两高辐合型暴雨。利用MM5V3.7进行了多组地形敏感试验,结果表明:场区北侧山脉对场区降水量影响明显,西昌东侧山脉对西昌降水量影响明显。地形梯度分析表明,西昌地区所处的河谷地形和场区所处喇叭口小地形,有利于中小尺度气压扰动的发生、发展和暴雨的产生,当地形梯度减弱时,降水量相应减弱。 相似文献
28.
DANG Yamin CHENG Chuanlu CHEN Junyong ZHANG Peng 《地球空间信息科学学报》2007,10(2):79-84
Determining the geodetic height of Mount Qomolangma was one of the very important missions in the 2005 Qomolangma height survey. There were three GPS networks in the survey: regional GPS crustal deformation network, geodetic GPS control network, and GPS measurement on the mountain summit. Data collection and processing were introduced. The final data processing strategy and reasonable geodetic height were fairly determined based on careful data analysis. 相似文献
29.
Retrieval single-doppler radar wind with variational assimilation method-part i: objective selection of functional weighting factors 总被引:1,自引:0,他引:1
In variational problem, the selection of functional weighting factors (FWF) is one of the key points for discussing many relevant studies. To overcome arbitrariness and subjectivity of the empirical selecting methods used widely at present, this paper tries to put forward in optimal objective selecting method of FWF. The focus of the study is on the weighting factors optimal selection in the variation retrieval single-Doppler radar wind field with the simple adjoint models. Weighting factors in the meaning of minimal variance are calculated out with the matrix theory and the finite difference method of partial differential equation. Experiments show that the result is more objective comparing with the factors obtained with the empirical method. 相似文献
30.