积雪季节变化特征的数值模拟及其敏感性试验   总被引：4，自引：0，他引：4  

陈海山  孙照渤 《气象学报》2004,62(3):269-284

文中利用综合陆面模式 (ComprehensiveLandSurfaceModel,CLSM )对法国ColdePorte 1 993/ 1 994 ,1 994 / 1 995年及BOREASSSA OJP 1 994 / 1 995年积雪个例进行了模拟试验 ,通过模拟结果与观测资料的对比 ,检验了CLSM对积雪变化特征的模拟能力 ,并通过敏感性试验探讨了降雪密度、积雪持水量等积雪参数化方案及植被对积雪模拟可能产生的影响。结果表明 :(1 )CLSM能够准确地模拟出积雪的变化过程 ,对积雪的演变特征作出了合理的描述 ;(2 )降雪密度、积雪持水量参数化方案对积雪模拟结果均具有一定的影响 :降雪密度参数化主要对积雪深度的模拟产生影响 ;而积雪持水量参数化方案对积雪的演变过程 ,尤其是积雪的消融 ,具有重要的作用 ;(3)有、无植被存在的情况下 ,积雪 土壤系统的变化过程存在显著的差别 ,植被通过改变积雪 /土壤表面的能量平衡 ,对积雪及土壤的变化过程产生重要影响 :植被的存在有利于积雪的维持 ,使得积雪融化进程推迟 ,冻结土壤的增温明显偏慢  相似文献   

岩石质量指标(RQD)的各向异性分析   总被引：9，自引：1，他引：9  

杜时贵  王思敬 《工程地质学报》1996,4(4):48-54

各向异性是工程岩体的重要工程特性, 岩石质量指标RQD具明显的各向异性。本文运用结构面网络模拟技术, 通过结构面间距、倾角、相对夹角以及结构面组数的敏感性分析, 探讨了RQD的各向异性规律。结合实际工程应用, 提出正确引用RQD指标的建议。  相似文献   

渗透率场敏感系数的数值计算   总被引：5，自引：1，他引：5       下载免费PDF全文

刘福平  杨长春 《地球物理学报》2003,46(1):131-137

由渗流微分方程定解问题，利用格林互易定理从理论上导出了渗透率场敏感系数 的计算公式，并借助于数值积分和差分方法给出了渗透率场敏感系数的离散形式. 由Peacem an方程建立了井压渗透率场敏感系数与网格压力渗透率场敏感系数的关系. 对理论模型利用 三维不均匀非稳定渗流场的压强数值解计算了井压对渗透率场的敏感系数，并用敏感系数的 直接计算方法进行了验证，结果表明本文的计算方法与直接计算方法相吻合.  相似文献   

Sensitivity analysis of a no-crossflow model for the transient flowmeter test     

Z. J. Kabala  H. K. El-Sayegh  H. P. Gavin 《Stochastic Environmental Research and Risk Assessment (SERRA)》2002,16(6):399-424

 Logarithmic sensitivities and plausible relative errors are studied in a simple no-crossflow model of a transient flowmeter test (TFMT). This model is identical to the model of a constant-rate pumping test conducted on a fully penetrating well with wellbore storage, surrounded by a thick skin zone, and situated in a homogeneous confined aquifer. The sensitivities of wellbore drawdown and wellface flowrate to aquifer and skin parameters are independent of the pumping rate. However, the plausible relative errors in the aquifer and skin parameters estimated from drawdown and wellface flowrate data can be proportionally decreased by increasing the pumping rate. The plausible relative errors vary by many orders of magnitude from the beginning of the TFMT. The practically important flowrate and drawdown measurements in this test, for which the plausible relative errors vary by less than one order of magnitude from the minimum plausible relative errors, can begin approximately when the dimensionless wellface flowrate exceeds q _D =q/Q≈0.4. During most of this stage of the test, the plausible relative errors in aquifer hydraulic conductivity (K _a ) are generally an order of magnitude smaller than those in aquifer specific storativity. The plausible relative errors in the skin hydraulic conductivity (K _s ) are generally larger than the plausible relative errors in the aquifer specific storativity when the thick skin is normal (K _s >K _a ) and smaller when the thick skin is damaged (K _s <K _a ). The specific storativity of the skin zone would be so biased that one should not even attempt to estimate it from the TFMT. We acknowledge Wiebe H. van der Molen for recommending the De Hoog algorithm and sharing his code. This research was partially supported by the US Geological Survey, USGS Agreement #1434-HQ-96-GR-02689 and North Carolina Water Resources Research Institute, WRRI Project #70165.  相似文献   

9000 years of chironomid assemblage dynamics in an Alpine lake: long-term trends, sensitivity to disturbance, and resilience of the fauna   总被引：2，自引：0，他引：2  

Oliver Heiri  André F. Lotter 《Journal of Paleolimnology》2003,30(3):273-289

Subfossil chironomid analysis was applied to a sediment core from Sägistalsee, a small lake at present-day tree-line elevation in the Swiss Alps. During the whole 9000-year stratigraphy the chironomid fauna was dominated by taxa typical of alpine lakes. Major faunistic trends were caused by changes in accumulation rates of three taxa, namely Procladius, Stictochironomus, and Tanytarsus lugens-type. In the early Holocene Procladius was the dominant taxon. In younger samples, Stictochironomus tended to have as high or higher abundances and both taxa showed an increase in accumulation rates. A possible cause of this succession is the decrease of lake-water depth due to infilling of the lake basin and changes in associated limnological parameters. The immigration of Picea (spruce) at ca. 6500 cal. ¹⁴C yrs BP and the resulting denser woodlands in the lake's catchment may have promoted this trend. During three phases, from ca. 70–1450, 1900–2350, and 3500–3950 cal. BP, remains of Procladius, Stictochironomus, and Tanytarsus lugens-type are absent from the lake sediment, whereas other typical lake taxa and stream chironomids show no change in accumulation rate. Together with sediment chemistry data, this suggests that increased oxygen deficits in the lake's bottom water during these intervals caused the elimination of chironomids living in the deepest part of the lake. All three periods coincide with increased human activity in the catchment, as deduced from palaeobotanical evidence. Therefore, enhanced nutrient loading of the lake due to the presence of humans and their livestock in the catchment is the most likely cause of the increased anoxia. The chironomid fauna reacted the same way to intensive pasturing during the last ca. 1500 years as to Bronze Age clear-cutting and more moderate pasturing during the Bronze, Iron, and Roman Ages, suggesting that alpine lake ecosystems can be extremely sensitive to human activity in the catchment. On the other hand, the chironomid assemblages show a considerable amount of resilience to human disturbance, as the chironomid fauna reverted to the pre-impact stage after the first two periods of human activity. In recent years, even though pasturing decreased again, the chironomid fauna has only partly recovered. This is possibly due to other human-induced changes in the lake ecosystem, e.g., the stocking of the lake with fish. The chironomid stratigraphy is difficult to interpret climatologically as the strongest changes in chironomid-inferred temperatures coincide with periods of intensive human activity in the catchment.  相似文献   

Numerical tools for geoscience computations: Semiautomatic differentiation—SD     

Abdulwahab A. Abokhodair 《Computational Geosciences》2007,11(4):283-296

This paper presents a differentiation method [referred to here as semiautomatic differentiation (SD)] based on generalization and extension of the Squire and Trapp formula for complex differentiation of real-valued functions. The performance of the generalized formulas for first-order derivatives is tested and compared with manual, automatic (AD), and finite difference (FD) techniques. My results show that, in terms of accuracy, the SD technique is competitive with AD, and in terms of implementation simplicity, it is identical to the FD method with the added advantage of being step-size insensitive and, hence, free from the step-size dilemma that plagues FD. Using central differencing in the complex plane, I extend the SD method to second-order derivatives, thus enabling approximation of the Hessians. Performance of the extension formulas is evaluated and compared with AD and FD methods. The results indicate that the differencing operation reduces the accuracy of the extension formulas by four to five orders of magnitude below that of the original Squire and Trapp formula. Nonetheless, compared to FD schemes, the SD method is six to seven orders of magnitude more accurate in all tests conducted. In addition, the extension formulas exhibit step-size (h) insensitive behavior over the entire h-range of the tests (1–10⁻³⁰), indicating high numerical stability of the schemes. I show by examples that SD provides a complete differentiation system that is computationally stable, efficient, highly accurate, and easy to implement.  相似文献   

几种鱼类培养细胞对不同干扰素敏感性的研究   总被引：5，自引：0，他引：5  

张义兵  王铁辉 《海洋湖沼通报》2000,(3):1-5

本文研究了四种鱼类培养细胞ＣＩＫ、ＣＡＢ、ＧＣＢ、ＢＲＥ对Ｈｕｉｆｎ－ａ,ＣＩＫ、ＣＡＢ、ＧＣＢ、ＧＲＥ、ＦＨＭ等五种鱼类培养细胞干扰素作用的敏感性。这四种鱼类培养细胞对ＨｕＩＦＮ－ａ不敏感,对五种鱼类培养细胞干扰素表现出相对一致的敏感性差异,其中ＧＲＥ细胞对鱼类干扰素最敏感,其次为ＣＡＢ、ＧＣＢ。ＣＩＫ细胞能产生高滴度的干扰素但对鱼类干扰素不敏感。不同病毒对干扰素作用的敏感性也不同。  相似文献   

孟加拉湾风暴Mala登陆期间地形敏感试验   总被引：1，自引：0，他引：1  

王曼  段旭  李华宏  刘建宇  符睿 《气象学报》2011,69(3):486-495

孟加拉湾是全球8个热带气旋易发生的地区之一。孟加拉湾风暴向偏北和偏东方向移动,会对中国青藏高原和西南地区形成重大影响,而孟加拉湾风暴的移动方向受到青藏高原和云贵高原大地形的影响很大。为了分析大地形对孟加拉湾风暴路径、结构变化和降水分布的作用和影响,文中利用WRF模式对2006年4月29—30日孟加拉湾风暴Mala的登陆过程进行数值模拟研究。试验结果表明:模拟风暴中心的路径和强度与实况虽有一定误差,但移动趋势均为东北方向,强度误差较小,表明WRF模式对本个例的模拟可以参考。通过不同地形高度敏感试验,分析风暴在登陆前后分别在全地形、半地形和零地形高度情况下的移动路径和速度、环流结构、动力结构以及在云南省产生的降水分布和强度。结果表明:风暴登陆前,大地形对风暴结构有间接影响,使高层出现倾斜。在风暴登陆过程中,地形的阻挡和摩擦作用能较明显影响风暴的移动路径和速度。风暴登陆后,地形抬升使风暴强度减弱,移动速度加快;结构由基本对称变为非对称,且斜压结构明显。地形对降水存在双重作用,一方面地形抬升使风暴产生的降水增加,另一方面地形摩擦使风暴强度减弱从而减少降水。  相似文献   

城区下垫面特征对成都地区一次暴雨过程影响的数值模拟   总被引：1，自引：0，他引：1  

谢娜  王咏青  施娟  倪萍 《高原气象》2011,30(6):1472-1480

利用NCEP/NCAR再分析资料对成都地区的一次区域性暴雨过程进行了诊断分析,并利用WRF模式对暴雨过程中城市下垫面的可能影响进行了敏感性试验。结果表明,WRF模式能较好地模拟出这次暴雨过程。改变城区下垫面特征后,与控制试验相比,敏感性试验的暴雨落区变化较小,强降雨中心面积有所增加,对四川盆地东部丘陵山区的温度增加影响...  相似文献   

浅层有限频率面波成像中的3D灵敏度核分析   总被引：1，自引：1，他引：0       下载免费PDF全文

鲁来玉  丁志峰  何正勤 《地球物理学报》2011,54(1):55-66

本文利用面波散射的模式耦合方法,基于波恩近似和远场假设,研究了有限频率面波三维灵敏度核,针对面波在工程应用中常遇到的水平分层的背景介质模型,计算了介质扰动引起的面波相位和幅度扰动的三维灵敏度核,分析了模式耦合对三维灵敏度核的影响.结果表明,仅考虑模式自身耦合的JWKB近似,介质密度和波速扰动引起的三维灵敏度核可以蜕化为...  相似文献