Sobol’ sensitivity analysis of parameters in the common land model for simulation of water and energy fluxes

The water and energy transfer of land surface is complex due to its large spatial and temporal variability. The modeling and simulation is an important means to study land water and energy transfer, but most selection and analysis of model parameters are empirical and qualitative. This paper has proposed a method of quantitatively identifying the most influential parameters of Common Land Model through Sobol?? sensitivity analysis. Considering sensible heat flux as the model output, the first order and total sensitivity indices of 25 model input parameters are estimated using an improved Sobol?? method. The simulated results are resampled using a bootstrapping method and the corresponding sensitivity indices are calculated. Confidence intervals for the bootstrapping sensitivity indices are estimated by using a percentile method. The results show that the parameters phi0 and porsl are the most important parameters, followed by ref(2,1), tran(2,1) and bsw. Five out of 25 parameters need to have an accurate evaluation, while the other parameters are fixed to a certain value. The sensitivity indices of parameters phi0 and porsl are decreasing after precipitation, while the sensitivity indices of parameters tran(2, 1) and ref(2, 1) are increasing after precipitation.     

An approach for estimating sustainable yield of karst water in data sparse regions

This study presents an approach for transferring the qualitative analysis of groundwater sustainability for development to quantitative evaluation by an analogy of two similar regions. A concept of groundwater exploitation sustainability (GES), which is an evaluation index based on water supply capability, eco-geo-environment maintaining capability and the harmony between water and society, is put forward. The fuzzy analytic hierarchy process method is applied to calculate the GES for the Xiangshan and Dianchang karst groundwater sources in the Huaibei city, Anhui Province, China. The GES of the Xiangshan karst system was calculated to be 0.53 and represents medium exploitation sustainability, while that for the Dianchang is relatively high with a value of 0.70. These two karst systems are separate units but have similar hydrogeological conditions. The Dianchang area had limited groundwater observation data, while the Xiangshan area had long series of observation data, which enabled the computation of the sustainable yield. The sustainable yield of the Xiangshan karst area was used to calibrate the GES, and develop a linear equation between the GES and sustainable yield, which was used to calculate the sustainable yield of the Diangchang karst area as 40.4 million m³.     

The twentieth century contiguous US temperature changes indicated by daily data and higher statistical moments

The daily surface air temperature data are used to assess the climate changes of the contiguous United States during the period of 1901 to 2000. The assessment is made through the first four statistical moments of the daily maximum, minimum, and mean temperature anomalies, the linear trends of the moments, and the changes of the anomalies?? probability density functions. The results on the first moment, i.e., the mean, are compared with the existing ones in terms of intra-annual means and their linear trends. Our first moment results agree with known ones and demonstrate a decrease from the 1930s to the 1960s and an increase from the 1970s to 2000. The temperature fluctuation is the smallest in the 1960s among the decades from 1931 to 2000. The trends of the higher (second-, third- and fourth-order) moments of the mean, maximum, and minimum surface air temperatures are calculated for the periods 1901?C2000, 1910?C1945, 1946?C1975, and 1976?C2000. The results show a decreasing trend of the second- and third-order moments of all the temperatures. The fourth-order moments of the mean and maximum surface air temperatures have increasing trends, but that of the minimum surface air temperature has a decreasing trend. The seasonal histograms of the mean, maximum, and minimum surface air temperatures are calculated for the three periods 1910?C1945, 1946?C1975, and 1976?C2000 for the stations which have the largest trend of maximum daily surface air temperature. An obvious change has been identified in the probability density functions. Among the changes of statistical parameters, the ones for the minimum temperature are larger than those for the maximum and mean temperatures.     

地震作用下骆驼城土遗址的安全性评价

以甘肃高台地区国家级重点文物保护单位骆驼城土遗址为研究对象,对其依次采用实地勘察、室内土工试验、统计分析、数值模拟四种手段进行了研究。将可靠度理论引入有限元动力分析中,利用APDL语言编制程序,使用蒙特卡洛法进行一千次的抽样数值模拟后进行抗震概率性分析。从而实现了土遗址抗震安全性评价的一种新方法和手段。计算结果对于骆驼城土遗址抗震防护及加固具有重要的参考价值,同时也为类似土遗址的防灾减灾工作提供一定依据。     

Tide-induced vertical suspended sediment concentration profiles: phase lag and amplitude attenuation

In tidal environments, the response of suspended sediment concentration (SSC) to the current velocity is not instantaneous, the SSC lagging behind the velocity (phase lag), and the amplitude of SSC variation decreasing with height above the bed (amplitude attenuation). In order to quantitatively describe this phenomenon, a one-dimensional vertical advection–diffusion equation of SSC is derived analytically for uniform unsteady tidal flow by defining a concentration boundary condition using a constant vertical eddy diffusivity and sediment settling velocity. The solution, in simple and straightforward terms, shows that the vertical phase lag increases linearly with the height above the bed, while the amplitude of the SSC variation decreases exponentially with the height. The relationship between the SSC and the normalized current velocity can be represented by an ellipse or a line, depending on the phase lag. The lag of sediment movement or “diffusion/settling lag” is the mechanism generating the phase lag effect. Field observations used for validation show that the theoretically predicted and the observed curves of the vertical SSC phase lag and amplitude attenuation show reasonable agreement. The procedure proposed in this paper substantially simplifies the modeling of suspended matter transport in tidal flows.     

CTL-713C型天气雷达发射机故障检修方法

通过分析CTL-713C型天气雷达发射机各组成部分工作原理,得出发射机工作信号流程示意图,提出了发射机故障诊断方法和原则,对发射机几种常见的故障现象及检修方法进行了分类,并通过实例分析对发射机故障诊断方法和原则进行了检验.     

Parameter estimation for a karst aquifer with unknown thickness using the genetic algorithm method

The combination of ecological fragility and agricultural activity in the loess hilly–gully regions of western China has received broad environmental concerns. In this region, rainfall and soil moisture can fatally influence crop production under dry land farming. In this study, field experiments were conducted, from March 2001 to September 2005, to demonstrate the variation of soil moisture and fertilizer contents at different depths in slope and terraced lands, and to evaluate the ecological impacts and economic benefits in the terraced land of Loess Plateau. The results of both field test and Grey model (GM) calculation show that the terraced land, as compared to the sloping land, in the agricultural area of the Loess Plateau tends to store and retain much water, promoting more favorable interactions between water and fertilizer. During the months from March to June of the year with less rainfall, the water supply for crop growth is mainly derived from the deep storage of soil moisture accumulated from July to September of the previous year. The field experiments indicate that the crop yield of the 3-year-old terraced lands was 27% higher than that of the sloping lands with slopes greater than 10°, and that the crop yield can increase by 27.07 to 52.78% in the following cultivation years. In particular, potato was found to be more drought-resistant than winter wheat, thus it is more suitable for the arid and semi-arid Loess Plateau regions.     

海洋沉积地质过程模拟:性质与问题及前景

探讨了海洋沉积地质数值模拟的功能问题.地球科学研究以正演方法(以数值模拟为代表)和反演方法(以地层记录分析为代表)的结合为特征.数值模拟作为一种重要的研究工具,具有获得过程和机理分析结果、形成工作假说、指导现场观测和采样的作用.与此同时,在正反演交融中模型本身也得到了提高和完善.在海洋沉积地质领域,数值模拟在沉积物输运...     

On the observed relationship between the Pacific Decadal Oscillation and the Atlantic Multi-decadal Oscillation

We studied the relationship between the dominant patterns of sea surface temperature (SST) variability in the North Pacific and the North Atlantic. The patterns are known as the Pacific Decadal Oscillation (PDO) and the Atlantic Multi-decadal Oscillation (AMO). In the analysis we used two different observational data sets for SST. Due to the high degree of serial correlation in the PDO and AMO time series, various tests were carried out to assess the significance of the correlations. The results demonstrated that the correlations are significant when the PDO leads the AMO by 1 year and when the AMO leads the PDO by 11–12 years. The possible physical processes involved are discussed, along with their potential implication for decadal prediction.     

Carbon and oxygen isotope chemostratigraphies of the Yangtze platform,South China: Decoding temperature and environmental changes through the Ediacaran

Multicellular animals first appeared on the earth during the Ediacaran period. However, the relationship between the abrupt biological evolution and environmental changes is still ambiguous. In order to examine seawater temperature and the carbon cycle through the Ediacaran, we analyzed the carbon and oxygen isotope compositions of carbonate rocks from drill cores from the Three Gorges area, South China. Importantly, the core samples include the Nantuo tillite, corresponding to the Marinoan glaciation, through the Doushantuo to the lower Dengying Fms. in ascending order.The δ¹³C profile displays five positive and five negative anomalies (PI-1 to 5 and NI-1 to 5), and the oxygen isotopes display very high absolute values around 0‰ with the highest at + 1.83‰. The combined δ¹⁸O and δ¹³C chemostratigraphies display both positive and negative correlations between the δ¹⁸O and δ¹³C values. The occurrence of the negative correlations supports the preservation of primary δ¹⁸O and δ¹³C values.The sample NI-4 has a negative correlation of the δ¹⁸O and δ¹³C excursions. The correlation supports a primary signature for both δ¹⁸O and δ¹³C variations. The positive δ¹⁸O excursion, accompanied by evidence of a eustatic sea-level fall, provides direct evidence for global cooling in the mid-Ediacaran; the 580 Ma Gaskiers Glaciation is a potential candidate for this global cooling event. The negative δ¹³C excursion was possibly caused by an increase in remineralization of dissolved organic carbon (DOC) due to enhanced continental weathering during the glaciation.Sample NI-5 is characterized by very low δ¹³C values, down to ? 10‰, corresponding to the Shuram-Wonoka-Pertatataka Excursion. The cause of the δ¹³C negative excursion is still not clear. However, a ubiquitous occurrence in excursions worldwide, and the lower δ¹³C values in deeper sections favor the enhancement of remineralization and respiration rather than secondary alteration, a restricted sea environment and lithification in coastal areas.