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21.
Several recent studies have shown the significance of representing groundwater in land surface hydrologic simulations. However, optimal methods for model parameter calibration in order to realistically simulate baseflow and groundwater depth have received little attention. Most studies still use globally constant groundwater parameters due to the lack of available datasets for calibration. Moreover, when models are calibrated, various parameter combinations are found to exhibit equifinality in simulated total runoff due to model parameter interactions. In this study, a simple lumped groundwater model is incorporated into the Community Land Model (CLM), in which the water table is interactively coupled to soil moisture through the groundwater recharge fluxes. The coupled model (CLMGW) is successfully validated in Illinois using a 22-year (1984–2005) monthly observational dataset. Baseflow estimates from the digital recursive filter technique are used to calibrate the CLMGW parameters. The advantage obtained from incorporating baseflow calibration in addition to traditional calibration based on measured streamflow alone is demonstrated by a Monte Carlo-type simulation analysis. Using the optimal parameter sets identified from baseflow calibration, flow partitioning and water table depth simulations using CLMGW are improved, and the equifinality problem is alleviated. For other regions that lack observations of water table depth, the baseflow calibration approach can be used to enhance parameter estimation and constrain water table depth simulations. 相似文献
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利用NCAR的公用陆面模式CLM4.0(Community Land Model 4.0),以1961~2010年普林斯顿大学的大气驱动场资料作为大气强迫场,对西南地区陆面过程变化进行了非耦合模拟试验。分析结果表明:西南地区降水呈现明显的干湿季节特征,季风期降水量分布为东北—西南走向,以印度缅甸一带向东北方向递减;非季风期近似呈东西梯度,以两湖地区为中心向西递减。全年而言,西南地区约有16.7%的降水首先被冠层截留,到达地面后约有60.5%以渗透的形式进入土壤,另有约17.1%形成地表径流,还有少部分降水以直接蒸发的形式加湿低层大气。各水循环因子分布与降水分布密切相关,其中冠层截留、地表径流、冠层蒸发的季风期与非季风期特征差异不大,而地下排水和地表蒸发在非季风期均明显高于非季风期,渗透过程则相反。非季风期西南地区水循环的蒸发高、渗透小、地下排水量显著,这三个过程的共同作用,造成西南地区冬春季陆面水份显著流失,是引发西南春旱的可能原因之一。 相似文献
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Integrated hydrologic models characterize catchment responses by coupling the subsurface flow with land surface processes. One of the major areas of uncertainty in such models is the specification of the initial condition and its influence on subsequent simulations. A key challenge in model initialization is that it requires spatially distributed information on model states, groundwater levels and soil moisture, even when such data are not routinely available. Here, the impact of uncertainty in initial condition was explored across a 208 km2 catchment in Denmark using the ParFlow.CLM model. The initialization impact was assessed under two meteorological conditions (wet vs dry) using five depth to water table and soil moisture distributions obtained from various equilibrium states (thermal, root zone, discharge, saturated and unsaturated zone equilibrium) during the model spin‐up. Each of these equilibrium states correspond to varying computation times to achieve stability in a particular aspect of the system state. Results identified particular sensitivity in modelled recharge and stream flow to the different initializations, but reduced sensitivity in modelled energy fluxes. Analysis also suggests that to simulate a year that is wetter than the spin‐up period, an initialization based on discharge equilibrium is adequate to capture the direction and magnitude of surface water–groundwater exchanges. For a drier or hydrologically similar year to the spin‐up period, an initialization based on groundwater equilibrium is required. Variability of monthly subsurface storage changes and discharge bias at the scale of a hydrological event show that the initialization impacts do not diminish as the simulations progress, highlighting the importance of robust and accurate initialization in capturing surface water–groundwater dynamics. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
25.
梁晓晔 《测绘与空间地理信息》2012,(6):196-197
基于笔者多年从事Geoway应用的相关工作经验,以Geoway 3.5在数字线划图数据制作中的应用为研究对象,探讨了DLG数据制作流程和质量检查方法,相信对从事相关工作的同行能有所裨益。 相似文献
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SiQiong Luo BoLi Chen ShiHua Lyu XueWei Fang JingYuan Wang XianHong Meng LunYu Shang ShaoYing Wang Di Ma 《寒旱区科学》2018,10(1):80-94
The simulation of soil temperature on the Tibetan Plateau (TP) plays a dominant role in the performance of both global climate and numerical weather forecast models. To improve the simulation of soil temperature on the TP, the Johansen soil thermal conductivity parameterization scheme was introduced into Community Land Model 3.5 (CLM3.5) and Regional Climatic Model 4 (RegCM4). The improved CLM3.5 and RegCM4-CLM were utilized to conduct offline and regional simulation experiments on the TP. Comparison of the new and old schemes revealed that CLM3.5 provides high thermal conductivity parameters of mineral soil solid on the TP. The Johansen scheme is more practical for the TP than the soil thermal conductivity parameterization in CLM3.5. The simulation of soil temperature and liquid water content was improved in offline experiment. The improved parameterization scheme can also reduce the simulation error of soil temperature in winter throughout the entire TP. 相似文献
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Runoff and soil moisture are two key components of the global hydrologic cycle that should be validated at local to global scales in Earth System Models (ESMs) used for climate projection. We have evaluated the runoff and surface soil moisture output by the Community Climate System Model (CCSM) along with 8 other models from the Coupled Model Intercomparison Project (CMIP5) repository using satellite soil moisture observations and stream gauge corrected runoff products. A series of Community Land Model (CLM) runs forced by reanalysis and coupled model outputs was also performed to identify atmospheric drivers of biases and uncertainties in the CCSM. Results indicate that surface soil moisture simulations tend to be positively biased in high latitude areas by most selected CMIP5 models except CCSM, FGOALS, and BCC, which share similar land surface model code. With the exception of GISS, runoff simulations by all selected CMIP5 models were overestimated in mountain ranges and in most of the Arctic region. In general, positive biases in CCSM soil moisture and runoff due to precipitation input error were offset by negative biases induced by temperature input error. Excluding the impact from atmosphere modeling, the global mean of seasonal surface moisture oscillation was out of phase compared to observations in many years during 1985–2004. The CLM also underestimated runoff in the Amazon, central Africa, and south Asia, where soils all have high clay content. We hypothesize that lack of a macropore flow mechanism is partially responsible for this underestimation. However, runoff was overestimated in the areas covered by volcanic ash soils (i.e., Andisols), which might be associated with poor soil porosity representation in CLM. Our results indicate that CCSM predictability of hydrology could be improved by addressing the compensating errors associated with precipitation and temperature and updating the CLM soil representation. 相似文献
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Magdalena Szuman Christian Berndt Colin Jacobs Angus Best 《Marine Geophysical Researches》2006,27(3):167-180
This study uses three acoustic instruments (different in their operating frequencies, 13, 3.5, and 6–10 kHz, and deployment
type, hull-mounted, surface-towed and deep-towed) to investigate and characterize the acoustic response of seafloor NE of
Oman in a frequency-independent manner. High-resolution control was achieved by having selected areas of our acoustic transects
ground-truthed by sampling and/or sea-floor photography. On the regional scale, the greatest degree of change in backscatter
amplitude was correlated with major changes of seabed morphology and lithology. However, small-scale roughness had the biggest
effect on amplitude on the local scale, i.e. within each area of specific seafloor type. The study also shows that seafloor
reflection amplitude changes are far more easily detected by deep-towed instrument than by surface-towed or hull-mounted systems.
Whilst there are significant changes in bioturbation types and density along the transects, the suite of instruments deployed
was not able to pick up the effect of the bioturbation on acoustic signals. 相似文献
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大陆溢流玄武岩的地球化学特征及起源 总被引：9，自引：0，他引：9
快速上涌的大陆溢流玄武岩（CFB），与大陆裂开存在密切的成因关系。CBF总体岩石及地球化学成分均一，富集同位素及不相容元素，但一些样品含有明显的亏损成分，反映出普遍的地幔不均一性，来自上下地幔边界及软流圈的地幔柱提供了CFB所需的主要物质和能量来源，地壳混染作用对CBF的成分影响不大，而受俯冲带脱水流体以及热地幔柱自身与围岩发生的交代作用影响。交代岩石圈地幔对CBF产生重要影响，很好地解释了CFB所具备的微量元素和同位素特征。 相似文献
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作物生长与气候的互馈是当前气候变化研究的热点之一。陆面模型作为一项重要的研究工具,其模型框架、算法设计及参数化方案的不同会直接导致模拟结果的不确定性。为探究陆面模型DLM(dynamic land model)和CLM5(community land model)在作物生长及农田热通量模拟方面的差异及原因,评估2个模型在华北平原作物研究中的适用程度,论文开展了冬小麦—夏玉米轮作站点的模拟对比研究。结果显示,DLM的夏玉米叶面积指数和生态系统总初级生产力的模拟值更高,与观测值更为接近;CLM5模型则在冬小麦模拟中略优。DLM的潜热模拟值与观测值的相关性普遍更高,可能反映了DLM采用的彭曼公式、双叶策略比CLM5采用基于水势梯度质量守恒、大叶策略的潜热计算方法更具优势。对于产量,模型当前的估测能力并不理想。总的来说,在默认设定下,2个模型的模拟结果能基本反映研究区农田站点内夏玉米和冬小麦的生长规律,但与实测值存在一定偏差。模型在该区域的适用性可能需要通过添加农田管理措施、算法优化和参数本地化等方式进一步提高。 相似文献