Patuxent Landscape Model: 4. Model application

Using the LHEM/SME the Patuxent Landscape Model (PLM) was built to simulate fundamental ecological processes in the watershed scale driven by temporal (nutrient loadings, climatic conditions) and spatial (land use patterns) forcings. The model addresses the effects of both the magnitude and spatial patterns of land use change and agricultural practices on hydrology, plant productivity, and nutrient cycling in the landscape.     

Patuxent landscape model: 1. Hydrological model development

We developed a spatially explicit, process-based model of the 2352 km² Patuxent river watershed in Maryland, and its subwatersheds to integrate data and knowledge over several spatial, temporal and complexity scales, and to serve as an aid to regional management. The model was developed using the Library of Hydro-Ecological Modules (LHEM, http://giee.uvm.edu/LHEM), which was designed to create flexible landscape model structures that can be easily modified and extended to suit the requirements of a variety of goals and case studies. The LHEM includes modules that simulate various aspects of ecosystem dynamics. In this paper we consider modules that represent the physical conditions in the environment (climatic factors, geoporphology), and hydrologic processes, both locally and spatially. Where possible the modules are formulated as Stella(R) models, spatial transport processes are presented as C++ code.     

Application of a land surface model for simulating rainfall streamflow hydrograph: 1. Model calibration

Different variants of parameters’ calibration of land surface model SWAP were examined with the aim to maximize the accuracy of reproducing rainfall runoff hydrograph. The optimization of parameter values was automated based on two different algorithms for the search of the global optimum of an objective function: a random search technique and a shuffled complex evolution method SCE-UA. In both cases, two objective functions, based on the mean systematic error and the Nash and Sutcliffe coefficient of efficiency, were used. The number of calibrated parameters varied from 10 to 15, and their values were within the reasonable range so as not to contradict the physical meaning and to ensure the best agreement between the simulated and observed daily river runoff. The streamflow hydrographs for some rivers in USA simulated with the use of different sets of optimized parameters were compared with observation data.     

Model calibration using hydropedological insights to improve the simulation of internal hydrological processes using SWAT+

Soils affect the distribution of hydrological processes by partitioning precipitation into different components of the water balance. Therefore, understanding soil-water dynamics at a catchment scale remains imperative to future water resource management. In this study, the value of hydropedological insights was examined to calibrate a processes-based model. Soil morphology was used as soft data to assist in the calibration of the Soil Water Assessment Tool (SWAT+) model at five different catchment scales (48, 56, 174, 674, and 2421 km²) in the Sabie River catchment, South Africa. The aim of this study was to calibrate the SWAT+ model to accurately simulate long-term monthly streamflow predictions as well as to reflect internal soil hydrological processes using a procedure focusing on hydropedology as a calibration tool in a multigauge system. Results indicated that calibration improved streamflow predictions where R² improved by 2%–8%. Nash-Sutcliffe Efficiency (NSE) improved from negative correlations to values exceeding 0.5 at four of the five catchment scales compared to the uncalibrated model. Results confirm that soil mapping units can be calibrated individually within SWAT+ to improve the representation of hydrological processes. Particularly, the spatial linkage between hydropedology and hydrological processes, which is captured within the soil map of the catchment, can be adequately reflected within the model simulations after calibration. This research will lead to an improved understanding of hydropedology as soft data to improve hydrological modelling accuracy.     

Directional borehole radar calibration

We are developing an innovative low-noise directional borehole radar system. Harsh and changing operating environments are a challenge to the low-noise sensitive electronic design. Additionally a system with such high sensitivity is susceptible to temperature changes and to component parameter variations. Therefore a calibration module was developed to calibrate the overall measurement system with a test signal generator. This calibration includes channel matching for accurate direction detection and sampling clock correction. After a brief introduction, testing and calibration methods are introduced. Additionally measurement results and figures depicting the practical results achieved thus far are included.     

标致性景观设计抗震避灾韧性评估模型分析

现有的抗震避灾韧性评估模型存在着评估精准性差、模型灵活性差的缺陷,为了解决上述问题,提出标致性景观设计抗震避灾韧性评估模型分析与研究。通过对现有模型的分析,对构建的抗震避灾韧性评估模型整体架构进行提出,以此为基础构建整体结构数值分析模型,并采用回归分析方法对非线性动力时程进行分析,得到标致性景观抗震避灾韧性评估指标-损伤指数,采用pushover分析方法对损伤分布系数进行计算,以得到的损伤分布系数为依据建立标致性景观性易损性曲面,由其推导出抗震避灾韧性指数公式,从而实现标致性景观设计抗震避灾韧性的评估。通过实验得到,与现有的抗震避灾韧性评估模型相比较,构建的抗震避灾韧性评估模型极大的提升了评估的精准性与模型的灵活性,充分说明构建的标致性景观设计抗震避灾韧性评估模型具备更好的评估性能。     

Accelerograph calibration and accelerogram correction

When measured earthquake accelerations are used as a basis for structural design, then acceleration errors of a few per cent are usually acceptable. However a number of tasks in structural design, and in earthquake engineering research, require measured accelerations with errors limited to a few parts per thousand. Such tasks include those which call for the calculation of angular accelerations, the comparison of acceleration spectra or the calculation of relative displacement Accurate accelerations may be obtained from existing accelerographs by applying the results of an accurate static calibration to an accelerogram, and then applying corrections for the effects of accelerometer resonance. This paper concentrates attention on the correction of static errors, including sensing direction errors and cross-axis interaction errors. For completeness there is a brief discussion of dynamic errors, which depend on accelerometer periods and dampings. It is concluded that earthquake accelerations may be obtained with errors of not much more than 0·001 g, the resolution of a typical accelerograph, at least for periods greater than 0·2 sec. When the accelerations have shorter periods, larger errors may arise due to the limited accuracy of the corrections for dynamic errors The static calibration of accelerographs, and the corresponding record correction procedures, are illustrated by application to the M.O.2 accelerograph.     

Deuterium tracing for the estimation of transpiration from trees Part 1. Field calibration

Flow rates calculated using the deuterium tracing method were compared with measurements of direct water uptake of excavated trees which had been inserted into water containers. Taking into account that the tracing method provides an estimate of the weighted mean flow rate over the period that the tracer pulse is present (the weighting factor is the relative concentration of the tracer as measured at the sampling point) agreement was obtained within the experimental error (about 10%) associated with the tracing method.     

Regional calibration of a watershed model

Abstract

As watershed models become increasingly sophisticated and useful, there is a need to extend their applicability to locations where they cannot be calibrated or validated. A new methodology for the regionalization of a watershed model is introduced and evaluated. The approach involves calibration of a watershed model to many sites in a region, concurrently. Previous research that has sought to relate the parameters of monthly water balance models to physical drainage basin characteristics in a region has met with limited success. Previous studies have taken the two-step approach: (a) estimation of watershed model parameters at each site, followed by (b) attempts to relate model parameters to drainage basin characteristics. Instead of treating these two steps as independent, both steps are implemented concurrently. All watershed models in a region are calibrated simultaneously, with the dual objective of reproducing the behaviour of observed monthly streamflows and, additionally, to obtain good relationships between watershed model parameters and basin characteristics. The approach is evaluated using 33 basins in the southeastern region of the United States by comparing simulations using the regional models for three catchments which were not used to develop the regional regression equations. Although the regional calibration approach led to nearly perfect regional relationships between watershed model parameters and basin characteristics, these “improved” regional relationships did not result in improvements in the ability to model streamflow at ungauged sites. This experiment reveals that improvements in regional relationships between watershed model parameters and basin characteristics will not necessarily lead to improvements in the ability to calibrate a watershed model at an ungauged site.     

形变标定格值计算软件

为提高地壳形变观测仪器格值标定的真实性、准确性和可靠性,根据《地震前兆台网运行管理办法》和《地震前兆台网形变观测与运行工作细则》,针对不同测项、不同仪器标定的规范要求及特点,应用Visual Basic语言编制了格值计算软件。本文主要介绍了软件的使用、格值计算、误差检查方法,结果以全国形变台网中心推荐的Word格式保存。对水管仪、水平摆、垂直摆仪直接从原始文件读取数据,提高了标定精度,实现了格值标定的半自动化。本软件已应用于河北省地震前兆数字化台站工作。     

New calibration of photo-electric nucleus counters

Summary A new calibration of the improved version of a photo-electric nucleus counter with a fog-tube of 3.85 cm air-column diameter and blotting-paper lining and of a photo-electric counter Model 1957 with air-column diameter of 2.5 cm and ceramic lining was carried out by adjusting the calibration curve of 1946 with reference to the considerably improved absolute (Aitken type) counter with stereophotomicrographic recording.The experimental arrangement for the calibration, the method of sampling, the nuclei used, the procedure of measuring, the evaluation of the measurements with the photo-electric and photographic counter are discussed and the effect of dampness of the graticule in the photographic counter and the influence of the ambient or initial temperature on the concentration measurements with both types of counters have been theoretically and experimentally investigated. On account of the considerable influence of the dampness of the graticule on the counting results we have used exclusively for this new calibration, measurements on a sufficiently damp graticule.The deduction of the new calibration tables consisting in the, adjustment of 7 fundamental points of the old calibration curve, is described. The agreement of the adjusted values for the two photoelectric counters with different air-column diameters and linings which refer to the same concentration, is very good; the maximum difference is less than 2%. Basic values of concentration curves for photo-electric counters with air-column diameter of 3.85 cm fitted with blotting-paper lining and of 2.5 cm diameter with ceramic lining. The new calibration is valid for an ambient temperature of 20°C.

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Zusammenfassung Es wurde eine Eichung des verbesserten photo-elektrischen Kernzählers mit einem Nebelrohr von 3.85 cm Durchmesser seiner Luftsäule und einem Futter aus Löschpapier und eines photo-elektrischen Kernzählers Modell 1957 mit einem Luftsäulendurchmesser von 2.5 cm und unglasiertem Tonfutter in der Weisedurchgeführt, dass die Eichkurve des Jahres 1946 mit Hilfe von Messungen des Beträchtlich verbesserten absoluten Kernzählers mit stereo-mikrophotographischer Registrierung adjustiert wurde.Die experimentelle Anordnung bei der Eichung, die Natur der zur Eichung verwendeten Kerne und ihre Stichprobenentnahme, die Methode der Messung mit dem photo-elektrischen und photographischen Kernzähler während der Eichung und die Auswertung der Messungen werden diskutiert. Es wurde ferner der Einfluss der Feuchtigkeit der Zählplatte im photographischen Kernzähler, und der Effekt der Anfangstemperatur oder der Temperatur der Umgebung auf die messungen der Konzentration mit beiden Typen von Kernzählern theoretisch und experimentell untersucht. Wegen des beträchtlichen Einflusses der Feuchtigkeit der Zählplatte auf die Resultate der Kernzählungen wurden für die neue Eichung ausschliesslich Messungen mit hinreichend feuchter Zählplatte benützt.Der bei der Ableitung der neuen Eichtabelle benützte Vorgang wird beschrieben. Er besteht in der Adjustierung von 7 Fundamentalpunkten der alten Eichkurve. Die Übereinstimmung der adjustierten Werte für die zwei photo-elektrischen Kernzähler mit verschiedenem Luftsäulendurchmesser und verschiedener Auskleidung, welche sich auf die gleiche Konzentration beziehen, ist sehr gut; die grösste Differenz ist kleiner als 2%.Grundwerte der Konzentration für 22 Extinktionen werden mitgeteilt, welche für die Konstruktion der neuen Eichkurven von photo-elektrischen Kernzählern mit einem Luftsäulendurchmesser von 3.85 cm und Fliesspapierauskleidung und von 2.5 cm Durchmesser und Tonfutter hinreichen.Die neue Eichung gilt für eine Temperatur der Umgebung der Kernzähler von 20°C.

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The research reported in this article has been sponsored and supported in part by the Geophysics Directorate of the Air Force Cambridge Research Center, Air Research and Development Command, United States Air Force, under Contract AF 61(052)-26, through the European Office, ARDC in Brussels.     

Radiocarbon calibration: The next generation

The discovery of the radiocarbon(14C)dating technique in the mid-twentieth century by Willard Libby and colleagues(Libby et al.,1949)revolutionised such fields as archaeology and palaeoclimatology that require robust chronological information to inform their study.Any sample yielding sufficient quantities of carbon could be dated in this manner,with the older age limit of the method(currently circa 50 to 60 thousand years ago)having been pushed back significantly since its inception.     

Simultaneous calibration of surface flow and baseflow simulations: a revisit of the SWAT model calibration framework

Accurate analysis of water flow pathways from rainfall to streams is critical for simulating water use, climate change impact, and contaminants transport. In this study, we developed a new scheme to simultaneously calibrate surface flow (SF) and baseflow (BF) simulations of soil and water assessment tool (SWAT) by combing evolutionary multi‐objective optimization (EMO) and BF separation techniques. The application of this scheme demonstrated pronounced trade‐off of SWAT's performance on SF and BF simulations. The simulated major water fluxes and storages variables (e.g. soil moisture, evapotranspiration, and groundwater) using the multiple parameters from EMO span wide ranges. Uncertainty analysis was conducted by Bayesian model averaging of the Pareto optimal solutions. The 90% confidence interval (CI) estimated using all streamflows substantially overestimate the uncertainty of low flows on BF days while underestimating the uncertainty of high flows on SF days. Despite using statistical criteria calculated based on streamflow for model selection, it is important to conduct diagnostic analysis of the agreement of SWAT behaviour and actual watershed dynamics. The new calibration technique can serve as a useful tool to explore the trade‐off between SF and BF simulations and provide candidates for further diagnostic assessment and model identification. Copyright © 2011 John Wiley & Sons, Ltd.