灵敏度在土结构性定量化研究中的应用

根据近年来土结构性定量化研究中的新进展,定义了土在变形过程中的两种灵敏度——应力灵敏度和应变灵敏度。以西安黄土为研究对象,分别制备不同深度的原状和重塑饱和试样进行固结试验,得到规律性相对比较稳定的两种灵敏度。对两种灵敏度曲线的形态及其对应的土在变形过程中的结构性的变化进行了分析,初步认为无论从求取的方便性还是规律的稳定性来说,应变灵敏度具有更大的优越性。     

Inverse modeling for seawater intrusion in coastal aquifers: Insights about parameter sensitivities,variances, correlations and estimation procedures derived from the Henry problem

Inverse modeling studies employing data collected from the classic Henry seawater intrusion problem give insight into several important aspects of inverse modeling of seawater intrusion problems and effective measurement strategies for estimation of parameters for seawater intrusion. Despite the simplicity of the Henry problem, it embodies the behavior of a typical seawater intrusion situation in a single aquifer. Data collected from the numerical problem solution are employed without added noise in order to focus on the aspects of inverse modeling strategies dictated by the physics of variable-density flow and solute transport during seawater intrusion. Covariances of model parameters that can be estimated are strongly dependent on the physics. The insights gained from this type of analysis may be directly applied to field problems in the presence of data errors, using standard inverse modeling approaches to deal with uncertainty in data.     

High resolution simulation of recent Arctic and Antarctic stratospheric chemical ozone loss compared to observations

Simulations of polar ozone losses were performed using the three-dimensional high-resolution (1^∘ × 1^∘) chemical transport model MIMOSA-CHIM. Three Arctic winters 1999–2000, 2001–2002, 2002–2003 and three Antarctic winters 2001, 2002, and 2003 were considered for the study. The cumulative ozone loss in the Arctic winter 2002–2003 reached around 35% at 475 K inside the vortex, as compared to more than 60% in 1999–2000. During 1999–2000, denitrification induces a maximum of about 23% extra ozone loss at 475 K as compared to 17% in 2002–2003. Unlike these two colder Arctic winters, the 2001–2002 Arctic was warmer and did not experience much ozone loss. Sensitivity tests showed that the chosen resolution of 1^∘ × 1^∘ provides a better evaluation of ozone loss at the edge of the polar vortex in high solar zenith angle conditions. The simulation results for ozone, ClO, HNO₃, N₂O, and NO _y for winters 1999–2000 and 2002–2003 were compared with measurements on board ER-2 and Geophysica aircraft respectively. Sensitivity tests showed that increasing heating rates calculated by the model by 50% and doubling the PSC (Polar Stratospheric Clouds) particle density (from 5 × 10⁻³ to 10⁻² cm⁻³) refines the agreement with in situ ozone, N₂O and NO _y levels. In this configuration, simulated ClO levels are increased and are in better agreement with observations in January but are overestimated by about 20% in March. The use of the Burkholder et al. (1990) Cl₂O₂ absorption cross-sections slightly increases further ClO levels especially in high solar zenith angle conditions. Comparisons of the modelled ozone values with ozonesonde measurement in the Antarctic winter 2003 and with Polar Ozone and Aerosol Measurement III (POAM III) measurements in the Antarctic winters 2001 and 2002, shows that the simulations underestimate the ozone loss rate at the end of the ozone destruction period. A slightly better agreement is obtained with the use of Burkholder et al. (1990) Cl₂O₂ absorption cross-sections.     

热带太平洋海温年际变化对海表风应力的响应及其敏感性试验

在GFDL海洋模式的基础上发展了一个高分辨率的太平洋环流模式,模式较好地模拟出太平洋上层海温的气候状态及其季节和年际变化的主要特征。用观测的1985～1995年海表风应力去强迫模式,清楚地模拟出相应的暖事件和冷事件。敏感性试验揭示,日界线附近持续的西风距平愈强,赤道中、东太平洋增暖愈大,其影响向东传播扩展,5个月左右可达太平洋东岸,传播速度与西风应力距平强度关系不大。     

江淮地区中尺度地形对一次梅雨锋暴雨的敏感性试验

利用美国俄克拉何马大学(University of Oklahoma)风暴分析预报中心研制的ARPS模式对1999后6月13～14日汀淮地区的特大暴雨进行了地形敏感性试验．分析结果表明：中尺度地形通过对动力场和水汽场的扰动对降水的落区和强度有重要影响．各个地形对降水的影响是不同的，同一个地形在不同时段对降水的影响也是不同的．地形和切变线的相对位置是造成这一影响的关键所在。     

The effect of the HO2+NO reaction rate constant on one-dimensional model calculations of stratospheric ozone perturbations

With the aid of a one-dimensional steady-state, stratospheric model we have calculated ozone changes coused by atmosphric injections of NO_x, N₂O and chlorofluoromethanes. Adopting the fast rate constant, for the reaction HO₂+NO»OH+NO₂ measured by Howard and Evenson, we calculate much smaller perturbations of the ozone layer by NO_x and N₂O additions than previously estimated, but about two times larger ozone reductions as a result of continued emissions of chlorofluoromethanes, CF₂Cl₂ and CFCl₃.The model results are sensitive to adopted values for the rate coefficients for the reactions HO₂+O₃»OH+2O₂ and OH+HO₂»H₂O+O₂ and the eddy diffusion profile near the tropopause. More accurate assessments of ozone perturbations require the development of photochemical models that incorporate meteorological processes in more than one dimension.     

Choice Modeler: A Web-based Spatial Multiple Criteria Evaluation Tool

This article presents a concept of a Web-based spatial multiple criteria evaluation tool for individual and group use called Choice Modeler (CM). CM was originally conceived as part of a larger Participatory Geographic Information System for Transportation project (PGIST; http://www.pgist.org ) aimed at developing and evaluating Internet-hosted capabilities to support participatory decision processes. CM is designed to be either a part of a larger information system such as PGIST or a standalone tool used for evaluation of decision variants. The decision support functions provided by CM aid in reducing the cognitive complexity of the decision space characterized by multiple decision options, evaluation criteria, and criterion weights. This is achieved by incorporating in CM the sensitivity analysis functions for the identification of criteria that do not influence the decision option ranking. Users can remove such criteria from further consideration and thus lessen the cognitive burden of evaluation, which may be essential in multi-stakeholder participatory decision processes. The additional capabilities of CM include a vote aggregation function to collate individual option rankings into a group ranking, and measures of agreement/disagreement to inform the participants about a group-derived desirability of specific decision options. The design of CM was implemented using Web-service architecture. In the article we describe the design of CM and discuss its advantages and limitations.     

The sensitivity of ECHAM4/ML to a double CO2 scenario for the Late Miocene and the comparison to terrestrial proxy data

For the Tortonian, Steppuhn et al. [Steppuhn, A., Micheels, A., Geiger, G., Mosbrugger, V., 2006. Reconstructing the Late Miocene climate and oceanic heat flux using the AGCM ECHAM4 coupled to a mixed-layer ocean model with adjusted flux correction. Palaeogeography, Palaeoclimatology, Palaeoecology, 238, 399–423] perform a model simulation which considers a generally lower palaeorography, a weaker ocean heat transport and an atmospheric CO₂ concentration of 353 ppm. The Tortonian simulation of Steppuhn et al. [Steppuhn, A., Micheels, A., Geiger, G., Mosbrugger, V., 2006. Reconstructing the Late Miocene climate and oceanic heat flux using the AGCM ECHAM4 coupled to a mixed-layer ocean model with adjusted flux correction. Palaeogeography, Palaeoclimatology, Palaeoecology, 238, 399–423] demonstrates some realistic trends: the high latitudes are warmer than today and the meridional temperature gradient is reduced. However, the Tortonian run also indicates some insufficiencies such as too cool mid-latitudes which can be due to an underestimated pCO₂ in the atmosphere. As a sensitivity study, we perform a further model experiment for which we additionally increase the atmospheric carbon dioxide (700 ppm). According to this CO₂ sensitivity experiment, we find a global warming and a globally more intense water cycle as compared to the previous Tortonian run. Particularly the high latitudes are warmer in the Tortonian CO₂ sensitivity run which leads to a lower amount of Arctic sea ice and a reduced equator-to-pole temperature difference. Our Tortonian CO₂ sensitivity study basically agrees with results from recent climate model experiments which consider an increase of CO₂ during the next century (e.g. [Cubasch, U., Meehl, G.A., Boer, G.J., Stouffer, R.J., Dix, M., Noda, A., Senior, C.A., Raper, S., Yap, K.S., 2001. Projections of Future Climate Change. In: Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, C.A. Johnson (eds.), Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, 525–582]) suggesting that the climatic response on a higher atmospheric CO₂ concentration is almost independent from the different settings of boundary conditions (Tortonian versus today). To validate the Tortonian model simulations, we perform a quantitative comparison with terrestrial proxy data. This comparison demonstrates that the Tortonian CO₂ sensitivity experiment tends to be more realistic than the previous Tortonian simulation by Steppuhn et al. [Steppuhn, A., Micheels, A., Geiger, G., Mosbrugger, V., 2006. Reconstructing the Late Miocene climate and oceanic heat flux using the AGCM ECHAM4 coupled to a mixed-layer ocean model with adjusted flux correction. Palaeogeography, Palaeoclimatology, Palaeoecology, 238, 399–423]. However, a high carbon dioxide concentration of 700 ppm is questionable for the Late Miocene, and it cannot explain shortcomings of our Tortonian run with ‘normal’ CO₂. In order to fully understand the Late Miocene climate, further model experiments should also consider the palaeovegetation.     

Are feldspar SAR protocols appropriate for post-IR IRSL dating?

Recently proposed post-infrared infrared stimulated luminescence (post-IR IRSL or pIR) dating protocols have largely overcome problems associated with anomalous fading and have become increasingly important for age determination of Quaternary sediments. Here, we investigate the suitability of the proposed post-IR IRSL protocols for accurate equivalent-dose estimation on K-feldspar extracts. Our research focuses on potential sensitivity changes between the natural signal and the first test dose signal in single-aliquot regenerative dose (SAR) procedures that are not detected and thus not corrected using test-dose responses.For these investigations, we employed the Single Aliquot Regeneration and Added dose (SARA) procedure, which combines equivalent-dose estimation with a dose recovery test. Results indicated that high-temperature preheats (>260 °C for 60 s) may induce a trapping sensitivity change in IRSL signals measured at low temperature (<100 °C). As this sensitivity change cannot be detected through test dose responses in the SAR protocol, it may result in an invalid equivalent-dose estimation. However, trapping sensitivity changes were not observed after low temperature preheats (<260 °C for 60 s), nor in pIR signals measured at elevated temperature (>100 °C) after a high temperature preheat. Our results indicate that the SAR protocol is appropriate for equivalent-dose determination using elevated-temperature pIR signals (e.g. pIR at 290 °C or multiple elevated temperature pIR at 250 °C). The SAR protocol may also be appropriate for equivalent-dose determination using low temperature pIR signals, provided that the combination of preheat and measurement temperature is carefully chosen to avoid the unwanted effects of sensitivity change during the first preheat.     

基于Born波路径的高斯束初至波波形反演

为了提高表层速度反演精度,本文提出了一种新的波形反演方法.该方法只利用初至波波形信息以减少波形反演对初始模型的依赖性,降低反演多解性与稳定性.由于只利用初至波波形信息,所以该方法利用高斯束计算格林函数和正演波场,以减少正演计算量.为了避免庞大核函数的存储,该方法基于Born波路径,利用矩阵分解算法实现方向与步长的累加计算.将此基于Born波路径的初至波波形反演方法应用于理论模型实验,并与声波方程全波形反演和初至波射线走时层析方法相对比,发现该方法的反演效果略低于全波形反演方法,但明显优于传统初至波射线走时层析方法,而计算效率却与射线走时层析相当.同时,相对于全波形反演,本文方法对初始模型的依赖性也有所降低.