2003年12月26日伊朗巴姆地震     

苏卫江  苏宗正 《山西地震》2004,(2):47-48

2003年12月26日伊朗巴姆发生Mw6．5地震，这次地震造成30000余人死亡。依据USGS及相关网站的有关资料，介绍了2003年全球因地震死亡的人数，伊朗巴姆市概况。叙述了伊朗巴姆地震的有关参数，余震及其分布，巴姆地区的历史地震活动，地震灾害、地震烈度与地震构造等。  相似文献   

Effect of clouds on the photodissociation of NO2: Observations and modelling     

Michiel van Weele  Peter G. Duynkerke 《Journal of Atmospheric Chemistry》1993,16(3):231-255

The role of clouds in photodissociation is examined by both modelling and observations. It is emphasized that the photodissociation rate is proportional to the actinic flux rather than to the irradiance. The actinic flux concerns the energy that is incident on a molecule, irrespective of the direction of incidence. The irradiance concerns the energy that is incident on a plane.As far as the modelling aspect is concerned, a multi-layer delta-Eddington model is used to calculate irradiances, actinic fluxes, and photodissociation rates of nitrogen dioxide J(NO₂) as a function of height in inhomogeneous atmospheres. For the considered wavelength interval [290–420 nm], Rayleigh scattering, ozone absorption, and Mie scattering and absorption by cloud drops and aerosols should be taken into account.Further, a three-layer model is used to calculate the actinic flux above and below a cloud, relative to the incident flux, in terms of cloud albedo, zenith angle, and the albedo of the underlying and overlying atmosphere. Cloud albedo is mainly determined by cloud optical thickness. An expression for the incloud actinic flux is given as a function of in-cloud optical thickness. The three-layer model seems to be a useful model for the estimation of photodissociation rates in dispersion models.It is stressed that both models in their present form cannot handle partial cloudiness.It is shown that if no clouds are present, the actinic flux depends primarily on solar zenith angle. Further, the incident flux at the top of the atmosphere diminishes downward into the atmosphere due to the increasing effect of scattering. Therefore, the actinic flux usually increases with height, although above clouds the actinic flux sometimes decreases with height due to a large contribution of the upward scattered light.For cloudy atmospheres, another important parameter with respect to the actinic flux is added: cloud optical thickness. Cloud optical thickness determines cloud albedo. It can be shown that incloud characteristics and cloud height are less important while describing the effect of a cloud on the actinic flux (outside the cloud). The in-cloud values of the actinic flux can exceed the values outside the cloud.Finally, using the photostationary state relationship, a comparison is performed between model results and ground-based measurements as well as in-cloud air craft measurements.  相似文献   

Morphological evolution of a barchan dune migrating past an offshore wind farm foundation     

Amelia J. Couldrey  Thomas Benson  Michiel A.F. Knaapen  Kerry V. Marten  Richard J.S. Whitehouse 《地球表面变化过程与地形》2020,45(12):2884-2896

As the number of manmade structures installed on the seafloor is increasing rapidly, we seek to understand the impact of these immobile obstacles on marine geomorphological processes, such as the evolution of bedforms. A 5.8 m diameter monopile foundation was installed at the case study offshore windfarm approximately 30 m ahead of an approaching barchan (crescent-shaped) dune. The impact of the monopile on the dune's evolution was analysed using six multibeam bathymetry surveys spanning 20 years. To substantiate this analysis, coupled three-dimensional numerical modelling of flows and sediment was conducted in which the scour inducing bed shear stresses were calculated from the modelled turbulent kinetic energy. Following the installation of the monopile, the mid-section of the dune accelerated and stretched in the direction of the wake of the monopile. Four years after the monopile's installation the rest of the dune had caught up, flattening out the slip face within half the dune's length downstream of the monopile. Due to the modified flow field, the dune was scoured deeply at the base of the monopile to a depth of 6.8 m (supported by the model results that predicted a scour depth exceeding 2 m over a period of just a few days). The surveyed volume of material scoured amounted to 8% of the total dune volume. Whilst the process of scouring occurs at a timescale of days to weeks, the dune migrated on average by 25 m/yr. The difference in the timescale of the two processes allowed the scouring to occur through the full thickness of the dune. The scoured dune profile recovered rapidly once the dune migrated downstream of the monopile. This article demonstrates how large geomorphological features can intercept and migrate past a monopile foundation without long-lasting impacts on the integrity of the feature or the foundation. © 2020 John Wiley & Sons, Ltd.  相似文献   

Engaging with “urban science”     

Ben Derudder  Michiel van Meeteren 《Urban geography》2019,40(4):555-564

In this Intervention we discuss possible engagements between an inherently diverse urban geography and an emergent “urban science” dealing with information technology-driven, quantitative analysis of urban data. Although initial responses from some quarters of the urban geography community have been dismissive, we highlight three ways in which urban geography could positively engage with urban science: (1) by exhibiting greater ownership of our discipline’s past and the legacy of spatial science; (2) by resisting equating post-positivism with anti-positivism; and (3) by recognizing that the inherent ability of urban science to address post-truth thinking can be a useful building block in a pluralist approach to urban geography. We contend that (a) urban geographers need to be open to the use of new urban science methods to interrogate the pressing issues of our time and (b) where appropriate, inject cautionary tales of the dangers of a naive positivism in an uncritical urban science.  相似文献   

Groundwater and Wells, 3rd Edition     

reviewed by E. Scott Bair 《Ground water》2009,47(5):619-619

  相似文献   

Global Sensitivity Analysis Techniques for Probabilistic Ground Water Modeling   总被引：2，自引：0，他引：2  

by Srikanta Mishra  Neil Deeds  Greg Ruskauff 《Ground water》2009,47(5):727-744

Global sensitivity analysis techniques are better suited for analyzing input-output relationships over the full range of parameter variations and model outcomes, as opposed to local sensitivity analysis carried out around a reference point. This article describes three such techniques: (1) stepwise rank regression analysis for building input-output models to identify key contributors to output variance, (2) mutual information (entropy) analysis for determining the strength of nonmonotonic patterns of input-output association, and (3) classification tree analysis for determining what variables or combinations are responsible for driving model output into extreme categories. These techniques are best applied in conjunction with Monte Carlo simulation-based probabilistic analyses. Two examples are presented to demonstrate the applicability of these methods. The usefulness of global sensitivity techniques is examined vis-a-vis local sensitivity analysis methods, and recommendations are provided for their applications in ground water modeling practice.  相似文献   

Ecohydrologic Process Modeling of Mountain Block Groundwater Recharge   总被引：1，自引：0，他引：1  

by Ian A. Magruder  William W. Woessner  Steve W. Running 《Ground water》2009,47(6):774-785

Regional mountain block recharge (MBR) is a key component of alluvial basin aquifer systems typical of the western United States. Yet neither water scientists nor resource managers have a commonly available and reasonably invoked quantitative method to constrain MBR rates. Recent advances in landscape-scale ecohydrologic process modeling offer the possibility that meteorological data and land surface physical and vegetative conditions can be used to generate estimates of MBR. A water balance was generated for a temperate 24,600-ha mountain watershed, elevation 1565 to 3207 m, using the ecosystem process model Biome-BGC (BioGeochemical Cycles) ( Running and Hunt 1993 ). Input data included remotely sensed landscape information and climate data generated with the Mountain Climate Simulator (MT-CLIM) ( Running et al. 1987 ). Estimated mean annual MBR flux into the crystalline bedrock terrain is 99,000 m³/d, or approximately 19% of annual precipitation for the 2003 water year. Controls on MBR predictions include evapotranspiration (radiation limited in wet years and moisture limited in dry years), soil properties, vegetative ecotones (significant at lower elevations), and snowmelt (dominant recharge process). The ecohydrologic model is also used to investigate how climatic and vegetative controls influence recharge dynamics within three elevation zones. The ecohydrologic model proves useful for investigating controls on recharge to mountain blocks as a function of climate and vegetation. Future efforts will need to investigate the uncertainty in the modeled water balance by incorporating an advanced understanding of mountain recharge processes, an ability to simulate those processes at varying scales, and independent approaches to calibrating MBR estimates.  相似文献   

Author'S Reply     

by Michael J. Ungs  Michael R. West  Bernard H. Kueper 《Ground water》2009,47(6):759-760

  相似文献   

On the Use and Error of Approximation in the Domenico (1987) Solution     

Comment by Anand Prakash 《Ground water》2009,47(6):758-759

  相似文献   

Use of Observations below Detection Limit for Model Calibration     

by Michael LeFrancois  and Eileen Poeter 《Ground water》2009,47(2):228-236

Censored (nondetect) values occur when chemical concentrations in water samples are near or below the level that can be measured by an analysis method. It is common to either delete or substitute values for nondetect observations for use in model calibration, but this practice can bias the estimated parameter values and the model predictions. A more realistic representation of the system is obtained from the calibration if we include such observations in a manner reflecting that we know only the value is below the detection limit. Consequently, we propose use of the censored-residual approach to including nondetect values as observations for calibration. In this approach, residuals are calculated as the detection limit minus the simulated value when the simulated value exceeds the detection limit, and the residual is assigned a value of zero when the simulated value is below the detection limit. The new censored-residual approach is particularly advantageous when calibrating transport models to low concentration data.  相似文献