区域中尺度模式云微物理参数化方案特征及其在中国的适用性

云微物理参数化方案在数值模式中起着重要的作用,是影响数值天气预报和气候预测准确性的最大因素。系统回顾了中尺度数值模式中云微物理参数化方案的研究进展,并统计分析了最近十余年云微物理参数化方案在中国范围内的敏感性试验研究成果。Lin方案和Rutledge-Hobbs方案奠定了中尺度模式中云微物理参数化方案的基础,其他方案都是直接或间接在这2个方案的基础上从多方面改进而形成的。这些改进主要体现在:①水凝物粒子分类数目;②冰核活化;③粒子谱分布描述函数;④粒子谱截距的取值;⑤粒子间相互转换阈值大小的设定。中国范围内云微物理参数化方案敏感性试验研究成果统计表明,使用WRF模式中Lin方案的模拟效果较好,MM5模式采用Goddard和Reisner方案效果较好。     

Anatomy of a closing window: Vulnerability to changing seasonality in Interior Alaska

Alaska is among the fastest warming places on Earth, and the Interior region is warming the most statewide. Significant regional-scale ecosystem services disruptions are affecting Alaska Natives’ subsistence hunting and harvest success. The well-being of rural native communities is still highly dependent on access and ability to harvest wild foods such as salmon and moose (Alces alces gigas) among many others. Over the last decade communities in the Koyukuk-Middle Yukon (KMY) region of Interior Alaska report an inability to satisfy their needs for harvesting moose before the hunting season closes, citing warmer falls, changing precipitation and water levels, and the regulatory framework as primary causes. Through the integration of ethnographic methods to record indigenous observations and understanding of climate (IC) with analysis of meteorological data, we provide a comprehensive picture of vulnerability to recent warming trends in the Koyukuk-Middle Yukon region of Interior Alaska, one that captures more than statistical analysis of “norms” can provide. We will demonstrate how low exposure resulting in a small shift in seasonality has truly socially significant effects to people “on the ground” when community sensitivity is high because of the convergence of multiple social-ecological stressors. In this case, a seemingly small climatic exposure when combined with high social-ecological system sensitivity results in vulnerability to this climate change-related seasonality shift because of: (a) the effects on moose and the social-ecological dynamics of the system, and (b) the importance of this time of the year to meeting annual subsistence needs.     

Transient analysis for fluid injection into a dome reservoir

A dome-shaped layer can be selected as a storage site for fluid injection. In this study, we develop a mathematical model for simulating transient head distribution in a heterogeneous and anisotropic dome-shaped layer due to a constant-head injection in a fully penetrating well. In the model, a form of step change is adopted to approximate the upper and lower boundaries of the dome and then the layer is split into two regions. The Laplace-domain solution of the model is developed using the Laplace transform and method of separation of variables. The transient injection rate at wellbore can then be obtained based on Darcy’s law and Bromwich integral method. The predicted head contours from the head solution show significant vertical flow components near the location of step change in the dome reservoir. The results of sensitivity analysis indicate that the hydraulic conductivity is the most sensitive parameter and the specific storage is the least sensitive one to the injection rate after a short period of injection time. In addition, the injection rate for a dome reservoir is also very sensitive to the change of the height for the reservoir near the injection well (first region) at a very early injection time. In contrast, the injection rate is more sensitive to the change of the height of the second region than that of the first region at late time. This analytical solution may be used as a primary tool to assess the capacity of fluid injection to various dome reservoirs.     

Geospatial scenario based modelling of urban and agricultural intrusions in Ramsar wetland Deepor Beel in Northeast India using a multi-layer perceptron neural network

In recent decades, the world has experienced unprecedented urban growth which endangers the green environment in and around urban areas. In this work, an artificial neural network (ANN) based model is developed to predict future impacts of urban and agricultural expansion on the uplands of Deepor Beel, a Ramsar wetland in the city area of Guwahati, Assam, India, by 2025 and 2035 respectively. Simulations were carried out for three different transition rates as determined from the changes during 2001–2011, namely simple extrapolation, Markov Chain (MC), and system dynamic (SD) modelling, using projected population growth, which were further investigated based on three different zoning policies. The first zoning policy employed no restriction while the second conversion restriction zoning policy restricted urban-agricultural expansion in the Guwahati Municipal Development Authority (GMDA) proposed green belt, extending to a third zoning policy providing wetland restoration in the proposed green belt. The prediction maps were found to be greatly influenced by the transition rates and the allowed transitions from one class to another within each sub-model. The model outputs were compared with GMDA land demand as proposed for 2025 whereby the land demand as produced by MC was found to best match the projected demand. Regarding the conservation of Deepor Beel, the Landscape Development Intensity (LDI) Index revealed that wetland restoration zoning policies may reduce the impact of urban growth on a local scale, but none of the zoning policies was found to minimize the impact on a broader base. The results from this study may assist the planning and reviewing of land use allocation within Guwahati city to secure ecological sustainability of the wetlands.     

横向各向同性地层中随钻声波测井模式波分析

针对横向各向同性地层随钻声波测井模型,通过模式分析的方法,考察了快速地层和慢速地层井孔内随钻单极子、偶极子和四极子声源激发的斯通利波、弯曲波和螺旋波的相速度频散和激发强度特征,计算了这些模式波对于地层弹性常数的灵敏度,并与电缆测井中的情况进行了比较.结果表明:随钻斯通利波在低频时对地层弹性常数中c₆₆的灵敏度较电缆测井中有了很大提高,可用于反演地层水平向横波速度;随钻偶极子最低阶弯曲波在低频时不能用于直接获取地层横波信息,但在慢速地层中频率较高(例如6 kHz)时却可以间接得到地层垂直向横波速度;随钻四极子螺旋波的特征与电缆测井中的类似,可用于获取地层垂直向横波速度.     

Stochastic strong ground motion simulations in sparsely-monitored regions: A validation and sensitivity study on the 13 March 1992 Erzincan (Turkey) earthquake

Stochastic simulations have recently become quite popular for estimating synthetic ground motion time histories. For seismically active regions that are not well-monitored or studied extensively, input parameters of the simulations should be carefully selected as the reliability of the simulation results directly depends on the accuracy of the input parameters. In the first part of this study, 13 March 1992 Erzincan (eastern Turkey) earthquake (Mw=6.6), which is recorded at only three strong ground motion stations, is simulated using the stochastic finite-fault method. The source and regional path parameters for this event are adopted from previously validated studies whereas the local site parameters are derived herein. In the second part of the paper, sensitivity of the simulation results with respect to small changes in selected input seismic parameters is investigated. The parameters for which sensitivities are computed include stress drop, crustal shear-wave quality factor and kappa operator. A change of 20% in stress drop value results in 14% change in PGA, whereas a 20% difference in the Q₀ value causes 17% change in PGA, and a 20% variation in kappa leads to 15% difference in PGA. Numerical experiments presented in this study prove that the ground motion simulations are prone to trade-off between the source, path and site filters. Hence, input models must be implemented carefully for reliable synthetic ground motions.     

Seasonal variation of upper layer circulation in the northern part of the East/Japan Sea

Seasonal variation of upper layer circulation in the northern part of the East/Japan Sea and its mechanism were investigated using empirical orthogonal function (EOF) analysis with satellite sea surface heights over the northern East/Japan Sea and a three-dimensional circulation model. The spatial structure and temporal variation of first EOF mode, which explains about 64% of the total variance, indicate that a large cyclonic circulation in the northern East/Japan Sea shows a semi-annual variation with maximum strength in summer and winter. According to numerical model result, the Liman Cold Current, accepted as a major current in the northern East/Japan Sea, is well mixed vertically by the winter monsoon and the current in the upper layer has a relatively deep structure, with a maximum westward speed of about 20 cm/s in winter. On the other hand, in summer the current has a stronger baroclinic structure of velocity than in winter. Numerical experiments showed that in summer the temporal variation of upper layer circulation is controlled by thermal forcing, such as sea surface heat flux and inflow of heat transport into the East/Japan Sea through the Korea/Tsushima Strait. Moreover, the cyclonic circulation in the upper layer of the northern East/Japan Sea is also generated and strengthened by the positive wind stress curl occupying most of the East/Japan Sea during the winter. The seasonal variation of each forcing that drives the circulation is responsible for the strength or weakness of the upper layer circulation in the northern East/Japan Sea. The contribution of each forcing to the seasonal variation of the upper layer circulation is examined through sensitivity experiments. According to these numerical experiments, the upper layer circulation in the northern East/Japan Sea is strengthened twice a year, in winter and summer, and this semi-annual variation is determined by a combination of wind (winter) and thermal (summer) forcing.     

A comparison between manganese nodules and cobalt crust economics in a scenario of mutual exclusivity

The past 20 years have been characterised by limited interest in the economic viability of deep seabed mining with the exception of those mineral ores rich in precious metals such as polymetallic sulphides. This paper goes against the tide. After reviewing the most significant literature, it compares the economic feasibility of mining polymetallic manganese nodules and cobalt-rich ferromanganese crusts in a scenario of mutual exclusivity. It uses a new indicator, the cobalt-nickel price ratio, whose aim is to verify at what metal prices the net present value of the two mining projects equalises. Previous research has shown that the turning margin between manganese nodules and cobalt crusts is a cobalt price of $50/kg. The present paper revises this by showing that the choice between mining crust and nodules depends on fluctuations in the price of nickel. A Monte Carlo simulation proves that cobalt crust mining could be reasonably preferred to manganese nodules at cobalt prices of $40-60/kg if the price of nickel fell below $11/kg. Within this condition, investors would receive the minimum acceptable internal rate of return of 15%, which is at a level of risk closer to the land-based mining. However, when the price of nickel passes the $11/kg threshold, the equilibrium between the two ventures can be reached only at a cobalt price greater than $100/kg, causing cobalt crust to become uncompetitive. Finally, the paper, recognising that prices are not unique drivers, introduces legal, political, technological and environmental concerns to show that the final choice between the two mining ventures cannot be merely driven by economic issues.     

2.5维复电阻率反演及其应用试验

自复电阻率法被提出以来,其区分矿与非矿方面的潜力就引起了人们的广泛关注,但反演问题一直没有得到较好的解决,已经严重影响和制约了该方法的应用和发展.对此,本文提出并实现了利用多个排列视电阻率和视相位数据的2.5维SIP联合反演方法.算法利用最小二乘原理构建了反演目标函数,为提高反演的稳定性,在反演方程中加入了Occam法的光滑模型约束.通过借助电场的偏导数形式,推导出了灵敏度矩阵的解析表达式,并应用互换定理对其进行精确求取.反演算法充分利用了电磁感应和激电效应中的异常信息,能够同时反演出二维地质断面上所有单元的四种复电阻率参数.最后,利用该反演程序对安徽某地区的SIP实测数据进行了反演成像,通过与已知钻井资料及CSAMT反演结果的对比分析表明,该反演算法具有良好的应用效果.