Modeling the impacts of drying trend scenarios on land systems in northern China using an integrated SD and CA model   总被引：4，自引：0，他引：4  

HUANG QingXu  HE ChunYang  LIU ZhiFeng & SHI PeiJun 《中国科学:地球科学(英文版)》2014,57(4):839-854

Climate-induced drought has exerted obvious impacts on land systems in northern China. Although recent reports by the Intergovernmental Panel on Climate Change (IPCC) have suggested a high possibility of climate-induced drought in northern China, the potential impacts of such drying trends on land systems are still unclear. Land use models are powerful tools for assessing the impacts of future climate change. In this study, we first developed a land use scenario dynamic model (iLUSD) by integrating system dynamics and cellular automata. Then, we designed three drying trend scenarios (reversed drying trend, gradual drying trend, and acceleration of drying trend) for the next 25 years based on the IPCC emission scenarios and considering regional climatic predictions in northern China. Finally, the impacts of drying trend scenarios on the land system were simulated and compared. An accuracy assessment with historic data covering 2000 to 2005 indicated that the developed model is competent and reliable for understanding complex changes in the land use system. The results showed that water resources varied from 441.64 to 330.71 billion m³ among different drying trend scenarios, suggesting that future drying trends will have a significant influence on water resource and socioeconomic development. Under the pressures of climate change, water scarcity, and socioeconomic development, the ecotone (i.e., transition zone between cropping area and nomadic area) in northern China will become increasingly vulnerable and hotspots for land-use change. Urban land and grassland would have the most prominent response to the drying trends. Urban land will expand around major metropolitan areas and the conflict between urban and cultivated land will become more severe. The results also show that previous ecological control measures adopted by the government in these areas will play an important role in rehabilitating the environment. In order to achieve a sustainable development in northern China, issues need to be addressed such as how to arrange land use structure and patterns rationally, and how to adapt to the pressures of climate change and socioeconomic development together.  相似文献   

离散选择模型研究进展   总被引：4，自引：2，他引：2  

王灿  王德  朱玮  宋姗 《地理科学进展》2015,34(10):1275-1287

本文从离散选择模型(discrete choice model, DCM)体系的一般原理和应用价值出发,总结了各经典模型的基本理论和典型应用,并概括了近来年一些重要的研究新动向。多项Logit模型(multinomial logit model, MNL)是离散选择模型体系的基础,具有简洁、可靠、易实现等优点,但也存在固有的理论缺陷,由此产生了对更加精细化模型的需求。替代的精细化模型中,嵌套Logit模型(nested logit model, NL)常用于处理备选项相关、“都不选”备选项、数据合并等问题,一般极值模型(generalized extreme value model, GEV)体系是其更一般的形式;混合Logit模型(mixed logit model, MXL)可用于解决随机偏好问题和多种相关问题,包括备选项相关、面版数据相关、随机系数相关、数据合并等,与之类似的潜在类别模型也有着广泛应用;多项Probit模型(multinomial probit model, MNP)具有极高的灵活性,但其复杂的模型设定与庞大的运算量大大制约了其应用范围。本文在研究新动向上介绍了4个重要的研究关注点：由多种经典模型形式相结合而成的复杂模型;面向RP/SP数据、定序、排序、多选等不同数据类型的适宜模型;基于各种受限理性选择策略的更为真实的模型;以及考虑选择的时空背景的模型。  相似文献   

The best catch data that can possibly be? Rejoinder to Ye et al. “FAO's statistic data and sustainability of fisheries and aquaculture”     

《Marine Policy》2017

Here we reply to a commentary by Ye et al. (Mar. Policy 2017; Ye et al.) on our article (Pauly and Zeller, 2017 [2]) commenting on FAO's interpretation of current fisheries trends in SOFIA 2016 (The State of World Fisheries and Aquaculture). We show how arguments such as FAO's catch statistics being “the best they can possibly be”, and other manifestations of FAO's difficulties in constructively engaging with comments compromises FAO's stated goal to engage with academia and civil society. This is particularly serious in an age where the value of an open scientific discourse is increasingly under threat, as is the food security of many poor countries in which fish supplied by domestic fisheries constitutes a strong component of local diets.  相似文献   

1961-2013年东北与华北气温变化速度空间差异     

赵建  任周鹏  王劲峰  徐成东  张前进 《地球信息科学学报》2017,19(7):909-914

全球气候的不断变化使得生物生境受到极大影响。气温作为最基本的气候要素,其变化迁移会胁迫生物对此做出响应,造成生物群落的迁徙。气温变化速度将气温看作物质的运动,能够直观地表示气温时空变化特征,对研究生物分布地理界限变化具有重要的指导意义。本文利用1961-2013年的全国每月平均温度数据集,分析了过去50多年中国东北与华北地区之间气温变化速度的区域差异。结果表明：东北与华北两地区整体气温变化速度均值为5.60 km/year,速度范围主要集中于0~9 km/year之间,约占总数的90%。东北地区气温变化速度均值大于华北地区。其中,东北速度均值为5.85 km/year,华北为5.41 km/year。从区域内部来看,东北地区气温变化速度整体较高,三省中黑龙江与吉林速度较高,辽宁省速度变化相对较小。华北气温变化速度高值区域主要分布在内蒙古高原与河北、天津的小部分地区,其他地区的气温变化速度则相对较小。  相似文献   

Evolution Characteristics and Development Trends of Sand Barriers     

NING Baoying  MA Jianxia  JIANG Zhide  CHEN Chun  ZHANG Xinli  LU Jingliang 《资源与生态学报(英文版)》2017,8(4):398-404

Sand barriers are one of the main measures used to prevent desertification and have been widely used in desertification control. Here, we use bibliometric methods and content analysis to summarize sand barrier type, applications and research. Existing problems in research are pointed out and revolution characteristics and development trends of sand barriers are discussed. We conclude that three main driving factors have stimulated sand barrier study: demand, technology and development concept. Developing environmentally friendly technology and promoting industrialization of sand area economies are future directions for sand barrier research.  相似文献   

Long-term variability in mesopause region temperatures over Fort Collins, Colorado (41°N, 105°W) based on lidar observations from 1990 through 2007     

Chiao-Yao She  David A. Krueger  Rashid Akmaev  Hauke Schmidt  Elsayed Talaat  Sam Yee 《Journal of Atmospheric and Solar》2009,71(14-15):1558-1564

During 1990–2007, there were 894 lidar observations of nocturnal mesopause region temperatures over Fort Collins, Colorado. In an earlier analysis with data to April 1997, an unexpected episodic warming, peaking in 1993 with a maximum value over 10 K, was reported and attributed to the Mount Pinatubo eruption in June 1991. With all data, long-term temperature trends from a 7-parameter linear regression analysis including solar cycle effect and long-term trends leads to a cooling of as much as 6.8 K/decade at 100 km, consistent with some reported observations but larger than model predictions. Including the observed episodic warming response in an 11-parameter nonlinear regression analysis reduces the maximum long-term cooling trends to 1.5 K/decade at 91 km, with magnitude and altitude dependences consistent with the prediction of two models, Spectral Mesosphere/Lower Thermosphere Model (SMLTM) and Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA). In addition, the mid-latitude middle-atmospheric response to solar flux variability in Thermosphere–Ionosphere-Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures is presented.  相似文献   

The effect of carbon dioxide cooling on trends in the F2-layer ionosphere     

Liying Qian  Alan G. Burns  Stanley C. Solomon  Raymond G. Roble 《Journal of Atmospheric and Solar》2009,71(14-15):1592-1601

The effect of carbon dioxide (CO₂) cooling on trends of h_mF₂ and N_mF₂ are investigated using a coupled thermosphere and ionosphere general circulation model. Model simulations indicate that CO₂ cooling not only causes contraction of the upper atmosphere and changes of neutral and ion composition but also changes dynamics and electrodynamics in the thermosphere/ionosphere. These changes determine the altitude dependence of ionospheric trends and complex latitudinal, longitudinal, diurnal, seasonal, and solar cycle variations of trends of h_mF₂ and N_mF₂. Under the CO₂ cooling effect, trends of N_mF₂ are negative with magnitude from 0% to −40% for doubled CO₂, depending on location, local time, season, and solar activity. The corresponding trends of h_mF₂ are mostly negative with a magnitude from 0 to −40 km, but can be positive with a magnitude from 0 to 10 km at night, with maximum positive trends occurring after midnight under solar minimum conditions.  相似文献   

1970—2009年伊金霍洛旗气象要素变化分析     

白利云  尤莉  周翠玲 《内蒙古气象》2011,(5):17-20

对伊金霍洛旗气象站1970—2009年气温、相对湿度、风向频率、风速、降水量、地面温度、日照时数逐月及年的观测资料进行了统计,分析了近40a7个要素的年际变化和突变特征,为气象站的迁站资料评估提供参考依据。结果显示,该站近40a平均气温和平均地面温度显著升高,平均风速明显减小,3个要素都有明显的突变特征。分析认为,这种变化特征除与区域气候变化的响应有关外,可能与该地城镇的发展及测站周边逐步出现较高建筑物的影响有关。  相似文献   

Using smoothers for comprehensive assessments of contaminant time series in marine biota   总被引：1，自引：1，他引：0  

Fryer  R. J.; Nicholson  M. D. 《ICES Journal of Marine Science》1999,56(5):779-790

  相似文献   

论地球系统四维成矿及矿床学研究趋向 ——七论矿床的成矿系列     

陈毓川  裴荣富  王登红  黄凡 《矿床地质》2020,39(5):745-753

矿床的成矿系列（简称“成矿系列”）概念是地球系统四维成矿的学术思想。成矿系列亦是矿床的一种新的分类——矿床自然分类。成矿系列概念的创新点：突出成矿在特定的时间域和特定的空间域（地质构造环境）,作为四维时空域整体进行成矿作用的成矿过程及其形成矿床的研究;厘定地球系统演化各个时空域中的成矿实体——矿床成矿系列,给每个矿床在地球演化的时空域中定位;开展各时空域成矿体之间的内在联系、组成的各层次成矿体系及地球成矿体系的研究;确定5类成矿作用（岩浆、变质、沉积、表生及非岩浆非变质含矿流体成矿作用）;建立成矿系列的5个序次,同时构成新的矿床自然分类体系。提出矿床学研究趋势与内容：深化矿床成因及其形成过程研究、地球系统四维时空域中区域成矿研究、急需战略性矿产研究、矿产预测、勘查与发展矿业的研究、配合找矿技术方法研发与应用。  相似文献