A Review of: “Pittsburgh and the Appalachians: Cultural and Natural Resources in a Postindustrial Age”     

《The Journal of geography》2012,111(1):37-38

Abstract

Geography is one of the subjects offered toward a diploma of the International Baccalaureate Organization. Like the others, its syllabus is regularly reviewed and revised to remain current. The advent of a revised syllabus brings overlap that can be challenging for teachers. The syllabus that is now coming to an end was described in 107(4–5) of the Journal of Geography. The present article compares that syllabus with the new one and, particularly, the demands the new syllabus will place on teachers and students alike.  相似文献   

Some Suggestions Concerning a Course of Study in Geography     

《The Journal of geography》2012,111(1):7-14

Abstract

Over the next decade or so, the National Assessment for Educational Progress in Geography and the Geographic Education Standards Project promise to give geography a new definition as a school subject. This will challenge the educational community to re-examine how geography is taught and learned across all the grade levels, K-12. If geography is to be perceived as an essential subject in preparing students for citizenship as adults, not only must its image change, but its content and the pedagogy that delivers it must be modified as well. To achieve those ends, new curricular models grounded in cogent and applicable research must develop through partnerships of teachers, teacher educators, learning theorists, and professional geographers.  相似文献   

Initiation and early development of barchan dunes: A case study of the Moroccan Atlantic Sahara desert   总被引：1，自引：0，他引：1  

Hicham Elbelrhiti 《Geomorphology》2012,138(1):181-188

This paper describes field measurements that document the formation of barchan dunes in the Moroccan Atlantic Sahara desert. The first mechanism described is the transformation of patches and proto-dunes at Cap Juby beach to barchan dunes of elementary size. This transformation is discussed in relation to the wind speed and saturation length. The second mechanism is the ejection of small barchans of elementary size by other small barchans in response to the perturbation of the target barchan by two other impacting small barchans. This remote initiation is discussed in relation to the bulk flux transported by the barchan dunes involved in this interaction and to their morphology. Other modes of barchan initiation observed in the field are also presented.  相似文献   

城市化水平增长曲线的类型、分段和研究方法   总被引：2，自引：0，他引：2  

陈彦光 《地理科学》2012,(1):12-17

城市化水平增长曲线可以分为S形和J形2大类别,其变化特征、动力学背景及研究方法也不尽相同。城市化曲线研究可以分为唯象分析和唯理分析2大途径,唯理研究包括城一乡人口异速生长、城一乡人口替代以及城乡人口迁移和转换3种路径,目前这些方法主要用于S形曲线研究,对J形曲线的探索不够深入。S形曲线是一种奇对称曲线,其模型导数却是一...  相似文献   

Models of Jupiter's growth incorporating thermal and hydrodynamic constraints     

Jack J. Lissauer  Olenka Hubickyj  Gennaro D'Angelo  Peter Bodenheimer 《Icarus》2009,199(2):338-350

We model the growth of Jupiter via core nucleated accretion, applying constraints from hydrodynamical processes that result from the disk-planet interaction. We compute the planet's internal structure using a well tested planetary formation code that is based upon a Henyey-type stellar evolution code. The planet's interactions with the protoplanetary disk are calculated using 3-D hydrodynamic simulations. Previous models of Jupiter's growth have taken the radius of the planet to be approximately one Hill sphere radius, RH. However, 3-D hydrodynamic simulations show that only gas within ∼0.25RH remains bound to the planet, with the more distant gas eventually participating in the shear flow of the protoplanetary disk. Therefore in our new simulations, the planet's outer boundary is placed at the location where gas has the thermal energy to reach the portion of the flow not bound to the planet. We find that the smaller radius increases the time required for planetary growth by ∼5%. Thermal pressure limits the rate at which a planet less than a few dozen times as massive as Earth can accumulate gas from the protoplanetary disk, whereas hydrodynamics regulates the growth rate for more massive planets. Within a moderately viscous disk, the accretion rate peaks when the planet's mass is about equal to the mass of Saturn. In a less viscous disk hydrodynamical limits to accretion are smaller, and the accretion rate peaks at lower mass. Observations suggest that the typical lifetime of massive disks around young stellar objects is ∼3 Myr. To account for the dissipation of such disks, we perform some of our simulations of Jupiter's growth within a disk whose surface gas density decreases on this timescale. In all of the cases that we simulate, the planet's effective radiating temperature rises to well above 1000 K soon after hydrodynamic limits begin to control the rate of gas accretion and the planet's distended envelope begins to contract. According to our simulations, proto-Jupiter's distended and thermally-supported envelope was too small to capture the planet's current retinue of irregular satellites as advocated by Pollack et al. [Pollack, J.B., Burns, J.A., Tauber, M.E., 1979. Icarus 37, 587-611].  相似文献   

涡动在南北半球平流层极涡崩溃过程中作用的比较   总被引：3，自引：1，他引：2  

魏科  陈文  黄荣辉 《大气科学》2008,32(2):206-219

比较了南北半球春季平流层极涡的崩溃过程以及涡动在此崩溃过程中的作用。极涡的崩溃时间以平流层极夜急流核区最后一次西风转换为东风的时间来确定。结果表明南北半球平流层极涡的崩溃过程有着共同的特点,涡动和非绝热加热过程都对极涡的崩溃起着重要的作用,在极涡崩溃前平流层行星尺度波动活动明显,极涡崩溃以后,这种波动活动便迅速减弱。其中从对流层上传的行星波决定着极涡的具体崩溃时间。两个半球的差别主要表现在南半球极涡崩溃过程一般始于平流层高层,然后逐渐下传,而北半球这种下传不是很明显。其次,北半球平流层极涡崩溃偏晚年,极涡的减弱有两次过程,第一次为快速变化过程,第二次变化比较缓慢,而南半球平流层极涡崩溃无论早晚年只有一次减弱过程。长期的变化趋势分析表明南北半球平流层极涡的崩溃时间逐渐推迟,特别是20世纪90年代中后期以来,这种推迟更加明显。进一步的研究还发现,伴随着平流层极涡的崩溃过程平流层和对流层存在强烈的动力耦合,南北半球极涡迅速减弱前,各自半球的环状模指数也由负指数增加为正指数,表明低层环流对于平流层极涡的崩溃起到重要的作用;同时极涡不同强度所对应的低层环状模指数也不同,这可能与不同强度平流层极涡对于上传的行星波的反射有关。  相似文献   

年际时间尺度上全球植被与大气相互作用的诊断分析     

李伟平  季劲钧  董文杰 《大气科学》2008,32(1):75-89

利用NOAA AVHRR得到的19年（1982～2000）全球月平均的叶面积指数（LAI）与ERA40近地面气温和CMAP降水进行时滞相关分析,并研究了LAI的年际变化对后期温度、降水的反馈作用。结果表明,大部分地区LAI与同期气温的相关性更好,30°N以北（以南）基本上为正（负）相关。LAI滞后一个月时,北半球中低纬度和20°S以南大部地区LAI与降水的正相关更强;而在北半球中纬度大陆东部和南半球热带地区,LAI与前一个月温度的关系更密切。LAI与温度的相关性在春、秋季最明显,LAI与降水的关系在雨季最密切。LAI对气温比较显著的正反馈主要分布在北半球中高纬度地区;20°S以南大部地区为比较显著的负反馈。LAI对降水比较显著的正反馈分散在北美大陆西北部、东欧平原南部、欧亚大陆东北部和热带沿海地区。中高纬度（尤其是北半球）大部分地区LAI 对气温、降水反馈部分的解释方差达到总方差的20%以上。  相似文献   

一个冰气相互作用数值模拟结果的可能统计解释     

刘喜迎  刘海龙  李薇  张学洪  俞永强 《气候与环境研究》2007,12(5):638-646

基于一个全球海-冰-气耦合模式的数值模拟结果,选取冬季格陵兰海海表面温度(SST)、海冰密集度、海表面感热通量等物理量以及3个相关区域海平面气压分别作经验正交函数展开,取第一模时间系数作相关分析。结果表明,上一年海冰密集度偏大(小)与来年的SST偏低(高)相联系,但二者同期相关性最大。当海气热通量交换变化超前一年时,其与SST相关性最大。模式最低层大气温度与海洋表面热通量之间的同时相关性最大,冬季模式最低层气温偏高(低)与海洋表面失去的感热、潜热通量偏少(多)相联系。气温、比湿都和冰岛低压区及格陵兰海的海平面气压相关性最强,冰岛低压气压偏低(高)与模式最低层气温和比湿偏高(低)相联系。所以,在海-冰-气年际尺度的相互作用中,主要关系是大气环流调整造成大气中云量和低层气温、湿度变化,进而影响海气界面上的通量交换,造成SST的变化。SST变化决定着海冰范围及海冰密集度的变化,但海冰变化时通过相变潜热的释放或吸收反过来对SST变化有较明显影响。  相似文献   

Sensitivity of the Carbon Storage of Potential Vegetation to Historical Climate Variability and CO_2 in Continental China     

毛嘉富  王斌  戴永久 《大气科学进展》2009,(1)

The interest in the national levels of the terrestrial carbon sink and its spatial and temporal variabil-ity with the climate and CO2 concentrations has been increasing.How the climate and the increasing atmospheric CO2 concentrations in the last century affect the carbon storage in continental China was in-vestigated in this study by using the Modified Sheffeld Dynamic Global Vegetation Model(M-SDGVM).The estimates of the M-SDGVM indicated that during the past 100 years a combination of increasing CO2 with...  相似文献   

下边界条件对北极涛动影响的数值模拟研究     

李艳  赵南  董敏 《气象学报》2009,67(3):388-396

利用NCAR大气模式CAM3.0探讨了包括山脉和海陆分布等下边界条件对北极涛动(AO)或北半球环状模(NAM)形成的影响.主要进行了控制试验和两个地形敏感性数值试验,对比了控制试验结果与资料分析结果.控制试验和NCEP/NCAR资料分析结果对比指出,CAM3.0模式能够较好地模拟出AO的水平环状结构和垂直相当正压结构.在去除山脉的敏感性试验中发现,AO中纬度北太平洋和北大西洋两个活动中心的强度、范围和位置发生变化.在水球敏感性试验中发现,AO两个大洋上的活动中心被环绕极地主活动中心的环状结构代替.两个敏感性试验共同表明,AO是大气内部某种过程作用的结果,它的存在本身不取决于下边界条件的改变.山脉和海陆分布主要影响的是AO的具体形态.通过控制试验和两个敏感性试验对比,又分析了准定常波和瞬变波对AO的影响.去除山脉和海陆分布热力差异共同强迫的准定常波,AO纬向平均纬向风高纬地区平流层异常最大值活动中心消失,这表明在平流层准定常波和纬向平均流的相互作用与AO活动关系密切.在只有对流层瞬变波作用时,AO仍然存在,表明准定常波不是AO存在的必要条件.平流层准定常波与平均流的相互作用和对流层瞬变波与平均流的相互作用与AO形成之间的具体关系有待通过E-P通量诊断进一步确定.  相似文献