Inter-Regional Comparisons on the Quaternary Large Mammalian Faunas between China and Sub-Saharan Africa

The current and dominant theory about the origin of modern humans is the out-of-Africa hypothesis, which asserts that populations of Homo sapiens left Africa 100,000 years ago and replaced indigenous populations of humans in Eurasia. Many scholars equated the out-of-Africa dispersal of humans with paleoenvironmental changes. However, until now, few have paid special attention to the faunal data and whether or not faunal patterns are supportive of the popular theory. Recent comparative study of the Chinese fauna shows that the communication of faunas between Africa and East Asia could have occurred during the Neogene, but it was very limited during the Pleistocene. In the Chinese Quaternary fauna, only 16% of the genera are also present in the sub-Saharan African fauna. There is also no element among the dominant taxa of the Chinese Quaternary fauna which can be related to the African fauna. There is no reliable proof for the existence of Hippopotamus and Giraffa, as well as Panthera leo, during the Quaternary in China. Two controversial taxa are Acinonyx and Crocuta, about which there is still argument concerning their species identification in Eurasia. It is possible that both of the genera have co-specific taxa in Africa and Eurasia. Although the two genera are confined to Africa today, they did have a long evolutionary history in China. For the Out of Africa hypothesis for Homo sapiens, the implications of the limited faunal interchanges between China and Africa are not completely clear yet.     

Body mass and water economy in the South American olivaceous field mouse along a latitudinal gradient: Implications for climate change

We compared geographic trends in body mass in a number of populations of the olivaceous field mouse (Abrothrix olivaceus,) along a latitudinal gradient in Chile, and tested the expected neutral tendency resulting from the opposite influences of environmental temperature and aridity across the gradient. Also, we studied water economy through physiological measurements of total evaporative water loss and urine osmolality in individuals from populations inhabiting two contrasting habitats (northern semiarid shrubland and southern temperate rainforest) and acclimated during six months to the same conditions. No change in male body mass with latitude was found across 39 populations. Evaporative water loss in rodents from the semiarid shrubland was significantly lower than that of individuals from the temperate rainforest, and urine osmolality was significantly higher in rodents from the semiarid habitat. We found a better tolerance of water shortage in the rodent population from the xeric habitat, thus suggesting the occurrence of local adaptation to the prevailing habitat conditions. The mechanisms by which rodents regulate their water economy in face of spatial and temporal fluctuations in environmental conditions constitute an essential component of the physiological flexibility that is necessary to cope with challenging climate change scenarios.     

Comparisons: colonial or cosmopolitan?

Editors' Note: The following is the ninth in the Singapore Journal of Tropical Geography Lecture Series. It is based on the plenary presentation of 3 September at the Annual Conference of the Royal Geography Society (with the Institute of British Geographers) held in London in 2010. In the search for a more international approach to theorizing cities, comparative methods hold considerable promise, although one concern might be that in their theoretical ambitions they foster a universalising approach rather than one appreciative of diverse and sometimes divergent urban experiences. The potentially universalizing ambitions of comparative methods lead some postcolonial theorists to question the extent to which comparativism carries the marks of colonial histories. Critics argue that some aspects of formal comparative methods can be traced to ambitious and geographically encompassing intellectual projects from the colonial era, when the interest and capacity to bring different parts of the world together within the same intellectual frame advanced significantly. This paper explores the complexities of these colonial lineages of comparative research with a view to assessing their implications for postcolonial comparative urbanism. It concludes by assessing the potential for more modest comparative experiments in a postcolonial vein through attending to the diverse vernacular cosmopolitanisms of cities. Following the spatialities of cities themselves has the potential to offer non‐universalizing but variously internationalizing theoretical engagements with different places.     

太平洋副热带高压及南亚高压在NCEP/NCAR和ECMWF再分析资料中的对比研究

利用NCEP/NCAR和ECMWF 1961～2000年北半球逐月平均的500 hPa和100 hPa高度场再分析资料对影响我国天气、气候的重要系统--北半球西太平洋副热带高压以及南亚高压做了对比研究,发现两者在不同的再分析资料中虽然具有一定的相似性,但也存在着明显的区别.在1980年以前两者存在较大差异.NCEP/NCAR再分析资料分析出的副高明显偏弱,而其所反映的副高的变化在幅度和强度上均大于ECMWF再分析资料的结果.进一步分析发现,NCEP/NCAR再分析资料所得出的副高的年代际变化可能是不真实的.在1969年、1979～1991年间,NCEP/NCAR再分析资料中的南亚高压中心强度明显比ECMWF的强,特别是1992～1995年间,NCEP/NCAR再分析资料中的南亚高压中心强度更强且中心范围更大.此外,NCEP/NCAR再分析资料所反映的南亚高压的变化在幅度和强度上也都大于ECMWF再分析资料的结果.     

中国大陆及邻近海域航磁——大地构造解释及分区

地表地质研究及中国航磁异常表明中国航磁大地构造具以下3种类型:沉积盖层区(深浅层结果反映正常构造层序)、构造盖层区(地表及浅层为外来推覆山系,与深部构成异常构造层序)和航磁异常地质历史时期各期沉积-构造事件叠加的记录。按郯庐断裂两侧华北、扬子地台区航磁-构造异常带的可比性,郯庐断裂总位移可达500km.中国大陆及邻近海域航磁-大地构造分区为:Ⅰ光蒙区、Ⅱ华北区、Ⅲ哈萨克斯坦区、Ⅳ塔里木区、Ⅴ青藏高原区、Ⅵ扬子区、Ⅶ华夏——台湾区。     

A comparison of multiscale methods for elliptic problems in porous media flow

We review and perform comparison studies for three recent multiscale methods for solving elliptic problems in porous media flow; the multiscale mixed finite-element method, the numerical subgrid upscaling method, and the multiscale finite-volume method. These methods are based on a hierarchical strategy, where the global flow equations are solved on a coarsened mesh only. However, for each method, the discrete formulation of the partial differential equations on the coarse mesh is designed in a particular fashion to account for the impact of heterogeneous subgrid structures of the porous medium. The three multiscale methods produce solutions that are mass conservative on the underlying fine mesh. The methods may therefore be viewed as efficient, approximate fine-scale solvers, i.e., as an inexpensive alternative to solving the elliptic problem on the fine mesh. In addition, the methods may be utilized as an alternative to upscaling, as they generate mass-conservative solutions on the coarse mesh. We therefore choose to also compare the multiscale methods with a state-of-the-art upscaling method – the adaptive local–global upscaling method, which may be viewed as a multiscale method when coupled with a mass-conservative downscaling procedure. We investigate the properties of all four methods through a series of numerical experiments designed to reveal differences with regard to accuracy and robustness. The numerical experiments reveal particular problems with some of the methods, and these will be discussed in detail along with possible solutions. Next, we comment on implementational aspects and perform a simple analysis and comparison of the computational costs associated with each of the methods. Finally, we apply the three multiscale methods to a dynamic two-phase flow case and demonstrate that high efficiency and accurate results can be obtained when the subgrid computations are made part of a preprocessing step and not updated, or updated infrequently, throughout the simulation. The research is funded by the Research Council of Norway under grant nos. 152732 and 158908.     

Homo erectus pekinensis''''s age and environment——with discussion on the relationship among Homo erectus from Beijing,Nanjing and Chenjiawo

This paper inspects the relationship between Homo erectus from Beijing, Nanjing and Chenjiawo on the viewpoint of environmental variations. Pieces of evidence show that Nanjing and Chenjiawo Homo erectus lived in glacial age at the Marine Oxygen Isotope Stage (MIS) 16, while Homo erectus pekinensis in major interglacial age at MISs 15-13. It is also recovered that the cave deposits in Tangshan, Nanjing, and Zhoukoudian, Beijing, as well as the deposits at the Homo erectus site in Chenjiawo, have undergone some similar development process. All of them originated from early-middle Middle Pleistocene, and have gone through the test of the major glacial age at MIS 16 and the major interglacial period at the paleosol stage S5. At the same time, they were also closely connected with some environment events, such as the uplift of the Qinghai-Xizang Plateau, the formation of glaciations and the loess accumulations.     

Using Vertical Aerial Photography to Estimate Mass Balance at a Point

The mass balance distribution over a 0.5 km² area of the lower part of South Cascade Glacier is obtained from remotely sensed measurements of its geometry and velocity field over two periods, 1992–93 and 1993–94. Vertical aerial photography from late summer 1992, 1993, and 1994 is analyzed photogrammetrically to get surface topography of South Cascade Glacier on a 100-meter square grid. The known bed topography is subtracted from the surface topography to get the ice thickness, and the surface topographies are subtracted from each other to get the thickness change. Annual displacement vectors, determined at points where natural features could be tracked from one year to the next, are contoured by hand and interpolated to the grid. Assuming that the ice follows Glen's flow law with exponent n = 3, and that 10% of the ice flow is due to sliding at the bed, the surface velocity is scaled by 0.82 to get the average velocity in the vertical ice column. The average velocities are combined with the thicknesses to calculate the flux divergence at each of 46 gridpoints on a 100-m square grid, where it is subtracted from the thickness change to get the mass balance.
Use of the same control points from year to year makes any systematic error in photogrammetric coordinates temporally constant, so such error has no effect on the mass balance estimate. Random error in coordinates is assumed to be uncorrelated from coordinate to coordinate, from point to point, from year to year; the standard error is estimated to be 1 m, resulting in a standard error in coordinate differences of about 1.5 m. A 1 m error in a vertical coordinate has nearly twice the effect on the estimated balance that one in a horizontal coordinate has and more than ten times the effect that one in ice thickness has. Compared with measurements at a stake, the estimated balances are about 1 m too negative.     

Mass Balance of the Greenland Ice Sheet: Can Modern Observation Methods Reduce the Uncertainty?

The future contribution to sea level change from the large ice sheets in Greenland and Antarctica is composed of two terms: (i) a background trend determined by the past climate and dynamic history of the ice sheets on a range of time scales (decadal, millennial or even longer); and (ii) a rise/fall related to future climate change, whether due to anthropogenic effects or natural climate variability. The accelerating development of remote sensing techniques for monitoring ice sheet behaviour, and the use of high-resolution general circulation models to estimate temperature and precipitation changes are likely to result in improved estimates of the sensitivity of ice sheet mass balance to climate change and thereby to narrow down the uncertainty of contribution (ii). Contribution (i) is much more difficult to assess, because the mass balance displays large temporal variability on year-to-year and even on decadal time scales that masks the long-term trend. So, although modern remote sensing techniques enable accurate measurement of ice sheet surface elevation change, the mass changes derived from such measurements, even if performed over a period of several years, might just reflect a statistical fluctuation around the long-term background trend, which we must know in order to assess the future ice sheet contribution to sea level change on century and longer time scales. The measured volume changes must therefore be evaluated on the background of short- and long-term accumulation rates (e.g. determined from ice cores and high-resolution ice radar) and dynamic model studies of ice sheet evolution on century, millennial and longer time scales. The problems are illustrated by using the Greenland ice sheet as an example.