CLIMATOLOGY: THE CHALLENGE FOR THE EIGHTIES     

John R. Mather  Richard T. Field  Laurence S. Kalkstein  Cort J. Willmott 《The Professional geographer》1980,32(3):285-292

Geographical climatology must systematically investigate the exchanges of heat, water, and momentum that occur at or near the earth's surface. Our discipline should focus upon surface features described under the general term “topoclimatology”as well as upon transfer processes occurring in the planetary boundary layer. Climatologists must increase their understanding of the synergistic relationships among climatic processes, surface features, and human actions. Methods of data collection, summary, analysis, and display also need to be improved. These challenges must be met in order that we may develop a better understanding of climate and improve our quantitative climatic analogues.  相似文献   

Crystal fractionation in the friction melts of seismic faults (Alpine Fault, New Zealand)     

Laurence N. Warr  Ben A. van der Pluijm 《Tectonophysics》2005,402(1-4):111

Compositional variations are documented in friction melts along the Hari Hari section of the Alpine Fault, New Zealand, with multiple stages of melt injection into quartzo-feldspathic schists. Intermediate to felsic melts were heterogeneous in composition, but all fractions show a common trend, with a tendency for the younger melt layers and glasses to be more alkali − (Na + K) and Si-enriched, while being depleted in mafic (Fe + Mg + Mn) components. These changes are attributed primarily to crystal fractionation of the melt during transport. Farther traveled molten layers were on the whole less viscous, mostly due to a higher melt-to-clast ratio; however, compositional change, together with a decrease in volatile content, produced a progressively more viscous liquid melt with time. The glass phase is interpreted as a remnant of this high viscosity felsic residual melt that was preserved during final quenching. Following initial failure, the formation of largely phyllosilicate-derived, volatile-rich, lower viscosity melt corresponds with a phase of fault weakening. Subsequent rapid crystal fractionation during melt transport, the loss of volatiles and freezing of residual melt contributed to the strengthening of the fault during seismic slip.  相似文献   

Using GIS in Areawide Pest Management: A Case Study in South Dakota     

Amber A. Beckler  B. Wade French  Laurence D. Chandler 《Transactions in GIS》2005,9(2):109-127

Infestations of corn rootworms (Coleoptera: Chrysomelidae) create economic and environmental concerns in the Corn Belt region of the United States. To supplement the population control tactics of areawide pest management programs, we believe that a better understanding of the spatial relationships between biotic and abiotic or physical factors at the landscape scale is needed. Our research used several geographical information systems (GIS) and spatial analytical techniques to examine relationships between corn rootworm metapopulation dynamics, soil texture, and elevation. Within GIS, several spatially explicit procedures were used that include an interpolation technique, spatial autocorrelation analysis, and contingency analysis. Corn rootworm metapopulation distributions were found to be aggregated and related to soil texture and elevation. We review techniques and discuss our preferences for using particular spatially explicit procedures. The information derived from the spatial analyses demonstrates how GIS can be used in areawide pest management to provide inputs for spatially explicit models to predict future pest populations and formulate more well‐informed pest management decisions. The techniques described in this paper could easily be extended to study the spatial dynamics between other pest populations in agricultural landscapes.  相似文献   

洞穴碳酸盐230Th-234U-238U测年初始钍校正的等时线研究     

蔡演军  Cheng Hai  安芷生  王先锋  Shen Chuan-Chou 《地球科学进展》2005,20(4):414-420

初始钍的校正是不纯沉积碳酸盐230Th 234U 238U测年的一个重要方面，洞穴石笋初始Th校正通常采用230Th/232Th的原子比值为（4.4±2.2）×10-6。多年来4种不同的等时线方法应用到不纯碳酸盐测年初始Th的校正中，其中全样品的等时线方法是目前公认的较为完善的一种方法。通过测定云南同一石笋2个不同层位的9个样品的U、Th同位素组成,并进行等时线分析，结果表明2层样品初始钍230Th/232Th原子比值分别为（3.5±2.8）×10-6和（10.6±2.2）×10-6，这说明即使在同一地区，由于其混入Th来源的复杂性，230Th/232Th初始比值在同一样品不同层位仍可能有较大的差异，因此不能够完全采用单一层位等时线获得的初始值对整个样品进行校正。考虑到在实验测量过程中，232Th含量的过高对于230Th的准确测定也有很大的影响，应尽量选择纯净石笋样品进行测年研究，在样品的选择和前处理过程中就减少初始钍的影响，这对获得高精度的测年结果有着重要的意义。  相似文献   

REFLECTIONS ON WATER RESOURCES RESEARCH     

Laurence L. Quill 《Ground water》1963,1(2):2-48

"Fortunately, this nation is well endowed with water. We get enough precipitation every year to cover the whole country with water 30 inches deep."  相似文献   

Projected 21st-century changes to Arctic marine access   总被引：1，自引：0，他引：1  

Scott R. Stephenson  Laurence C. Smith  Lawson W. Brigham  John A. Agnew 《Climatic change》2013,118(3-4):885-899

Climate models project continued Arctic sea ice reductions with nearly ice-free summer conditions by the mid-21st century. However, how such reductions will realistically enable marine access is not well understood, especially considering a range of climatic scenarios and ship types. We present 21st century projections of technical shipping accessibility for circumpolar and national scales, the international high seas, and three potential navigation routes. Projections of marine access are based on monthly and daily CCSM4 sea ice concentration and thickness simulations for 2011–2030, 2046–2065, and 2080–2099 under 4.5, 6.0, and 8.5 W/m² radiative forcing scenarios. Results suggest substantial areas of the Arctic will become newly accessible to Polar Class 3, Polar Class 6, and open-water vessels, rising from ~54 %, 36 %, and 23 %, respectively of the circumpolar International Maritime Organization Guidelines Boundary area in the late 20th century to ~95 %, 78 %, and 49 %, respectively by the late 21st century. Of the five Arctic Ocean coastal states, Russia experiences the greatest percentage access increases to its exclusive economic zone, followed by Greenland/Denmark, Norway, Canada and the U.S. Along the Northern Sea Route, July-October navigation season length averages ~120, 113, and 103 days for PC3, PC6, and OW vessels, respectively by late-century, with shorter seasons but substantial increases along the Northwest Passage and Trans-Polar Route. While Arctic navigation depends on other factors besides sea ice including economics, infrastructure, bathymetry, and weather, these projections are useful for strategic planning by governments, regulatory agencies, and the global maritime industry to assess spatial and temporal ranges of potential Arctic marine operations in the coming decades.  相似文献   

Temperature and precipitation responses to El Niño-Southern Oscillation in a hierarchy of datasets with different levels of observational constraints     

Garcia-Villada  Laurence P.  Donat  Markus G.  Angélil  Oliver  Taschetto  Andréa S. 《Climate Dynamics》2020,55(9-10):2351-2376

Climate Dynamics - El Niño-Southern Oscillation (ENSO) is the dominant mode of climate variability, affecting climate conditions over large areas of the globe. There are, however, substantial...  相似文献   

PAH transport by sinking particles in the open Mediterranean Sea: a 1 year sediment trap study   总被引：1，自引：0，他引：1  

Bouloubassi I  Méjanelle L  Pete R  Fillaux J  Lorre A  Point V 《Marine pollution bulletin》2006,52(5):560-571

One year time series of sinking particles were collected at two depths in the open Mediterranean Sea and analysed for polycyclic aromatic hydrocarbons (PAH). Average total PAH concentrations were 593+/-284 ng g(-1) at 250 m and 551 +/- 198 ng g(-1) at 2850 m. Total PAH fluxes averaged 73 +/- 58 ng m(-2) d(-1) at 250 m and 53 +/- 39 ng m(-2) d(-1) at 2850 m. Contamination levels and, thus, exposure of marine organisms to PAH are comparable in surface and deep waters. Deep waters appear as a significant, yet overlooked, PAH sink. PAH temporal patterns show noticeable seasonality. This is partly due to varying levels of specific components such as the winter increase of pyrolytic PAH. Downward transport processes and the nature of sinking particles also impact on PAH fluxes, as inferred during periods of increasing productivity. Different phase-associations and interactions with particulate organic carbon for low-MW fossil PAH and high-MW pyrolytic PAH influence their downward transport efficiency.  相似文献   

中国自下而上城市化的发展及其机制   总被引：177，自引：8，他引：169  

崔功豪  马润潮 《地理学报》1999,54(2):106-115

改革开放以来的实践证明,中国确定存在着二元城市化模式,而农村城市化在中国整个城市化过程中已经和正在起着重要作用。作者在肯定了小城镇为主休的农村城市化的作用下,从城市化启动力的角度指出,这各发生在农村地域,由地方政府和农民群体力量推动的城市化是一种自下而上的城市化过程,具有明显的中国特色。文章并由此分析了自下而上城市化的发展阶段探讨了其在国家方针政策指导影响的政府、农民、外部力量共同作用下的运行机制  相似文献   

Comparison of stress-dependent geophysical,hydraulic and mechanical properties of synthetic and natural sandstones for reservoir characterization and monitoring studies     

Ismael Himar Falcon-Suarez  Kelvin Amalokwu  Jordi Delgado-Martin  Ben Callow  Katleen Robert  Laurence North  Sourav K. Sahoo  Angus I. Best 《Geophysical Prospecting》2019,67(4):784-803

Synthetic rock samples can offer advantages over natural rock samples when used for laboratory rock physical properties studies, provided their success as natural analogues is well understood. The ability of synthetic rocks to mimic the natural stress dependency of elastic wave, electrical and fluid transport properties is of primary interest. Hence, we compare a consistent set of laboratory multi-physics measurements obtained on four quartz sandstone samples (porosity range 20–25%) comprising two synthetic and two natural (Berea and Corvio) samples, the latter used extensively as standards in rock physics research. We measured simultaneously ultrasonic (P- and S-wave) velocity and attenuation, electrical resistivity, permeability and axial and radial strains over a wide range of differential pressure (confining stress 15–50 MPa; pore pressure 5–10 MPa) on the four brine saturated samples. Despite some obvious physical discrepancies caused by the synthetic manufacturing process, such as silica cementation and anisotropy, the results show only small differences in stress dependency between the synthetic and natural sandstones for all measured parameters. Stress dependency analysis of the dry samples using an isotropic effective medium model of spheroidal pores and penny-shaped cracks, together with a granular cohesion model, provide evidence of crack closure mechanisms in the natural sandstones, seen to a much lesser extent in the synthetic sandstones. The smaller grain size, greater cement content, and cementation under oedometric conditions particularly affect the fluid transport properties of the synthetic sandstones, resulting in lower permeability and higher electrical resistivity for a similar porosity. The effective stress coefficients, determined for each parameter, are in agreement with data reported in the literature. Our results for the particular synthetic materials that were tested suggest that synthetic sandstones can serve as good proxies for natural sandstones for studies of elastic and mechanical properties, but should be used with care for transport properties studies.  相似文献