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81.
Teaching GIS in Geography* 总被引:2,自引:0,他引:2
Although numerous courses in geographic information systems (GIS) have been introduced into the geography curriculum over the past few years, there has been remarkably little debate over the issues involved. This paper first discusses the arguments for geography as an appropriate disciplinary setting for GIS teaching at the undergraduate level. This is followed by a discussion of the nature of GIS courses and their appropriate place in the undergraduate geography curriculum. The final section of the paper describes the NCGIA Core Curriculum project and examines its significance in this broader context. 相似文献
82.
Philip A. Helmke Douglas P. Blanchard Larry A. Haskin Karen Telander Charles Weiss Jeffrey W. Jacobs 《Earth, Moon, and Planets》1973,8(1-2):129-148
The concentrations of major and trace elements have been determined in igneous rocks from Apollo 15. All materials analyzed have typical depletions of Eu except for minerals separated from sample 15085. Four samples have concentrations of trace elements that are similar to those of KREEP. The samples of mare basalt from Apollo 15 have higher concentrations of FeO, MgO, Mn, and Cr and lower concentrations of CaO, Na2O, K2O, and rare-earth elements (REE) as compared to the samples of mare basalt from Apollos 11, 12, and 14. The samples can be divided into two groups on the basis of their normative compositions. One group is quartz normative and has low concentrations of FeO while the other is olivine normative and has high concentrations of FeO. The trace element data indicate that the samples of olivine normative basalt could be from different portions of a single lava flow. At least two and possible three parent magmas can be identified from the samples of the quartz normative group on the basis of their concentration ratios of Sm to Eu. Within each group, the compositions of the samples appear to be related by crystallization of olivine or pyroxene. Significant variations of the ratio of concentration of Sm to Eu cannot be produced without plagioclase-liquid equilibrium. The source material of mare basalt may be depleted in Eu. Alternatively, the magmas may have assimilated a small volume of material similar to KREEP.Paper dedicated to Prof. Harold C. Urey on the occasion of his 80th birthday on 29 April 1973. 相似文献
83.
Quantifying Organization of Atmospheric Turbulent Eddy Motion Using Nonlinear Time Series Analysis 总被引:3,自引:0,他引:3
Using three methods from nonlinear dynamics, we contrast the level of organization inthe vertical wind velocity (w) time series collected in the atmospheric surface layer(ASL) and the canopy sublayer (CSL) for a wide range of atmospheric stability ()conditions. The nonlinear methods applied include a modified Shannon entropy, waveletthresholding, and mutual information content. Time series measurements collected overa pine forest, a hardwood forest, a grass-covered forest clearing, and a bare soil, desertsurface were used for this purpose. The results from applying all three nonlinear timeseries measures suggest that w in the CSL is more organized than that in the ASL, and that as the flows in both layers evolve from near-neutral to near-convective conditions, the level of organization increases. Furthermore, we found that the degree of organization in w associated with changes in is more significant than the transition from CSL to ASL. 相似文献
84.
New R-matrix calculations of electron impact excitation rates in Caxv are used to derive theoretical electron density diagnostic emission line intensity ratios involving 2s
22p
2–2s2p
3 transitions, specifically R
1=I(208.70 Å)/I(200.98 Å), R
2=I(181.91 Å)/I(200.98 Å), and R
3=I(215.38 Å)/I(200.98 Å), for a range of electron temperatures (T
e=106.4–106.8 K) and densities (N
e=109–1013 cm–3) appropriate to solar coronal plasmas. Electron densities deduced from the observed values of R
1, R
2, and R
3 for several solar flares, measured from spectra obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab, are found to be consistent. In addition, the derived electron densities are in excellent agreement with those determined from line ratios in Caxvi, which is formed at a similar electron temperature to Caxv. These results provide some experimental verification for the accuracy of the line ratio calculations, and hence the atomic data on which they are based. A set of eight theoretical Caxv line ratios involving 2s
22p
2–2s2p
3 transitions in the wavelength range 140–216 Å are also found to be in good agreement with those measured from spectra of the TEXT tokamak plasma, for which the electron temperature and density have been independently determined. This provides additional support for the accuracy of the theoretical line ratios and atomic data. 相似文献
85.
Robert E. NovakMichael J. Mumma Michael A. DiSanti Neil Dello Russo Karen Magee-Sauer 《Icarus》2002,158(1):14-23
We present absolute abundances and latitudinal variations of ozone and water in the atmosphere of Mars during its late northern spring (Ls=67.3°) shortly before aphelion. Long-slit maps of the a1Δg state of molecular oxygen (O2) and HDO, an isotopic form of water, were acquired on UT January 21.6 1997 using a high-resolution infrared spectrometer (CSHELL) at the NASA Infrared Telescope Facility. O2(a1Δg) is produced by ozone photolysis, and the ensuing dayglow emission at 1.27 μm is used as a tracer for ozone. Retrieved vertical column densities for ozone above ∼20 km ranged between 1.5 and 2.8 μm-atm at mid- to low latitudes (30°S-60°N) and decreased outside that region. A significant decrease in ozone density is seen near 30°N (close to the subsolar latitude of 23.5°N). The rotational temperatures retrieved from O2(a-X) emissions show a mean of 172±2.5 K, confirming that the sensed ozone lies in the middle atmosphere (∼24 km). The ν1 fundamental band of HDO near 3.67 μm was used as a proxy for H2O. The retrieved vertical column abundance of water varies from 3 precipitable microns (pr-μm) at ∼30°S to 24 pr-μm at ∼60°N. We compare these results with current photochemical models and with measurements obtained by other methods. 相似文献
86.
Toshifumi Yanagisawa Yasushi Muraki Yutaka Matsubara Fumio Abe Kimiaki Masuda Sachiyo Noda Takahiro Sumi Yuji Kato Mitsuaki Fujimoto Shuji Sato Ian Bond Nicholas Rattenbury Philip Yock Pam Kilmartin John Hearnshaw Micheal Reid Denis Sullivan Brian Carter Richard Dodd Garry Nankivell Noiman Rumsey Morihiro Honda Maki Sekiguchi Masanori Yoshizawa Takashi Nakamura Humitaka Sato Seiji Kabe Makoto Kobayashi Yoshiyuki Watase Jun Jugaku Toshiharu Saito Barbel Koribalsky 《Experimental Astronomy》2000,10(4):519-535
We have constructed a large, mosaic CCD camera called MOA-cam2 which has 4096 × 6144-pixelsto search for gravitational microlensing events. MOA-cam2 has three4096 × 2048-pixel SITe CCD chips, which have a very high quantum efficiency (nearly 80% in the wave region 500 to 800 nm),and three buttable sides. We have placed the threechips side by side with 100 m dead space. MOA-cam2 has been installed on the 61 cm Boller and Chivens telescope of the MOA collaboration at the Mt. John University Observatory (MJUO) in NewZealand since July 1998. The field coverage is 0.92° × 1.38° per exposure. The technical details of MOA-cam2 and the first images obtained with the Boller and Chivens telescope are presented. MOA-cam2 introduces a second phase of research on gravitational microlensing by the MOA collaboration. 相似文献
87.
Karen L. Aplin 《Surveys in Geophysics》2006,27(1):63-108
Atmospheric electrification is not a purely terrestrial phenomenon: all Solar System planetary atmospheres become slightly
electrified by cosmic ray ionisation. There is evidence for lightning on Jupiter, Saturn, Uranus and Neptune, and it is possible
on Mars, Venus and Titan. Controversy surrounds the role of atmospheric electricity in physical climate processes on Earth;
here, a comparative approach is employed to review the role of electrification in the atmospheres of other planets and their
moons. This paper reviews the theory, and, where available, measurements, of planetary atmospheric electricity which is taken
to include ion production and ion–aerosol interactions. The conditions necessary for a planetary atmospheric electric circuit
similar to Earth’s, and the likelihood of meeting these conditions in other planetary atmospheres, are briefly discussed.
Atmospheric electrification could be important throughout the solar system, particularly at the outer planets which receive
little solar radiation, increasing the relative significance of electrical forces. Nucleation onto atmospheric ions has been
predicted to affect the evolution and lifetime of haze layers on Titan, Neptune and Triton. Atmospheric electrical processes
on Titan, before the arrival of the Huygens probe, are summarised. For planets closer to Earth, heating from solar radiation
dominates atmospheric circulations. However, Mars may have a global circuit analogous to the terrestrial model, but based
on electrical discharges from dust storms. There is an increasing need for direct measurements of planetary atmospheric electrification,
in particular on Mars, to assess the risk for future unmanned and manned missions. Theoretical understanding could be increased
by cross-disciplinary work to modify and update models and parameterisations initially developed for a specific atmosphere,
to make them more broadly applicable to other planetary atmospheres. 相似文献
88.
A reanalysis of the relationship between strong westerlies and precipitation in the Great Plains and Midwest regions of North America 总被引:1,自引:0,他引:1
Robert K. Booth John E. Kutzbach Sara C. Hotchkiss Reid A. Bryson 《Climatic change》2006,76(3-4):427-441
A conceptual model relating expanded or strengthened mid-latitude summer westerlies with summer precipitation patterns has been used to explain past drought events in the Great Plains and Midwest of North America, including drought between 1200 and 1400 AD. However, this relationship was originally described using 20 years of instrumental data from the mid 20{th} century, and has not been verified with modern datasets. We reinvestigated the relationship between July westerlies and precipitation in the United States using instrumental records of the last 55 years. We also investigated whether changes in summer zonal flow patterns associated with precipitation anomalies represent a shift in the latitude of peak westerly winds or an increase in wind speed, or a combination of both.Finally, we briefly compare the pattern of precipitation anomalies to paleoclimatic records of drought between 1200 and 1400 AD. Results confirm that strong westerlies are associated with a band of decreased precipitation extending from the northern Rockies into the Midwest. Changes in summer westerlies associated with these patterns are characterized by a strengthening of mean westerly winds, with only a slight southward shift of peak winds over the Atlantic. Changes in the strength of the westerlies over both the Pacific and Atlantic appear to be important to precipitation deficits in the Midwest. Proxy-climate records from 1200 to 1400 AD indicate widespread drought in the Great Plains and Midwest, consistent with the hypothesis of stronger westerlies at this time. However, drought conditions also extended to other regions of North America, indicating a more detailed understanding of the potential causes and synoptic climatology is needed. 相似文献
89.
Karen Holm Olsen 《Climatic change》2007,84(1):59-73
The challenges of how to respond to climate change and ensure sustainable development are currently high on the political
agenda among the world’s leading nations. The Clean Development Mechanism (CDM) is part of the global carbon market developing
rapidly as part of the Kyoto response towards the mitigation of global warming. One of the aims of the CDM is to achieve sustainable
development in developing countries, but uncertainty prevails as to whether the CDM is doing what it promises to do. Close
to 200 studies on the CDM have been carried out since its birth in 1997 including peer-reviewed articles and reports from
the grey literature. This review of the literature serves to assess the state of knowledge on how the CDM contributes to sustainable
development (SD) including poverty alleviation. The main finding of the review is that, left to market forces, the CDM does
not significantly contribute to sustainable development. 相似文献
90.
Robert J. Kieber Joan D. Willey Robert F. Whitehead Seth N. Reid 《Journal of Atmospheric Chemistry》2007,58(3):219-235
Significant photodegradation of chromophoric dissolved organic matter (CDOM) in rainwater was observed after exposure to simulated
sunlight. Fluorescence excitation emission spectra (EEMS) of precipitation revealed the presence of four major peaks all of
which degraded upon photolysis with the greatest loss in the region characteristic of marine CDOM. Photobleaching of absorbance
also occurred in the wavelength region between 250 and 375 nm with the greatest loss of absorbance in the upper end of the
UV-A region near 275 nm. There was a strong positive correlation between absorbance loss and total integrated fluorescence
loss suggesting these optical properties and the degree to which they are photobleached in rainwater are directly related.
The quantum yield of CDOM photodegradation in rainwater decreased dramatically with increasing wavelength and decreasing energy
of incoming radiation with the average quantum yield at 325 nm approximately an order of magnitude greater than at 460 nm.
The similarity of photolytic response between rainwater and Cape Fear estuarine CDOM indicates that some fraction of the compounds
that make up rainwater CDOM may be derived from surface sources and/or that the processes that produce or modify humic-like
substances in the atmosphere result in similar types of compounds as non-atmospheric processes. 相似文献