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61.
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The effect of the IMF on the position of the Sq focus in summer has been discussed by Matsushita who found an apparent poleward motion of the focus on days when the IMF was directed away from the Sun compared to those when the IMF was directed towards the Sun. However, his analysis took no account of the well known phase variability in Sq(H) . It is shown here that if quiet days are separated into 'normal quiet days', NQDs (defined for a station on the poleward side of the focus as days when the minimum in H occurs between 0830 and 1330 LT) and 'abnormal quiet days', AQDs (minimum in H occurring outside the NQD range), then the apparent poleward motion of the focus only occurs on AQDs and even then only when the IMF is directed away from the Sun. This effect is found to occur in both summer and winter and is probably of magnetospheric origin.  相似文献   
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63.
A method based on Bochner's theorem is described for demonstrating the positive-definiteness of variogram models and for generating classes of valid variogram functions.Work performed while on leave at the Centre de Géostatistique et de Morphologie Mathématique.  相似文献   
64.
Measuring the sustainability of a city, and ranking the city against other cities, is increasingly seen as a way to achieve urban sustainability. A number of studies have highlighted how Sydney is unsustainable, with two recent ranking exercises appearing to confirm these findings by placing Sydney below many other Australian cities for urban sustainability. These two exercises are situated within international moves towards ranking cities. The article explores the assumptions and criteria used by Mercer in its Eco-City Index and the Australian Conservation Foundation in its Sustainable Cities Index. The conclusion discusses how Sydney could become more sustainable, and identifies why normative urban sustainability rankings should be recognised for their potential while simultaneously being treated with caution.  相似文献   
65.
Acquiring a mechanistic understanding of the role of biotic feedbacks for the links between atmospheric CO2 concentrations and temperature is essential for trustworthy climate predictions. Currently, computer-based simulations are the only available tool to estimate the global impact of biotic feedbacks on future atmospheric CO2 and temperatures. Here we propose an alternative and complementary approach by using materially closed, energetically open analogue/physical models of the carbon cycle. We argue that there is unexplored potential in using a materially closed approach to improve our understanding of the magnitude and direction of many biotic carbon feedbacks and that recent technological advances make this feasible. We also suggest how such systems could be designed and discuss the advantages and limitations of establishing physical models of the global carbon cycle.  相似文献   
66.
Based on homogenized land surface air temperature (SAT) data (derived from China Homogenized Historical Temperature (CHHT) 1.0), the warming trends over Northeast China are detected in this paper, and the impacts of urban heat islands (UHIs) evaluated. Results show that this region is undergoing rapid warming: the trends of annual mean minimum temperature (MMIT), mean temperature (MT), and mean maximum temperature (MMAT) are 0.40 C decade?1, 0.32 C decade?1, and 0.23 C decade?1, respectively. Regional average temperature series built with these networks including and excluding “typical urban stations” are compared for the periods of 1954–2005. Although impacts of UHIs on the absolute annual and seasonal temperature are identified, UHI contributions to the long-term trends are less than 10% of the regional total warming during the period. The large warming trend during the period is due to a regime shift in around 1988, which accounted for about 51% of the regional warming.  相似文献   
67.
Solar soft X-ray (XUV) radiation is highly variable on all time scales and strongly affects Earth’s ionosphere and upper atmosphere; consequently, the solar XUV irradiance is important for atmospheric studies and for space weather applications. Although there have been several recent measurements of the solar XUV irradiance, detailed understanding of the solar XUV irradiance, especially its variability during flares, has been hampered by the broad bands measured in the XUV range. In particular, the simple conversion of the XUV photometer signal into irradiance, in which a static solar spectrum is assumed, overestimates the flare variations by more than a factor of two as compared to the atmospheric response to the flares. To address this deficiency in the simple conversion, an improved algorithm using CHIANTI spectral models has been developed to process the XUV Photometer System (XPS) measurements with its broadband photometers. Model spectra representative of quiet Sun, active region, and flares are combined to match the signals from the XPS and produce spectra from 0.1 to 40 nm in 0.1-nm intervals for the XPS Level 4 data product. The two XPS instruments are aboard NASA’s Solar Radiation and Climate Experiment (SORCE) and Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED) satellites. In addition, the XPS responsivities have been updated for the latest XPS data processing version. The new XPS results are consistent with daily variations from the previous simple conversion technique used for XPS and are also consistent with spectral measurements made at wavelengths longer than 27 nm. Most importantly, the XPS flare variations are reduced by factors of 2 – 4 at wavelengths shorter than 14 nm and are more consistent, for the first time, with atmospheric response to solar flares. Along with the details of the new XPS algorithm, several comparisons to dayglow and photoelectron measurements and model results are also presented to help verify the accuracy of the new XUV irradiance spectra.  相似文献   
68.
Houser  Chris  Vlodarchyk  Brent  Wernette  Phil 《Natural Hazards》2019,97(3):1395-1405
Natural Hazards - Informing and warning beach users about the danger posed by the rip current hazard remain a difficult challenge. Recent evidence suggests that warning signs and flags alone have...  相似文献   
69.
The geological mapping carried out by William Smith, which resulted in the publication of his famous map in 1815, was remarkable in many respects, not least because it relied on him being able to make consistent and accurate observations on the rock types he encountered during his fieldwork. This ability, gained from his many years studying rocks, allowed him to observe features with his own eyes (or at the very least, with the aid of a simple magnifying device) that others could not. We take a new look at William Smith's original stratigraphical sequences, and with samples collected from his classic field areas (many of which are around the city of Bath, Somerset, UK), demonstrate how spatial mineralogy mapping can be incorporated into the modern age of digital mapping.  相似文献   
70.
The Rum Layered Suite (NW Scotland) is generally regarded as one of a handful of classic examples of open‐system layered mafic‐ultramafic intrusions, or ‘fossilized’ basaltic magma chambers, world‐wide. The eastern portion of the Rum intrusion is constructed of sixteen repeated, coupled, peridotite–troctolite units. Each major cyclic unit has been linked to a major magma replenishment event, with repeated settling out of ‘crops’ of olivine and plagioclase crystals to form the cumulate rocks. However, there are variations in the lithological succession that complicate this oversimplified model, including the presence of chromitite (>60 vol. percent Cr‐spinel) seams. The ~2 mm thick chromitite seams host significant platinum‐group element (PGE) enrichment (e.g. ~2 ppm Pt) and likely formed in situ, i.e. at the crystal mush–magma interface. Given that the bulk of the world's exploited PGE come from a layered intrusion that bears remarkable structural and lithological similarities to Rum, the Bushveld Complex (South Africa), comparisons between these intrusions raise intriguing implications for precious metal mineralization in layered intrusions.  相似文献   
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