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1.
This paper discusses the current status of calculating infrared cooling by CO2 in the mesosphere and lower thermosphere. It is desirable to have fast but accurate procedures for use in dynamic models. The most difficult region is from 70 to 90 km, where cooling rates are strongly influenced or, in the case of the summer mesopause region, dominated by the absorption of radiation emitted by underlying layers, with the hot bands and isotopic bands playing a significant role. A three-energy-level model is derived for the excited population levels of a CO2 molecule. Vibrational-vibrational coupling between isotopes is also included as significant. Results from model calculations for cooling rates and NLTE source functions are presented. Global average infrared cooling rates appear to be in reasonable balance with solar heating rates, considering the uncertainties in calculating both these terms. Radiative cooling rates by CO2 above 100 km are strongly dependent on atomic oxygen concentrations and on the rate of energy exchange between atomic oxygen and CO2. Likewise, NO cooling, which is important above 120 km, is proportional to atomic oxygen concentrations. Since CO2, NO and O concentrations can all vary with motions, these dependencies suggest interesting feedbacks to atmospheric dynamics.  相似文献   

2.
Observations of nitric oxide (NO) by the Solar Mesosphere Explorer (SME) during equinox indicate a lower-thermosphere equatorial minimum which is at variance with theoretical predictions. To address this discrepancy a zonally averaged model of the thermosphere and upper mesosphere is used to evaluate the influence of a latitude variation in turbulence. Five numerical simulations were performed with different latitude structures of eddy diffusion (KT), ranging from uniform in latitude, peaks at low, mid-, or high-latitude, to a hemispherically asymmetric distribution. A local increase in eddy diffusion causes the lower thermosphere to cool and induces a latitude pressure gradient that drives horizontal and vertical winds. The circulation, turbulent transport and temperature dependent chemistry act to change the distribution of species. Comparison of the model predictions of NO with SME data, and simulated wind and temperature structure with empirical climatology, indicates a preference for a midlatitude peak in KT.  相似文献   

3.
Monthly simulations of the solar semidiurnal tide in the 80–100 km height regime are presented. These calculations benefit from the recent heating rates provided by Groves G. V. (1982a,b) (J. atmos. terr. Phys. 44, 111; 44, 281), the zonally-averaged wind, temperature and pressure fields developed for the new COSPAR international reference atmosphere [Labitzke K., Barnett J. J. and Edwards B. (1985) Handbook for MAP 16, 318], and eddy diffusivities determined from gravity wave saturation climatologies and used by Garcia R. R. and Solomon S. (1985) (J. geophys. Res. 90, 3850) to simulate oxygen photochemistry and transport in the mesosphere and lower thermosphere. Some of the main characteristics of the observed semidiurnal tide at middle and high latitudes are reproduced in our simulations: larger amplitudes in winter months than in summer months, and the bi-modal behavior of the phase with summer-like and winter-like months separated by a quick transition around the two equinoxes. The phase transition is also more rapid in the spring, consistent with observations. The wavelengths are also longer in summer than in winter, at least below 95 km (whereas in July and August the simulations exhibit some discrepancies above this altitude), similar to the observational data. Semidiurnal amplitudes are generally smaller and the phases more seasonally symmetric at middle and low latitudes, as compared with the tidal structures above about 50° latitude. In addition, hemispheric differences in the mean zonal wind result in marked asymmetries in tidal behavior between the Arctic and Antarctic regions, and suggest that a comparative study of tide, gravity wave and mean flow interactions in the Arctic and Antarctic mesosphere and lower thermosphere would be fruitful.  相似文献   

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The behaviour of the diurnal tide at 95 km over various years between 1965 and 1986 is studied using radar data from Heiss Island (81°N), Mawson (67°S), Molodezhnaya (68°S) and Scott Base (78°S). The observations are also compared with the model results of FORBES and HAGAN [(1988) Planet. Space Sci. 36, 579] for the same latitudes. There are substantial fluctuations in amplitude and phase at all stations, particularly in winter. Phase fluctuations can be as large as a uniform random distribution over the 24-h cycle. In summmer the phases of the meridional components are well defined and suggest the presence of a dominant symmetric mode. The meridional amplitudes are larger in summer whereas the zonal components have a greater variation and show no significant variation with season.  相似文献   

6.
The application of radiocarbon dating to archaeological samples generally requires calibration of 14C dates to calendar ages and interpretation of dating errors. In this paper, four recent methods of age calibration are assessed, particularly with regard to their quality of error treatment. Recent experimental research has suggested that commonly quoted errors on “raw” 14C dates may require enlargement to more realistic levels, which, when incorporated in the calibration schemes, produce a considerable increase in the size of the typical calibrated interval. A general decrease in the sensitivity of 14C dating using single, “normal precision” dates is implied. Thus typical calibrated age intervals range from 300 to 1300 years (approximate 95% confidence level), with little improvement resulting if “high precision” calibration systems are used to correct “normal precision” dates. Of the four methods considered here, that proposed by Neftel is found to provide the most objective, flexible, comprehensive and “easy to use” scheme. This method is particularly recommended for its treatment of errors both on the dates to be calibrated and on the calibration curve itself.  相似文献   

7.
The design of a projectile delivery system often plays a critical role in the durability and breakage patterns associated with spent projectile points. This paper presents the results of an experimental project designed to examine projectile point durability and breakage patterns between three different hafting methods. Specifically, we compare two asphaltum hafting techniques drawn from archaeological and ethnohistoric accounts from the Central Valley of California with a more stereotypical cross-hatched sinew hafting system. Our results suggest a small yet statistically significant increase in durability among asphaltum hafted points, opening the door to future research on these ethnohistorically documented hafting techniques.  相似文献   

8.
The skeletal remains of unidentifiable persons, recovered in recent years from the churchyard adjoining the House of Correction in Oslo, included 91 instances in which the maxillae and/or mandibles had been preserved, and these were examined. The length of the apical translucent zone in unsectioned teeth and the amount of secondary dentine deposit have been regarded as two of the most reliable factors in odontological age estimation. This study has used two methods, each using one of these factors, on single-rooted teeth from, respectively, 78 and 76 individuals. The distribution of age at death, as estimated from the two dental methods and from anthropological criteria, was then compared with the distribution of age at death of 380 individuals recorded in the church register for the House of Correction. Age calculations from secondary dentine, measured indirectly on dental radiographs of premolars, and estimates based on anthropological criteria both seemed to approximate to the chronological age distribution better than age estimates based on the length of the apical translucent zone. Statistical analyses indicated that all three methods of age estimation were significantly different (p<0.05). When compared with the church register, each method assigned a lower percentage of individuals to the younger and older age-groups and a higher percentage to those in the middle. No statistical difference could be found between the age distribution from the church register and estimates from either anthropological criteria or dental radiographs; but when age estimates based on these two latter methods were compared, 39.5 per cent differed by more than 10 years.  相似文献   

9.
The effectiveness of the implementation process in EC regional programmes has been subject to more attention in recent years. In the meantime, some inhibiting factors that influence the level of success and failure of the implementation of regional programmes have been revealed, while others are still being researched. The obstacles in implementing the Integrated Mediterranean Programme of Eastern Central Greece (IMP‐ECG) were found to include a widespread lack of know‐how in the integrated planning techniques which had to be applied, the dominance of a traditional centrist administrative apparatus, the inadequate supervision and monitoring of the programmes and, lastly, the invincible power of clientelism with its adverse effects on the intended objectives of the programme. Unquestionably the experience of the IMP‐ECG can justifiably be used as a lesson to improve the quality of implementation of current and forthcoming EC regional programmes.  相似文献   

10.
We propose new methods for evaluating the spatial distributionof firms. To assess whether firms are concentrated or dispersed,economists have tradi-tionally used indices that analyse theheterogeneity of a spatial structure at a single geographiclevel. We introduce distance-based methods, Besag's L function(derived from Ripley's K function) and Diggle and Chetwynd'sD function to describe simultaneously spatial distribution atdifferent geographical scales. Our empirical applications considerthe distribution of French manufacturing firms in the Parisarea and in France generally. For some geographic levels, resultsshow significant concentration or dispersion of firms accordingto their sector of activity.  相似文献   

11.
This article is motivated by a concern for the cost‐effectiveness of anti‐poverty outlays; much of its focus is on the targeting of Rural Public Works (RPW) and the Integrated Rural Development Programme (IRDP) over the period 1987–93. It is argued that benefits to the rural poor of larger outlays on these two major anti‐poverty programmes are likely to be limited, given their mistargeting. Large sections of the rural poor were not covered in 1987. Worse, the non‐poor were in a majority among the participants. Although the evidence is mixed, there was a worsening of the targeting of both RPW and IRDP, with RPW maintaining a slight superiority, over the period 1987–93. Yet IRDP was more cost‐effective in both years, using a somewhat limited measure of cost‐effectiveness. Large unspent balances due largely to slow disbursal of allocations and bunching of expenditure in a few months are linked to changes in cost‐effectiveness. Wastage and diversion of funds are unavoidable, in a context of corrupt bureaucracy and capture of locally elected bodies such as Panchayats by a few influential persons. Short of drastic changes in the design and implementation of RPW and IRDP, substantially larger outlays may thus accomplish little in terms of poverty alleviation.  相似文献   

12.
Nadein, K.S. & Perkovsky, E.E. 2 July 2019. Small and common: the oldest tropical Chrysomelidae (Insecta: Coleoptera) from the lower Eocene Cambay amber of India. Alcheringa XXX, X–X. ISSN 0311-5518.

Three new genera and species of flea beetles (Chrysomelidae: Alticini) are described from the lowermost Eocene Cambay amber: Cambaltica paleoindica Nadein, gen. et sp. nov., Protorthaltica setosella Nadein, gen. et sp. nov., and Davidaltica cambayensis Nadein, gen. et sp. nov. These taxa share a zoogeographic affinity with extant Oriental and Afrotropical flea beetle faunas, with similarities to Afrotropical elements interpreted to be a result of Neogene migrations from Laurasia to Africa. The flea beetles within the Cambay amber are characterized by their small body size (1.2–1.9?mm), and the absence or rarity of larger flea beetles in the Cambay amber forest is assumed to be evidence for a progressive increase in the average body size of tropical flea beetles beginning in the early Eocene.

Konstantin S. Nadein [], University of Kiel, Zoological Institute, Functional Morphology and Biomechanics, Am Botanischen Garten 1–9, Kiel, Germany; Evgeny E. Perkovsky [], Schmalhausen Institute of Zoology, National Academy of Science of Ukraine, Bogdana Khmelnitskogo Str. 15, Kiev, Ukraine, Borissiak Paleontological Institute of the Russian Academy of Sciences, Profsoyuznaya Str. 123, Moscow, 117997, Russia.  相似文献   

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Two norms frequently used in archaeological seriation are compared. Although these norms are equivalent in some particular cases, this is not true in general both from a computational point of view and in the archaeological sense.  相似文献   

16.
We investigate the problem of internal fracturing of the columns of a building of cultural importance (the Crypt of the “Cattedrale di Otranto”, Apulia, Italy), using a multi-disciplinary approach, integrating different non-destructive techniques (Microclimatic and Geophysical). In fact historic buildings, over centuries, may accumulate a high concentration of water and/or moisture that increases significantly the deterioration rate, diminishing the mechanical resistance.  相似文献   

17.
旧州河遗址位于三峡库区香溪宽谷地段长江右岸的一处坡地上,隶属丁湖北省秭归县郭家坝镇旧州河居委会。它尔临长江,南至苏溪沟,两接柑桔场,北连楚下井村,尔北与秭归县老县城归州相距约3公里。通往旧州河新场镇的简易公路呈东西向从遗址东  相似文献   

18.
《中国地方志》2005,(5):30-32
第二轮修志中, 青岛市崂山区史志办公室把创建地情资料中心、地情文献中心、区域研究和课题咨询中心“三个中心”作为开拓和推动史志事业发展的方向和硬措施。从提高对“三个中心”建设的认识、推进“三个中心”建设到扩大“三个中心”影响入手, 为第二轮修志营造了良好的工作氛围。  相似文献   

19.
On the 19th and 20th September 1981 heavy rain fell throughout Scotland. Almost 140mm was recorded for the 24 hours up to 9.00 am on the 20th at Dundonnell in Wester Ross, an event with a recurrence interval of approximately 120 years. The storm generated a peak discharge of c.60m3 s‐1 on the Ardessie Burn which drains a 13.3km2 catchment on the northwestern slopes of An Teallach. The resulting flood caused severe localised bank erosion and partially destroyed a fish farm. The total volume of measured flood deposits exceeded 1800 tonnes, approximately equal to 14 years normal average annual non‐dissolved sediment output. The identification of specific sediment source areas and deposition sites allows an assessment of geomorphic work in terms of direct landscape adjustment in response to extreme rainfall. The flood stresses the importance of rare events in the landscape evolution of upland environments and the influence of antecedent catchment conditions.  相似文献   

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