The semidiurnal tides at the midlatitude lower thermosphere over East Siberia

Results from the study of semidiurnal tides in the horizontal wind field at 85–95 km over East Siberia are presented. The seasonal variation of tidal amplitudes and the effects of stratospheric warmings are discussed.     

Infrared radiative cooling in the mesosphere and lower thermosphere

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.     

Diurnal tide in the Antarctic and Arctic mesosphere/lower thermosphere regions

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.     

The impact of gravity waves on nitric oxide in the lower thermosphere

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 (K_T), 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 K_T.     

Monthly simulations of the solar semidiurnal tide in the mesosphere and lower thermosphere

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.     

A comparison of three methods of measuring tidal oscillations in the lower thermosphere using EISCAT common programmes

The EISCAT Common Programme can be used in three ways to monitor tidal oscillations in the lower thermosphere. In Common Programme One (CPI) tristatic observations provide measurements of the ion-velocity vector at several heights in the E-region and one height in the F-region. In Common Programme Two (CP2) monostatic measurements give profiles of ion velocity in the E-region while tristatic measurements give continuous measurements of ion velocity in the F-region. From the ion velocities and the ion-neutral collision frequency, the vector of the E-region neutral wind can be determined and both east-west and north-south components of the diurnal, semi-diurnal and ter-diurnal oscillations can be identified. CP1 and CP2 also provide profiles of the field-aligned ion velocity, and these can be used to calculate the north-south component of the neutral wind without knowing the ion-neutral collision frequency, but the result is affected by any vertical component of neutral velocity. The three methods are compared and the advantages of CP2 demonstrated.     

Sex estimation using cervical dental measurements in an archaeological population from Iran

Sex estimation of skeletal remains is one of the major components of forensic identification of unknown individuals. Teeth are a potential source of information on sex and are often recovered in archaeological or forensic contexts due to their post-mortem longevity. Currently, there is limited data on dental sexual dimorphism of archaeological populations from Iran. This paper represents the first study to provide a dental sex estimation method for Iron Age populations. The current study was conducted on the skeletal remains of 143 adults from two Iron Age populations in close temporal and geographic proximity in the Solduz Valley (West Azerbaijan Province of Iran). Mesiodistal and buccolingual cervical measurements of 1334 maxillary and mandibular teeth were used to investigate the degree of sexual dimorphism in permanent dentition and to assess their applicability in sex estimation. Data was analysed using discriminant function analysis (SPSS 23), and posterior probabilities were calculated for all produced formulae. The results showed that incisors and canines were the most sexually dimorphic teeth, providing percentages of correct sex classification between 86.4 and 100 % depending on the measurement used. The combination of canines and other teeth improved significantly the level of correct sex classification. The highest percentages of sex classification were obtained by the combination of canines and incisors (100 %) and canines and molars (92.3 %). The present study provided the first reference standards for sex estimation using odontometric data in an Iranian archaeological population. Cervical measurements were found to be of value for sex assessment, and the method presented here can be a useful tool for establishing accurate demographic data from skeletal remains of the Iron Age from Iran.     

Short-lived bursts of plasma velocity in the auroral zone. I. Observational evidence from radar measurements

Sudden bursts of plasma velocity, including an equatorward component, are often observed by EISCAT in the evening and midnight sectors. Typically, these bursts last for about 3–7 min, and are repeated in a quasi-periodic sequence. Quasi-periodic equatorward bursts are also observed by the SABRE coherent scatter radar and these measurements confirm that the pattern can extend over several degrees of latitude and at least 10° of longitude.     

Intense turbulence in the polar mesosphere : rocket and radar measurements

Simultaneous observations of polar mesospheric summer echoes (PMSE) have been made with two different frequency radars during the launch of a sounding rocket designed to measure the fluctuations in the electron density in the same height range. The cross-section for radar backscatter deduced from the rocket probe data under the assumption of isotropic turbulence is in reasonable agreement with the measured signals at both 53.5 MHz with the mobile SOUSY radar and 224 MHz with the EISCAT VHF radar, which correspond to backscatter wavelengths of about 3 and 0.75 m, respectively. Some controversy exists over the relative roles of turbulent scatter vs specular reflections in PMSE. A number of characteristics of the data obtained in this experiment are consistent with nearly isotropic, intense meter-scale turbulence on this particular day. Since equally compelling arguments for the importance of an anisotropic-type mechanism have been presented by other experimenters studying PMSE, we conclude that both isotropic and anisotropic mechanisms must operate. We have found the inner scale for the electron fluctuation spectrum, which corresponds to the diffusive subrange for that fluid, and have compared it to the inner scale for the neutral gas. The latter was found from the Kolmogorov microscale, which in turn depends on the energy dissipation rate in the gas. We found the dissipation rate from the spectral width of the 53.5 MHz backscatter signal and from the rocket electron density fluctuation data. The diffusive subrange was found to occur at a wavelength a factor of about 10 times smaller than the viscous subrange. This corresponds to a Schmidt number of about 100. High Schmidt numbers have been reported in recent measurements of the diffusion coefficient of the electrons in this height range made with the EISCAT incoherent scatter radar. About 15 min after the rocket flight an extremely high radar reflectivity was found with the SOUSY system. We have been able to reproduce this high level theoretically by scaling the rocket data with an increase in the neutral turbulence energy dissipation rate by a factor of 14 as deduced from the SOUSY spectral width, an increase in the electron density which is consistent with riometer data, and a 33% decrease in the electron density gradient scale length which is hypothesized. We also estimate the radar reflectivity at 933 MHz and conclude that signals in excess of thermal scatter levels would have occurred at the peak of the event studied, provided that the electron fluctuation spectrum decreases as k⁻⁷ in the viscous subrange. If the spectrum has an exponential form, however, a turbulent source cannot explain the enhanced 933 MHz echoes reported by EISCAT.     

Reanalysis of in situ permeability measurements in the Barbados décollement

A cased and sealed borehole in the Northern Barbados accretionary complex was the site of the first attempts to measure permeability in situ along a plate boundary décollement. Three separate efforts at Hole 949C yielded permeability estimates for the décollement spanning four orders of magnitude. An analysis of problems encountered during installation of the casing and seals provides insights into how the borehole conditions may have led to the wide range of results. During the installation, sediments from the surrounding formation repeatedly intruded into the borehole and casing. Stress analysis shows that the weak sediments were deforming plastically and the radial and tangential stresses around the borehole were significantly lower than lithostatic. This perturbed stress state may explain why the test pressure records showed indications of hydrofracture at pressures below lithostatic, and permeabilities rose rapidly as the estimated effective stress dropped below 0.8 MPa. Even after the borehole was sealed, the plastic deformation of the formation and relatively large gap of the wire wrapped screen allowed sediment to flow into the casing. Force equilibrium calculations predict sediment would have filled the borehole to 10 cm above the top of the screen by the time slug tests were conducted 1.5 years after the borehole was sealed. Reanalysis of the slug test results with these conditions yields several orders of magnitude higher permeability estimates than the original analysis which assumed an open casing. Overall the results based on only the tests with no sign of hydrofracture yield a permeability range of 10^?14–10^?15 m² and a rate of increase in permeability with decreasing effective stress consistent with laboratory tests on samples from the décollement zone.     

The Water Balance and Groundwater Resources in Connection with the Vertical Water Exchange in the Upper Zone of the Earth's Crust

For research on regional estimates of the water balance and future water-resource planning, it is important to determine the amount of water leakage downward across the base level, i.e. from the upper layers of the earth's crust drained by streams to the lower layers. The author presents a methodology based on water-balance equations that shows such leakage to be negligible in terms of the margin of error of precipitation and evapotranspiration records. It can therefore be assumed that the groundwater discharge into streams is practically identical with the recharge of groundwater reserves through percolation.     

西安鱼化寨遗址仰韶文化土坑墓发掘简报

一、遗址概况鱼化寨遗址位于西安市雁塔区鱼化寨街道鱼化寨村西北侧,皂河西岸的二级台地上,今西安外事学院北校区西北部。遗址东、北两侧被皂河环绕,地势中心高,周围低(图一)。2002年～     

Accurate measurements with primitive instruments: the “paradox” in the qanat design

Qanats are up to 3000 years old artificial sub-horizontal underground water channels, 5–80 km long, widespread in Iran, but also common in western China, Arabia and the Mediterranean; they were excavated from the bottom of vertical shafts, starting from their exit and advancing upstream till main, productive wells, constructed at the very beginning of the project were met. Successful qanat excavation therefore required accurate geodetic design, though based on primitive instruments; an apparent “paradox”, obscured by the tremendous social and economic significance of qanats controlling lifestyle in arid regions.     

非动力性与动力性的合奏——新时期中国农村改革后蓬勃发展的纵向条件分析

20世纪70年代末80年代初中国农村改革顺利铺开,并取得了举世嘱目的成就。但这并不仅仅在于当时农民的探索、地方官员的默许以及中央控制的放松和政策的支持。如果从社会发展的纵向来分析,这一时期的中国农村与50年代初期相比,已经具备了推进改革的较充分的历史条件,而正是有了这些历史条件,中国在这一时期进行的农村改革,才能够顺势启动并迅速发展,从而实现了中国农村"水到渠成"的伟大历史转折。     

Susceptibility measurements,optical and X-ray analysis to explain the origin of archaeological magnetic anomalies in Tavoliere lowland (Southern Italy)

Since 2002 a non-invasive investigation integrating aerial photography and high-resolution magnetometry has been carried out for reconstructing extensive ancient settlements in Tavoliere lowland (Southern Italy). Relevant magnetic anomalies were detected in all the surveyed sites allowing a precise mapping of the buried structures over more than 150 ha. Next to this research susceptibility measurements, PXRD, XRF and optical analysis were also performed in order to explain the origin of the notable magnetization contrast between the anthropogenic structures and the embedding materials, generating the measured signals. This last study was accomplished, in 2006, in Monte S. Vincenzo site, a vast Neolithic village where the remotely sensed data were also used to guide some direct inspection. Trial archaeological excavations brought to light parts of C-shaped compounds, providing complete information on the geometry and location of the sources of magnetic signals. Profiting by the archaeological feedback, the susceptibility contrast between the soil filling the ditches and the calcareous substratum was assessed in situ. A synthetic model based on this information was created and compared with the experimental data. The infilling material was also sampled for laboratory analysis: the presence of several magnetic minerals (pyroxenes, monometric magnetite, haematite) was ascertained. Furthermore optical analyses showed different types of volcanic and igneous products such as pumices, melanite garnets and lava fragments. Geomorphological and archaeometric evidence allowed us to relate these materials to activity of the Mt. Vesuvius volcano. Eventually their possible spatial distribution was inferred from recent studies on ash transportation and deposition during explosive activity.     

Columbanus in Europe: the evidence from the Epistulae

The continental career of Columbanus has long attracted the attention of scholars because of his achievement as a writer, monastic founder and reformer, and political actor. His Epistulae are one of the most important pieces of evidence in understanding his attitudes and purposes during his twenty‐year sojourn on the Continent, and they emphasize the importance of his ecclesiastical and secular relationships. However, the Epistulae have seldom been analysed independently and together, as their study has often been focused on single letters or specific aspects of the collection. This paper looks at the Epistulae in a more general way, to point out what they tell us about Columbanus's theological and ecclesiastical positions, and the connections he established on the Continent.