Parameterization of the radiative flux divergence in the 9.6 μm O3 band

A parameterization of the cooling rate of the Earth's atmosphere in the height region of approximately 20–75 km due to radiation transfer in the 9.6 μm O₃ band is proposed. A general random band model is used to calculate the radiation transmission. The parameterization takes into consideration a peculiar feature of the radiative transfer—the height step increases with growing distance from the level for which cooling is calculated. A simple method of accounting for the variation of the vertical profile of the absorbing gas is proposed and utilized. The procedure proposed is multiparametric: 22 parameters are prescribed for calculating cooling at a given level. The procedure can be recommended for calculating radiative cooling for any temperature and ozone profile not having a small- or meso-scale structure. It can be used, in particular, for modelling of the middle atmospheric circulation.     

On the role of the 9.6 μm O3 band in the energetics of the mesosphere and lower thermosphere

Radiative cooling and heating in the 9.6 μm O₃ band has been calculated for the 50–105 km region. The NLTE effects due to the excitation of the ozone ν₃ vibrations by atmospheric and solar radiation and by the release of chemical energy into vibrations upon recombination of O + O₂ into O₃ have been taken into account. It is shown that the LTE approximation is good for altitudes below 70 km where fundamental transitions comprise the main contribution to the cooling rate. Above 70 km, the contribution of the hot transitions to radiative cooling may exceed the contribution of the fundamental ones. In the presence of chemical excitation, part of the chemical energy radiates in the hot transitions, resulting in an additional cooling rate of about 0.5 K/day at 90 km. A method of parameterizing radiative heating which is based on the separation of the effects of fundamental and hot transitions in the 9.6 μm O₃ band is proposed.     

The 4.8 and 9.6 μm O3 band emissions in the middle atmosphere

For the 40–115 km atmospheric layer, the populations of 19 vibrational states of the O₃ molecule have been calculated for sets of vertical profiles of temperature and concentration of O and O₃. A peculiar feature of the day and night time vertical profiles of the vibrational temperature of the states is at its maximum in the height range 75–90 km which is due to the formation of vibrationally excited molecules of O₃ in the recombination: O₂ + O + M → O₃ + M. On the basis of the calculated populations of the states, the limb and downward atmospheric emissions in the 4.8 and 9.6 μm O₃ bands have been estimated, as well as the contributions of the constituents of the band of vibrational transitions.     

The dynamics of ion layer generation in the 80–150 km altitude region at low and mid-latitudes

The association of sporadic ion and sporadic sodium layers in the low-latitude, 90–100 km altitude region suggests that we must look beyond the windshear theory for details of the formation mechanism of sporadic layers in the 80–150 km altitude region. We present evidence, including specific 85–105 km results from the AIDA-89 and the ALOHA-90 campaigns, that 80–150 km altitude sporadic layers—including sporadic sodium layers—are generated in a complex interplay of tidal and acoustic-gravity wave (AGW) dynamics with temperature-dependent chemistry where wave-produced temperature variations are both adiabatic and dissipative or turbulent (non-reversible) in origin. We suggest that layering processes are best studied with an instrument cluster that includes sodium and iron lidars, MST radar (turbulence), incoherent scatter radar (electron concentration and winds), meteor radar techniques (winds), passive optical/IR imaging techniques, and appropriate rocket payloads to study a significant volume of the 80–150 km altitude region. We introduce the concept of volumtric radar and lidar techniques.     

A non-LTE radiative transfer model for infrared bands in the middle atmosphere. II. CO2 (2.7 and 4.3 μm) and water vapour (6.3 μm) bands and N2(1) and O2(1) vibrational levels

A non-equilibrium radiative transfer model has been applied to the 2.7 and isotopic 4.3 μm bands of CO₂, together with that of H₂O at 6.3 μm and the first excited vibrational levels of the nitrogen and oxygen molecules. The radiative transfer has been treated by a modified Curtis matrix method that allows inclusion of non-thermal sources, such as vibrational-vibrational energy exchange. The populations of the different levels have been obtained by solving a system of coupled equations, including those for the 15 μm bands. Results from the model are compared to previously reported results. A detailed study of where solar energy initially absorbed by CO₂ bands finally goes is also presented.     

VLF radiation generated by a loop antenna in P2 layer of the ionosphere—2. Interpretation of the measurements

The results of an experiment on radiation and reception of VLF waves with a frequency of 5 kHz in the F2 layer of the ionosphere are compared with theoretical calculations made in the framework of the linear theory of a loop antenna in a plane-stratified plasma. The measurements made outside the Storey cone can be explained in the framework of the linear theory by the proper modification of the ionosphere model. The wave polarization differs from circular polarization on the boundary of caustic cone, due to non-linear effects.     

The measurement of diurnal variations of electron concentration in the 60–100 km ionosphere at Arecibo

The Arecibo 430 MHz incoherent scatter radar was used to observe the diurnal variation of electron concentration in the 6–100 km altitude region on 14 August 1977. This report is an evaluation of the technique and includes a fairly complete discussion of errors involved. Although interference remains a serious problem, the results are useful down to about 60 km altitude and a minimum density of about 50 electrons cm⁻³. Characteristic statistical plus systematic errors indicate that an observed 100 electrons cm⁻³ value actually lies between 50 and 180 electrons cm⁻³ assuming no interference. Observed variations of electron concentration include not only those due to basic solar control but also at least one wavelike feature characterized by phase shift with altitude. These results should prove particularly useful as constraints to time dependent models of the D-region chemistry.     

Long-term trends in planetary wave activity (2–15 days) at 80–100 km inferred from radio wave absorption

The daytime radio wave absorption in the lower ionosphere measured by the A3 method (oblique incidence on the ionosphere) in central and southeastern Europe is used to study long-term trends in the planetary wave activity in the period range of 2–15 days in the upper middle atmosphere. In central Europe we have found no trends in the 1960s and 1980s, but a positive trend in the 1970s (early 1970s- early 1980s); in southeastern Europe we have not established any trend in the 1970s, but a positive one in the 1980s (beginning in late 1970s). These trends are of non-solar origin. They are possibly an indication of changes of anthropogenic origin in the Earth's atmosphere.     

VLF radiation generated by a loop antenna in F2 layer of the ionosphere—1. Theory

In 1987 an experiment on the transmission and reception of VLF electromagnetic waves was carried out in the Earth's ionosphere. The interpretation of the experiment required an elaboration of the theory of a loop antenna in a plane-stratified plasma with parameters changing along the external magnetic field. Formulae for the wave field at arbitrary distances from the antenna have been obtained. Asymptotic expansions for the wave field permit us to construct an effective numeral algorithm for the calculation of the signal when the far zone approximation does not hold and in the presence of the fine structure.     

The economic factor in the Sino-Vietnamese split, 1972–75: An analysis of Vietnamese archival sources

Relying on so far untapped Vietnamese archival sources, this article examines the impact of China's gradual curtailment of its economic assistance to the Democratic Republic of Vietnam's (DRV) war and economic recovery efforts and its implications for Sino-Vietnamese relations between 1972 and 1975. While Beijing's gradual reduction of aid to the DRV during this period was primarily motivated by the declining importance of North Vietnam to China's strategic security combined with the reality of China's domestic economic hardship which largely resulted from the disastrous Cultural Revolution of 1966–69, Hanoi's reactions and policy responses were driven by their deep-rooted perception of Beijing's insincerity and hidden intention to keep Vietnam weak. The Sino-Vietnamese conflict that ensued after 1975 was not inevitable; Hanoi's leaders launched concerted diplomatic efforts to improve economic relations with Beijing throughout 1975 because they clearly recognised the importance of China's continued economic assistance and preferential trade agreements to its first five year plan (1976–80). However, Beijing's unchanged position and hasty decision to totally cut off aid to Vietnam and additionally take punitive economic measures against Vietnam's first five-year plan in late 1975 while at the same time increasing economic and military aid to the Democratic Kampuchea compelled Hanoi to tilt closer towards Moscow.     

Climatologies of semi-diurnal and diurnal tides in the middle atmosphere (70–110 km) at middle latitudes (40–55°)

The radars utilized are meteor (2), medium-frequency (2) and the new low-frequency (1) systems: analysis techniques have been exhaustively studied internally and comparatively and are not thought to affect the results. Emphasis is placed upon the new height-time contours of 24, 12 h tidal amplitudes and phases which best display height and seasonal structures; where possible high resolution (10 d) is used (Saskatoon) but all stations provide monthly mean resolution. At these latitudes the semi-diurnal tide is generally larger than the diurnal (10–30 m s⁻¹ vs. < 10 ms⁻¹), and displays less month to month variability. The semi-diurnal tide does show significant regular seasonal structure; wavelengths are generally small (⩽50 km) in winter, large in summer (≲ 100 km), and these states are separated by rapid equinoctial transitions. There is some evidence for less regularity toward 40°C. Coupling with mean winds is apparent. The diurnal tide has weaker seasonal variations; however there is a tendency for vertical wavelengths and amplitudes to be larger during summer months. On occasions in winter and fall wavelengths may be less than 50 km. Again the seasonal transitions are in phase with reversals of the zonal wind. Agreement with new numerical models is to be shown encouraging.     

Are rocks still water‐wet in the presence of dense CO2 or H2S?

The various modes of acid gas storage in aquifers, namely structural, residual, and local capillary trapping, are effective only if the rock remains water‐wet. This paper reports an evaluation, by means of the captive‐bubble method, of the water‐wet character in presence of dense acid gases (CO₂, H₂S) of typical rock‐forming minerals such as mica, quartz, calcite, and of a carbonate‐rich rock sampled from the caprock of a CO₂ storage reservoir in the South‐West of France. The method, which is improved from that previously implemented with similar systems by Chiquet et al. (Geofluids 2007; 7 : 112), allows the advancing and receding contact angles, as well as the adhesion behavior of the acid gas on the mineral substrate, to be evaluated over a large range of temperatures (up to 140°C), pressures (up to 150 bar), and brine salinities (up to NaCl saturation) representative of various geological storage conditions. The water‐receding (or gas‐advancing) angle that controls structural and local capillary trapping is observed to be not significantly altered in the presence of dense CO₂ or H₂S. In contrast, some alteration of the water‐advancing (or gas‐receding) angle involved in residual trapping is observed, along with acid gas adhesion, particularly on mica. A spectacular wettability reversal is even observed with mica and liquid H₂S. These results complement other recent observations on similar systems and present analogies with the wetting behavior of crude oil/brine/mineral systems, which has been thoroughly studied over the past decades. An insight is given into the interfacial forces that govern wettability in acid gas‐bearing aquifers, and the consequences for acid gas geological storage are discussed along with open questions for future work.     

How Much Do We Actually Know? A Comparison of the Organization of Preventive Archaeology in Romania and in Europe, 2000–15

This study focuses on the organization of preventive archaeology in Romania and several other European countries over the last fifteen years. It provides data comparing the number and density of archaeological sites in Romania identified as a result of large-scale investment projects. It also discusses some important aspects regarding the financial and human resources involved in preventive archaeological excavations in Romania and other European countries. The paper attempts to outline the steps that need to be taken in Romania to ensure the continuing preservation of archaeology. These are: 1. A proper understanding of the importance of certain sites in comparison to others; 2. An accurate understanding of the importance of Article 9 of the Valletta Convention, which focuses on the concept of ‘public awareness’; 3. Prioritizing archaeological projects with useful results; 4. The creation of accurate digital databases, using GIS platforms. Ultimately, it is argued that we need to excavate, but we need even more to preserve, capitalize, and promote the archaeological patrimony, to facilitate the access of the public to archaeological sites, and to make people understand why it is crucial to protect our monuments.     

Archaeometric evidences of the 4th–2nd century BC amphorae productions in north eastern Sicily

This work focuses on the petro-archaeometric analysis of several transport amphorae dated back from 4th to 2nd century BC which were found in various archaeological excavations recently carried out in Messina and Milazzo (north eastern Sicily). These amphorae, generally known as Graeco-Italic, raise the problem of the identification of their production areas. Petrographic analyses proved the presence of two groups characterised by the presence of coarse metamorphic or volcanic inclusions and one group with finer metamorphic inclusions. Multivariate statistical analyses made it possible to detect the production area of the amphorae with metamorphic inclusion in north eastern Sicily, comparing them with locally produced bricks and clay sediments cropping out near the ancient cities. On the contrary, the studied amphorae rich in volcanic inclusions have petrographic and chemical features which can be attributed to production areas in the Campanian region.     

An assessment of winds data (60–110 km) obtained in real-time from a medium frequency radar using the radio wave drifts technique

In a recent paper (Meek, 1980) a fast and efficient method for analysing ionospheric drift records was described. The technique is well suited to real-time analysis.Examples of winds data (60–110 km) obtained from the medium frequency (2.2 MHz) radar at Saskatoon (52°N, 107°W) during 1980 are described here. The quantity and quality of data obtained during typical summer and winter months are discussed. Height time cross-sections of mean winds and tides are also shown.     

Late Pleistocene Techno-traditions in Southern Africa: A Review of the Still Bay and Howiesons Poort, c. 75–59?ka

The focus of this paper is on two remarkable techno-traditions in the prehistory of southern Africa, the c. 75?C71?ka Still Bay and the c. 65?C59?ka Howiesons Poort. These were periods when the technological and behavioural repertoire of early Homo sapiens expanded rapidly to include novel technologies such as heat treatment of lithic materials, pressure flaking of stone points, manufacture of complex armatures including the bow and arrow, and the production of symbolic artefacts including shell beads and engraved ochre, bone and ostrich eggshell. In this paper I first review briefly the historical background relating to the recognition of these techno-traditions; second, concentrate on the archaeological sites known to contain these assemblages within southern Africa; and third, discuss aspects of the precocious material culture that appears during these phases.