Thermal radiation from cloudless skies in Granada

Summary Data on thermal radiation from clear skies obtained at Granada from May to November 1983 were utilized to carry out a detailed comparison between measured and calculated values of longwave radiation with several analytical and empirical equations. The goal of this work is to check the aplicability of these equations to Granada conditions. The results obtained for all the equations are quite satisfactory. Nevertheless, Idso's formula significantly overestimates our experimental results, probably as a consequence of the differences in atmospheric dust conditions between our test area and the location for which that equation was originally derived. A reduction in the independent coefficient, in accordance with previous results of other authors, provides a better fit to our data set and clearly shows the climatological dependence of the constants in the estimation equations.

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Zusammenfassung Die von Mai bis November 1983 in Granada gesammelten Daten über Wärmestrahlung bei klarem Himmel wurden dazu verwendet, um einen detaillierten Vergleich zwischen gemessenen und errechneten Werten der langwelligen Strahlung aus verschiedenen analytischen und empirischen Gleichungen durchzuführen. Das Ziel dieser Arbeit ist es, die Anwendbarkeit dieser Gleichungen auf die Verhältnisse in Granada zu überprüfen. Die gewonnenen Ergebnisse sind für alle diese Gleichungen ganz zufriedenstellend. Idsos Formel überschätzt jedoch deutlich unsere experimentellen Ergebnisse, möglicherweise als Folge der unterschiedlichen atmosphärischen Staubbedingungen in unserem Testgebiet und dem Standort, für den die Gleichung ursprünglich abgeleitet wurde. Eine Reduktion des unabhängigen Koeffizienten, in Übereinstimmung mit früheren Ergebnissen anderer Autoren, bietet eine bessere Anpassung an unseren Datensatz und zeigt deutlich die klimatologische Abhängigkeit der Konstanten in Schätzungsgleichungen.

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With 3 Figures     

Diabatic wind and temperature profiles obtained from a 100 m tower: A statistical comparison of model performances

More than 8000 10-min profiles of wind and temperature obtained during an extensive field experiment have been analyzed. The study was carried out in the environs of Valladolid (Spain) where a 100-m and a 6-m meteorological tower are located. Less than 20% of data were discarded due to equipment failure. Because of its exceptional flatness, the site is almost ideal for model performance comparisons.Predicted profiles of wind speed and potential temperature at 12, 26, 51, and 100 m heights were obtained using the methods proposed by Berkowicz and Prahm (1982) and San José (1983) based on values observed on a 6 m tower. Statistical t, F, and R tests were used to determine bias, scatter and correlation. The data were classified according to atmospheric stratification and height above ground. Finally, a determination was made of the predicted wind speeds and potential temperatures that fell within the 1 and 20% confidence ranges centered at the measured value. San José's method performed better than did that of Berkowicz and Prahm for the temperature profiles in both unstable and stable conditions. However, no significant differences were found for the wind speed profiles.     

Zirconolite,allanite and hoegbomite in a marble skarn from the Bergell contact aureole: implications for mobility of Ti,Zr and REE

Zirconolite, allanite and hoegbomite are present as accessory phases in a metasomatically altered spinel-calcite-marble from the contact with the Bergell intrusives (Switzerland/Italy). Textural relationships indicate a step-wise alteration of spinel to 1) hoegbomite or corundum + magnetite, 2) margarite and 3) chlorite. Replacement of spinel by hoegbomite can be described by the substitution 1.94(Mg²⁺, Fe²⁺, Zn²⁺, Mn²⁺, Ca²⁺)Ti⁴⁺ +0.12(OH^–) where Al³⁺ and Fe³⁺ are held constant. The average composition of the Bergell hoegbomites is given by the formula Fe _0.97 ²⁺ Mg_0.69Zn_0.04Ti_0.17Al_3.94Fe _0.06 ³⁺ O_7.98(OH)_0.02 and seems to be imposed by the composition of pre-existing spinel. During the first two steps of spinel alteration, calcite was replaced by anorthite+phlogopite, and the rare earth element(REE)-bearing minerals zirconolite, allanite and sphene were formed. Allanites have characteristic chondrite-normalized REE patterns with enrichment in the light REE. The zirconolite patterns show a marked increase in concentration from La to Ce, followed by an almost constant section. Sphene lacks detectable La, and its REE patterns vary from grain to grain. Contemporaneous formation of phlogopite, REE-bearing minerals and hoegbomite during replacement of the spinel-calcite-marble indicates that the metamorphic fluid introduced potassium along with REE and other high valence cations (Ti⁴⁺, Zr⁴⁺, U⁴⁺, Th^4A3804265, Nb^5A3804265, Y^3A3804265) possibly as polynuclear complexes. The abundance of fluorine-bearing phlogopite and fluor-apatite as well as their close association with REE-bearing minerals and hoegbomite suggests F^– and PO ₄ ^3– as likely ligands for complexing of the above mentioned elements.     

The two-step shape and timing of the last deglaciation in Antarctica

The two-step character of the last deglaciation is well recognized in Western Europe, in Greenland and in the North Atlantic. For example, in Greenland, a gradual temperature decrease started at the Bölling (B) around 14.5 ky BP, spanned through the Alleröd (A) and was followed by the cold Younger Dryas (YD) event which terminated abruptly around 11.5 ky BP. Recent results suggest that this BA/YD sequence may have extended throughout all the Northern Hemisphere but the evidence of a late transition cooling is still poor for the Southern Hemisphere. Here we present a detailed isotopic record analyzed in a new ice core drilled at Dome B in East Antarctica that fully demonstrates the existence of an Antarctic cold reversal (ACR). These results suggest that the two-step shape of the last deglaciation has a worldwide character but they also point to noticeable interhemispheric differences. Thus, the coldest part of the ACR, which shows a temperature drop about three times weaker than that recorded during the YD in Greenland, may have preceded the YD. Antarctica did not experienced abrupt changes and the two warming periods started there before they started in Greenland. The links between Southern and Northern Hemisphere climates throughout this period are discussed in the light of additional information derived from the Antarctic dust record.     

Surface conductivity in rocks: a review

Electrical properties of rocks depend on composition (i.e. bulk properties of the constituents), micro structure (i.e. geometrical arrangement of the constituents) and interfacial effects. We consider here a rock as a three component system — grains, pores, and interfaces — in order to account for the observed behaviour. We review first the main results relative to DC. conductivity. Surface conductivity effects show up clearly in the case of shaly formations or at low salinities. Although Archies' law (1942) and Waxman and Smits model (1968) are widely used, a more physically based model is that of Johnson and Sen (1988). We review also the variable frequency conductivity (complex conductivity) data and models. The important effect in that case is the enhancement of the dielectric constant at low frequencies (Knight and Nur, 1987) which can be interpreted as a geometrical effect although electrochemical interactions may also play an important role at low frequencies, depending on the rock type.     

Shallow seismicity at Montagne Pelée volcano,Martinique, Lesser Antilles

Continuous seismic monitoring at Martinique since the 1902 eruption of the Montagne Pelée volcano did not detect local earthquakes for the first 70 years. For the only eruption which occurred in this time span in 1929 the seismograph was 20 km away and of a standard type, not particularly suited for the detection of small-scale local seismicity. Improvement of the monitoring array over the last 15 years with the installation of sensors on the volcano itself allowed the detection of signals of local origin which were interpreted as being due to surface sources, such as rockfalls and landslides. Since December 1985 seismic sources in the volcano itself, i.e. small earthquakes at shallow depth, were identified and located with the aid of a temporary upgrading of the array close to these weak sources. Such an onset of local seismicity could not have been detected with previous seismic equipment; such episodes of seismicity in the volcano might have occurred in the past, apparently quiescent history of the volcano as the reinterpretation of seismograms of some events in 1976 would indicate, without evolving to more important volcanic phenomena. For seismographs on volcanoes the constant upgrading of observation capabilities is certainly perferred to a strict continuity of standard observations.     

Le régime thermique des eaux de l'Ardèche dans son cours inférieur

A study of the thermal regime of the Lower Ardeche River was carried out from July 1982 to December 1984 using a chemical method (sucrose inversion) and a continuous temperature recorder. Yearly, monthly and daily temperature fluctuations were analyzed. The main factors that influence thermal variations are air temperature and geomorphology of the canyon. The hydrological regime is responsible of the water temperature fluctuations between years Despite the low winter temperatures, the Lower Ardeche can be classified among Mediterranean rivers, which typically have a very high maximum in summer.      

Least-squares prediction of horizontal coordinate distortions in Canada

A least-squares prediction method is described to estimate horizontal coordinate distortions at lower order points of a network using known coordinate differences (NAD27 coordinate distortions Δϕ′s and Δλ′s) at higher order points between NAD27 coordinates and coordinates derived from a recent (MAY 76), relatively distortion free, adjustment of these points. Empirical autocovariance functions of Δϕ and Δλ and crosscovariance function between Δϕ and Δλ are derived from some 5,250 data points and modelled using series of exponential functions. Empirical mean square values of Δϕ and Δλ, which are a measure of the distortions in NAD27 ϕ and λ, are 0.051 and 0.645 arcsecs² respectively. The corresponding mean value of the product ΔϕΔλ, which is a measure of the correlation between Δϕ and Δλ, is 0.056 arcsecs². The accuracy obtainable for predicted Δϕ and Δλ at an arbitrary point (e.g., lower order station) is a function of the accuracy and configuration of known Δϕ′s and Δλ′s in the surrounding area. Accuracies obtainable for various types of data configuration are given. Under favorable conditions taking place in about 60% of cases, accuracies in terms of ms agreement with known values of 0″.02 (0.6 m) and 0″.01 (0.2 m along parallel at latitude 50°) for the predicted latitude and longitude distortions are obtainable. Finally, a comparison with a method based on the use of complex polynomials is made. Presented at International Symposium on Geodetic Networks and Computations, Munich, August–September 1981.     

Caracteristiques de la Distribution des Gisements à Etain et Tungstene Dans L'Ouest de L'Europe

Résumé L'analyse de la distribution des gisements et indices à Sn-W de la province ouesteuropéenne permet de constater une organisation en bandes parallèles, alternativement à Sn et à W dominant. Leur orientation relativement constante, N 110 dans le Massif Central français et E-W dans le Nw de l'Ibérie, et leur indépendance par rapport aux axes structuraux de l'orogène varisque, suggèrent l'existence d'anisotropies crustales antérieures aux granitisations varisques. En effet, le comportement géochimique de Sn-W dans les processus de différenciation magmatique, et une polarité éventuelle du magmatisme dans l'orogène varisque, ne suffisent pas seuls à expliquer une telle distribution. Il faut rechercher ces anisotropies géochimiques bien avant la mise en place des granites peu différenciés subautochtones tardi-dévoniens qui sont déjà spécialisés en Sn. Depuis le Cadomien même, les granitoïdes qui ont concentré Sn-W par cristallisation fractionnée et fusion répétées ont été des révélateurs de plus en plus efficaces pour Sn, un peu moins pour W qui est surtout concentré par une phase hydrothermale. Deux grandes époques de mise en place des minéralisations en Sn-W peuvent être ainsi attribuées à deux lignées différenciées de granitoïdes: 1) namurienne et westphalienne dans le Massif Central; 2) westphalienne et autunienne dans le NW de la péninsule ibérique. Les gisements s'ordonnent suivant deux directions. Les unes N 110/N 90 sont les structures plicatives qui guident la mise en place des granites namuriens à westphaliens. Les autres sont N 20/N160 et guident les différenciations du toit des granites.

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The Sn-W spatial distribution (deposits and occurrences) in the west-european province emphazises an alternating W and Sn rich banded pattern. The bands have a fairly constant trend (N 110 in the french Massif Central, E-W in the northwestern Iberia) and are generally independant of that of the variscan orogenic domains. This supports the idea of crustal anisotropies previous to late paleozoïc granite emplacement. The banded organization is not readily explained by the geochemical behaviour of Sn-W during the magmatic evolution and the possible magmatic polarity of the orogen. So, geochemical anisotropies must be sought in rocks older than the late devonian poorly differentiated subautochtonous granites which were already anomalous in Sn. Since cadomian time, the granites which have concentrated Sn and W through repeated fractionate crystallization and remelting have been more and more effective revealers for Sn, a little less for W, which especially concentrates through hydrothermal processes. So, two main periods of Sn-W mineralization can be bound to two differentiated suites of granites: 1) Namurian-Westphalian in the french Massif Central; 2) Westphalian-Autunian in the north-western Iberia. The ore deposits occur along two directions: N 110/N 90 which are the trends of late fold axis and the guide of the setting of namurian granites and N 20/N 160 the trends of zones of differentiation in the roofs of the granites.