Global radiation within corn

Global and net solar radiation profiles were measured by traversing sensors at four heights in a square-sown plot and a row plot of field corn on four relatively cloudless days in August 1972. The fluxes and their vertical distributions are discussed. A numerical model of the short-wave radiation fluxes in a canopy is presented. Using leaf area index and fixed leaf radiative properties, calculated values of radiation are within 10% of measurements in most instances. The performance under predominantly beam or diffuse radiation is similar and model values of crop albedo compare well with values calculated from radiation measurements above the crops.     

Implications of uncertain future fossil energy resources on bioenergy use and terrestrial carbon emissions

The magnitude and character of the global resource base of fossil fuels is a key determinant of the evolution of the future global energy system and corresponding fossil fuel carbon emissions. What is less well understood is the potential magnitude of impact of the availability of fossil fuels, due to the interaction with biomass energy, on agriculture, land use, ecosystems and therefore carbon emissions from land-use change. This paper explores these links and implications. We show that if oil resources are limited, then the consequently higher price for liquids induces both the use of coal-to-liquids technology deployment, but also enhanced production of bioenergy crops particularly in a business-as-usual scenario. This in turn implies greater pressure to convert unmanaged ecosystems to produce bioenergy, and higher rates of terrestrial carbon emissions from land use.     

Nighttime temperature field in a valley

Summary An analysis of the nighttime near-surface temperature field at 27 stations in a deep mountain valley has been carried out for 5 nights during which drainage winds developed. It was found that a simple exponential function of time and the pressure level of each station accurately represents the temperature evolution during the night. Of particular interest is the fact that above a particular pressure elevation the temperature increases during the night.

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Nächtliches Temperaturfeld in einem Tal

Zusammenfassung Es wurde eine Analyse des nächdichen oberflächennahen Temperaturfeldes an 27 Stationen in einem tiefen Gebirgstal für funf Nächte, in denen Bergwind auftrat, durchgeführt. Es stellte sich heraus, da\ die Temperaturentwicklung während der Nacht exakt durch eine einfache Exponentialfunktion der Zeit und des Druckniveaus jeder Station beschrieben wird. Von besonderem Interesse ist die Tatsache, da\ die Temperatur während der Nacht über einem bestimmten Druckniveau ansteigt.

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With 3 Figures     

Greenhouse warming may moderate British storminess

Summary An analysis of data pertaining to the period 1861–1986 reveals that (1) a 1 °C rise in the mean annual air temperature of the British Isles has historically been associated with a 35% drop in the percentage of days that the United Kingdom has experienced cyclonic flow, and (2) a 2 °C increase in the mean annual air temperature over the sea to the north has typically been matched by a 60% drop in the percentage of days that the isles have experienced cyclonic flow originating from that source region. These findings raise significant questions about the oft-reported claim that CO₂-induced global warming will lead to an increase in world storminess.With 3 Figures     

Rare earth element geochemistry of Late Cenozoic alkaline lavas of the McMurdo Volcanic Group, Antarctica

Rare earth element (REE) concentrations were determined in 16 Ross Island and northern Victoria Land alkaline lava samples which were representative of four lava lineages of the McMurdo Volcanic Group, Antarctica. A kaersutite and two feldspar mineral separates were also analysed.

Two of the lava lineages, a basanite to nepheline benmoreite and a basanite to phonolite, have similar chondrite-normalized REE fractionation patterns, with a continuous enrichment of light and heavy REE and depletion of middle REE. The patterns result from the fractionation of olivine, clinopyroxene, spinels, feldspar, kaersutite and apatite. Kaersutite is an important fractionated phase responsible for the middle REE depletion.

Another of the lava lineages is mildly potassic with trachyandesite to peralkaline K-trachyte lavas which have partly overlapping REE fractionation patterns. There is a depletion in REE from tristanite to K-trachyte. Fractionation of olivine, clinopyroxene, feldspar and apatite probably control the REE chemistry of the lineage, greater degrees of apatite fractionation deplete the K-trachyte in REE relative to the tristanite. Feldspar fractionation in the genesis of the peralkaline K-trachyte is shown by a large negative Eu anomaly (Eu/Eu* = 0.10).

A nepheline hawaiite to anorthoclase phonolite lava lineage from the Erebus Centre shows enrichment of REE, although minor overlapping in the middle REE does occur. Anorthoclase phonolite has a positive Eu anomaly (Eu/Eu* = 1.31), indicating possible accumulation of anorthoclase. The lineage resulted from fractionation of olivine, clinopyroxene, magnetite and apatite.     

Heat flow and lithospheric thermal regime in the Northeast German Basin

New values of surface heat flow are reported for 13 deep borehole locations in the Northeast German Basin (NEGB) ranging from 68 to 91 mW m^− 2 with a mean of 77 ± 3 mW m^− 2. The values are derived from continuous temperature logs, measured thermal conductivity, and log-derived radiogenic heat production. The heat-flow values are supposed free of effects from surface palaeoclimatic temperature variations, from regional as well as local fluid flow and from thermal refraction in the vicinity of salt structures and thus represent unperturbed crustal heat flow. Two-D numerical lithospheric thermal models are developed for a 500 km section along the DEKORP-BASIN 9601 deep seismic line across the basin with a north-eastward extension across the Tornquist Zone. A detailed conceptual model of crustal structure and composition, thermal conductivity, and heat production distribution is developed. Different boundary conditions for the thickness of thermal lithosphere were used to fit surface heat flow. The best fit is achieved with a thickness of thermal lithosphere of about 75 km beneath the NEGB. This estimate is corroborated by seismological studies and somewhat less than typical for stabilized Phanerozoic lithosphere. Modelled Moho temperatures in the basin are about 800 °C; heat flow from the mantle is about 35 to 40 mW m^− 2. In the southernmost part of the section, beneath the Harz Mountains, higher Moho temperatures up to 900 to 1000 °C are shown. While the relatively high level of surface heat flow in the NEGB obviously is of longer wave length and related to lithosphere thickness, changes in crustal structure and composition are responsible for short-wave-length anomalies.     

Supergene geochemistry and crystal morphology of gold in a semiarid weathering environment: application to gold exploration

Oxidation of sulfide- and carbonate-rich vein gold deposits under semiarid conditions can be represented as a three-stage process, each creating supergene environments conducive to dissolution and reprecipitation of gold-silver alloys. The three-stage weathering process of sulfide-carbonate gold veins is depth-dependent, and develops from the relatively young, lowermost weathering horizon just below the water table, through an intermediate weathering horizon in the oxidation zone above the water table, and culminating in the oxide-rich upper saprolite and oxisol.Neoformed gold crystals in the weathering profile have distinct composition and morphologic characteristics from the hypogene gold crystals associated with the sulfide- and carbonate-rich ores. Two distinct types of secondary gold are present in the weathering profile: (1) gold crystals associated with sulfates and arsenates; and (2) gold crystals associated with iron and aluminum oxides/hydroxides, or with kaolinite. The distinct crystal morphologies and mineralogical associations of primary and secondary gold are useful in prospecting for gold deposits in weathered terrains.     

Lithostratigraphy of the Mérida (Wisconsinan) glaciation and Pedregal interstade, Mérida Andes, northwestern Venezuela

At Pedregal, more than 40 m of sediments are exposed within a ‘fan complex’ formed between lateral moraines of the adjacent Mucuchache and El Caballo valleys. Early and late Mérida (Wisconsinan) glaciations are represented by till and till plus proglacial sediments, respectively. A middle Wisconsinan interstadial event, here termed the Pedregal interstade, began at the end of the Early Mérida glaciation at approximately 60 ka BP. Following the retreat of ice from the small Pedregal Basin, a lake formed when the local drainage was blocked due to movement of the Mesa de Caballo along the Boconó Fault. Shallow lake or no-lake phases lasted approximately a few hundred to, at most, 2000 years, and each lake phase was marked by peat accumulation. Four of seven peats identified formed during sufficiently long intervals for soil profiles (incipient to mature Spodosols) also to develop. The Spodosol with the strongest development (Eb/Bsb/Coxb/Cub horizons) is found adjacent to the lowest peat and reflects ongoing early Mérida stadial (MIS 3) conditions; the youngest peats, associated with weak podzolic soils (Eb/Bsb horizons), formed under slightly warmer interstadial conditions, presumably with less soil water. Cyclic lacustrine deposition is related to lake level and relative depth fluctuations, due in part to variable shoreline/delta progradation and shallowing as the lake deepened in general. Whereas final drainage of the lake is related to movement of the Boconó Fault and breach of the moraines that form the Mesa de Caballo, earlier lake level fluctuations appear related to climate change. Radiocarbon dating of the peats suggests they are related to warmer periods and may tentatively correlate with small ‘interstadials’ or ‘D-O events’ detected in the oxygen-isotope record of Greenland ice cores and North Atlantic marine sediments.     

Chemical and physical studies of type 3 chondrites—IV: Annealing studies of a type 3.4 ordinary chondrite and the metamorphic history of meteorites

Samples of a type 3.4 chondrite have been annealed at 400–1000°C for 1–200 hours, their thermoluminescence properties determined and analyzed for K, Na, Mn, Sc and Ca by instrumental neutron activation analysis. After annealing at ?900°C, the samples showed a 50% decrease in TL sensitivity, while after annealing at 1000°C it fell to 0.1-0.01 times its unannealed value and loss of Na and K occurred. The TL and compositional changes resemble those observed for the equilibrated Kernouve chondrite after similar annealing treatments, except that the sharp TL decrease, and element loss, occurred at ~ 1100°C; this difference is presumably due to petrographic differences in the feldspar of the two meteorites. The temperature and the width of the TL peak showed a discontinuous increase after annealing at 800°C; peak temperature jumped from 130 to 200°C and peak width increased from 90 to 150°C. The activation energies for these TL changes are 7–10 kcal/mole. Similar increases in the TL peak temperature have been reported in TL studies of Amelia, VA, albite, where they were associated with the low to high-temperature transformation. However, the activation energy for the transformation is ~80 kcal/mole. These changes in TL emission characteristics resemble trends observed in type 3 ordinary chondrites and it is suggested that type 3.3–3.5 chondrites have a low-feldspar as TL phosphor and > 3.5 have high-feldspar as the phosphor. Thermoluminescence therefore provides a means of palaeothermometry for type 3 ordinary chondrites.