Evaporation from a blanket bog in a foggy coastal environment     

Jonathan S. Price 《Boundary-Layer Meteorology》1991,57(4):391-406

Frequent fog severely restricts evaporation from blanket bogs in Newfoundland because it more than halves the radiant energy input, and it eliminates the vapor pressure deficit, resulting in evaporation at the equilibrium rate (average = 0.99 during fog). During these periods, there is no surface resistance to evaporation because the bog has been wetted by fog drip, and although the latent heat flux dominates over sensible heat (average = 0.8), both are small. In contrast, the surface dries during clear periods, increasing the surface resistance to evaporation so that sensible heat becomes more important ( = 1.05). When the mosses are dry, evaporation is below the equilibrium rate ( = 0.87), although the higher available energy ensures that actual evaporation is higher. During clear periods, daily evaporation averaged 2.5 mm, compared to 1.1 and 0.7 mm for fog and rain, respectively. The suppressed evaporation at this site is important in maintaining appropriate hydrological conditions for blanket bog development.  相似文献   

Equilibrium dihedral angles in the system H2O−CO2−NaCl-calcite,and implications for fluid flow during metamorphism     

Marian B. Holness  Colin M. Graham 《Contributions to Mineralogy and Petrology》1991,108(3):368-383

Fluid-calcite-calcite dihedral angles have been measured for fluids in the system H₂O−CO₂−NaCl, between 1 and 2 kbar, and 550–750° C. It is found that the calcite-calcite-H₂O dihedral angle decreases steadily with addition of NaCl from a value of about 80° (pure water) to 44° (60 wt% NaCl). The CO₂−H₂O system displays a well-defined minimum at , with a dihedral angle of 50°, in contrast to those of pure CO₂ and H₂O which are 90° and 80° respectively. Experiments containing fluids which are immiscible at run conditions showed a bimodal distribution of dihedral angles in the CO₂−H₂O−NaCl system, which can be approximately correlated with the compositions of the two fluid phases. Such bimodality was only observed for immiscible fluids in the H₂O−NaCl system if the quench rate exceeded about 200°C per min. This is probably due to the extremely rapid establishment of the single phase dihedral angle on quenching. The fluid phase topology in devolatilising marbles will only be a connected network for very saline brines and fluids with close to 0.5. Fluids trapped in fluid inclusions in calcite grains in marbles may be predominantly H₂O-rich or CO₂-rich, and of low salinity. All other fluid compositions in the H₂O−CO₂−NaCl-calcite system will occupy isolated pores, the largest of which will grow at the expense of the smallest. Escape of fluid produced during devolatilisation reactions under such conditions will occur by fluid overpressuring and hydrofracture. In contrast, previous experimental studies of quartz-fluid dihedral angles between 950° and 1100° C (Watson and Brenan 1987) predict that quartz-dominated lithologies will permit pervasive flow of H₂O−NaCl fluids, but not of H₂O−CO₂ fluids. Documented geological examples of differences in permeability and fluid flow mechanism between metamorphic argillites, psammites and limestones which support the results of the experimental studies are discussed.  相似文献   

Impact of the spatial arrangement of land management practices on surface runoff for small catchments     

F. Colin  R. Moussa  X. Louchart 《水文研究》2012,26(2):255-271

Predicting the impact of land use changes on the hydrological response is crucial for water resource management. In the particular case of small catchments (1–10 km²), distributed models could provide useful answers regarding the effects of cultivation practices and man‐made works on water fluxes. However, the impacts of specific land use spatial arrangements are difficult to predict because of the prohibitive number of possible cases to consider. Focusing on surface runoff, this article describes a strategy based on a water particle tracking routine to be plugged‐in a distributed model that is designed to determine the spatial arrangements of land management practices that have the greatest impact on volume, peak discharge and lag time at the catchment outlet. A case study is described; the hydrological response of the Roujan catchment (Herault, France) is simulated with the MHYDAS model. The Roujan catchment contains a vineyard in a Mediterranean climate in a landscape in which weeding practices highly influence the partition between soil infiltration and runoff. Results showed that the proposed strategy is much more efficient than a random approach to design the spatial arrangements of the vineyard weeding practices with the greatest impact. Therefore, the proposed strategy may lead to innovative policies for the spatial planning of land management practices. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

The vandalizing effects of irresponsible core sampling: a call for a new code of conduct     

Colin MacFadyen 《Geology Today》2010,26(4):146-151

In 1989 the UK's Geologists' Association (GA) published the Code of Conduct for Rock Coring, a best practice guide to rock sampling by means of coring. The preparation of a code in the UK was required following acts of thoughtlessness by some researchers that permanently defaced outcrops ruining their photographic value. Despite the existence of the GA Code the vandalizing effects of irresponsible coring continue to this day and the cumulative effects are becoming increasingly apparent to even the most casual observers. As well as damaging exposures, irresponsible coring is tarnishing the reputation of geological science and there is concern that relations with landowners may be threatened by irresponsible coring, which may impact upon future sampling and research in the worst affected areas. Consequently, there is an urgent requirement for the reestablishment and promotion of a ‘Code of Conduct for Rock Coring’ based on the principles of the GA Code. To maximize awareness of the code and to ensure good practice guidance is not lost with the passage of time, its ethos could become enshrined in Earth science educational programmes. Just as importantly, adherence to the code could become an integral component of the standard ethical procedure conditions, attached to research funding for projects involving rock sampling.  相似文献   

Non‐linear response of current‐meter compasses: Research note     

David A. Booth  Colin Griffiths 《大气与海洋》2013,51(3):611-616

Abstract

A non‐linear response in current‐meter compasses is examined in terms of its effect on the measured residual current. It is shown that, even for a compass response within typical manufacturers’ specifications, the induced errors are important for regions where the residual speed is less than about 10% of the peak tidal current. In an M₂ current, the non‐linearity also induces an M₄ signal, but this is not sufficiently large to be easily detected by tidal analyses.  相似文献   

Palaeozoic corals: their evolution and palaeoecology     

Colin Scrutton 《Geology Today》1999,15(5):184-193

In recent years, our understanding of Palaeozoic corals has increased enormously. Several new groups have been discovered, extending the range of corals back to the early Cambrian, and we now have a clearer idea of the relationships between them. None of them was a direct ancestor to the post‐Palaeozoic corals. Similarly, the ecology of Palaeozoic corals differed from that of their living relatives in important respects. Palaeozoic corals were principally adapted for life on soft substrates and were not the spectacular reef‐builders that modern corals have become. However, their contribution to Palaeozoic ecosystems is nonetheless fascinating. Their structural adaptations and growth‐forms can tell us much about life and processes on Palaeozoic sea floors.  相似文献   

Caldera formation in the Rum Central Igneous Complex, Scotland     

Valentin R. Troll  C. Henry Emeleus  Colin H. Donaldson 《Bulletin of Volcanology》2000,62(4-5):301-317

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Developing building-damage scales for lahars: application to Merapi volcano,Indonesia     

Susanna F. Jenkins  Jeremy C. Phillips  Rebecca Price  Kate Feloy  Peter J. Baxter  Danang Sri Hadmoko  Edouard de Bélizal 《Bulletin of Volcanology》2015,77(9):1-17

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Evaluation of a low‐cost temperature measurement system for environmental applications     

Jason Hubbart  Timothy Link  Colin Campbell  Doug Cobos 《水文研究》2005,19(7):1517-1523

Thermochron iButtons incorporate the latest in digital technology, making them smaller, less expensive, durable and potentially more reliable than many other temperature logging devices. The objective of this study was to test the accuracy of an inexpensive air temperature measurement system, composed of a Thermochron iButton and radiation shield. Sixty‐one iButtons were subjected to a sequence of two water baths (0 °C and 24·9 °C) to assess the absolute accuracy of the sensors. Five solar radiation shields were tested in a greenhouse setting to evaluate the reduction in radiative heating. Significant differences (p < 0·05) were detected between instruments subsequent to both water‐bath treatment analyses. The accuracy of the sensors was well within the manufacturer's stated specification of ±1·0 °C with a collective temperature variance of ±0·21 °C. Temperature responses generated by the Thermochron iButtons in different radiation shields were consistent, but varied significantly (p < 0·05) from 28 to 44 °C based on diurnal temperature ranges. Results indicate that the Thermochron iButton is an accurate, inexpensive alternative to more expensive temperature data‐logging systems, and is well suited for obtaining quality spatially distributed data for hydrologic and water quality investigations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

An Embedded Model Estimator for Non-Stationary Random Functions Using Multiple Secondary Variables     

Daly  Colin 《Mathematical Geosciences》2022,54(5):979-1015

Mathematical Geosciences - An algorithm for non-stationary spatial modelling using multiple secondary variables is developed herein, which combines geostatistics with quantile random forests to...  相似文献