A TEST OF THE RADIATIVE ENERGY BALANCE OF THE SHAW MODEL FOR SNOWCOVER     

G. N. FLERCHINGER  J. M. BAKER  E. J. A. SPAANS 《水文研究》1996,10(10):1359-1367

Snow and ice present interesting challenges to hydrologists. Simulating the radiative balance over snow, which is an important part of surface–atmosphere interactions, is particularly challenging because of the decay in albedo over time and the difficulty in estimating surface temperature and incoming long-wave radiation fluxes. Few models are available that include a comprehensive energy and water balance for cold season conditions. The simultaneous heat and water model (SHAW) is a detailed, physical process model of a vertical, one-dimensional canopy–snow–residue–soil system which integrates the detailed physics of heat and water transfer through a plant canopy, snow, residue and soil into one simultaneous solution. Detailed provisions for metamorphosis of the snowpack are included. The SHAW model was applied to data for one winter/spring season (November to May) on a ploughed field in Minnesota without prior calibration to test the performance of the radiation components. Maximum snow depth during this period was 30 cm. For the nearly 100 days of snowcover, the model accounted for 69% of the variation in net solar radiation, 66% of the variation in incoming long-wave radiation, 87% of the variation in emitted long-wave radiation, 26% of the variation in net long-wave radiation and 55% of the variation in net radiation balance. Mean absolute error in simulated values ranged from 10 W m⁻² for emitted long-wave radiation to 27 W m⁻² for the entire net radiation balance. Mean bias error ranged from 8 W m⁻² for emitted long-wave radiation to −16 W m⁻² for the entire net radiation balance. When the entire 170 days of simulation, which included periods without snowcover, were included in the analysis, the variation in observed values increased greatly. As a result, the variation in observed values accounted for by the model increased to 97, 71, 93, 56 and 94%, respectively, while the mean absolute and mean bias errors in simulated values remained nearly the same. Model modifications and parameter adjustments necessary to improve winter-time simulation were investigated. Simulation results suggest that the SHAW model may be a useful tool in simulating the interactive influences of radiative transfer at the surface–atmosphere interface.  相似文献   

LAND‐USE CHANGE IN THE ATLANTIC COASTAL PINE BARRENS ECOREGION     

TERRY L. SOHL  LAURI B. SOHL 《Geographical review》2012,102(2):180-201

Information on the rates, characteristics, and drivers of land‐use change are vital for addressing the impacts and feedbacks of change on environmental processes. The U.S. Geological Survey's Land Cover Trends project is conducting a consistent, national analysis of the rates, causes, and consequences of land‐use change. In this article we assess change in the Atlantic Coastal Pine Barrens ecoregion from 1973 to 2000. Urban lands expanded by more than 900 square kilometers during the study period. Land‐use change in the ecoregion followed the tenets of “Forest Transition Theory” (ftt ) prior to the study period, but forest lands experienced consistent declines from 1973 to 2000. Increasing government regulation during the study period, consistent with concept of the “Quiet Revolution” (qr ), mitigated forest loss during the latter half of the study period. Generalized theories, including ftt and the qr , are valuable, but local and regional determinants of comparative land rents ultimately drive land‐use change at this scale.  相似文献   

A strong regional temperature signal in low‐elevation Huon pine     

K. J. ALLEN  D. M. DREW  G. M. DOWNES  R. EVANS  E. R. COOK  M. BATTAGLIA  P. J. BAKER 《第四纪科学杂志》2013,28(5):433-438

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Variations in the discharge and organic matter content of stalagmite drip waters in Lower Cave,Bristol     

ANDY BAKER  WILLIAM L. BARNES  PETER L. SMART 《水文研究》1997,11(11):1541-1555

Six drip waters, which were actively depositing stalagmites in Lower Cave, Bristol, were analysed both for discharge and luminescence properties. Drip discharges were determined for two different years, and show a complex response to surface precipitation variations. Inter annual variability in drip discharge is demonstrated to be significantly higher than intra-annual variability, and discharge was demonstrated both to increase and decrease non-linearly with increased precipitation. Drip waters demonstrate a correlation between their luminescence intensity and drip discharge, with increased luminescence in winter as more organic matter is flushed through the aquifer. The strength of the relationship between luminescence intensity and discharge increases with increased discharge. The results presented here have implications for the palaeoenvironmental interpretation of annual growth laminae and the growth rates of stalagmite samples. © 1997 John Wiley & Sons, Ltd.  相似文献   

Experimental hydrothermal alteration of a martian analog basalt: Implications for martian meteorites     

Leslie L. BAKER  Deborah J. AGENBROAD  Scott A. WOOD 《Meteoritics & planetary science》2000,35(1):31-38

Abstract— A number of martian meteorite samples contain secondary alteration minerals such as Ca‐Mg‐Fe carbonates, Fe oxides, and clay minerals. These mineral assemblages hint at hydrothermal processes occurring in the martian crust, but the alteration conditions are poorly constrained. This study presents the results of experiments that examined the alteration of a high‐Fe basalt by CO₂‐saturated aqueous fluids at 23 and 75 °C and by mixed H₂O‐CO₂ vapors at 200 and 400 °C and water‐rock ratios of 1:1 and 1:10. Results indicate that observable alteration of the basalt takes place after runs of only seven days. This alteration includes mobilization of silica into phases such as opal‐CT and quartz, as well as the formation of carbonates, oxides, and at some conditions, zeolites and hydrous silicates. The degree of alteration increases with run temperature and, in high‐temperature vapor experiments, with increasing water content of the vapor. The degree of alteration and the mineralogy observed in the martian meteorites suggests that none of these samples were exposed to aqueous fluids for long periods of time. Nakhla and Lafayette probably interacted with water for relatively brief periods of time; if so, silica may have been leached from the parent rocks by the altering fluids. Allan Hills 84001 shows possible evidence for very limited interaction with an aqueous fluid, but the overall slight degree of alteration described for this meteorite strongly suggests that it never interacted extensively or at high temperature with any water‐bearing fluid. Elephant Moraine A79001 may not have been altered by aqueous fluids at all. The results of this study best support models wherein the meteorite parent rocks were wetted intermittently or for brief periods of time rather than models that invoke long‐term reaction with large volumes of water. Our experiments studied alteration of a high‐Fe basalt by dilute, CO₂‐saturated, aqueous solutions at 23 and 75 °C and by mixed H₂O‐CO₂ vapors at 200 and 400 °C. The results suggest that alteration of the parent rock takes place even after very short reaction times of seven days. All experiments produced carbonate minerals, including calcite, and in some cases, magnesite, siderite, and ankerite. A free silica phase, either opal, quartz, or hydrated silica, formed in most experiments. More altered experiments also contained minerals such as zeolites and hydrous phyllosilicates. Clay minerals were not observed to form in any experiments. In aqueous fluids, higher temperature corresponded with a higher degree of alteration, whereas changing fluid composition had no observable effect. In high‐temperature vapors, the degree of alteration was controlled by temperature and the proportion of H₂O to CO₂, with water‐rock ratio also playing a role in transport of silica. Application of these results to martian meteorites that contain secondary alteration minerals suggests that none of the martian rocks underwent extensive interaction with aqueous fluids. Nakhla and Lafayette contain clay minerals, which suggests that they interacted with water to some extent, possibly at elevated temperatures. Although ALH84001 shows possible evidence of very limited interaction with aqueous fluids, EETA79001 does not. These results support models for the alteration of these meteorites that do not invoke long‐term interaction with water or reaction with large volumes of water. Except for some models for alteration of ALH84001, this conclusion agrees with most of the literature on alteration of martian meteorites.  相似文献   

On and Off the North China Craton: Where is the Archaean Keel?   总被引：67，自引：2，他引：65  

FAN  W. M.; ZHANG  H. F.; BAKER  J.; JARVIS  K. E.; MASON  P. R. D.; MENZIES  M. A. 《Journal of Petrology》2000,41(7):933-950

Geophysical data indicate that the lithosphere beneath the NorthChina Craton (NCC) is  相似文献   

Geology and jungle fieldwork in eastern Indonesia     

SIMON BAKER  ROBERT HALL  EMILY FORDE 《Geology Today》1994,10(1):18-23

Collecting geological information from the jungles and islands of eastern Indonesia depends largely on traditional fieldwork methods involving much footwork and messing about in boats. Coupled with modern laboratory and computing techniques, information gained on the ground is being used to interpret the tectonic development of east Indonesia, the Philippine Sea and the western Pacific.  相似文献   

'SLABBER': a useful device for subsampling box cores     

BRADFORD L. BENGGIO  TERRY A. NELSEN 《Sedimentology》1984,31(6):879-882

ABSTRACT
The 'SLABBER', a plexiglass device designed for subsampling box cores, was used at sea with excellent results. The SLABBER allowed visual inspection of any existing sedimentary features, and also provided storage, when necessary for subsamples. When the features were present, X-radiography of the SLABBER subsamples clearly showed sediment layering, evidence of bioturbation and orientation of shell material, all with apparent minimal disturbance of these structures.  相似文献   

Time- and method-dependent size distributions of fine-grained sediments     

TERRY A. NELSEN 《Sedimentology》1983,30(2):249-259

ABSTRACT With increased interest in fine-grained sediments it is imperative that a firm basis exist for comparative studies of these cohesive sediments. In this study the size distributions of continental slope and rise muds are shown to be dependent on both method and duration of sample pretreatment. Statistical analysis of 171 size distributions indicates that of the four most frequently used sample preparation methods (soak, stir, shake and ultrasonify) the time required to reach a 'terminal' distribution beyond which no 'fine-shift' was detected varied from 15 minutes to > 90 hours for a given sample solely as a function of preparation method. Data from this study also indicate that sample preparation by simple soaking alone will probably yield fine-grained sediments which, when analysed by pipette or microsedimentation accumulation balance, undergo a continuous change in size distribution during analysis and may never reach a 'terminal' distribution during the analysis time. On the other hand stirring and ultrasonification were shown to be the most rapid and consistent methods for obtaining a sample's'terminal'distribution.  相似文献   

Estimation of observation impact using the NRL atmospheric variational data assimilation adjoint system   总被引：2，自引：0，他引：2  

ROLF H. LANGLAND  NANCY L. BAKER 《地球，A辑:动力气象学与海洋学》2004,56(3):189-201

An adjoint-based procedure for assessing the impact of observations on the short-range forecast error in numerical weather prediction is described. The method is computationally inexpensive and allows observation impact to be partitioned for any set or subset of observations, by instrument type, observed variable, geographic region, vertical level or other category. The cost function is the difference between measures of 24-h and 30-h global forecast error in the Navy Operational Global Atmospheric Prediction System (NOGAPS) during June and December 2002. Observations are assimilated at 00 utc in the Naval Research Laboratory (NRL) Atmospheric Variational Data Assimilation System (NAVDAS). The largest error reductions in the Northern Hemisphere are produced by rawinsondes, satellite wind data, and aircraft observations. In the Southern Hemisphere, the largest error reductions are produced by Advanced TIROS Operational Vertical Sounder (ATOVS) temperature retrievals, satellite wind data and rawinsondes. Approximately 60% (40%) of global observation impact is attributed to observations below (above) 500 hPa. A significant correlation is found between observation impact and cloud cover at the observation location. Currently, without consideration of moisture observations and moist processes in the forecast model adjoint, the observation impact procedure accounts for about 75% of the actual reduction in 24-h forecast error.  相似文献