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121.
Allison M. Thomson Robert A. Brown Steven J. Ghan R. Cesar Izaurralde Norman J. Rosenberg L. Ruby Leung 《Climatic change》2002,54(1-2):141-164
Crop growth models, used in climate change impact assessments to project production on a local scale, can obtain the daily weather information to drive them from models of the Earth's climate. General Circulation Models (GCMs), often used for this purpose, provide weather information for the entire globe but often cannot depict details of regional climates especially where complex topography plays an important role in weather patterns. The U.S. Pacific Northwest is an important wheat growing region where climate patterns are difficult to resolve with a coarse scale GCM. Here, we use the PNNL Regional Climate Model (RCM) which uses a sub-grid parameterization to resolve the complex topography and simulate meteorology to drive the Erosion Productivity Impact Calculator (EPIC) crop model. The climate scenarios were extracted from the PNNL-RCM baseline and 2 × CO2 simulationsfor each of sixteen 90 km2 grid cells of the RCM, with differentiation byelevation and without correction for climate biases. The dominant agricultural soil type and farm management practices were established for each grid cell. Using these climate and management data in EPIC, we simulated winter wheat production in eastern Washington for current climate conditions (baseline) and a 2 × CO2 `greenhouse' scenario of climate change.Dryland wheat yields for the baseline climate averaged 4.52 Mg ha–1 across the study region. Yields were zero at high elevations where temperatures were too low to allow the crops to mature. The highest yields (7.32 Mgha–1) occurred at intermediate elevations with sufficientprecipitation and mild temperatures. Mean yield of dryland winter wheat increased to 5.45 Mg ha–1 for the 2 × CO2 climate, which wasmarkedly warmer and wetter. Simulated yields of irrigated wheat were generally higher than dryland yields and followed the same pattern but were, of course, less sensitive to increases in precipitation. Increases in dryland and irrigated wheat yields were due, principally, to decreases in the frequency of temperature and water stress. This study shows that the elevation of a farm is a more important determinant of yield than farm location in eastern Washington and that climate changes would affect wheat yields at all farms in the study. 相似文献
122.
S.D KellyK.M Kemner J.B FeinD.A Fowle M.I Boyanov B.A BunkerN Yee 《Geochimica et cosmochimica acta》2002,66(22):3855-3871
X-ray absorption fine structure (XAFS) measurements was used at the U L3-edge to directly determine the pH dependence of the cell wall functional groups responsible for the absorption of aqueous UO22+ to Bacillus subtilis from pH 1.67 to 4.80. Surface complexation modeling can be used to predict metal distributions in water-rock systems, and it has been used to quantify bacterial adsorption of metal cations. However, successful application of these models requires a detailed knowledge not only of the type of bacterial surface site involved in metal adsorption/desorption, but also of the binding geometry. Previous acid-base titrations of B. subtilis cells suggested that three surface functional group types are important on the cell wall; these groups have been postulated to correspond to carboxyl, phosphoryl, and hydroxyl sites. When the U(VI) adsorption to B. subtilis is measured, observed is a significant pH-independent absorption at low pH values (<3.0), ascribed to an interaction between the uranyl cation and a neutrally charged phosphoryl group on the cell wall. The present study provides independent quantitative constraints on the types of sites involved in uranyl binding to B. subtilis from pH 1.67 to 4.80. The XAFS results indicate that at extremely low pH (pH 1.67) UO22+ binds exclusively to phosphoryl functional groups on the cell wall, with an average distance between the U atom and the P atom of 3.64 ± 0.01 Å. This U-P distance indicates an inner-sphere complex with an oxygen atom shared between the UO22+ and the phosphoryl ligand. The P signal at extremely low pH value is consistent with the UO22+ binding to a protonated phosphoryl group, as previously ascribed. With increasing pH (3.22 and 4.80), UO22+ binds increasingly to bacterial surface carboxyl functional groups, with an average distance between the U atom and the C atom of 2.89 ± 0.02 Å. This U-C distance indicates an inner-sphere complex with two oxygen atoms shared between the UO22+ and the carboxyl ligand. The results of this XAFS study confirm the uranyl-bacterial surface speciation model. 相似文献
123.
A low-angle tracking technique based on a novel high-resolution algorithm is presented. The new high-resolution algorithm, which is called the forward-backward nonlinear prediction (FBNLP) method, replaces the linear predictor in the conventional forward-backward linear prediction (FBLP) method with a nonlinear one to try to improve the tracking in a realistic naval environment, Real radar tracking data over the sea, which were recorded with a 32-element sampled aperture antenna on an “over-water” path, were used in this study. They were recorded in a multipath environment, i.e., one where, in addition to the customary direct signal, an indirect signal was also received by the antenna system, and separation of these two signals was less than one standard beamwidth. The performance of the FBNLP method is shown to be better than that of the modified FBLP algorithm for the data sets used in this paper 相似文献
124.
An approach is presented for the prediction of linear and nonlinear load–deformation behaviour of laterally loaded pile groups. The individual pile response is obtained by the conventional p–y curve technique, while group interaction is modelled using the Mindlin's solution. Good agreement is observed when comparing the present method of analysis with the commonly used interaction factor approach for the computation of response of pile groups embedded in a homogenous, isotropic elastic half-space. The predicted pile group behaviour also compares favourably with existing field data on laterally loaded pile groups in soft clay. 相似文献
125.
Yuk Yee Yan 《Singapore journal of tropical geography》1997,18(2):210-217
The universal scale of apparent temperature (AT) and clo, a unit measuring the amount of clothing insulation required to maintain comfort, were used to examine the weather stress in Hong Kong. Hourly AT and clo values were computed using hourly air temperature, wind speed, vapour pressure and cloud cover data from 1980 to 1994. Results of both AT and clo reflected highly corresponding changes of thermal stress. It is found that the most stressful time in winter and summer occurred in the early morning and afternoon, and cool weather and tropical ensembles were required to surmount the extreme weather stress respectively. A greater percent of time with severe heat stress than those with extreme cold stress was discovered. These results also indicated that clo is a more informative weather stress index than AT since it provides both the thermal stress and clothing requirements to sustain comfort. 相似文献
126.
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128.
Yuk Yee Yan Department of Geography Hong Kong Baptist University Kowloon Tong Hong Kong 《地理学报(英文版)》1997,(4)
I.IntroductionClimatehaslongbeenknowntohaveaprominentinfluenceonresidentialenergyconsumption,particularlytheuseofelectricityinspaceheatingandcooling.InHongKong,therewasanincreaseof207percentinresidentialelectricityconsumption,from8414terajoule(TJ)in1980to25827T… 相似文献
129.
Leung CC Jefferson TA Hung SK Zheng GJ Yeung LW Richardson BJ Lam PK 《Marine pollution bulletin》2005,50(12):33-1719
130.