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1.
利用ECMWF再分析数据验证PRECIS对中国区域气候的模拟能力   总被引:8,自引:8,他引:51  
本文利用1979~1983年的ECMWF再分析数据作为准观测侧边界条件驱动Hadley气候预测和研究中心的区域气候模式系统PRECIS,验证PRECIS对中国区域的气候模拟能力。选择典型的观测站点北京模拟的日最高,最低气温、太阳短波总辐射和月均降水量与观测结果进行直接比较,显示:PRECIS具有很强的模拟地面气候季节变化的能力。全国740个台站的观测与模拟值的统计分析表明:尽管模拟的最高,最低气温在0℃附近有一‘锯齿’状的偏差,PRECIS能够很好地模拟全国范围最高,最低气温的型态分布特征;从全国范围看,模拟的降水值偏高,但显示出很强的模拟极端降水事件的能力;模拟的地面太阳短波总辐射与全国122个台站的观测结果的比较显示:PRECIS模拟的辐射值偏高,全国范围内约高22%。因此,当应用PRECIS输出结果进行气候变化的影响评价时,需要对模式的输出结果进行订正。  相似文献
2.
考虑地面灌水技术制约的灌溉制度优化   总被引:2,自引:2,他引:7  
制定作物灌溉制度不仅要考虑补充根层土壤水分以满足作物需求,还应考虑灌水方法对灌水量的限制。为研究我国华北地区地面灌溉条件下冬小麦-夏玉米连作的节水灌溉制度,在河北省雄县进行了连续3年不同灌水处理试验,用水量平衡模型ISAREG对各处理进行数值模拟,从而验证了选定的模型和参数。采用该模型模拟了不同水文年冬小麦-夏玉米连作的多种灌溉制度,对各方案的灌水次数、灌水量、降雨和灌溉水量损失以及作物产量等因素进行了对比,并对现行灌溉制度进行了评价。结果显示:雄县现行灌溉定额大大超过了灌溉需水量,主要原因是地面灌水技术的制约,如田面不平、进地流量过小或畦块过大等,造成难以控制小水量灌溉。为研究既能满足作物基本需水要求,又使灌溉水量损失最小的最佳灌水定额,用模拟地面灌溉水流运动的SRFR模型模拟不同生长阶段的灌溉,得到了每次灌溉时不同流量条件下的最小灌水量,以及灌水效率与灌水量的关系,据此提出了与灌水技术改进措施相结合的不同水文年的灌溉制度优化方案。  相似文献
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基于SPAC系统的作物腾发量模型的试验研究   总被引:1,自引:1,他引:0       下载免费PDF全文
通过田间试验对河北省2004年和2005年棉花、冬小麦和夏玉米不同生育期的冠层温度、地表温度和叶面积指数进行测定,根据能量平衡方程和空气动力学方程,结合当地气象资料推导出作物腾发量模型,并与棉花、冬小麦和夏玉米不同生育期实际腾发量比较发现:作物腾发量模型计算值不仅反映了这3种作物不同生育期腾发量的变化规律,而且与实际腾发量平均值的相对误差2004年分别为8.46%、4.76%和12.85%,2005年分别为3.42%、1.65%和0.84%,因此可以利用作物腾发量模型来计算作物腾发量,该研究为监测土壤墒情和确定作物缺水指标提供了理论依据.  相似文献
5.
Empirical habitat selection models aid managers by predicting distribution patterns, but recent critiques urge a fuller application of available methods. We used a suite of habitat modelling techniques to identify factors influencing the distribution of brown-headed cowbirds (Molothrus ater), a brood parasite capable of causing population declines in some host species. We used data on cowbird occurrence in the Southern Gulf Islands, Canada, to estimate the influence of landscape features on cowbird distribution beginning with a set of a priori models based on literature. Best models were also constructed using stepwise logistic and autologistic regression, and using only widely available data, and these models and their predictive maps were then evaluated. Cowbirds were predicted by proximity to potential feeding areas and landscape context. The best logistic model included landcover, cattle, and distance to urban area and agriculture. Model performance was improved by autologistic regression, and models restricted to widely available data were only slightly poorer. All models were robust to internal validation using bootstrapping and when compared to an independent empirical dataset of parasitism rates of a host on 12 sites monitored for up to 8 years. Our predictive maps for cowbirds should help land managers make spatial predictions about cowbird impact on particular hosts, as well as evaluate land-use decisions that could influence cowbird abundance and host fitness. We evaluated several approaches to habitat modelling of interest to conservationists and make suggestions for future studies when spatial predictions are likely to affect decisions in conservation and land use planning.  相似文献
6.
Species conservation largely depends on knowledge of habitat needs of target species. GIS-models are increasingly used to assess habitat preferences and distribution of target species, but their accuracy is constrained by availability of digital data layers. We developed a two-steps approach aiming at showing pros and cons of landscape (GIS)- and site-level habitat models, identifying key habitat factors for conservation of a threatened bird species, the red-backed shrike Lanius collurio. A spatially explicit GIS-model was generated using landscape variables, and a second model at site level was developed using fine-scale variables measured on the ground. The GIS-based model was then extrapolated to the entire region to obtain a map of distribution of suitable habitats. Positive associations between shrike occurrence and both hedgerow length and partial shrub cover were detected at both scales. Shrikes were also positively associated with grassland cover at landscape level and with partial cover of untilled herbaceous vegetation at the finer scale, and negatively affected by lucerne cover. The GIS-model led to an affordable map of predicted habitat suitability which should help conservationists to focus on different local priorities, but was unable to identify effects of untilled and lucerne cover. Site-level model gave fine details for habitat management, but its application elsewhere requires ground-measurements of factors. Combining the multiscale models could indicate more urgent actions at large scales (e.g. maintaining suitable habitats, or improving connectivity among isolated patches) and draw a detailed figure of the most suitable habitat for the species. Shrike occurrence was associated with a higher number of shrub and tree species: the indicator value of the species should ensure general benefits for biodiversity from dedicated management.  相似文献
7.
探讨了APEX(Agricultural Policy/Environmental eXtender)模型在淮河流域中上游的适宜性。将APEX模型用于淮河流域中上游监测资料较匮乏的3个径流小区,用日径流/产沙的实测值和模拟值校正和验证模型,用校正过的模型评价不同土地管理措施的长期水土保持效益(1981~2005)。在模型校正阶段,3个小区日径流量和产沙量的平均百分误差绝对值(APE)小于20%,平均纳希-苏特克利夫有效系数(EF)大于0.6,平均尺。大于0.7;在模型验证阶段,3个小区日径流量和产沙量的平均APE小于12%,平均EF大于0.5,平均R^2大于0.7,APEX模型可模拟出径流、产沙的日变异。在水土保持效益评价结果中,与对照(休闲地)相比,管理措施2(林地-水平沟)的径流量平均减少37%,产沙量平均减少89%,管理措施1(林草混交-水平梯田)的水土保持效益要略低于管理措施2,构建水平沟、水平梯田以及增加地表植被是控制该地区水土流失的有效措施。研究结果表明:APEX模型适应性强,可用于预测和评价淮河流域中上游不同土地管理措施下的水土流失,这为资料匮乏地区研究土壤侵蚀提供了一种新的思路和工具。  相似文献
8.
探讨了APEX(Agricultural Policy/Environmental eXtender)模型在淮河流域中上游的适宜性。将APEX模型用于淮河流域中上游监测资料较匮乏的3个径流小区,用日径流/产沙的实测值和模拟值校正和验证模型,用校正过的模型评价不同土地管理措施的长期水土保持效益(1981~2005)。在模型校正阶段,3个小区日径流量和产沙量的平均百分误差绝对值(APE)小于20%,平均纳希-苏特克利夫有效系数(EF)大于0.6,平均R2大于0.7;在模型验证阶段,3个小区日径流量和产沙量的平均APE小于12%,平均EF大于0.5,平均R2大于0.7,APEX模型可模拟出径流、产沙的日变异。在水土保持效益评价结果中,与对照(休闲地)相比,管理措施2(林地-水平沟)的径流量平均减少37%,产沙量平均减少89%,管理措施1(林草混交-水平梯田)的水土保持效益要略低于管理措施2,构建水平沟、水平梯田以及增加地表植被是控制该地区水土流失的有效措施。研究结果表明:APEX模型适应性强,可用于预测和评价淮河流域中上游不同土地管理措施下的水土流失,这为资料匮乏地区研究土壤侵蚀提供了一种新的思路和工具。  相似文献
9.
Validation of spatially distributed models using spatially distributed data represents a vital element in the development process; however, it is rarely undertaken. To a large extent, this reflects the problems associated with assembling erosion rate data, at appropriate temporal and spatial scales and with a suitable spatial resolution, for comparison with model results. The caesium-137 (137Cs) technique would appear to offer considerable potential for meeting this need for data, at least for longer timescales. Nevertheless, initial attempts to use 137Cs for model validation did not prove successful. This lack of success may be explained by the important role of tillage erosion in redistributing soil within agricultural fields and, therefore, contributing to the 137Cs-derived soil redistribution rates. This paper examines the implications of tillage erosion for the use of 137Cs in erosion model validation and presents an outline methodology for the use of 137Cs in model validation. This methodology acknowledges and addresses the constraints imposed by the need to: (1) separate water and tillage erosion contributions to total soil redistribution as represented in 137Cs derived rates; (2) account for lateral mixing of 137Cs within fields as a result of tillage translocation; (3) simulate long-term water erosion rates using the model under evaluation if 137Cs-derived water erosion rates are to be used in model validation. The methodology is dependent on accurate simulation of tillage erosion and tillage translocation. Therefore, as greater understanding of tillage erosion is obtained, the potential for the use of 137Cs in water erosion model validation will increase. Caesium-137 measurements remain one of the few sources of spatially distributed erosion information and, therefore, their potential value should be exploited to the full.  相似文献
10.
Fifteen upland soils collected from the major arable areas in NOrth China were used to assess the availability of soil sulfur(S) to plants in a pot experiment.Soils were extracted with various reagents and the extractable S was determined using turbidimetric method or inductively coupled plasma atomic emission spectrometry (ICP-AES),respectively.In addition,mineralizable organic S,organic S,N/S ratio,sulfur availability index(SAI) and available sulfur correction value(ASC) in soils were also determined.The S amout extracted by 1.5g L^-1 CaCl2 was nearly equivalent to that by 0.25mol L^-1 KCl(40℃),and both of them were slightly smaller than that by 0.01 molL^-1 Ca(H2PO4)2 solution,as measured by turbidimetric method or ICP-AES.The extractable S measured by turbidimetric method was consistently smaller than that by ICP-AES.All methods tested except that for organic S and N/S ratio produced satisfactoy results in the regression analyses of the relationships between the amounts of S extracted and plant dry matter weight and S uptake in the pot experiment,In general,0.01 mol L^-1 Ca(H2PO4)2-extracted S determined by ICP-AES or turbidimetric method and 0.25mol L^-1 KCl(40℃)-extracted S determined by ICP-AES appeared to be the best indicators for evaluation of soil available S.  相似文献
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