村级农业支出对农民收入的影响     

史贝贝  杨菲 《地域研究与开发》2017,36(3)

基于中国267个村级层面的微观调查数据,运用多元线性回归模型考察村级农业支出对农民人均纯收入的影响;考虑到农业支出村和非农业支出村之间可能存在着个体差异和样本选择性偏误,本研究使用了倾向得分匹配法,在消除差异与选择性偏误后准确地估计村级农业支出对农民收入的影响.研究结果发现:村级农业支出显著地提高了农民的人均纯收入,并且该结论在使用最邻近匹配、核匹配以及半径匹配进行检验的基础上仍然具有良好的稳健性.因此,政府应该加大对农业的投资力度,重点改善农业生产的基础设施条件,增加对农业的科技投入,以此提高农民收入.  相似文献   

基于GIS的城镇土地定级估价方法研究     

邹小平  陈军  张正禄 《武汉大学学报(信息科学版)》1995,(4)

根据城镇土地定级估价的工作特点，研究基于ＧＩＳ技术的城镇土地定级估价方法。在较为系统地分析了我国现行城镇土地定级估价方法的基础上，提出了在ＧＩＳ支持下进行城镇土地定级和基准地价评估的基本方法和步骤，并以ＡｒｃＣＡＤ为支撑软件，进行了城镇土地定级估价软件的设计研制。用于自动完成定级估价因素／子分值计算。土地级别确定、基准地价测算及成果输入等，并以浙江城镇为例进行了应用实验。  相似文献   

Bayesian analyses of seasonal runoff forecasts     

R. Krzysztofowicz  S. Reese 《Stochastic Environmental Research and Risk Assessment (SERRA)》1991,5(4):295-322

Forecasts of seasonal snowmelt runoff volume provide indispensable information for rational decision making by water project operators, irrigation district managers, and farmers in the western United States. Bayesian statistical models and communication frames have been researched in order to enhance the forecast information disseminated to the users, and to characterize forecast skill from the decision maker's point of view. Four products are presented: (i) a Bayesian Processor of Forecasts, which provides a statistical filter for calibrating the forecasts, and a procedure for estimating the posterior probability distribution of the seasonal runoff; (ii) the Bayesian Correlation Score, a new measure of forecast skill, which is related monotonically to theex ante economic value of forecasts for decision making; (iii) a statistical predictor of monthly cumulative runoffs within the snowmelt season, conditional on the total seasonal runoff forecast; and (iv) a framing of the forecast message that conveys the uncertainty associated with the forecast estimates to the users. All analyses are illustrated with numerical examples of forecasts for six gauging stations from the period 1971–1988.  相似文献   

胶东地区金矿化区域性变异及评价     

张光前 《地球科学》1991,16(3):319-324

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四种定量降水预报客观订正方法对比研究   总被引：1，自引：0，他引：1  

苏翔  袁慧玲  朱跃建 《气象学报》2021,79(1):132-149

基于2019年全年、不同季节、不同预报时效的欧洲中期天气预报中心模式的定量降水预报,检验评估了频率匹配、最优TS评分、最优百分位、概率匹配4种定量降水预报客观订正法的综合性能。利用理想模型研究了不同雨带位移偏差和干湿偏差情形下频率匹配法与最优TS评分的表现,并通过个例订正展示了4种定量降水预报订正法的基本特征。结果表明:频率匹配与最优TS评分仅能对确定性预报的降水量级进行调整,最优百分位和概率匹配法通过引入集合预报信息可在一定程度上改变预报的降水落区。频率匹配法以频率偏差最优为目标,可以很好地消除模式的干湿偏差,但仅在位移偏差较小且存在较大干湿偏差时提升原始预报的TS评分。最优TS评分法难以改进存在弱湿偏差的中雨预报的TS评分,而最优百分位法利用集合预报信息可以显著提升所有降水等级的TS评分,在较长预报时效下优势尤其明显,但也存在春、夏两季湿偏差较大的问题。概率匹配法由于没有使用历史实况信息,在暴雨订正中干偏差较大。经济价值模型检验评估表明,最优百分位法在暴雨量级的风险决策中具有较高的参考价值。   相似文献   

A novel analysis of consumption-based carbon footprints in China: Unpacking the effects of urban settlement and rural-to-urban migration     

《Global Environmental Change》2016

Urbanization in developing countries greatly contributes to growing carbon emissions. Although studies have documented the urbanization effect, the science of consumption-based footprint assessments has yet to unpack various effects during the process of urbanization. Based on household expenditure data, this study innovatively proposes a methodology to conceptually and statistically deconstruct the observed urbanization effects on carbon footprint into selection effects and migration effects, which consist of human settlement effects and purposeful changes of migration (such as income and residential location). Applying propensity score matching and regression on the 2010 China Family Panel Study, we find that the apparent carbon-footprint difference between rural residents and migrants is about 1.5 t CO₂e per capita. The migration effects account for about 2/3 of the apparent difference and the remaining 1/3 is due to selection effects. Urban settlement effects and the purposeful changes account for 73% and 27% of the migration effects, respectively. Transport sector is the key driver of carbon-footprint growth: it accounts for 60% of the migration effects. We conclude that travel behavior of rural migrants, currently in scarcity in the lite rature, merits further investigation, and policies should emphasize transit-oriented land use and transportation to achieve low-carbon urbanization.  相似文献   

THE APPLICATION OF HOMEMADE FY-2 SATELLITE INFRARED DATA TO MM5     

LIU Qing  SHEN Tong-li 《热带气象学报(英文版)》2006,12(1)

1 INTRODUCTION In the end of 1980's, an operational system for 3-D variation and assimilation of meteorological data was set up in the U.S.A that supplemented data assimilation,retrieval of satellite data and numerical prediction each other. NWP was thus improved. Towards the end of 1990's, satellite observations were extensively used in NWP at ECMWF to upgrade the quality of analysis and forecasting.  相似文献   

On Earthquake Predictability Measurement: Information Score and Error Diagram     

Yan Y. Kagan 《Pure and Applied Geophysics》2007,164(10):1947-1962

We discuss two methods for measuring the effectiveness of earthquake prediction algorithms: The information score based on the likelihood ratio and error diagrams. For both of these methods, closed form expressions are obtained for the renewal process based on the gamma and lognormal distributions. The error diagram is more informative than the likelihood ratio and uniquely specifies the information score. We derive an expression connecting the information score and error diagrams. We then obtain the estimate of the region bounds in the error diagram for any value of the information score. We discuss how these preliminary results can be extended for more realistic models of earthquake occurrence.  相似文献   

安徽省WRF模式短时强降水的预报检验     

吴瑞姣  邱学兴  周昆  魏凌翔 《气象科技》2020,48(2):254-262

利用2005—2015年安徽省内1162个站点观测资料简要分析了短时强降水的时空分布特征,并利用中国气象局CLDAS(CMA Land Data Assimilation System)近实时降水资料检验2012—2015年安徽省WRF(Weather Research and Forecast)模式对短时强降水的预报性能,探讨不同空间插值方法、检验方法对预报效果的影响,以评估模式预报短时强降水的应用价值和使用注意事项。结果表明:短时强降水主要发生在大别山区和皖南山区;一年中发生次数呈单峰分布,集中于6—8月;日变化呈双峰状,强峰为北京时间下午15:00—19:00,弱峰为06:00—09:00,两个低谷分别为01:00、12:00前后。在两分类评分TS(Threat Score)检验中,各个季节评分均十分低,插值方法对TS评分影响不大。邻域法FSS评分(Fractions Skill Score)检验中,春季FSS评分低,最高仅可达15%,空间窗、时间窗、时间超前或滞后变化对FSS评分的影响不如夏季、秋季明显;夏季,不考虑时间窗时,单独的时间超前或滞后不能提高预报准确率;秋季,模式分别滞后1h或滞后2h预报结果优于同期预报,而超前1h或超前2h预报结果低于同期预报,表明秋季WRF模式对短时强降水的预报有一定滞后性。  相似文献   

基于EC模式闪电格点概率预报模型及应用     

周威  张武龙  康岚  魏庆  但玻  银航 《气象科技》2020,48(6):862-870

基于EC（0.25°×0.25°）模式预报资料和闪电定位资料，结合雷暴三要素形成条件，分别从水汽、能量、热力、动力等几个方面挑选预报因子，利用主成分分析方法配料权重系数，并根据海拔高度将四川划分为四川盆地、攀西地区、川西高原3个不同的区域分别建立预报模型，研发了四川省闪电格点概率预报产品。检验结果表明：四川盆地在概率预报值为70%以上时，预报效果较好，TS评分为0.294；攀西地区和川西高原在概率预报值为60%以上时，预报效果较好，TS评分分别为0.302和0.299。  相似文献