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1.
The soil freeze–thaw controls the hydrological and carbon cycling and thus affects water and energy exchanges at land surface. This article reported a newly developed algorithm for distinguishing the freeze/thaw status of surface soil. The algorithm was based on information from Advanced Microwave Scanning Radiometer Enhanced (AMSR‐E) which records brightness temperature (Tb) in the afternoon and after midnight. The criteria and discriminant functions were obtained from both radiometer observations and model simulations. First of all, the microwave radiation from freeze–thaw soil was examined by carrying out experimental measurements at 18·7 and 36·5 GHz using a Truck‐mounted Multi‐frequency Microwave Radiometer (TMMR) in the Heihe River of China. The experimental results showed that the soil moisture is a key component that differentiates the microwave radiation behaviours during the freeze–thaw process, and the differences in soil temperature and emissivity between frozen and thawed soils were found to be the most important criteria. Secondly, a combined model was developed to consider the impacts of complex ground surface conditions on the discrimination. The model simulations quite followed the trend of in situ observations with an overall relation coefficient (R) of approximately 0·88. Finally, the ratio of Tb18·7H (horizontally polarized Tb at 18·7 GHz) to Tb36·5V was considered primarily as the quasi‐emissivity, which is more reasonable and explicit in measuring the microwave radiation changes in soil freezing and thawing than the spectral gradient. By combining Tb36·5V to indicate the soil temperature variety, a Fisher linear discrimination analysis was used to establish the discriminant functions. After being corrected by TMMR measurements, the new discriminant algorithm had an overall accuracy of 86% when validated by 4‐cm soil temperature. The multi‐year discriminant results also provided a good agreement with the classification map of frozen ground in China. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
硝酸盐氮氧同位素反硝化细菌法测试研究 总被引：2，自引：0，他引：2
进入21世纪,硝酸盐氮氧同位素测试技术的显著进展是反硝化细菌法测试技术的建立。反硝化细菌法具有可同时分析浓度低至μg/L的硝酸盐氮氧同位素组成、免去复杂的样品预处理、分析时间大大缩短以及从复杂溶液中只转化NO3-为N2O等优点。实验过程由细菌挑选和培养、样品NO3-转化为N2O、N2O提取纯化、同位素测试以及同位素测试结果校正等几个关键步骤组成。国外研究结果显示该技术不仅可用于海水和淡水中硝酸盐同位素测试,而且还可用于土壤样品,并得到不断的完善和应用;国内建立了这一技术,在包气带和地下水硝酸盐污染研究中取得重要进展。由于该技术诸多优点,建议大力促进这一技术在我国的研究和应用,希望有关部门加大支持力度,进一步完善该技术并推广应用。 相似文献
3.
基于TIGGE多模式集合的24小时气温BMA
概率预报 总被引：7，自引：1，他引：6
利用TIGGE(THORPEX Interactive Grand Global Ensemble)单中心集合预报系统(ECMWF、United Kingdom Meteorological Office、China Meteorological Administration和NCEP)以及由此所构成的多中心模式超级集合预报系统24小时地面日均气温预报,结合淮河流域地面观测率定贝叶斯模型平均(Bayesian model averaging,BMA)参数,从而建立地面日均气温BMA概率预报模型.由此针对淮河流域进行地面日均气温BMA概率预报及其检验与评估,结果表明BMA模型比原始集合预报效果好;单中心的BMA概率预报都有较好的预报效果,其中ECMWF最好.多中心模式超级集合比单中心BMA概率预报效果更好,采用可替换原则比普通的多中心模式超级集合BMA模型计算量小,且在上述BMA集合预报系统中效果最好.它与原始集合预报相比其平均绝对误差减少近7%,其连续等级概率评分提高近10%.基于采用可替换原则的多中心模式超级集合BMA概率预报,针对研究区域提出了极端高温预警方案,这对防范高温天气有着重要意义. 相似文献
4.
Formation of an Interactive User-Oriented Forecasting System: Experience from Hydrological Application in Linyi, Eastern China 总被引：1，自引：0，他引：1 
下载免费PDF全文
下载免费PDF全文 YAN Zhongwei HAN Jiarui JIAO Meiyan CHEN Jing YE Qian ZHAO Linn TU Kai 《Acta Meteorologica Sinica》2012,26(1):13-25
Having provided an overview of the ideas of developing user-oriented interactive forecast system (UIFS) emerging in recent years,the authors proposed an idealized framework of the new-generation meteorological system,which includes the initial user-end module for configuring the forecast target,the physical predictive and downscaling components,and an incessant assessing module in association with decision-making at the user-end.A case study was carried out with a focus on applying the TIGGE (THORPEX Interactive Grand Global Ensemble;THORPEX stands for The Observing System Research and Predictability Experiment) precipitation forecasts for the hydrological users in Linyi,a region richest in rivers and reservoirs in eastern China.The preliminary results exhibited great potential of improvement in applications of weather forecasts by combining the user-end information.Although the TIGGE results provided by existing national/international operating models were independent from the user-end,the case study enlightened ways of establishing an iteratively self-improving UIFS involving user-orientation throughout the forecast process. 相似文献
5.
一个适用于我国北方的沙尘暴天气数值预测系统及其应用试验 总被引：32，自引：19，他引：13
将澳大利亚新南威尔士大学(UNSW)邵亚平发展的具有清晰风蚀物理学概念的起沙数值模式、输送模式与PSU/NCAR的中尺度气象预报模式MM5进行耦合,以高精度中国区域的GIS(Geographic Information System)数据为基础,建立了一个较完整的沙尘暴起沙和输送过程的预测系统.该预测系统可以预测地面起沙率和大气中沙尘浓度.在此基础上,采用该系统对2002年3～4月3次影响我国北方大部分地区的沙尘(暴)天气的起沙和输送过程进行了模拟试验.试验结果表明模拟的沙尘浓度与地面天气现象及卫星云图的沙尘天气范围比较一致,预测系统对沙尘天气的起沙和输送过程有较好的模拟能力.北方上述大范围沙尘天气的沙尘源地为蒙古国的南戈壁省、东戈壁省,内蒙古中西部,河北省北部,山西省东北部,甘肃和青海北部等地区.起沙中贡献最大的粒子粒径为2～11μm和11～22 μm,能够长时间、长距离输送的沙尘也是上述大小的粒子,沙尘粒子的垂直输送高度一般在500 hPa以下. 相似文献
6.
Many observational studies have shown that deformation, like vertical vorticity and divergence, is closely related to the occurrence and distribution of strong precipitation. In this paper, to involve deformation in precipitation diagnosis, a new parameter called potential deformation(PD) is derived and then applied to precipitation detection within a simulated mesoscale convective system(MCS). It is shown that PD includes both stretching deformation and shearing deformation and shares similar characteristics with deformation insofar as it does not change with the rotating coordinate. Diagnosis of the simulated MCS reveals that PD performs well in tracing the MCS' precipitation. In terms of their distributional pattern, the large-value areas of PD are similar to the precipitation in the different development stages of the MCS. A detailed analysis of the physical processes contained within the PD shows that it can reflect the three-dimensional moisture variation,vertical wind shear and wind deformation within the MCS. These structures are usually a comprehensive reflection of the characteristics of the surface cold pool, rear inflow jet, downward cold air flow and upward warm moist flow within the precipitating convective cells. For this reason, the PD shows much stronger anomalies in the precipitating atmosphere than the non-precipitating atmosphere, which implies considerable potential for its application in detecting heavy precipitation within MCSs. 相似文献
7.
世界大都会区城际轨道交通的发展规律 总被引：2，自引：0，他引：2
通过选取世界255 个大都会区城际轨道交通样本,对城际轨道交通的发展历程、空间分布和网络特征进行了规律性总结;在此基础上,进一步分析城际轨道交通规模与大都会区人口、用地、经济规模之间的相关关系,构建多个回归模型;最后,应用于珠江三角洲区域,对其城际轨道交通的规模和布局进行预测。模型显示,世界大都会区城际轨道交通的规模与经济的相关程度最高,其次是人口和用地,而人均城际轨道规模与人均GDP和人口密度呈指数相关,其中,与人均GDP正相关,与人口密度负相关。应用模型得到,珠三角城际轨道交通的规划规模超前于现有经济发展水平,但低于人口发展水平。近期应重点建设广州、佛山、深圳、东莞4 个城市重要节点的城际轨道交通,构建广佛和广深两条走廊,并联系珠海、中山、肇庆、惠州、江门的中心城区,形成以广州为中心的放射状布局;远期则需要进一步加大广州、深圳、佛山、东莞、珠海、中山的线网密度,扩大线网的覆盖范围,并对外围的肇庆、惠州和江门适当增加联系的节点,最终形成网络状布局。 相似文献
8.
基于人类尺度营建的古城道路网经过历史演化具有分形结构.在汽车成为道路设计导向的背景下,立足于分形连接的古城道路网应回归人性化出行的视角,应用Hausdorff维数简化分析法,长度--半径维数分析法及分枝数目--半径维数分析法,对1735年,1893年,1949年及2014年四个时期西安古城道路网进行了分形维数的测算,揭示了道路网分形演化趋势和不同时期的分形特征,探讨了演化原因并确定了分形演化过程中的三个阶段(不断向更高层次演化阶段;演化到较高等级,但外部因素对道路网产生逆向扰动;处于较高层级,但交通方式变革使基于人类尺度的道路网在结构和功能上发生局部蜕变),指出目前西安古城道路网在结构和功能上的局部蜕化趋势不容忽视,并针对问题提出应推崇适宜步行和自行车出行的模式典范,对古城道路网保护乃至整个古城的可持续发展具有重要意义. 相似文献
9.
Geostatistical analyses and fractionation of heavy metals in urban soil from industrial district in Weinan, NW China 总被引：1，自引：1，他引：0
The concentrations of metals (Pb, Cr, Ba, Zn, V, Mn, Co, Cu, Ni and As) in 38 soil samples collected from the industrial district in Weinan (NW China) were determined by wavelength dispersive X-ray fluorescence spectrometry. The magnetic parameters of soil including low-/high-frequency susceptibility and frequency-dependent susceptibility were measured. The modified three-step BCR sequential extraction procedure was used to evaluate mobility, availability and persistence of trace elements in urban soil samples. Multivariate (principal component analysis, clustering analysis and correlation analysis) and geostatistical analysis (ArcGIS tools) were applied to the obtained data to evaluate the analytical results and to identify the possible pollution sources of metals as well as geo-spatial distributions. The results revealed that the sampling area was mainly influenced by two main sources: (1) Ba, Cu, Pb, Cr and Zn were mainly derived from industrial sources, which combined with coal combustion as well as traffic factor. The mobility sequence based on the sum of the BCR sequential extraction stages was: Pb (53.79 %) > Zn (51.78 %) > Cu (50.96 %) > Ba (42.59 %) > Cr (18.47 %). Pb was the metal predominantly associated (~46.86 %) with the form bound to Fe/Mn oxides, and the highest percentage of Zn was exchangeable and carbonate-bound fraction. Cu was present mainly in organic fraction, while the residual fraction was the most dominant solid phase pool of Cr (~81.53 %) and Ba (~57.41 %). (2) Mn, V, Co, As and Ni in the study area were consistently from natural sources. The analysis of enrichment factors indicated that urban soils in Weinan City were classified as having significant enrichment by Ba, Cu, Pb, Cr and Zn. The overall results proposed the future tactics for Weinan environment quality control on a local scale that concerned not only the levels of risky, but also the industrial emission abatement techniques as well as urban setting. 相似文献
10.
基于近年来涌现的有关新一代气象预报系统发展的认识,本文提出用户导向的交互式预报系统的概念模型。新系统强调在用户信息分析的基础上,发展从用户出发再回到用户不断自我改善的预报流程。系统组成的关键模块包括：用户端风险决策动态需求分析模块、物理预测模块、用户目标量的降尺度模块,用户端专业耦合模块及用户风险决策模块。文中阐述了系统中各模块间的联系、用户端信息在系统中的反馈作用以及具体的“交互式”方式。以临沂地区水文用户为例,以引发洪涝的降水事件为预报对象,利用TIGGE全球超集合预报,初步构建了一个临沂水文用户导向的可能致洪降水交互式预报系统。这个具备迭代式自我完善功能的新型预报系统包含了汛期随时变化的用户决策信息、由前期影响雨量和当前水文条件决定的可变致洪降水阈值以及一个动态的用户端预报水平和不确定性评估模块。初步结果表明,结合用户端信息的预报优于未考虑用户信息的预报结果,从而更直接地帮助用户进行防汛决策。个例研究也为发展更完整的用户导向预报系统提供了参考。 相似文献