耦合MOD16和SMAP的微波土壤湿度降尺度研究     

孙灏  周柏池  李欢  阮琳 《遥感学报》2021,25(3):776-790

局域尺度上的水文或农业应用亟需较高空间分辨率的土壤湿度(SM)数据,微波土壤湿度空间降尺度是实现这一需求的重要途径。其中"光学/热红外与微波数据融合"的降尺度方法展现出了较大的应用潜力,然而这类方法依赖于遥感地表温度LST (Land Surface Temperature)或由LST分解得到的SM指数,受限于LST"云污染"、LST与SM解耦效应和LST分解不确定性等问题。为规避上述问题,本文通过构建3种地表蒸散效率LEE(Land surface Evapotranspiration Efficiency)与SM的降尺度函数关系(指数、余弦、余弦平方),利用MODIS地表蒸散数据(MOD16A2)计算得到的LEE (空间分辨率500 m)实现了SMAP土壤湿度产品(空间分辨率36 km)的空间降尺度。研究从动态范围、能量守恒、SM地面稀疏验证站、SM地面核心验证站等角度对降尺度算法进行评价分析。结果表明,本算法有效增加了原SM产品的空间细节特征、保持了原SM产品的动态范围并且降尺度前后能量守恒;与地面验证数据的对比分析表明,降尺度结果有效保持了原SM与地面实测数据的良好一致性;敏感性分析表明,余弦平方函数对MOD16A2产品误差的敏感性相对最小。  相似文献   

VLBI技术在地震前兆分析中的应用探讨     

魏二虎  周培来  程晓晖  李冠 《测绘信息与工程》2009,34(1)

分析探讨了地震的形成机制.总结了目前地震预报技术的现状,探讨了VLBI技术在地震形成机制研究中的应用及其在地震前兆分析中的潜在能力.  相似文献   

Restoration of tidal freshwater vegetation using controlled reduced tide (CRT) along the Schelde Estuary (Belgium)     

S. Jacobs  O. Beauchard  E. Struyf  T. Cox  T. Maris  P. Meire 《Estuarine, Coastal and Shelf Science》2009

Throughout the world, tidal marshes are being restored to obtain natural protection against recurring storm surges and sea level rise and to preserve the resources these habitats provide. Managed realignment, or breaching of the seaward dikes, is a restoration technique increasingly used; yet unsuitable site elevation has been a major constraint to habitat development. Controlled reduced tide (CRT), a new technique to implement tidal regime on low elevated sites, could offer solutions for several problems associated with reconstruction or mitigation of tidal marshes.  相似文献   

Tracking stormwater discharge plumes and water quality of the Tijuana River with multispectral aerial imagery     

Jan Svejkovsky  Nikolay P. Nezlin  Neomi M. Mustain  Jamie B. Kum 《Estuarine, Coastal and Shelf Science》2010

Spatial–temporal characteristics and environmental factors regulating the behavior of stormwater runoff from the Tijuana River in southern California were analyzed utilizing very high resolution aerial imagery, and time-coincident environmental and bacterial sampling data. Thirty nine multispectral aerial images with 2.1-m spatial resolution were collected after major rainstorms during 2003–2008. Utilizing differences in color reflectance characteristics, the ocean surface was classified into non-plume waters and three components of the runoff plume reflecting differences in age and suspended sediment concentrations. Tijuana River discharge rate was the primary factor regulating the size of the freshest plume component and its shorelong extensions to the north and south. Wave direction was found to affect the shorelong distribution of the shoreline-connected fresh plume components much more strongly than wind direction. Wave-driven sediment resuspension also significantly contributed to the size of the oldest plume component. Surf zone bacterial samples collected near the time of each image acquisition were used to evaluate the contamination characteristics of each plume component. The bacterial contamination of the freshest plume waters was very high (100% of surf zone samples exceeded California standards), but the oldest plume areas were heterogeneous, including both polluted and clean waters. The aerial imagery archive allowed study of river runoff characteristics on a plume component level, not previously done with coarser satellite images. Our findings suggest that high resolution imaging can quickly identify the spatial extents of the most polluted runoff but cannot be relied upon to always identify the entire polluted area. Our results also indicate that wave-driven transport is important in distributing the most contaminated plume areas along the shoreline.  相似文献   

具有高阶奇点的2n+1次系统     

宋立温 《中国海洋大学学报(自然科学版)》2007,37(5):834-836

研究1类具有2个零特征根和1个4n2 2n 1阶奇点的2n 1次系统,并给出了极限环存在与否的条件。  相似文献   

Inexact Newton methods and the method of lines for solving Richards' equation in two space dimensions     

Michael D. Tocci  C.T. Kelley  Cass T. Miller  Christopher E. Kees 《Computational Geosciences》1998,2(4):291-309

Richards' equation (RE) is often used to model flow in unsaturated porous media. This model captures physical effects, such as sharp fronts in fluid pressures and saturations, which are present in more complex models of multiphase flow. The numerical solution of RE is difficult not only because of these physical effects but also because of the mathematical problems that arise in dealing with the nonlinearities. The method of lines has been shown to be very effective for solving RE in one space dimension. When solving RE in two space dimensions, direct methods for solving the linearized problem for the Newton step are impractical. In this work, we show how the method of lines and Newton-iterative methods, which solve linear equations with iterative methods, can be applied to RE in two space dimensions. We present theoretical results on convergence and use that theory to design an adaptive method for computation of the linear tolerance. Numerical results show the method to be effective and robust compared with an existing approach.  相似文献   

An elliptic problem with integral constraints with application to large-scale geophysical flows     

A.J. Meir  Irad Yavneh 《Computational Geosciences》1998,2(4):337-346

We present a weak formulation of a non-standard elliptic equation whose boundary values are determined in part by integral relations. Existence and uniqueness of its solution are proved, and a finite element discretization is described, analyzed, and implemented on a test problem. The equation is a generalization of one that is solved during integration of the three-dimensional Quasigeostrophic equations, which model large-scale rotating stratified flows, where the integral constraints represent conservation of physical properties.  相似文献   

1990～2000年中国稻田甲烷排放变化模拟   总被引：3，自引：0，他引：3  

王平  魏丽  杜筱玲  张稳  黄耀  孙文娟  刘文英 《地球信息科学学报》2008,10(5):573-577

甲烷（CH^₄）是大气中重要的温室气体之一。研究我国稻田的甲烷排放年际变化,客观评估我国稻田CH^₄排放量,对于区域乃至全球大气CH^₄浓度的贡献具有积极意义。本文将一个比较成熟的稻田甲烷排放模型CH^₄MOD和G IS空间化数据库结合,模拟估计了中国大陆1990～2000年水稻生长季稻田甲烷排放的年际变化。模拟结果表明:从1990年到2000年,我国稻田甲烷排放量具有比较明显的年际波动,其中1993～1995年由于播种面积较少,甲烷排放为一个低谷,排放量约为5.37Tg;其他年份的排放量在5.93～6.22Tg之间。虽然1997年之后我国水稻播种面积比1993年之前少约1.84×10⁶hm²,但两个时期的甲烷排放量却基本相等,这主要是由于1997年之后单位面积稻田甲烷的排放也较1993年之前高的缘故。从空间格局方面讲,我国稻田甲烷排放的高值区主要分布在湖南、湖北、江西、广东、广西、四川、江苏和安徽,东北地区稻田甲烷排放在20世纪90年代有逐年增加的趋势。  相似文献   

基于MOD16数据的渭河流域地表实际蒸散发时空特征   总被引：4，自引：0，他引：4  

位贺杰  张艳芳  朱妮  王鹏涛  喻元 《中国沙漠》2015,35(2):414-422

基于流域水量平衡法,利用水文数据和气象数据对渭河流域MOD16-ET(实际蒸散发)数据进行精度验证; 利用2000-2012年MOD16-ET数据和GIS技术定量分析了渭河流域(分为干流、泾河、北洛河3个子流域)地表实际蒸散发年际和年内的时空变化特征。结果表明:(1) 3个子流域的实测降水空间插值结果与MOD16-ET估算结果比较,相对误差平均值为8.36%,渭河干流误差较小,其他2个子流域误差相对较大; (2) 3个子流域上游至下游的ET剖面线变化不同,明显受地表覆盖类型影响; (3) ET值年内分布大致呈单峰型格局,季节变化特征为夏季(177.14 mm)> 秋季(105.22 mm)> 春季(92.97 mm)> 冬季(77.50 mm); (4) 基于栅格尺度的ET值年际变化特征空间分布,各子流域下游以降低趋势为主,渭河中游和上游以升高趋势为主,北洛河、泾河中游和上游以基本不变趋势为主,具体影响因素的定量分析仍需MODIS资料的时间累积。  相似文献   

基于MOD16产品的鄱阳湖流域地表蒸散量时空分布特征   总被引：17，自引：0，他引：17  

吴桂平  刘元波  赵晓松  叶春 《地理研究》2013,32(4):617-627

基于MOD16遥感数据集,统计分析了鄱阳湖流域2000-2010年地表蒸散量的年际和年内时空变化状况,探讨了不同地表类型下蒸散量的差异性变化特征。研究表明:①MOD16产品的精度能够满足鄱阳湖流域地表蒸散量时空变化分析的要求;②流域内平均蒸散量的年际波动较大,以2003年、2007年尤为突出,分别超出多年平均值49.28 mm和46.71 mm。ET空间格局呈现四周高、中间低的分布规律,尤其在高植被覆盖区蒸散量较大;③年内蒸散量呈单峰型分布,季节性变化特征明显,地表蒸散主要集中在5-9月份,最高值出现在7月;④土地利用特点基本影响着流域蒸散量的分布状况。蒸散强度大小按地表类型排序依次为林地>草地>农田>裸地>城镇。研究结果对鄱阳湖流域旱涝灾害成因分析、生态需水量研究等均具有一定的理论和实践参考意义。  相似文献