-
20世纪60年代以来,伴随着航空航天技术的快速发展,文献[1]首先提出遥感这一名词。遥感是指在不直接接触的情况下,对目标物或自然现象进行远距离感知的一门探测技术[2]。定量遥感或称遥感定量化,是利用遥感传感器获取地表地物的电磁波信息,在先验知识和计算机系统支持下,定量获取观测目标参量或特性的方法与技术。作为新兴的遥感信息获取与分析方法,定量遥感强调通过数学的或物理的模型将遥感信息与观测地表目标参量联系起来,定量反演或推算出某些地学目标参量[3, 4]。
但是,由于光学遥感对云雾不具有穿透性,其成像方式特点决定只能提供表层的时空信息描述,在需要对地物具有一定穿透性的应用中受到很大限制,多云雾山丘地区表现尤为明显[5]。于是,微波遥感在多云雾地区发挥着越来越重要的作用,在土地覆盖分类、土壤水分和植被生物量估算等方面取得了较好的应用效果。但是,对于植被覆盖条件下的土壤水分估算仍然存在许多问题[6]。另外,目前基于后向散射系数的森林生物量反演多基于经验模型,其普适性受到限制,并且后向散射系数在高生物量区域会存在饱和现象。干涉雷达技术发展能够提供植被的垂直结构参数,极大地提高了植被(特别是森林)生物量的反演精度[7, 8, 9, 10]。但是由于时间去相关现象在波长低于P波段的其他波段较为严重(特别是森林区域)[11, 12],而目前星载SAR数据波长都小于P波段,因此时间去相关现象严重制约了干涉SAR的应用,而预计2020年发射的P波段BIOMASS卫星则有可能解决该问题[11]。
此外,在地形起伏剧烈的山丘地区,无论是光学遥感还是微波遥感都受到地形因素的严重影响。对于光学遥感,地形主要从两方面影响光学影像,即辐射效应以及双向反射率分布函数(bidirectional reflectance distribution function, BRDF)效应[13]。辐射效应是指由于地形起伏,向阳面和背阳面接收到的入射光能量不同,从而造成遥感图像上向阳面更加明亮;BRDF效应是指地物并非朗伯体,入射角的变化会导致观测到的地物本身的反射率发生变化[14]。因此,如果不正确校正地形的影响,即便是相同特性的地物也会因为地形影响而显示出不同的波谱反射率,从而影响遥感应用的精度。目前,地形校正修正的反射率在遥感定量应用中还不太成熟,为减缓地形影响,常用的方式是利用具有波段比形式的植被指数来代替直接利用波段反射率进行研究,因为具有波段比形式的植被指数能够消除大部分的地形影响[15, 16],如归一化植被指数(normalized difference vegetation index, NDVI)、归一化红外指数(normalized difference infrared index, NDII)等。对于被动微波,地形起伏同样会引起地形坡面辐射偏差,文献[17, 18, 19]表明地形可引起约15 K的地表辐射能量变化。地形主要从两方面影响被动微波遥感[19]:1)高程的变化会改变大气中辐射传输的路径;2)倾斜坡度之间辐射的相互作用会增强有效辐射。对于主动微波遥感,地形的影响更为严重,其影响主要分为:1)几何畸变,SAR为斜距成像,地形起伏变化会导致SAR图像上透视收缩、叠掩、顶底位移和阴影等几何畸变的现象[5];2)雷达亮度的变化,地形起伏会导致地表有效散射面积的变化,从而使传感器接收到的总能量发生变化。同时,透视收缩,叠掩现象都会导致雷达亮度的改变,透视收缩使能量相对集中,从而致使该区域雷达亮度偏大。并且雷达的侧视成像原理使其更容易受到地形影响产生阴影现象,阴影区域因为没有任何回波信号,其对应SAR图像区域雷达亮度为零[20];3)局部入射角效应,如森林区域、入射角的变化会导致微波在冠层中传播路径不同,从而导致后向散射机理的变化,进一步致使获取的雷达后向散射系数的变化[21, 22]。因此有效去除地形对微波遥感影响的方法具有重要意义。
以中国西南地区(云南、贵州、四川等)为代表的多云雾山丘地区,以亚热带季风气候为主导,空气湿度大,多云雾且地形复杂,地表空间异质性强,为遥感的定量化应用带来极大的挑战和困难。综上所述,多云雾山丘地区的遥感定量化应用主要面临以下问题:1)数据时空连续性问题。云雾的干扰将严重影响光学影像的质量和数据时空连续性,导致数据缺乏,为后续基于光学遥感影像的相关研究工作带来极大的困难;而主动微波数据则因成像方式、数据共享等因素难以大范围长时间序列覆盖,在实际应用中受到很大限制。2)地形影响问题。山丘地区地形起伏严重,无论是光学数据还是微波数据都会受到严重的地形影响。地形会给光学数据同时带来辐射影响以及BRDF影响,并且会给微波数据带来几何畸变、辐射亮度变化、以及局部入射角效应的影响。3)地表空间异质性问题。山丘地区地貌复杂,地表空间异质性较强,导致在利用遥感开展定量研究工作中因地表空间异质性而引起的混合像元、尺度效应更加严重。4)病态反演问题。地表的复杂性和遥感可获取信息的有限性决定了基于物理模型的遥感反演的本质是病态反演。此外,以植被可燃物含水率(fuel moisture content, FMC)为代表的弱敏感参数由于其光谱弱敏感性,使得在异质性较强的山丘地区的反演难度更大。因此,本文在分析和总结多云雾山丘地区遥感定量化理论与方法体系基础上,对本文的研究团队近年来的相关研究进展进行介绍。
Theory and Application Status of Quantitative Remote Sensing in Cloudy and Hilly Regions
-
摘要: 在分析光学与微波遥感各自的应用现状及面临的挑战的基础上,从数据层、数据预处理和定量化理论与方法3个层面详细分析和总结了适用于多云雾山丘地区复杂环境的遥感定量化应用理论与方法,包括面向对象的反演策略、主被动遥感协同、时间序列建模、前向模型地形效应修正、弱敏感参数反演等。同时,结合研究团队近年在多云雾山丘地区遥感定量应用的研究实践,给出西南地区的土地连续变化监测、森林火灾风险评估、干旱监测、植被覆盖条件下的土壤水分主被动遥感反演等方面的应用实例。Abstract: With the rapid development of the Earth observation technologies, remote sensing plays an increasingly important role in the applications of global change, ecological environment, territorial resources, natural disasters, national defense, smart city, and other applications. Accompanied by the development and improvement for the theories and applications of the quantitative remote sensing, there are still many unprecedented challenges. Because of the Earth complexity of the surface and the limitation of the remote sensing information, the quantitative applications of remote sensing generally are hampered by ill-posed inversion, scale effect, and other problems. Especially for cloudy and hilly regions, sufficiently influenced by the cloud, topography, and spatial heterogeneity, the quantitative applications of remote sensing becomes more difficult. Based on the analysis of the application status and the challenges faced by optical and microwave remote sensing, this paper reviews the theory and approaches applied for cloudy and hilly regions from the perspective of remote sensing data, preprocessing, and the quantitative theory and approaches, which include object-oriented inversion strategy, synergy of active and passive remote sensing, time series modeling, topographic correction of the forward model, and inversion of weak sensitive parameters. In addition, specific application examples are presented based on the recent research and practice achieved by the team of the authors, including continuous change detection of land cover, forest fire risk assessment, drought monitoring, and soil moisture retrieval under vegetation cover from active and passive remote sensing in the southwest China.
-
[1] 宁津生, 陈俊勇, 李德仁, 等.测绘学概论[M].武汉:武汉大学出版社, 2008. NING Jin-sheng, CHEN Jun-yong, LI De-ren, et al. Introduction to geomatics[M]. Wuhan:Wuhan University Press, 2008. [2] 孙家抦.遥感原理与应用[M].武汉:武汉大学出版社, 2003. SUN Jia-bing. Principles and applications of remote sensing[M]. Wuhan:Wuhan University Press, 2003. [3] 李小文.定量遥感的发展与创新[J].河南大学学报(自然科学版), 2006, 35(4):49-56. http://www.cnki.com.cn/Article/CJFDTOTAL-HDZR200504011.htm LI Xiao-wen. Retrospect, prospect and innovation in quantitative remote sensing[J]. Journal of Henan University (Natural Science), 2006, 35(4):49-56. http://www.cnki.com.cn/Article/CJFDTOTAL-HDZR200504011.htm [4] 梁顺林, 李小文, 王锦地.定量遥感:理念与算法[M].北京:科学出版社, 2013. LIANG Shun-ling, LI Xiao-wen, WANG Jin-di. Quantitative remote sensing:concept and algorithm[M]. Beijing:Science Press, 2013. [5] WOODHOUSE I H. Introduction to microwave remote sensing[M]. Boca Raton:CRC Press, 2005. [6] 施建成, 杜阳, 杜今阳, 等.微波遥感地表参数反演进展[J].中国科学:地球科学, 2012, 42(6):814-42. http://www.cnki.com.cn/Article/CJFDTOTAL-JDXK201206005.htm SHI Jian-cheng, DU Yang, DU Jin-yang, et al. Progresses on microwave remotesensing of land surface parameters[J]. Science China:Earth Sciences, 2012, 42(6):814-42. http://www.cnki.com.cn/Article/CJFDTOTAL-JDXK201206005.htm [7] KOCH B. Status and future of laser scanning, synthetic aperture radar and hyperspectral remote sensing data for forest biomass assessment[J]. ISPRS Journal of Photogrammetry and Remote Sensing, 2010, 65(6):581-590. doi: 10.1016/j.isprsjprs.2010.09.001 [8] CLOUDE S, PAPATHANASSIOU K. Three-stage inversion process for polarimetric SAR interfer-ometry[C]//Radar, Sonar and Navigation, IEE Proceedings.[S.l]:IET, 2003, 150(3):125-134. [9] CLOUDE S R, PAPATHANASSIOU K P. Polarimetric SAR interferometry[J]. IEEE Transactions on Geoscience and Remote Sensing, 1998, 36(5):1551-1565. doi: 10.1109/36.718859 [10] CLOUDE S R. Polarization coherence tomography[J]. Radio Science, 2006, 41(4):1-27. [11] LE TOAN T, QUEGAN S, DAVIDSON M, et al. The BIOMASS mission:Mapping global forest biomass to better understand the terrestrial carbon cycle[J]. Remote Sensing of Environment, 2011, 115(11):2850-2860. doi: 10.1016/j.rse.2011.03.020 [12] LEE S K, KUGLER F, PAPATHANASSIOU K P, et al. Quantifying temporal decorrelation over boreal forest at L-and P-band[C]//20087th European Conference on Synthetic Aperture Radar (EUSAR). Friedrichshafen:VDE, 2008:1-4. [13] IQBAL M. An introduction to solar radiation[M]. New York, USA:Academic, 1983. [14] SOENEN S A, PEDDLE D R, COBURN C A. A modified sun-canopy-sensor topographic correction in forested terrain[J]. IEEE Transactions on Geoscience and Remote Sensing, 2005, 43(9):2148-2159. doi: 10.1109/TGRS.2005.852480 [15] LIAO Z, HE B, QUAN X. Modified enhanced vegetation index for reducing topographic effects[J]. Journal of Applied Remote Sensing, 2015, 9(1):096068-096068. doi: 10.1117/1.JRS.9.096068 [16] MATSUSHITA B, YANG W, CHEN J, et al. Sensitivity of the enhanced vegetation index (EVI) and normalized difference vegetation index (NDVI) to topographic effects:a case study in high-density cypress forest[J]. Sensors, 2007, 7(11):2636-2651. doi: 10.3390/s7112636 [17] KERR Y, SECHERRE F, LASTENET J, et al. SMOS:Analysis of perturbing effects over land surfaces[C]//2003 International Geoscience and Remote Sensing Symposium (IGARSS). Toulouse:IEEE, 2003, 2:908-910. [18] TALONE M, CAMPS A, MONERRIS A, et al. Surface topography and mixed-pixel effects on the simulated L-band brightness temperatures[J]. IEEE Transactions on Geoscience and Remote Sensing, 2007, 45(7):1996-2003. doi: 10.1109/TGRS.2007.898254 [19] TZLER M C, STANDLEY A. Technical note:relief effects for passive microwave remote sensing[J]. 2000, 21(12):2403-2412. http://cn.bing.com/academic/profile?id=2068380000&encoded=0&v=paper_preview&mkt=zh-cn [20] 张王菲.星载SAR遥感反演中地形辐射校正的关键技术研究[D].昆明:昆明理工大学, 2011. http://cdmd.cnki.com.cn/article/cdmd-10674-1012262925.htm ZHANG Wang-fei. Research on the key technologies of topographic radiation correction in satellite borne SAR remote sensing retrieval[D]. Kunming:Kunming University, 2011. http://cdmd.cnki.com.cn/article/cdmd-10674-1012262925.htm [21] CASTEL T, BEAUDOIN A, STACH N, et al. Sensitivity of space-borne SAR data to forest parameters over sloping terrain. Theory and experiment[J]. International Journal of Remote Sensing, 2001, 22(12):2351-2376. doi: 10.1080/01431160121407 [22] ULANDER L M. Radiometric slope correction of synthetic-aperture radar images[J]. IEEE Transactions on Geoscience and Remote Sensing, 1996, 34(5):1115-1122. doi: 10.1109/36.536527 [23] ARVIDSON T, GASCH J, GOWARD S N. Landsat 7's long-term acquisition plan-an innovative approach to building a global imagery archive[J]. Remote Sensing of Environment, 2001, 78(1):13-26. http://cn.bing.com/academic/profile?id=2015135807&encoded=0&v=paper_preview&mkt=zh-cn [24] IRISH R R. Landsat 7 automatic cloud cover assessment[C]//International Society for Optics and Photonics. Bellingham:SPIE, 2000:348-355. [25] SIMPSON J J, STITT J R. A procedure for the detection and removal of cloud shadow from AVHRR data over land[J]. IEEE Transactions on Geoscience and Remote Sensing, 1998, 36(3):880-897. doi: 10.1109/36.673680 [26] SAUNDERS R W, KRIEBEL K T. An improved method for detecting clear sky and cloudy radiances from AVHRR data[J]. International Journal of Remote Sensing, 1988, 9(1):123-150. doi: 10.1080/01431168808954841 [27] DERRIEN M, FARKI B, HARANG L, et al. Automatic cloud detection applied to NOAA-11/AVHRR imagery[J]. Remote Sensing of Environment, 1993, 46(3):246-267. doi: 10.1016/0034-4257(93)90046-Z [28] ACKERMAN S A, STRABALA K I, MENZEL W P, et al. Discriminating clear sky from clouds with MODIS[J]. Journal of Geophysical Research:Atmospheres (1984-2012), 1998, 103(D24):32141-32157. doi: 10.1029/1998JD200032 [29] IRISH R R, BARKER J L, GOWARD S N, et al. Characterization of the Landsat-7 ETM+ automated cloud-cover assessment (ACCA) algorithm[J]. Photo-Grammetric Engineering & Remote Sensing, 2006, 72(10):1179-1188. http://cn.bing.com/academic/profile?id=2166251851&encoded=0&v=paper_preview&mkt=zh-cn [30] ZHU Z, WOODCOCK C E. Object-based cloud and cloud shadow detection in Landsat imagery[J]. Remote Sensing of Environment, 2012, 118(6):83-94. http://cn.bing.com/academic/profile?id=2028240797&encoded=0&v=paper_preview&mkt=zh-cn [31] ZHU Z, WANG S, WOODCOCK C E. Improvement and expansion of the Fmask algorithm:Cloud, cloud shadow, and snow detection for Landsats 4-7, 8, and Sentinel 2 images[J]. Remote Sensing of Environment, 2015, 159:269-277. doi: 10.1016/j.rse.2014.12.014 [32] JU J, ROY D P. The availability of cloud-free Landsat ETM+ data over the conterminous United States and globally[J]. Remote Sensing of Environment, 2008, 112(3):1196-1211. doi: 10.1016/j.rse.2007.08.011 [33] MAALOUF A, CARR P, AUGEREAU B, et al. A bandelet-based inpainting technique for clouds removal from remotely sensed images[J]. IEEE Transactions on Geoscience and Remote Sensing, 2009, 47(7):2363-2371. doi: 10.1109/TGRS.2008.2010454 [34] ROY D P, JU J, LEWIS P, et al. Multi-temporal MODIS-Landsat data fusion for relative radiometric normalization, gap filling, and prediction of Landsat data[J]. Remote Sensing of Environment, 2008, 112(6):3112-3130. doi: 10.1016/j.rse.2008.03.009 [35] HAGOLLE O, HUC M, PASCUAL D V, et al. A multi-temporal method for cloud detection, applied to FORMOSAT-2, VENμS, LANDSAT and SENTINEL-2 images[J]. Remote Sensing of Environment, 2010, 114(8):1747-1755. doi: 10.1016/j.rse.2010.03.002 [36] HELMER E H, RUEFENACHT B. A comparison of radiometric normalization methods when filling cloud gaps in Landsat imagery[J]. Canadian Journal of Remote Sensing, 2007, 33(4):325-340. doi: 10.5589/m07-028 [37] TSENG D C, TSENG H T, CHIEN C L. Automatic cloud removal from multi-temporal SPOT images[J]. Applied Mathematics and Computation, 2008, 205(2):584-600. doi: 10.1016/j.amc.2008.05.050 [38] ZHU X, GAO F, LIU D, et al. A modified neighborhood similar pixel interpolator approach for removing thick clouds in Landsat images[J]. IEEE Geoscience and Remote Sensing Letters, 2012, 9(3):521-525. doi: 10.1109/LGRS.2011.2173290 [39] LIANG S. Quantitative remote sensing of land surfaces[M]. Hoboken:John Wiley & Sons, 2005. [40] DOZIER J, FREW J. Atmospheric corrections to satellite radiometric data over rugged terrain[J]. Remote Sensing of Environment, 1981, 11:191-205. doi: 10.1016/0034-4257(81)90019-5 [41] DOZIER J, FREW J. Rapid calculation of terrain parameters for radiation modeling from digital elevation data[J]. IEEE Transactions on Geoscience and Remote Sensing, 1990, 28(5):963-969. doi: 10.1109/36.58986 [42] VERMOTE E F, TANR D, DEUZ J L, et al. Second simulation of the satellite signal in the solar spectrum, 6S:an overview[J]. IEEE Transactions on Geoscience and Remote Sensing, 1997, 35(3):675-686. doi: 10.1109/36.581987 [43] VERMOTE E, TANR D, DEUZ J, et al. Second simulation of a satellite signal in the solar spectrum-vector (6SV)[J]. 6S User Guide Version, 2006, 3:1-55. https://www.researchgate.net/profile/Jean_Jacques_Morcrette/publication/247461276_Second_simulation_of_a_satellite_signal_in_the_solar_spectrum-vector_6SV/links/548eb79a0cf2d1800d8448c3.pdf?inViewer=0&pdfJsDownload=0&origin=publication_detail [44] SANDMEIER S, ITTEN K I. A physically-based model to correct atmospheric and illumination effects in optical satellite data of rugged terrain[J]. IEEE Transactions on Geoscience and Remote Sensing, 1997, 35(3):708-717. doi: 10.1109/36.581991 [45] SHUAI Y, MASEK J G, GAO F, et al. An algorithm for the retrieval of 30 m snow-free albedo from Landsat surface reflectance and MODIS BRDF[J]. Remote Sensing of Environment, 2011, 115(9):2204-2216. doi: 10.1016/j.rse.2011.04.019 [46] LI F, JUPP D L, REDDY S, et al. An evaluation of the use of atmospheric and BRDF correction to standardize Landsat data[J]. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2010, 3(3):257-270. doi: 10.1109/JSTARS.2010.2042281 [47] WEN J, LIU Q, LIU Q, et al. Parametrized BRDF for atmospheric and topographic correction and albedo estimation in Jiangxi rugged terrain, China[J]. International Journal of Remote Sensing, 2009, 30(11):2875-2896. doi: 10.1080/01431160802558618 [48] LI F, JUPP D L, THANKAPPAN M, et al. A physics-based atmospheric and BRDF correction for landsat data over mountainous terrain[J]. Remote Sensing of Environment, 2012, 124:756-770. doi: 10.1016/j.rse.2012.06.018 [49] PIERDICCA N, PULVIRENTI L, MARZANO F S. Simulating topographic effects on spaceborne radiometric observations between L and X frequency bands[J]. IEEE Transactions on Geoscience and Remote Sensing, 2010, 48(1):273-282. doi: 10.1109/TGRS.2009.2028881 [50] CURLANDER J C. Location of spaceborne SAR imagery[J]. IEEE Transactions on Geoscience and Remote Sensing, 1982(3):359-364. http://cn.bing.com/academic/profile?id=2057517948&encoded=0&v=paper_preview&mkt=zh-cn [51] TOUTIN T. Review article:Geometric processing of remote sensing images:models, algorithms and methods[J]. International Journal of Remote Sensing, 2004, 25(10):1893-1924. doi: 10.1080/0143116031000101611 [52] LEBERL F W. Radargrammetric image processing[M]. Landon:Artech House, 1990, [53] KONECNY G, SCHUHR W. Reliability of radar image data[C]//1988 International Society for Photogrammetry and Remote Sensing (ISPRS) Congress. Kyoto:Elsevier, 1988. [54] JOHNSEN H, LAUKNES L, GUNERIUSSEN T. Geocoding of fast-delivery ERS-l SAR image mode product using DEM data[J]. International Journal of Remote Sensing, 1995, 16(11):1957-1968. doi: 10.1080/01431169508954532 [55] SMALL D. Flattening gamma:Radiometric terrain correction for SAR imagery[J]. IEEE Transactions on Geoscience and Remote Sensing, 2011, 49(8):3081-3093. doi: 10.1109/TGRS.2011.2120616 [56] 李震, 廖静娟.合成孔径雷达地表参数反演模型与方法[M].北京:科学出版社, 2011. LI Zhen, LIAO Jing-juan. Land surface parameter inversion model and method for synthetic aperture radar[M]. Beijing:Science Press, 2013. [57] ACERBI-JUNIOR F, CLEVERS J, SCHAEPMAN M. The assessment of multi-sensor image fusion using wavelet transforms for mapping the Brazilian Savanna[J]. International Journal of Applied Earth Observation and Geoinformation, 2006, 8(4):278-288. doi: 10.1016/j.jag.2006.01.001 [58] HILKER T, WULDER M A, COOPS N C, et al. A new data fusion model for high spatial-and temporal-resolution mapping of forest disturbance based on Landsat and MODIS[J]. Remote Sensing of Environment, 2009, 113(8):1613-1627. doi: 10.1016/j.rse.2009.03.007 [59] YANG J, WRIGHT J, HUANG T S, et al. Image super-resolution via sparse representation[J]. IEEE Transactions on Image Processing, 2010, 19(11):2861-2873. doi: 10.1109/TIP.2010.2050625 [60] SONG H, HUANG B. Spatiotemporal satellite image fusion through one-pair image learning[J]. IEEE Transactions on Geoscience and Remote Sensing, 2013, 51(4):1883-1896. doi: 10.1109/TGRS.2012.2213095 [61] GAO F, MASEK J, SCHWALLER M, et al. On the blending of the Landsat and MODIS surface reflectance:Predicting daily Landsat surface reflectance[J]. IEEE Transactions on Geoscience and Remote Sensing, 2006, 44(8):2207-2218. doi: 10.1109/TGRS.2006.872081 [62] HILKER T, WULDER M A, COOPS N C, et al. Generation of dense time series synthetic Landsat data through data blending with MODIS using a spatial and temporal adaptive reflectance fusion model[J]. Remote Sensing of Environment, 2009, 113(9):1988-1999. doi: 10.1016/j.rse.2009.05.011 [63] ZHU X, CHEN J, GAO F, et al. An enhanced spatial and temporal adaptive reflectance fusion model for complex heterogeneous regions[J]. Remote Sensing of Environ-ment, 2010, 114(11):2610-2623. doi: 10.1016/j.rse.2010.05.032 [64] 杨燕, 田庆久.水稻LAI参数的Hyperion反演研究[J].遥感技术与应用, 2007, 22(3):345-350. http://www.cnki.com.cn/Article/CJFDTOTAL-YGJS200703008.htm YANG Yan, TIAN Qing-jiu. The study of deducing leaf area index of rice of hyperion[J]. Remote Sensing Technology and Application, 2007, 22(3):345-350. http://www.cnki.com.cn/Article/CJFDTOTAL-YGJS200703008.htm [65] 陈健, 倪绍祥, 李云梅.基于神经网络方法的芦苇叶面积指数遥感反演[J].国土资源遥感, 2008, 72(2):62-67. http://www.cnki.com.cn/Article/CJFDTOTAL-GTYG200802014.htm CHEN Jian, NI Shao-xiang, LI Yun-mei. LAI retrieval of reed canopy using the neural network method[J]. Remote Sensing for Land & Resources, 2008, 72(2):62-67. http://www.cnki.com.cn/Article/CJFDTOTAL-GTYG200802014.htm [66] BROUGHAM R. The relationship between the critical leaf area, total chlorophyll content, and maximum growth-rate of some pasture and crop planst[J]. Annals of Botany, 1960, 24(4):463-474. http://cn.bing.com/academic/profile?id=2136942826&encoded=0&v=paper_preview&mkt=zh-cn [67] BANNARI A, KHURSHID K S, STAENZ K, et al. A comparison of hyperspectral chlorophyll indices for wheat crop chlorophyll content estimation using laboratory reflectance measurements[J]. IEEE Transactions on Geoscience and Remote Sensing, 2007, 45(10):3063-3074. doi: 10.1109/TGRS.2007.897429 [68] SI Y, SCHLERF M, ZURITA-MILLA R, et al. Mapping spatio-temporal variation of grassland quantity and quality using MERIS data and the PROSAIL mode[J]. Remote Sensing of Environment, 2012, 121:415-425. doi: 10.1016/j.rse.2012.02.011 [69] CURRAN P J, EDWARD J M. The relationships between the chlorophyll concentration, LAI and reflectance of a simple vegetation canopy[J]. International Journal of Remote Sensing, 1983, 4(2):247-255. doi: 10.1080/01431168308948544 [70] GITELSON A A, VINA A, CIGANDA V, et al. Remote estimation of canopy chlorophyll content in crops[J]. Geophysical Research Letters, 2005, 32(8):1-4. http://cn.bing.com/academic/profile?id=2109006150&encoded=0&v=paper_preview&mkt=zh-cn [71] 乔振民, 邢立新, 李淼淼, 等. Hyperion数据玉米叶绿素含量制图[J].遥感技术与应用, 2012, 27(2):275-281. http://www.cnki.com.cn/Article/CJFDTOTAL-YGJS201202017.htm QIAO Zhen-min, XING Li-xin, LI Miao-miao, et al. Mapping of maize chlorophyll content with hyperion data[J]. Remote Sensing Technology and Application, 2012, 27(2):275-281. http://www.cnki.com.cn/Article/CJFDTOTAL-YGJS201202017.htm [72] TUCKER C J. Remote sensing of leaf water content in the near infrared[J]. Remote Sensing of Environment, 1980, 10(1):23-32. doi: 10.1016/0034-4257(80)90096-6 [73] DARVISHZADEH R, SKIDMORE A, SCHLERF M, et al. Inversion of a radiative transfer model for estimating vegetation LAI and chlorophyll in a heterogeneous grassland[J]. Remote Sensing of Environment, 2008, 112(5):2592-604. doi: 10.1016/j.rse.2007.12.003 [74] HE B, QUAN X, XING M. Retrieval of leaf area index in alpine wetlands using a two-layer canopy reflectance model[J]. International Journal of Applied Earth Observation and Geoinformation, 2013, 21:78-91. doi: 10.1016/j.jag.2012.08.014 [75] CHEN X, AN S, CHEN J, et al. A review on forest ecosystem biophysical parameter retrieval from remotely sensed data[J]. Chin J Ecol, 2005, 24(9):1074-1079. http://cn.bing.com/academic/profile?id=2351552346&encoded=0&v=paper_preview&mkt=zh-cn [76] COMBAL B, BARET F, WEISS M. Improving canopy variables estimation from remote sensing data by exploiting ancillary information. Case study on sugar beet canopies[J]. Agronomie, 2002, 22(2):205-215. doi: 10.1051/agro:2002008 [77] COMBAL B, BARET F, WEISS M, et al. Retrieval of canopy biophysical variables from bidirectional reflectance:Using prior information to solve the ill-posed inverse problem[J]. Remote Sensing of Environment, 2003, 84(1):1-15. doi: 10.1016/S0034-4257(02)00035-4 [78] 李小文, 王锦地, 胡宝新, 等.先验知识在遥感反演中的作用[J].中国科学:D辑, 1998, 28(1):67-72. http://www.cnki.com.cn/Article/CJFDTOTAL-JDXK199801011.htm LI Xiao-wen, WANG Jin-di, HU Bao-xin, et al. On utilization of a priori knowledge in inversion of remote sensing models[J]. Science China (Series D), 1998, 28(1):67-72. http://www.cnki.com.cn/Article/CJFDTOTAL-JDXK199801011.htm [79] ATZBERGER C. Object-based retrieval of biophysical canopy variables using artificial neural nets and radiative transfer models[J]. Remote Sensing of Environment, 2004, 93(1):53-67. http://cn.bing.com/academic/profile?id=2030078894&encoded=0&v=paper_preview&mkt=zh-cn [80] 阎广建, 吴均.光谱先验知识在植被结构遥感反演中的应用[J].遥感学报, 2002, 6(1):1-6. http://www.cnki.com.cn/Article/CJFDTOTAL-YGXB200201000.htm YAN Guang-jian, WU Jun. Spectral prior knowledge and its use in the remote sensing based inversion of vegetation structure[J]. Journal of Remote Sensing, 2002, 6(1):1-6. http://www.cnki.com.cn/Article/CJFDTOTAL-YGXB200201000.htm [81] 蔡博峰, 绍霞.基于PROSPECT+ SAIL模型的遥感叶面积指数反演[J].国土资源遥感, 2007, 2:39-43. http://www.cnki.com.cn/Article/CJFDTOTAL-GTYG200702011.htm CAI Bo-feng, SHAO Xia. Leaf area index retrieval based on remotely sensed data and PROSPECT+ SAIL model[J]. Remote Sensing For Land & Resources, 2007, 2:39-43. http://www.cnki.com.cn/Article/CJFDTOTAL-GTYG200702011.htm [82] ATZBERGER C, RICHTER K. Spatially constrained inversion of radiative transfer models for improved LAI mapping from future Sentinel-2 imagery[J]. Remote Sensing of Environment, 2012, 120:208-218. doi: 10.1016/j.rse.2011.10.035 [83] 行敏锋.生态脆弱区植被生物量和土壤水分的主被动遥感协同反演[D].成都:电子科技大学, 2015. XING Min-feng. Integration study to retrieve vegetation biomass and soil moisture simultaneously using active and passive remote sensing data in ecologically vulnerable area[D]. Chengdu:University of Electronic Science and Technology of China, 2015. [84] LEPRIEUR C, VERSTRAETE M M, PINTY B. Evaluation of the performance of various vegetation indices to retrieve vegetation cover from AVHRR data[J]. Remote Sensing Reviews, 1994, 10(4):265-284. doi: 10.1080/02757259409532250 [85] QUAN X, HE B, LI X, et al. Retrieval of grassland live fuel moisture content by parameterizing radiative transfer model with interval estimated LAI[J]. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2016, 9(2):910-920. doi: 10.1109/JSTARS.2015.2472415 [86] MONTESANO P, COOK B, SUN G, et al. Achieving accuracy requirements for forest biomass mapping:a spaceborne data fusion method for estimating forest biomass and LiDAR sampling error[J]. Remote Sensing of Environment, 2013, 130:153-170. doi: 10.1016/j.rse.2012.11.016 [87] RAUSTE Y. Multi-temporal JERS SAR data in boreal forest biomass mapping[J]. Remote Sensing of Environ-ment, 2005, 97(2):263-275. doi: 10.1016/j.rse.2005.05.002 [88] ZRIBI M, BAGHDADI N, HOLAH N, et al. New methodology for soil surface moisture estimation and its application to ENVISAT-ASAR multi-incidence data inversion[J]. Remote Sensing of Environment, 2005, 96(3):485-496. http://cn.bing.com/academic/profile?id=2163470201&encoded=0&v=paper_preview&mkt=zh-cn [89] OH Y, SARABANDI K, ULABY F T. An empirical model and an inversion technique for radar scattering from bare soil surfaces[J]. IEEE Transactions on Geoscience and Remote Sensing, 1992, 30(2):370-381. doi: 10.1109/36.134086 [90] DUBOIS P C, VAN ZYL J, ENGMAN T. Measuring soil moisture with imaging radars[J]. IEEE Transactions on Geoscience and Remote Sensing, 1995, 33(4):915-926. doi: 10.1109/36.406677 [91] SHI J, WANG J, HSU A Y, et al. Estimation of bare surface soil moisture and surface roughness parameter using L-band SAR image data[J]. IEEE Transactions on Geoscience and Remote Sensing, 1997, 35(5):1254-1266. doi: 10.1109/36.628792 [92] FUNG A K, LI Z, CHEN K-S. Backscattering from a randomly rough dielectric surface[J]. IEEE Transactions on Geoscience and Remote Sensing, 1992, 30(2):356-369. doi: 10.1109/36.134085 [93] HE B, XING M, BAI X. A synergistic methodology for soil moisture estimation in an Alpine prairie using radar and optical satellite data[J]. Remote Sensing, 2014, 6(11):10966-10985. doi: 10.3390/rs61110966 [94] BAI X, HE B, LI X. Optimum surface roughness to parameterize advanced integral equation model for soil moisture retrieval in prairie area using radarsat-2 data[J]. IEEE Transactions on Geoscience and Remote Sensing, 2016, 54(4):2437-2449. doi: 10.1109/TGRS.2015.2501372 [95] ATTEMA E, ULABY F T. Vegetation modeled as a water cloud[J]. Radio Science, 1978, 13(2):357-364. doi: 10.1029/RS013i002p00357 [96] BRACAGLIA M, FERRAZZOLI P, GUERRIERO L. A fully polarimetric multiple scattering model for crops[J]. Remote Sensing of Environment, 1995, 54(3):170-179. doi: 10.1016/0034-4257(95)00151-4 [97] FERRAZZOLI P, GUERRIERO L. Emissivity of vegetation:Theory and computational aspects[J]. Journal of Electromagnetic Waves and Applications, 1996, 10(5):609-628. doi: 10.1163/156939396X00559 [98] ULABY F T, SARABANDI K, MCDONALD K, et al. Michigan microwave canopy scattering model[J]. International Journal of Remote Sensing, 1990, 11(7):1223-1253. doi: 10.1080/01431169008955090 [99] DE ROO R D, DU Y, ULABY F T, et al. A semi-empirical backscattering model at L-band and C-band for a soybean canopy with soil moisture inversion[J]. IEEE Transactions on Geoscience and Remote Sensing, 2001, 39(4):864-872. doi: 10.1109/36.917912 [100] SAATCHI S S, MOGHADDAM M. Estimation of crown and stem water content and biomass of boreal forest using polarimetric SAR imagery[J]. IEEE Transactions on Geoscience and Remote Sensing, 2000, 38(2):697-709. doi: 10.1109/36.841999 [101] SAATCHI S S, MCDONALD K C. Coherent effects in microwave backscattering models for forest canopies[J]. IEEE Transactions on Geoscience and Remote Sensing, 1997, 35(4):1032-1044. doi: 10.1109/36.602545 [102] SANTORO M, BEER C, CARTUS O, et al. Retrieval of growing stock volume in boreal forest using hyper-temporal series of Envisat ASAR ScanSAR backscatter measurements[J]. Remote Sensing of Environment, 2011, 115(2):490-507. doi: 10.1016/j.rse.2010.09.018 [103] CARTUS O, SANTORO M, KELLNDORFER J. Mapping forest aboveground biomass in the Northeastern United States with ALOS PALSAR dual-polarization L-band[J]. Remote Sensing of Environment, 2012, 124:466-478. doi: 10.1016/j.rse.2012.05.029 [104] STOW D, HAMADA Y, COULTER L, et al. Monitoring shrubland habitat changes through object-based change identification with airborne multispectral imagery[J]. Remote Sensing of Environment, 2008, 112(3):1051-1061. doi: 10.1016/j.rse.2007.07.011 [105] 马建伟.全色波段高空间分辨遥感影像特定目标变化检测技术研究[D].北京:中国科学院遥感应用研究所, 2006. http://cdmd.cnki.com.cn/article/cdmd-80070-2006157799.htm MA Jian-wei. Change detection of specified targetin high spatial resolution panchromatic imagery[D]. Beijing:Insitute of Remote Sensing Applications Chinese Academy of Sciences, 2006. http://cdmd.cnki.com.cn/article/cdmd-80070-2006157799.htm [106] READ J M, LAM N S N. Spatial methods for characterising land cover and detecting land-cover changes for the tropics[J]. International Journal of Remote Sensing, 2002, 23(12):2457-2474. doi: 10.1080/01431160110106140 [107] KEUCHEL J, NAUMANN S, HEILER M, et al. Automatic land cover analysis for Tenerife by supervised classification using remotely sensed data[J]. Remote Sensing of Environment, 2003, 86(4):530-541. doi: 10.1016/S0034-4257(03)00130-5 [108] BRUZZONE L, PRIETO D F. Unsupervised retraining of a maximum likelihood classifier for the analysis of multitemporal remote sensing images[J]. IEEE Transactions on Geoscience and Remote Sensing, 2001, 39(2):456-460. doi: 10.1109/36.905255 [109] FULLER R, SMITH G, DEVEREUX B. The characterisation and measurement of land cover change through remote sensing:problems in operational applications?[J]. International Journal of Applied Earth Observation and Geoinformation, 2003, 4(3):243-253. doi: 10.1016/S0303-2434(03)00004-7 [110] ZHU Z, WOODCOCK C E, OLOFSSON P. Continuous monitoring of forest disturbance using all available Landsat imagery[J]. Remote Sensing of Environment, 2012, 122:75-91. doi: 10.1016/j.rse.2011.10.030 [111] HUANG C, GOWARD S N, MASEK J G, et al. An automated approach for reconstructing recent forest disturbance history using dense Landsat time series stacks[J]. Remote Sensing of Environment, 2010, 114(1):183-198. doi: 10.1016/j.rse.2009.08.017 [112] ZHU Z, WOODCOCK C E. Continuous change detection and classification of land cover using all available Landsat data[J]. Remote Sensing of Environment, 2014, 144:152-171. doi: 10.1016/j.rse.2014.01.011 [113] 全兴文.高原湿地植被参数遥感定量反演及同化技术研究[D].成都:电子科技大学, 2013. http://cdmd.cnki.com.cn/article/cdmd-10614-1013334344.htm QUAN Xing-wen. Quantitative retrieval methods anddata assimilation technology forvegetational parameters in alpinewetland[D]. Chengdu:University of Electronic Science and Technology of China, 2013. http://cdmd.cnki.com.cn/article/cdmd-10614-1013334344.htm [114] 柳钦火.环境遥感定量反演与同化[M].北京:科学出版社, 2011. LIU Qin-huo. Quantitative retrieval and assimilation of environmental remote sensing[M]. Beijing:Science Press, 2011. [115] CHARNEY J, HALEM M, JASTROW R. Use of incomplete historical data to infer the present state of the atmosphere[J]. Journal of the Atmospheric Sciences, 1969, 26(5):1160-1163. doi: 10.1175/1520-0469(1969)026<1160:UOIHDT>2.0.CO;2 [116] NOUVELLON Y, MORAN M S, SEEN D L, et al. Coupling a grassland ecosystem model with Landsat imagery for a 10-year simulation of carbon and water budgets[J]. Remote Sensing of Environment, 2001, 78(1):131-149. http://cn.bing.com/academic/profile?id=2057680602&encoded=0&v=paper_preview&mkt=zh-cn [117] WEISS M, TROUFLEAU D, BARET F, et al. Coupling canopy functioning and radiative transfer models for remote sensing data assimilation[J]. Agricultural and Forest Meteorology, 2001, 108(2):113-128. doi: 10.1016/S0168-1923(01)00234-9 [118] TALAGRAND O. Assimilation of observations, an introduction[J]. Journal-Meteorological Society of Japan Series 2, 1997, 75:81-99. http://cn.bing.com/academic/profile?id=85093244&encoded=0&v=paper_preview&mkt=zh-cn [119] RABIER F. Overview of global data assimilation developments in numerical weather-prediction centres[J]. Quarterly Journal of the Royal Meteorological Society, 2005, 131(613):3215-3233. doi: 10.1256/qj.05.129 [120] QUAN X, HE B, XING M. Use of data assimilation technique for improveing the retrieval of leaf area index in time-series in alpine wetlands[C]//2012 International Geoscience and Remote Sensing Symposium (IGARSS). Munich:IEEE, 2012:754-756. [121] SONG C, WOODCOCK C E. Monitoring forest succession with multitemporal Landsat images:Factors of uncertainty[J]. IEEE Transactions on Geoscience and Remote Sensing, 2003, 41(11):2557-2567. doi: 10.1109/TGRS.2003.818367 [122] TURNER D P, COHEN W B, KENNEDY R E, et al. Relationships between leaf area index and Landsat TM spectral vegetation indices across three temperate zone sites[J]. Remote Sensing of Environment, 1999, 70(1):52-68. doi: 10.1016/S0034-4257(99)00057-7 [123] SCHAAF C B, LI X, STRAHLER A H. Topographic effects on bidirectional and hemispherical reflectances calculated with a geometric-optical canopy model[J]. IEEE Transactions on Geoscience and Remote Sensing, 1994, 32(6):1186-1193. doi: 10.1109/36.338367 [124] YEBRA M, DENNISON P E, CHUVIECO E, et al. A global review of remote sensing of live fuel moisture content for fire danger assessment:Moving towards operational products[J]. Remote Sensing of Environment, 2013, 136:455-468. doi: 10.1016/j.rse.2013.05.029 [125] DANSON F, BOWYER P. Estimating live fuel moisture content from remotely sensed reflectance[J]. Remote Sensing of Environment, 2004, 92(3):309-321. doi: 10.1016/j.rse.2004.03.017 [126] RIANO D, VAUGHAN P, CHUVIECO E, et al. Estimation of fuel moisture content by inversion of radiative transfer models to simulate equivalent water thickness and dry matter content:Analysis at leaf and canopy level[J]. IEEE Transactions on Geoscience and Remote Sensing, 2005, 43(4):819-826. doi: 10.1109/TGRS.2005.843316 [127] YEBRA M, CHUVIECO E, RIANO D. Estimation of live fuel moisture content from MODIS images for fire risk assessment[J]. Agr Forest Meteorol, 2008, 148(4):523-536. doi: 10.1016/j.agrformet.2007.12.005 [128] YEBRA M, CHUVIECO E. Generation of a species-specific look-up table for fuel moisture content assessment[J]. IEEE J Sel Top Appl Earth Observ Remote Sens, 2009, 2(1):21-26. doi: 10.1109/JSTARS.2009.2014008 [129] YEBRA M, CHUVIECO E. Linking ecological information and radiative transfer models to estimate fuel moisture content in the mediterranean region of Spain:Solving the ill-posed inverse problem[J]. Remote Sensing of Environment, 2009, 113(11):2403-2411. doi: 10.1016/j.rse.2009.07.001 [130] JURDAO S, YEBRA M, GUERSCHMAN J P, et al. Regional estimation of woodland moisture content by inverting radiative transfer models[J]. Remote Sensing of Environment, 2013, 132:59-70. doi: 10.1016/j.rse.2013.01.004 [131] YEBRA M, DENNISON P E, CHUVIECO E, et al. A global review of remote sensing of live fuel moisture content for fire danger assessment:Moving towards operational products[J]. Remote Sensing of Environment, 2013, 136:455-468. doi: 10.1016/j.rse.2013.05.029 [132] WANG L L, HUNT E R, QU J J, et al. Remote sensing of fuel moisture content from ratios of narrow-band vegetation water and dry-matter indices[J]. Remote Sensing of Environment, 2013, 129:103-110. doi: 10.1016/j.rse.2012.10.027 [133] XING M, QUAN X, LI X, et al. An extended approach for biomass estimation in a mixed vegetation area using ASAR and TM data[J]. Photogrammetric Engineering & Remote Sensing, 2014, 80(5):429-438. http://cn.bing.com/academic/profile?id=2321359569&encoded=0&v=paper_preview&mkt=zh-cn [134] HE B, LIAO Z, QUAN X, et al. A Globle grassland drought index (GDI) product:Algorithm and validation[J]. Remote Sensing, 2015, 7(10):12704-12736. doi: 10.3390/rs71012704 [135] LI X, HE B, QUAN X, et al. Use of the standardized precipitation evapotranspiration index (SPEI) to characterize the drying trend in southwest China from 1982-2012[J]. Remote Sensing, 2015, 7(8):10917-10937. doi: 10.3390/rs70810917