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1.
遥感土壤水分对蒸散发估算的影响 总被引：1，自引：0，他引：1
地表实际蒸散发是联系陆表水循环、能量平衡和碳收支等物理过程的重要生态水文变量,同时也是目前水循环研究中的薄弱点,定量化土壤水分对蒸散发的胁迫作用是估算地表蒸散发的一个关键过程和难点。本研究基于2018年9月闪电河流域水循环与能量平衡遥感综合试验星—机—地联合观测数据,采用机载观测和卫星遥感反演土壤水分输入到ETMonitor模型估算地表实际蒸散发,在时间和空间两个维度上评估不同土壤水分产品对蒸散发估算的影响。从时间变化上来说,与地面观测蒸散发时间序列相比,基于ESA CCI (European SpaceAgency Climate Change Initiative)融合土壤水分产品、SMAP (Soil Moisture Active and Passive)土壤水分产品和国产风云三号气象卫星(FY-3C)土壤水分产品估算的蒸散发最接近地面站点观测蒸散发,而基于ASCAT (TheAdvanced Scatterometer)和SMOS (Soil Moisture Ocean Salinity)土壤水分估算蒸散发分别明显的高于和低于地面观测蒸散发。从空间分布上来说,利用卫星反演土壤水分估算的蒸散发与基于机载观测土壤水分估算蒸散发具有一致的空间分布,能较好地反映该区域地表蒸散的空间分布格局,其中基于SMAP和SMOS土壤水分估算蒸散发与基于机载观测土壤水分估算蒸散发空间一致性最好。本研究评估遥感反演土壤水分对蒸散发影响,对区域及全球遥感蒸散发估算和土壤水分产品评估具有一定的指导意义。 相似文献
2.
土壤水分不仅是陆面过程中重要的变量,同时也是全球水循环中的关键参数。为了获得高分辨率的土壤水分数据,本文将基于自适应窗口的土壤水分降尺度方法应用在闪电河流域,以1 km MODIS产品(地表温度和归一化植被指数)作为辅助数据,对9 km的SMAP被动微波土壤水分(SMAP土壤水分)数据进行降尺度,得到研究区1 km的降尺度土壤水分数据。利用地面站点实测土壤水分和机载被动微波土壤水分(机载土壤水分)对降尺度土壤水分和SMAP土壤水分进行了验证,并对辅助数据和降尺度方法本身展开分析以探讨降尺度过程中的不确定性来源。结果表明:(1)本文使用的基于自适应窗口的土壤水分降尺度方法能够有效地提高SMAP土壤水分的空间分辨率,在进一步丰富土壤水分分布细节变化信息的同时,还能够保留SMAP土壤水分的空间变化特征并与其保持值域一致。(2) 3种基于像元尺度的土壤水分数据(机载土壤水分、SMAP土壤水分和降尺度土壤水分)与站点实测土壤水分之间的相关性并不高,这主要与点、面数据之间的空间匹配不一致、空间代表性不同以及有效验证的数据量有限有关。而与站点数据验证相比,降尺度土壤水分和SMAP土壤水分均和机载土壤水分数据相关性较好。(3) SMAP土壤水分与辅助数据之间的相关性比机载土壤水分与辅助数据之间的较高,而这两种土壤水分数据之间存在的这种偏差主要受到空间尺度、观测配置、参数反演算法和选用的辅助数据等因素的影响。(4)针对验证结果的不确定性,通过增加辅助数据或改变土壤水分估算模型结构进而修改降尺度模型的方式在本研究中并不能显著提高降尺度结果的精度,如何进一步提高降尺度精度仍是未来需要研究的重点。 相似文献
3.
《国土资源遥感》2021,(2)
为进一步研究风云三号(FY-3B)土壤水分降尺度获取高分辨率土壤水分的方法,使其更适用于农业、水文、生态等区域尺度的应用要求,以MODIS为数据源,青藏高原那曲地区为研究区,利用表观热惯量模型(apparent thermal inertia,ATI)与温度植被指数(temperature vegetation index,TVI)模型在不同植被覆盖度下适用的特点,构建综合ATI与TVI的土壤水分反演模型;结合低分辨率FY-3B土壤水分产品,利用土壤水分降尺度方法,获取高分辨率下土壤水分反演模型系数,并得到高分辨率土壤水分。通过与地面观测数据对比,降尺度后土壤水分与实测数据的R~2在0.4以上,RMSE在0.055～0.103 cm~3/cm~3之间,表明降尺度后的土壤水分能够较好地反映区域土壤水分的空间分布与变化。 相似文献
4.
风云四号卫星东南沿海热带气旋强度深度学习估算 总被引：1，自引：0，他引：1
热带气旋TC（Tropical Cyclone）是影响中国的一个重要天气系统。TC强度准确估测对台风灾害防御具有至关重要的意义。本文基于第二代静止气象卫星风云四号（FY-4A）多通道扫描成像辐射计AGRI（Advanced Geosynchronous Radiation Imager）资料，建立了台风强度识别的深度卷积神经网络模型CNN（Convolutional Neural Network），对台风强度不同等级和台风中心最大风速进行了试验。结果表明，CNN模型具有良好的高维非线性处理能力和算法稳定性，能对TC强度进行有效估计，不同TC强度等级识别精度均在97%以上，近中心最大风速平均绝对误差MAE（Mean Absolute Error）为1.75 m/s，均方根误差RMSE（Root Mean Square Error）为2.04 m/s。CNN可有效挖掘卫星TC形态的深层信息，对台风强度的定量化估测具有较高的应用前景。 相似文献
5.
遥感叶面积指数产品精度和不确定性需要通过地面测量的数据来验证。因为两者的空间尺度差异,验证前需要通过尺度转换方法将这两种数据的尺度统一。将泰勒级数展开模型进行改进后,可以用于解决叶面积指数遥感产品验证中地面测量数据与遥感产品尺度不匹配的问题,同时可以针对每个数据定量给出误差。将误差在阈值范围内的实测数据作为地面参考值对遥感产品进行验证。本文利用这种方法将黑河综合遥感联合实验数据集中的地面测量叶面积指数尺度上升到遥感像元尺度,并与MODIS,GLASS LAI遥感产品进行了比较。 相似文献
6.
基于遥感的区域尺度森林地上生物量估算研究 总被引：1，自引：0，他引：1
森林是陆地生态系统最大的碳库,精确估算森林生物量是陆地碳循环研究的关键。首先从机载LiDAR数据中提取高度和密度统计量,采用逐步回归模型进行典型样区生物量估算;然后利用机载LiDAR数据估算的生物量作为样本数据,与多光谱遥感数据Landsat8 OLI的波段反射率及植被指数建立回归模型,实现区域尺度森林地上生物量估算。实验结果显示,机载LiDAR数据估算的鼎湖山样区生物量与地面实测生物量的相关性R2达0.81,生物量RMSE为40.85 t/ha,说明机载LiDAR点云数据的高度和密度统计量与生物量存在较高的相关性。以机载LiDAR数据估算的生物量为样本数据,结合多光谱遥感数据Landsat8 OLI估算粤西北地区的森林地上生物量,精度验证结果为:R2为0.58,RMSE为36.9 t/ha;针叶林、阔叶林和针阔叶混交林等3种不同森林类型生物量的估算结果为:R2分别为0.51(n=251)、0.58(n=235)和0.56(n=241),生物量RMSE分别为24.1 t/ha、31.3 t/ha和29.9 t/ha,估算精度相差不大。总体上看,利用遥感数据可以开展区域尺度的森林地上生物量估算,为森林固碳监测提供有力的参考数据。 相似文献
7.
利用AMSR2和MODIS数据的土壤冻融相变水量降尺度方法 总被引：1，自引：0，他引：1
本文基于站点实测土壤温度和土壤湿度数据分析,发现温度指数TI(Temperature Index)和土壤冻融相变水量呈现幂函数关系,温度指数能够反映相变水量的变化。使用MODIS地表温度产品计算温度指数,在AMSR2卫星观测尺度上与相变水量建立了关系,从而对土壤冻融相变水量进行了降尺度研究。采用CTP-SMTMN数据采集仪观测网络上的站点观测到土壤水分对土壤冻融相变水量降尺度结果进行了验证。结果表明,土壤冻融相变水量降尺度结果与实测值较为接近,在土壤相变水量大于0.01(m3/m3)时,RMSE为0.0085(m3/m3),MAE为0.0059(m3/m3)。这种通过温度指数对土壤相变水量进行降尺度的方法具有简便,可行,可靠的优势,适合在冻融交替期计算较湿润土壤在冻融过程中产生的相变水量。同时,这种降尺度方法能够生成小尺度上的相变水量产品,实现了热红外遥感和被动微波遥感的优势整合,对研究地气水热平衡,气候变化,土壤冻结强度以及冻融侵蚀强度等具有重要意义。 相似文献
8.
遥感反演与模型模拟是获取全球土壤湿度数据的两种基本手段,遥感反演可以获得相对较高的空间分辨率,但往往存在时空缝隙;陆面模型能够模拟土壤湿度的时空连续演进,但空间分辨率往往较粗。为此,集成二者的互补优势,提出一种融合微波遥感与模型模拟的全球无缝土壤湿度数据生成方法。具体地,针对SMAP(soil moisture active passive）卫星9 km土壤湿度数据的空缺区域,引入GLDAS Noah 0.25°的模型同化数据,建立二者之间的时空融合模型,通过对模型数据的降尺度实现对遥感数据的填补,进一步基于泊松方程方法进行残差校正,进而生成高精度的9 km日尺度土壤湿度无缝数据。实验结果证明,该方法可以有效结合遥感观测的空间分辨率优势与模型模拟的时空连续优势,提供时空无缝全球土壤湿度数据,更好地满足全球尺度水循环监测与水资源管理的需求。 相似文献
9.
遥感试验是进行遥感原理的验证、遥感模型与反演方法的发展、遥感产品的真实性检验,推动卫星计划的论证实施及其观测在地球系统科学中应用的重要途径。在闪电河流域水循环与能量平衡遥感综合试验中,利用机载L波段主被动一体化微波探测仪开展了以土壤水分为首要目标的大型航空遥感试验。其中,被动探测部分即微波辐射计采用微带天线,辅以机械扫描方式进行多角度成像观测。为有效支撑微波辐射计数据的处理及定量反演,必须对机载微波辐射计进行实时定标,本文采用分步定标法进行辐射亮温的定标,即在实验室对定标链路中的噪声源进行定标,得出对应的辐射亮温;飞行试验中,利用该两个参考点得到辐射计输出电压和亮温的关系,同时选取试验区域附近的水体作为外定标参考点,进行定标方程的修正。结果表明,机载辐射亮温与地面参考点(草地)模拟亮温比较吻合,二者对比结果显示均方根误差最小为0.93 K (2018-09-26,H极化),无偏均方根误差最小为0.96 K (2018-09-24,V极化),有效支撑了国产L波段微波辐射计相关卫星计划的论证以及后续的定量反演与降尺度等相关研究工作的开展。 相似文献
10.
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
11.
Significant advances have been achieved in generating soil moisture (SM) products from satellite remote sensing and/or land surface modeling with reasonably good accuracy in recent years. However, the discrepancies among the different SM data products can be considerably large, which hampers their usage in various applications. The bias of one SM product from another is well recognized in the literature. Bias estimation and spatial correction methods have been documented for assimilating satellite SM product into land surface and hydrologic models. Nevertheless, understanding the characteristics of each of these SM data products is required for many applications where the most accurate data products are desirable. This study inter-compares five SM data products from three different sources with each other, and evaluates them against in situ SM measurements over 14-year period from 2000 to 2013. Specifically, three microwave (MW) satellite based data sets provided by ESA's Climate Change Initiative (CCI) (CCI-merged, -active and -passive products), one thermal infrared (TIR) satellite based product (ALEXI), and the Noah land surface model (LSM) simulations. The in-situ SM measurements are collected from the North American Soil Moisture Database (NASMD), which involves more than 600 ground sites from a variety of networks. They are used to evaluate the accuracies of these five SM data products. In general, each of the five SM products is capable of capturing the dry/wet patterns over the study period. However, the absolute SM values among the five products vary significantly. SM simulations from Noah LSM are more stable relative to the satellite-based products. All TIR and MW satellite based products are relatively noisier than the Noah LSM simulations. Even though MW satellite based SM retrievals have been predominantly used in the past years, SM retrievals of the ALEXI model based on TIR satellite observations demonstrate skills equivalent to all the MW satellite retrievals and even slightly better over certain regions. Compared to the individual active and passive MW products, the merged CCI product exhibits higher anomaly correlation with both Noah LSM simulations and in-situ SM measurements. 相似文献
12.
Yunqiao Shu Simon Stisen Karsten H. Jensen Inge Sandholt 《International Journal of Applied Earth Observation and Geoinformation》2011
Data from the first operational Chinese geostationary satellite Fengyun-2C (FY-2C) satellite are applied in combination with Moderate Resolution Imaging Spectroradiometer (MODIS) satellite products for the assessment of regional evapotranspiration over the North China Plain. The approach is based on the improved triangle method, where the temperature–vegetation index space includes thermal inertia. Two thermal infrared channels from FY-2C are used to estimate surface temperature (Ts) based on a split window algorithm originally proposed for the MSG-SEVIRI sensor. Subsequently the high temporal resolution of FY-2C data is exploited to give the morning rise in Ts. Combined with the 16 days composite MODIS vegetation indices product (MOD13) at a spatial resolution of 5 km, evaporative fraction (EF) is estimated by interpolation in the ΔTs–NDVI triangular-shaped scatter space. Finally, regional actual evapotranspiration (ET) is derived from the evaporative fraction and available energy estimated from MODIS surface albedo products MCD43. Spatial variations of estimated surface variables (Ts, EF and ET) corresponded well to land cover patterns and farmland management practices. Estimated ET and EF also compared well to lysimeter data collected for the period June 2005–September 2007. The improved triangle method was also applied to MODIS products for comparison. Estimates based on FY-2C products proved to provide slightly better results than those based on MODIS products. The consistency of the estimated spatial variation with other spatial data supports the use of FY-2C data for ET estimation using the improved triangle method. Of particular value is the high temporal frequency of image acquisitions from FY-2C which improves the likelihood of obtaining cloud free image acquisitions as compared to polar orbiting sensors like MODIS. 相似文献
13.
Tata V. S. Udaya Bhaskar Chiranjivi Jayaram Saurabh Bansal K Krishna Mohan Debadatta Swain 《Journal of the Indian Society of Remote Sensing》2017,45(1):113-122
The Oceansat-2 scatterometer (OSCAT) of the Indian Space Research Organization (ISRO), provides surface wind speed and direction with a spatial resolution of 50 km × 50 km. With a revisit time of 2 days it had provided ocean surface wind vectors over the global oceans. In the present work, an attempt has been made to generate two day composite of OSCAT wind vectors using Data-Interpolating Variational Analysis (DIVA) and compare them with daily composite winds to check how better is the two day composites in comparison to daily composites. The daily and two days composite wind vectors of zonal (U) and meridional (V) components have been validated with wind measurements from in situ buoys and Advanced Scatterometer (ASCAT) for the year 2012 over the tropical Indian Ocean region. The statistical comparison with the in situ measurements and ASCAT has shown that the two-day OSCAT wind composites are slightly better than the daily composite winds. The improvement in the statistics can be attributed to the use of ascending and descending passes pertaining to two days which results in fewer gaps between passes, thereby reducing the interpolation errors. 相似文献
14.
2013年中国发射了首颗进行全球导航卫星系统(global navigation satellite system,GNSS)掩星观测的气象卫星风云3号C星(Fengyun-3C,FY-3C),且已发布自2014年6月以来的FY-3C掩星大气产品,但目前还未见将其应用于大气边界层的相关研究。首次尝试利用FY-3C折射率产品确定边界层高度并进一步进行空间分布分析。结果表明,在小波协方差变换法基础上,进行尖锐度约束,能够确定FY-3C掩星低层大气折射率廓线中可能存在的突变,反演边界层高度。所得到的2015―2018年各年边界层高度全球分布在不同纬度及海洋和陆地上的差异基本体现了边界层与地表气候及地形的关系,但FY-3C折射率产品在低层大气的精度和垂直分辨率相对较低。因此,反演成功率总体上较低,反演结果对边界层高度空间分布细节特征的呈现仍有待提升。 相似文献
15.
The aim of the study was to evaluate flash flood potential areas in the Western Cape Province of South Africa, by integrating remote sensing products of high rainfall intensity, antecedent soil moisture and topographic wetness index (TWI). Rainfall has high spatial and temporal variability, thus needs to be quantified at an area in real time from remote sensing techniques unlike from sparsely distributed, point gauge network measurements. Western Cape Province has high spatial variation in topography which results in major differences in received rainfall within areas not far from each other. Although high rainfall was considered as the major cause of flash flood, also other contributing factors such as topography and antecedent soil moisture were considered. Areas of high flash flood potential were found to be associated with high rainfall, antecedent precipitation and TWI. Although TRMM 3B42 was found to have better rainfall intensity accuracy, the product is not available in near real time but rather at a rolling archive of three months; therefore, Multi- sensor precipitation estimate rainfall estimates available in near real time are opted for flash flood events. Advanced Scatterometer (ASCAT) soil moisture observations were found to have a reasonable r value of 0.58 and relatively low MAE of 3.8 when validated with in situ soil moisture measurements. The results of this study underscore the importance of ASCAT and TRMM satellite datasets in mapping areas at risk of flooding. 相似文献
16.
Satellite rainfall products (SRPs) are becoming more accurate with ever increasing spatial and temporal resolution. This evolution can be beneficial for hydrological applications, providing new sources of information and allowing to drive models in ungauged areas. Despite the large availability of rainfall satellite data, their use in rainfall-runoff modelling is still very scarce, most likely due to measurement issues (bias, accuracy) and the hydrological community acceptability of satellite products.In this study, the real-time version (3B42-RT) of Tropical Rainfall Measurement Mission Multi-satellite Precipitation Analysis, TMPA, and a new SRP based on the application of SM2RAIN algorithm (Brocca et al., 2014) to the ASCAT (Advanced SCATterometer) soil moisture product, SM2RASC, are used to drive a lumped hydrologic model over four basins in Italy during the 4-year period 2010–2013.The need of the recalibration of model parameter values for each SRP is highlighted, being an important precondition for their suitable use in flood modelling. Results shows that SRPs provided, in most of the cases, performance scores only slightly lower than those obtained by using observed data with a reduction of Nash–Sutcliffe efficiency (NS) less than 30% when using SM2RASC product while TMPA is characterized by a significant deterioration during the validation period 2012–2013. Moreover, the integration between observed and satellite rainfall data is investigated as well. Interestingly, the simple integration procedure here applied allows obtaining more accurate rainfall input datasets with respect to the use of ground observations only, for 3 out 4 basins. Indeed, discharge simulations improve when ground rainfall observations and SM2RASC product are integrated, with an increase of NS between 2 and 42% for the 3 basins in Central and Northern Italy. Overall, the study highlights the feasibility of using SRPs in hydrological applications over the Mediterranean region with benefits in discharge simulations also in well gauged areas. 相似文献
17.
The timing of seasonal snowmelt in high-latitude tundra has implications ranging from local biological productivity to global atmospheric circulation, yet remains difficult to quantify, particularly at large spatial scales. Snowmelt detection in such remote polar environments is possible using satellite-based microwave scatterometers, such as NASA’s QuikSCAT. QuikSCAT measured scattering in Ku-band, which is sensitive to snowmelt signals, from 1999 until the antenna failed in 2009. The Advanced Scatterometer (ASCAT) (2006–2021 (projected) operational), which operates at C-band, may be able to extend the QuikSCAT record, but existing techniques fail to adequately monitor tundra environments. Here, we designed a departure threshold algorithm to produce a consistent 15-year time series of melt onset for the tundra of the Alaskan North Slope, using the overlap period for the enhanced resolution datasets to calibrate the ASCAT melt detection record against QuikSCAT. We produced a time series of day of year of melt onset for 4.45 km x 4.45 km grid cells on the Alaskan North Slope from 2000–2014. Time series validation with in situ mean daily air temperature produced mean R2 values of 0.75 (QuikSCAT) and 0.72 (ASCAT). We qualitatively observed a difference between early-season melt, which occurred rapidly and was driven by strong wind events, and more typical melt, which occurred gradually along a latitudinal gradient. We speculate that future melt timing will have greater frequency of early-season onset as climate change destabilizes the high-latitude atmosphere. 相似文献
18.
For more than six years, the Soil Moisture and Ocean Salinity (SMOS) mission has provided multi angular and full-polarization brightness temperature (TB) measurements at L-band. Geophysical products such as soil moisture (SM) and vegetation optical depth at nadir (τnad) are retrieved by an operational algorithm using TB observations at different angles of incidence and polarizations. However, the quality of the retrievals depends on several surface effects, such as vegetation, soil roughness and texture, etc. In the microwave forward emission model used in the retrievals (L-band Microwave Emission Model, L-MEB), soil roughness is modelled with a semi-empirical equation using four main parameters (Qr, Hr, Nrp, with p = H or V polarizations). At present, these parameters are calibrated with data provided by airborne studies and in situ measurements made at a local scale that is not necessarily representative of the large SMOS footprints (43 km on average) at global scale. In this study, we evaluate the impact of the calibrated values of Nrp and Hr on the SM and τnad retrievals based on SMOS TB measurements (SMOS Level 3 product) over the Soil Climate Analysis Network (SCAN) network located in North America over five years (2011–2015). In this study, Qr was set equal to zero and we assumed that NrH = NrV. The retrievals were performed by varying Nrp from −1 to 2 by steps of 1 and Hr from 0 to 0.6 by steps of 0.1. At satellite scale, the results show that combining vegetation and roughness effects in a single parameter provides the best results in terms of soil moisture retrievals, as evaluated against the in situ SM data. Even though our retrieval approach was very simplified, as we did not account for pixel heterogeneity, the accuracy we obtained in the SM retrievals was almost systematically better than those of the Level 3 product. Improved results were also obtained in terms of optical depth retrievals. These new results may have key consequences in terms of calibration of roughness effects within the algorithms of the SMOS (ESA) and the SMAP (NASA) space missions. 相似文献
19.
2013年,中国发射了首颗进行全球导航卫星系统(global navigation satellite system,GNSS)无线电掩星观测的气象卫星FY-3C,其掩星数据产品已由国家卫星气象中心(national satellite meteorological center,NSMC)发布.基于FY-3C附加相位... 相似文献