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1.
针对欧洲中程天气预报中心实时大气数据中由于水平及垂直分辨率变化所引起的大气压跳跃,利用再分析大气数据（ERA-Interim）及去平滑球谐分析方法计算重力恢复与气候实验卫星（gravity recovery and climate experiment,GRACE）大气去混频模型,从谱域、空域角度及利用主成分分析方法比较其与标准大气与海洋去混频模型的差距,并采用星间距离变率残差作为标准衡量两种模型的优劣。结果表明:两种模型之间精度相近,用于计算时变重力场模型时其影响可忽略,但在用于计算下一代卫星重力场模型时,需考虑其影响。 相似文献
2.
在高精度大地测量观测数据处理和相关地球物理解释中,大气负荷由于影响较大,需要考虑。利用全球大气模型和区域气象站气压数据,采用移去恢复方法和球谐分析方法,计算了三峡地区大气负荷对地壳形变和重力变化的影响。提供了一种利用局部气压数据改善该区域大气负荷影响变化计算效果的合理算法,提高局部气压数据和全球模型数据利用的合理性和准确性。研究发现,大气负荷对垂直形变的影响在空间分布上中长波占优,在三峡地区的年变化幅度大于20 mm,对地面重力变化影响的年变化幅度一般不超过10 μGal,对水平形变影响较小。 相似文献
3.
为克服GRACE卫星数据空间分辨率粗糙的局限性,本文以高空间分辨率的PCR-GLOBWB数据为基础,构建了加权、乘权及误差分配降尺度方法,将GRACE卫星在河北省的水储量变化数据的空间分辨率由0.50°提高至0.05°。结果表明:加权降尺度方法不仅保留了GRACE数据的原始空间分布特征,还刻画了局部细节特征;误差分配降尺度方法结果较为理想,但在格网交界处的信号存在跳跃现象;乘权降尺度方法表现最差,与GRACE存在明显差异。经实测数据验证可知,加权降尺度方法与实测值拟合程度最好,相关系数最高可达0.81。本文为获取河北省高空间分辨率地下水储量数据提供了有效保障。 相似文献
4.
融合Landsat ETM+和MODIS数据估算高时空分辨率地表短波反照率 总被引：2，自引：0，他引：2
提出一种通过融合高空间低时间分辨率、低空间高时间分辨率地表短波反照率,来估算高时空分辨率地表短波反照率的方法。首先,利用Landsat ETM+数据,通过窄波段到宽波段的转换得到一景或多景空间分辨率较高的ETM+蓝天空短波反照率;然后,在MODIS短波反照率产品基础上,以天空光比例因子为权重,得到空间分辨率较低的MODIS蓝天空短波反照率;最后,利用STARFM(Spatial and Temporal Adaptive Reflectance Fusion Model)模型融合ETM+短波反照率的空间变化信息和MODIS短波反照率的时间变化信息,得到高时空分辨率的地表短波反照率。针对STARFM模型在异质性区域估算精度降低的问题,通过以MODIS反照率影像各像元的端元(各地类)反照率取代MODIS像元反照率来提取时空变化等信息参与STARFM模型的融合过程,达到提高异质性区域估算精度的目的。结果显示,直接利用STARFM模型估算得到的高空间分辨率地表短波反照率处在合理的精度范围内(RMSE0.02),用改进后的STARFM模型估算得到的异质性区域短波反照率和真实ETM+短波反照率间的相关系数增大。 相似文献
5.
大气加权平均温度(T m)是全球导航卫星系统(GNSS)反演大气水汽(PWV)的关键参数。然而,已有经验T m模型难以捕获T m的日周期变化,限制了其在高时间分辨率GNSS-PWV监测中的应用。利用大气再分析资料可获取高时间分辨率的T m信息,但需使用高精度的T m垂直递减率模型对其进行高程改正。针对已有T m垂直递减率模型建模仅使用单一格网点数据等不足,本文引入滑动窗口算法,利用2012—2016年的MERRA-2再分析资料建立了顾及时变垂直递减率的中国区域水平分辨率分别为1°×1.25°、2°×2.5°和4°×5°的T m垂直递减率格网模型(简称“CTm-H1、CTm-H2和CTm-H3模型”)。联合2017年的MERRA-2、GGOS大气格网数据和探空站资料,对CTm-H模型进行精度检验,并与中国区域统一的T m垂直递减率模型(简称“统一模型”)进行比较分析。结果表明:①以MERRA-2格网数据为参考值,通过CTm-H模型将MERRA-2地表格网数据改正到分层格网数据各层高度处检验,CTm-H 3个模型性能相当,在两种T m数据高程差异较大时,CTm-H模型表现出显著的优势,相比于统一模型,精度(RMS值)整体提高了30%。②以探空站资料为参考值,通过CTm-H模型将MERRA-2地表格网数据和GGOS大气格网产品分别改正到探空站高度处检验,与统一模型相比,CTm-H 3个模型的精度整体分别提高了3%和5%,且CTm-H和统一模型的精度相比于未顾及垂直改正提升较大,尤其在中国西部地区表现出显著的优势。总体而言,CTm-H 3个模型在中国区域均具有较高的精度,不需要实测气象参数即可提供中国区域近地空间范围内(本文指0~10 km的高程范围)任意位置实时高精度的T m高程改正值,因此,它在中国区域的实时高精度GNSS水汽探测中具有重要的应用。 相似文献
6.
一种高时空分辨率NDVI数据集构建方法-STAVFM 总被引：1，自引：1，他引：0
ETM NDVI可以用来在30m的尺度上开展植被的监测,然而在Landsat卫星16天的重访周期和云污染等因素的影响下,常常会在相当长的一段时间内无法获取有效的ETM NDVI数据,给这一尺度下的植被动态监测带来了一定困难。相比之下,MODIS虽然在空间上只有250m分辨率的NDVI产品,却可以每天进行相同区域的监测。针对ETM空间分辨率高和MODIS时间分辨率高的特点,本研究选择实验区,基于对STARFM方法的改进,构建不同时空分辨率NDVI的时空融合模型-STAVFM,使用该模型对ETM NDVI与MODIS NDVI融合,构建了高时空分辨率NDVI数据集。研究结果表明,通过MODIS NDVI时间变化信息与ETM NDVI空间差异信息的有机结合,实现缺失高空间分辨率NDVI的有效预测（3景预测NDVI与实际NDVI的相关系数分别达到了0.82、0.90和0.91）,从而构建高时空分辨率NDVI数据集。所构建的高时空分辨率NDVI数据集在时间上保留了高时间分辨率数据的时间变化趋势,空间上又反映了高空间分辨率数据的空间细节差异。 相似文献
7.
《国土资源遥感》2021,(3)
时空数据融合能够有效提高高空间分辨率遥感数据的时间分辨率,但是目前广泛使用的时空自适应反射率融合模型在突变区域的预测效果不佳。针对这一问题,提出一种基于分层策略的时空融合模型(hierarchical spatial-temporal fusion model,H-STFM)。该模型首先根据相邻时刻低空间分辨率数据的反射率差值,将待预测的目标像元分为物候变化像元和突变像元;然后对物候变化像元进行线性回归预测,对突变像元进行加权滤波预测;最后将物候变化和突变区域的预测结果利用优化的时间加权函数融合生成最后预测图像。以两组中分辨率遥感数据MODIS和Landsat图像为基础数据进行实验对H-STFM模型进行了定性与定量评价。结果表明,提出模型的实验结果在方差误差与相对无量纲全局误差方面表现明显优于时空自适应融合模型。 相似文献
8.
随着遥感技术的发展,遥感数据日益增加。然而,受传感器限制及云雨天气影响,单一传感器难以获取高时空分辨率的遥感影像,从而在一定程度上影响全球及区域环境变化研究。遥感影像时空融合理论与技术的发展为解决这一问题提供了有效途径。近年来,国内外学者提出了大量的时空融合算法,但对于复杂地表景观区域空间细节的融合仍存在挑战,地表非均质区域时空融合的精度有待提高。为此,本文提出了一种面向非均质区域的空间增强型时空融合模型。首先,基于混合像元分解原理与遥感数据空间特征尺度不变性假设,将低分辨率光谱变化降尺度为高分辨率光谱变化值;然后,基于不同分辨率遥感数据光谱关系的时间不变性假设,获得最终融合影像。试验结果表明,相对于常用融合模型STARFM、FSDAF,本文模型既能有效反映不同地物物候变化信息,同时能更好地保留地表的空间细节,增强了非均质地表覆盖区域融合影像的空间特征与效果;本文模型的均方根误差RMSE、相关系数r及结构相似性指标SSIM平均值分别达到0.024、0.898、0.897,相对于常用融合模型STARFM、FSDAF,RMSE平均值分别降低了6.71%和4.33%,r平均值分别提高了1.9... 相似文献
9.
针对我国近岸高浑浊水体区域MODIS短波红外波段大气校正产品中存在的信号饱和及条带问题,利用神经网络模型,采用准同步的HJ-1A/B卫星CCD影像及实测遥感反射率数据对MODIS/Terra水色遥感大气校正产品进行了质量改进。改进后结果与MODIS/Terra遥感反射率产品相比,平均相对误差为13.3%,信号饱和区域修复结果与实测数据各波段平均相对误差为28.2%。结果表明,该方法在保证结果精度的情况下,能有效地修复MODIS/Terra水色波段因为信号饱和而产生的数据空白区域,同时也能较好地解决MODIS/Terra大气校正产品中的条带问题。 相似文献
10.
高时空分辨率 NDVI 数据集构建方法 总被引：7，自引：1，他引：6
针对ETM 空间分辨率高和MODIS 时间分辨率高的特点, 选择官厅水库上游为实验区, 基于对STARFM
方法的改进, 构建不同时空分辨率NDVI 的时空融合模型-STAVFM, 使用该模型对ETM NDVI 与MODIS NDVI 融
合, 构建了高时空分辨率NDVI 数据集。研究结果表明, STAVFM 根据植被变化特点定义了有效时间窗口, 在考虑
物候影响的同时改进了时间维的加权方式, 通过MODIS NDVI 时间变化信息与ETM NDVI 空间差异信息的有机结
合, 实现缺失高空间分辨率NDV 相似文献
11.
There are two spurious jumps in the atmospheric part of the Gravity Recovery and Climate Experiment-Atmosphere and Ocean De-aliasing level 1B (GRACE-AOD1B) products, which occurred in January-February of the years 2006 and 2010, as a result of the vertical level and horizontal resolution changes in the ECMWFop (European Centre for Medium-Range Weather Forecasts operational analysis). These jumps cause a systematic error in the estimation of mass changes from GRACE time-variable level 2 products, since GRACE-AOD1B mass variations are removed during the computation of GRACE level 2. In this short note, the potential impact of using an improved set of 6-hourly atmospheric de-aliasing products on the computations of linear trends as well as the amplitude of annual and semi-annual mass changes from GRACE is assessed. These improvements result from 1) employing a modified 3D integration approach (ITG3D), and 2) using long-term consistent atmospheric fields from the ECMWF reanalysis (ERA-Interim). The monthly averages of the new ITG3D-ERA-Interim de-aliasing products are then compared to the atmospheric part of GRACE-AOD1B, covering January 2003 to December 2010. These comparisons include the 33 world largest river basins along with Greenland and Antarctica ice sheets. The results indicate a considerable difference in total atmospheric mass derived from the two products over some of the mentioned regions. We suggest that future GRACE studies consider these through updating uncertainty budgets or by applying corrections to estimated trends and amplitudes/phases. 相似文献
12.
Validation of GOCE gravity field models by means of orbit residuals and geoid comparisons 总被引：6，自引：3，他引：3
Three GOCE-based gravity field solutions have been computed by ESA’s high-level processing facility and were released to the
user community. All models are accompanied by variance-covariance information resulting either from the least squares procedure
or a Monte-Carlo approach. In order to obtain independent external quality parameters and to assess the current performance
of these models, a set of independent tests based on satellite orbit determination and geoid comparisons is applied. Both
test methods can be regarded as complementary because they either investigate the performance in the long wavelength spectral
domain (orbit determination) or in the spatial domain (geoid comparisons). The test procedure was applied to the three GOCE
gravity field solutions and to a number of selected pre-launch models for comparison. Orbit determination results suggest,
that a pure GOCE gravity field model does not outperform the multi-year GRACE gravity field solutions. This was expected as
GOCE is designed to improve the determination of the medium to high frequencies of the Earth gravity field (in the range of
degree and order 50 to 200). Nevertheless, in case of an optimal combination of GOCE and GRACE data, orbit determination results
should not deteriorate. So this validation procedure can also be used for testing the optimality of the approach adopted for
producing combined GOCE and GRACE models. Results from geoid comparisons indicate that with the 2 months of GOCE data a significant
improvement in the determination of the spherical harmonic spectrum of the global gravity field between degree 50 and 200
can be reached. Even though the ultimate mission goal has not yet been reached, especially due to the limited time span of
used GOCE data (only 2 months), it was found that existing satellite-only gravity field models, which are based on 7 years
of GRACE data, can already be enhanced in terms of spatial resolution. It is expected that with the accumulation of more GOCE
data the gravity field model resolution and quality can be further enhanced, and the GOCE mission goal of 1–2 cm geoid accuracy
with 100 km spatial resolution can be achieved. 相似文献
13.
A sliding window technique is used to create daily-sampled Gravity Recovery and Climate Experiment (GRACE) solutions with the same background processing as the official CSR RL04 monthly series. By estimating over shorter time spans, more frequent solutions are made using uncorrelated data, allowing for higher frequency resolution in addition to daily sampling. Using these data sets, high-frequency GRACE errors are computed using two different techniques: assuming the GRACE high-frequency signal in a quiet area of the ocean is the true error, and computing the variance of differences between multiple high-frequency GRACE series from different centers. While the signal-to-noise ratios prove to be sufficiently high for confidence at annual and lower frequencies, at frequencies above 3 cycles/year the signal-to-noise ratios in the large hydrological basins looked at here are near 1.0. Comparisons with the GLDAS hydrological model and high frequency GRACE series developed at other centers confirm CSR GRACE RL04’s poor ability to accurately and reliably measure hydrological signal above 3–9 cycles/year, due to the low power of the large-scale hydrological signal typical at those frequencies compared to the GRACE errors. 相似文献
14.
J. Neumeyer F. Barthelmes O. Dierks F. Flechtner M. Harnisch G. Harnisch J. Hinderer Y. Imanishi C. Kroner B. Meurers S. Petrovic Ch. Reigber R. Schmidt P. Schwintzer H. -P. Sun H. Virtanen 《Journal of Geodesy》2006,79(10-11):573-585
Gravity recovery and climate experiment (GRACE)-derived temporal gravity variations can be resolved within the μgal (10?8 m/s 2) range, if we restrict the spatial resolution to a half-wavelength of about 1,500 km and the temporal resolution to 1 month. For independent validations, a comparison with ground gravity measurements is of fundamental interest. For this purpose, data from selected superconducting gravimeter (SG) stations forming the Global Geodynamics Project (GGP) network are used. For comparison, GRACE and SG data sets are reduced for the same known gravity effects due to Earth and ocean tides, pole tide and atmosphere. In contrast to GRACE, the SG also measures gravity changes due to load-induced height variations, whereas the satellite-derived models do not contain this effect. For a solid spherical harmonic decomposition of the gravity field, this load effect can be modelled using degree-dependent load Love numbers, and this effect is added to the satellite-derived models. After reduction of the known gravity effects from both data sets, the remaining part can mainly be assumed to represent mass changes in terrestrial water storage. Therefore, gravity variations derived from global hydrological models are applied to verify the SG and GRACE results. Conversely, the hydrology models can be checked by gravity variations determined from GRACE and SG observations. Such a comparison shows quite a good agreement between gravity variation derived from SG, GRACE and hydrology models, which lie within their estimated error limits for most of the studied SG locations. It is shown that the SG gravity variations (point measurements) are representative for a large area within the accuracy, if local gravity effects are removed. The individual discrepancies between SG, GRACE and hydrology models may give hints for further investigations of each data series. 相似文献
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Evaluation and validation of mascon recovery using GRACE KBRR data with independent mass flux estimates in the Mississippi Basin 总被引：1，自引：1，他引：0
S. Klosko D. Rowlands S. Luthcke F. Lemoine D. Chinn M. Rodell 《Journal of Geodesy》2009,83(9):817-827
The direct recovery of surface mass anomalies using GRACE KBRR data processed in regional solutions provides mass variation
estimates with 10-day temporal resolution. The approach undertaken herein uses a tailored orbit estimation strategy based
solely on the KBRR data and directly estimates mass anomalies from the GRACE data. We introduce a set of temporal and spatial
correlation constraints to enable high resolution mass flux estimates. The Mississippi Basin, with its well understood surface
hydrological modelling available from the Global Land Data Assimilation System (GLDAS), which uses advanced land surface modeling
and data assimilation techniques, and a wealth of groundwater data, provides an opportunity to quantitatively compare GRACE
estimates of the mass flux in the entire hydrological column with those available from independent and reliable sources. Evaluating
GRACE’s performance is dependent on the accuracy ascribed to the hydrological information, which in and of itself is a complex
challenge (Rodell in Hydrogeol J, doi:, 2007). Nevertheless, the Mississippi Basin is one of the few regions having a large hydrological signal that can support
a meaningful GRACE comparison on the spatial scale resolved by GRACE. The isolation of the hydrological signal is dependent
on the adequacy of the forward mass flux modeling for tides and atmospheric pressure variations. While these models have non-uniform
global performance they are excellent in the Mississippi Basin. Through comparisons with the independent hydrology, we evaluate
the effect on the solution of changing correlation times and distances in the constraints, altering the parameter recovery
for areas external to the Mississippi Basin, and changing the relative strength of the constraints with respect to the KBRR
data. The accuracy and stability of the mascon solutions are thereby assessed, especially with regard to the constraints used
to stabilize the solution. We show that the mass anomalies, as represented by surface layer of water within regional cells
have accuracy estimates of ±2–3 cm on par with the best hydrological estimates and consistent with our accuracy estimates
for GRACE mass anomaly estimates. These solutions are shown to be very stable, especially for the recovery of semi-annual
and longer period trends, where for example, the phase agreement for the dominant annual signal agrees at the 10-day level
of resolution provided by GRACE. This validation confirms that mascons provide critical environmental data records for a wide
range of applications including monitoring ground water mass changes. 相似文献