共查询到20条相似文献,搜索用时 31 毫秒
1.
HY-2A卫星微波散射计主要用于测量海表面的风速和风向,为了满足其风速和风向的测量精度要求,必须对其进行在轨辐射定标。本文基于散射计在开阔大洋的观测数据,利用经过定标的seawinds散射计后向散射系数数据,分析了海洋目标定标法的定标精度,结果表明定标精度可以达到0.15 dB,且模式函数对定标结果的影响为系统偏差,说明海洋目标定标法需要选用高精度的模式函数。然后,采用相同的海洋目标定标算法,实现了HY-2A卫星微波散射计的在轨辐射定标,获得HY-2A卫星微波散射计VV极化的定标系数为-1.79 dB,HH极化的定标系数为-1.73 dB。最后,利用NDBC浮标观测数据,检验HY-2A卫星微波散射计反演的风矢量精度,证明获得的定标系数可以明显提高HY-2A卫星微波散射计反演风矢量的精度。 相似文献
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目前可遥感反演的海上风能参量主要为平均风速和平均风功率密度,缺乏对风能方向性参量的反演。本文建立了以风向频率、风能密度方向分布为核心的风能方向性参量体系及相应的反演方法,使用2007年—2016年ASCAT星载散射计观测数据进行了反演实验,并利用海上现场观测数据对反演结果进行比较验证,通过理论分析和模拟实验对反演方法的数据量需求和误差传递进行了分析。结果表明,90%的反演结果通过了所有的同一性检验,验证了其有效性和准确性;风向频率和风能密度方向分布准确反演所需的最小数据量分别为350条和800条;遥感反演的风速风向数据的误差使得最终反演的风能方向性参量趋于离散,真实的风能方向分布越集中,对其影响越敏感。 相似文献
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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
4.
Sandip R. Oza R. K. K. Singh N. K. Vyas B. S. Gohil Abhijit Sarkar 《Journal of the Indian Society of Remote Sensing》2011,39(2):147-152
The identification of sea-ice has frequently been cited as one of the most important tasks for deriving the sea-ice parameters
and to avoid erroneous retrieval of wind vector over sea-ice infested oceans using space-borne scatterometer data. Discrimination
between sea-ice and ocean is ambiguous under the high wind and/or thin/scattered ice conditions. The pre-launch technique
developed for Oceansat-2, utilizes the dual-polarized QuikSCAT scatterometer data by using the spatio-temporal coherence properties
of sea ice in addition to backscatter coefficient and the Active Polarization Ratio. Results were compared with the operational
sea-ice products from National Snow and Ice Data Center. The threshold API value of −0.025 was found optimum for sea-ice and
ocean discrimination. The overall sea-ice identification accuracy achieved was of the order of 95 per cent, ranging from 92.5%
(during December in Southern Hemisphere) to 98% (during March in Northern Hemisphere). The applicability of the algorithm
for both the Arctic as well as Antarctic makes it suitable for its operational use with the Oceansat-2 scatterometer data. 相似文献
5.
QuikSCAT在台风监测中的应用 总被引:4,自引:0,他引:4
利用成熟发展的台风自身在风向上的涡旋型特征和风眼处风速相对周围较低的特征, 分别采用搜索QuikSCAT反演风向的涡旋中心, 风速或后向散射系数的台风中心区域在局部最小值点的方法定位获得了台风中心位置信息。在风矢量反演过程中采用QSCAT-1模型、借助Holland的台风模式, 修正了反演过程中的风向误差, 提高了台风中心定位的准确性。同时, 将该方法应用到对台风路径和强度监测中, 利用QuikSCAT对台风的连续观测资料分析得出台风强度和路径信息, 其中台风路径结果与美国国家飓风中心(NHC)通过最佳路径分析得到的台风路径结果基本一致, 但在台风强度结果上存在较大误差。为提高台风强度监测精度, 在反演过程中采用大风地球物理模型NN-T-GMF代替QSCAT-1模型, 使台风强度监测结果精度提高。结果表明, QuikSCAT可以有效监测海上台风路径和强度发展, 为进一步推断台风的强度发展和移动趋势提供帮助。 相似文献
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《Geoscience and Remote Sensing Letters, IEEE》2009,6(3):481-485
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利用大气压强、温度、密度等与风场之间的关系,通过大气折射指数、高度及温度数据均可以推算出大气风场,选用2007年1、4、7和10月COSMIC掩星观测的压强和折射率、高度、温度等月平均数据,构建了三种推算大气风场的方法。从风场的纬度高度分布、经度纬度分布及纬圈平均纬向风在不同季节的特性等方面,将计算结果与ECMWF ERA-interim再分析风场结果进行对比,发现计算结果与模式风场基本一致,能够反映出中高纬度大气风场的变化规律,偏差随高度的增高而逐渐增大,1hPa等压面以下偏差在10m/s以内。采用不同掩星数据推算出的大气风场之间的彼此差别很小,折射率与温度资料推算的大气风场几乎相同,高度数据推算出的风场相对前两者偏差稍大,但一般不超过2m/s。 相似文献
10.
Eurico J. D’Sa 《地理信息系统科学与遥感》2014,51(2):139-157
Variability in surface chlorophyll (Chl) concentrations derived from the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) were examined in conjunction with river discharge, QuikSCAT satellite-derived winds, and sea surface height (SSH) anomaly data along the Louisiana coast, USA. Surface Chl distributions exhibited rapid response to strong northerly winds following a frontal passage. A comparison of time series (1998–2010) river discharge and monthly Chl data indicated Chl variability to be well correlated to seasonal river discharge only for locations near the two river deltas, while offshore, enhancements in Chl during fall–winter was likely due to cross-shelf transport or mixing associated with strong northerly wind stress. Variance in Chl examined using wavelet analysis applied to nearly 10 years (1998–2007) of SeaWiFS data indicated patterns of significant Chl variability due to combined enhanced wind and river discharge, offshore flows associated with Ekman transport and coastal wind convergence, and the effect of Hurricane Rita in 2005. Instances of significant Chl variance were also observed to occur during years of large hypoxic zone size suggesting potential linkages to hypoxia. SSH anomaly imagery indicated the presence of warm-core eddies that were responsible for the offshore dispersal of elevated Chl observed in the monthly SeaWiFS imagery. Overall, the use of multi-satellite data better described the forcing and patterns of Chl distributions along the river-dominated Louisiana coast and shelf. 相似文献
11.
Tran N. Girard-Ardhuin F. Ezraty R. Feng H. Femenias P. 《Geoscience and Remote Sensing Letters, IEEE》2009,6(1):77-81
This letter presents the development of a sea ice flag algorithm for the Envisat altimetry mission to detect sea ice corrupted sea surface height data within quality control processing. The algorithm takes advantage of having both passive and active microwave sensors on the same platform with coregistered measurements. Its performances have been evaluated based on collocations between the along-track Envisat data with reference maps built from combination of daily grids of sea ice concentration from SSM/I sensors and backscatter cross section from SeaWinds scatterometer on QuikSCAT satellite. 相似文献
12.
一种修正的星载散射计反演海面风场的场方式反演算法 总被引:10,自引:0,他引:10
由于卫星散射计探视雷达回波的各向异性的双调和性质,同时由于散向散射物理模型函数的非线性及信号中存在噪声,使得常规点方式风场反演哕向有多至4个解的多解存在。给出了一种改进的场方式钣演方法,利用该人卫星散射计测量的后向散射强度的数据中唯一反演出大尺度海洋风场。通过数值模拟和实际算例计算表明反演过程在风向、风速上都与真解是吻合的。从结果可以看到,所采用的改进的场方式反演方法对模拟数据或真实散射计探测海面 相似文献
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S.R. Oza S. PanigrahyJ.S. Parihar 《International Journal of Applied Earth Observation and Geoinformation》2008
Estimation of crop area, growth and phenological information is very important for monitoring of agricultural crops. However, judicious combination of spatial and temporal data from different spectral regions is necessary to meet the requirement. This study highlights the use of active microwave QuikSCAT Ku-band scatterometer and Special Sensor Microwave/Imager (SSM/I) passive microwave radiometer data to derive information on important phenological phases of rice crop. The wetness index, a weekly composite product derived using brightness temperatures from 19, 37 and 85 GHz channels of SSM/I, was used to identify the puddling period. Ku-band scatterometer data provided the signal of transplanted rice seedlings since they acts as scatterers and increases the backscattering. Dual peak nature of temporal backscatter curve around the heading stage of rice crop was observed in Ku-band. The decrease of backscatter after first peak was associated with the threshold value of 60% crop canopy cover. The symmetric (Gaussian) and asymmetric (lognormal) curve fits were attempted to derive the date of initiation of the heading phase. The temporal signature from each of these sensors was found to complement each other in crop growth monitoring. Image showing pixel-wise timings of heading stage revealed the differences exists in various parts of the study area. 相似文献
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利用全球导航卫星系统反射(global navigation satellite system reflectometry, GNSS-R)信号对海面风速进行反演时,连续地球物理模式函数常用于建立时延-多普勒图像(delay/Doppler map, DDM)特征值与风速之间的映射关系。该模型在DDM较少的风速范围内(0~5 m/s及12~20 m/s)存在较大系统偏差。为解决该问题,提出了一种自适应累积分布函数(cumulative distribution function, CDF) 匹配方法。该方法将反演风速序列与参考风速序列进行CDF匹配,并利用最小二乘自适应地寻找最优阶数多项式,对风速偏差序列进行拟合和改正。公开数据实验验证结果表明,在0~5 m/s和12~20 m/s内,改正后的反演风速均方根误差分别减小了6%和15%,系统偏差分别减小了45%和25%,明显提升了少样本情况下的反演精度,反演风速更符合自然界中风速分布。 相似文献
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《地理信息系统科学与遥感》2013,50(4):242-257
The influence of regional features on the accuracy of single- and twoparameter algorithms for radioaltimeter determination of the speed of the near-surface wind over the ocean was investigated. The analysis was made using data from contact measurements (NDBC buoys) and the TOPEX/POSEIDON satellite radioaltimeter (wavelength 2.1 cm). It is shown that the nature of the waves, to a considerable degree related to regional conditions, exerts a strong influence on the accuracy in wind speed determination, resulting in an error in wind speed determination of 2-2.5 m/s. A new approach to the wind speed retrieval problem is proposed, making it possible to reduce the retrieval error to a level comparable with the best existing algorithms. 相似文献
17.
ERS散射计全球海面风场数据处理与ElNino海面风场异常观测 总被引:1,自引:0,他引:1
星载散射测量技术是获取全球海面风场的有效手段。该文研究了欧洲遥感卫星(ERS) 散射计全球海面风场数据的处理分析技术。对1997 年3 月、6 月和12 月的全球海面风场数据进行平均处理,并同时与1996 年6 月和1995 年10 月的观测数据进行对比,利用遥感技术发现了赤道太平洋西部的风场异常,从遥感资料上分析了1997 年El Nino 现象的海面风场( 风速与风向) 异常变化特征。研究结果显示了星载微波散射计在全球变化监测中的重要作用。 相似文献
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旋翼无人机测算风速风向技术研究 总被引:1,自引:1,他引:0
目前大部分民用无人机没有准确测量风速、风向和预警风场的功能,然而森林火灾扑救等多种场景需要无人机可以提供准确的风速。本文提出了一种基于旋翼无人机坐标数据测算风速风向的技术,通过无人机主机RTK坐标信息及方位角、倾角数据精准获取螺旋桨点相对坐标信息,选择不同负载条件下无人机以1~16 m/s的不同速度分别飞行30 s以上,根据螺旋桨坐标信息变化数值,结合风洞测试数据及风场动力学原理,研究风速与旋翼无人机倾角关系,并通过风洞试验检验该方法精度;并可根据无人机RTK推算出的螺旋桨坐标变化信息判断风向。结果表明,无人机风速与旋翼无人机倾角呈正相关关系;无人机负载加重时,对应受风速干扰的倾角会相对减小;无人机飞行受阵风干扰出现噪点的概率,高海拔区域大于低海拔区域;并建立六旋翼无人机飞行倾角的风速估算模型y=-1.043 5+1.150 1x,该模型测算风速的中误差值为0.966,绝对值小于1,满足应急指挥现场对无人机测量风速精度要求。该方法得到风速测算精度高,可以为旋翼无人机实时获取风速风向提供一种可行方法,具有一定的实用价值。 相似文献
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A Ka-band backscatter model and an algorithm for measurement of the wind speed and direction over the sea surface by a frequency-modulated continous-wave radar demonstrator system operated in scatterometer mode have been developed. To evaluate the proposed algorithm, a simulation of the wind vector retrieval has been performed. 相似文献
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We show that the amplitude of the Global Positioning System (GPS) signals in the radio occultation (RO) experiments is an indicator of the activity of the gravity waves (GW) in the atmosphere. The amplitude of the GPS RO signals is more sensitive to the atmospheric wave structures than is the phase. Early investigations used only the phase of the GPS occultation signals for statistical investigation of the GW activity in the height interval 10–40 km on a global scale. In this study, we use the polarization equations and Hilbert transform to find the 1-D GW radio image in the atmosphere by analyzing the amplitude of the RO signal. The radio image, also called the GW portrait, consists of the phase and amplitude of the GW as functions of height. We demonstrate the potential of this method using the amplitude data from GPS/Meteorology (GPS/MET) and satellite mission Challenge Mini-satellite Payload (CHAMP) RO events. The GW activity is nonuniformly distributed with the main contribution associated with the tropopause and the secondary maximums related to the GW breaking regions. Using our method we find the vertical profiles of the horizontal wind perturbations and its vertical gradient associated with the GW influence. The estimated values of the horizontal wind perturbations are in fairly good agreement with radiosonde data. The horizontal wind perturbations v(h) are ±1 to ±5 m s with vertical gradients dv/dh ±0.5 to ±15 m s km at height 10–40 km. The height dependence of the GW vertical wavelength was inferred through the differentiation of the GW phase. Analysis of this dependence using the dispersion relationship for the GW gives the estimation of the projection of the horizontal background wind velocity on the direction of the GW propagation. For the event considered, the magnitude of this projection changes between 1.5 and 10 m s at heights of 10–40 km. We conclude that the amplitude of the GPS occultation signals contain important information about the wave processes in the atmosphere on a global scale. 相似文献