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51.
基于大气辐射传输理论分别建立Ku波段和C波段的降雨模型,模拟热带气旋降雨区洋面的雷达回波并反演了洋面10 m风场,用于研究降雨对测风的影响以及风云三号双频风场雷达 (WFR) 的测风能力。分析表明:回波的衰减或增强取决于降雨衰减项和后向散射项的相对大小;热带气旋的降雨使反演风速偏小,风向精度降低,Ku波段相对于C波段更易受影响,在高风速 (超过30 m·s-1) 条件下,可达5~20 m·s-1的负风速偏差。反演结果表明:双频反演的新方法能够结合Ku波段与C波段的优势,双频最大似然估计 (MLE) 方法在分辨率上优于C波段单频反演,相对Ku单频反演能降低降雨对测风的衰减作用,结合双频MLE方法和C波段单频反演优势的分区反演方法可以显著减小降雨偏差,提高风速反演精度,在有风云三号湿度计同步观测的条件下,是提高热带气旋降雨区测风精度的有效手段。 相似文献
52.
最大似然估计法被认为是海面风场反演的最佳方法,目前被用来处理SeaWinds散射计数据。风矢量求解算法是风场反演算法的核心内容。最大似然法的目标函数形式决定了在风场反演过程中必须采用数值方法求解风矢量,而传统数值求解方法运算量大。该文对最大似然估计的风场反演方法的基本原理和具体过程进行探讨,根据其目标函数的一般分布特征,提出一种较为高效的数值风矢量搜索算法。用SeaWinds散射计的12A实测数据和相应的L2B数据验证了该算法的可行性。 相似文献
53.
54.
ASCAT散射计风场在我国近海的初步检验与应用 总被引:3,自引:1,他引:3
为了弥补中国近海海区缺乏洋面风场观测资料,提高海洋气象预报能力,对MetOP-A极轨卫星搭载的ASCAT散射计反演风场资料和中国气象局在近海布设的18个浮标站测风资料进行对比。结果表明,离岸较远的海域中ASCAT反演风场的质量要优于离岸较近的海域,在较远的海域中,ASCAT风速和浮标观测风速的平均偏差为0.9 m·s~(-1),ASCAT的风速高于浮标站的风速,平均绝对偏差和均方根误差分别为1.2和1.4 m·s~(-1),风速的相关系数为0.94。统计特征分析结果显示,ASCAT散射计风场资料在中国近海有较好的可信度,在高风速的时候,ASCAT和浮标资料一致性较好,而低风速时候,ASCAT比浮标略偏大。目前,中央气象台正在逐步开展ASCAT资料的业务应用,ASCAT洋面的MICAPS格式产品和图形产品现已实现准实时运行。 相似文献
55.
Naoto Ebuchi 《Journal of Oceanography》1999,55(5):575-584
By using wind vector fields observed by the NASA Scatterometer (NSCAT) and significant wave heights observed by the TOPEX/POSEIDON and European Remote Sensing Satellite-2 (ERS-2) altimeters, one-dimensional fetch growth of wind waves has been investigated under conditions of strong wind and high waves caused by the East Asian winter monsoon in the Sea of Japan. The evolution of fetch-limited wind waves can be observed by the altimeters along their ground tracks. The fetch is estimated by using vector wind fields observed by NSCAT. The derived growth characteristics of wind waves are compared with empirical relationships between the non-dimensional fetch and significant wave height proposed by previous studies. Good agreement is discernible with Toba's fetch graph formula normalized by the friction velocity, while Wilson's well-known formula normalized by the wind speed at a height of 10 m tends to underestimate the wave height under such severe conditions of high wind and very long fetch. This discrepancy is explained by the wind-speed dependence of the drag coefficient. A simple correction to Wilson's formula for the high wind conditions is proposed and compared with the observed data. 相似文献
56.
57.
The Chinese marine dynamic environment satellite HY-2B was launched in October 2018 and carries a Ku-band scatterometer. This paper focuses on the accuracies of HY-2B scatterometer wind data during the period from November 2018 to May 2021. The HY-2B wind data are validated against global moored buoys operated by the U.S. National Data Buoy Center and Tropical Atmosphere Ocean, numerical model data by the National Centers for Environmental Prediction, and the Advanced Scatterometer data issued b... 相似文献
58.
U. R. Rao P. S. Desai P. C. Joshi P. C. Pandey B. S. Gohil B. Simon 《Journal of Earth System Science》1998,107(1):33-43
Detailed analysis of the surface winds over the Indian Ocean derived from ERS-1 scatterometer data during the years 1993 and
1994 has been used to understand and unambiguously identify the onset phase of south-west monsoon. Five day (pentad) averaged
wind vectors for the period April to June during both years have been examined to study the exact reversal of wind direction
as well as the increase in wind speed over the Arabian Sea in relation to the onset of monsoon over the Indian west coast
(Kerala). The related upper level humidity available from other satellites has also been analysed.
The results of our analysis clearly show a consistent dramatic reversal in wind direction over the western Arabian Sea three
weeks in advance of the onset of monsoon. The wind speed shows a large increase coinciding with the onset of monsoon. These
findings together show the dominant role of sea surface winds in establishing the monsoon circulation. The study confirms
that the cross equatorial current phenomenon becomes more important after the onset of monsoon. 相似文献
59.
A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to that between wind and the radar backscattering cross section. Therefore, the relationship between significant wave height and the radar backscattering cross section is established with a neural network algorithm, which is, if the average wave period is ≤7s, the root mean square of significant wave... 相似文献
60.
已有的SeaWinds散射计反演结果误差评价包括两种方法:一是与其他数据来源进行对比,如与数值气象预报产品或浮标风场数据对比;二是从风场反演结果的空间一致性进行判断.文中采用二维几何中心矩定量描述象元解空间中模糊解区域(与真解最接近的模糊解区域)的图谱特征,如图像椭圆的主轴倾角、长短轴比以及总灰度值;研究了总灰度值与风矢量反演误差的关系.结果表明,当总灰度值大于某一阈值时,风矢量反演误差将被限制在一个较小的范围之内.根据图像椭圆总灰度的这一特性,设计了一种新的基于总灰度约束特性的滤波算法.通过与浮标风矢量 相似文献