ERS-2 SAR反演海洋风矢量的研究

Abstract

SAR (Synthetic Aperture Radar) 反演海洋风矢量是当今微波遥感领域非常有意义的前沿课题.本文首先介绍了星载SAR估算海面风向、风速的基本原理和三种主流反演算法,接着给出反演的流程图以及重要步骤.然后,以2002年5月7日香港地区ERS-2 SAR海洋图像为例,对经典的SWDA(SAR Wind Direction Algorithm)-谱分析方法加以改进,求得具有180°模糊度的风向,并用香港天文台气象浮标实测数据消除了风向不确定性.最后,利用CMOD4GMF(Geophysical Model Function,地球物理模式函数)计算得到海面上10m高的风速.与气象浮标站实测资料相比,利用ERS-2 SAR图像获取的海面风向、风速的精度均较高.这一结果表明:如果对SAR预先进行ADC(Analog toDigital Converter)改正以及精确校准,结合改进的SWDA和CMOD4,可以获得高精度的风矢量. SAR(Synthetic Aperture Radar) wind retrieval is a hot research topic in current Remote Sensing field.In this paper the principle of space borne SAR ocean wind retrieval and three related retrieval algorithms are introduced firstly.Then,the flowchart of the retrieval procedures is provided.As an example,ERS-2 SAR image covering Hong Kong region acquired on May 7,2002 is used for wind vector retrieval.The classic SAR Wind Direction Algorithm-spectral method is improved,and applied for the retrieval.The wind direction thus estimated is however with 180°ambiguity.Buoy data collected by the Hong Kong Observatory are then used to resolve the uncertainty.Finally,the GMF(Geophysical Model Function)-CMOD4 is adopted to estimate the wind speed at the height of 10m above sea level.Compared with the data recorded by Hong Kong Observatory,the error in the wind direction and average wind speed are very small.The results show that accurate ADC(Analog to Digital Converter) compensation and image calibration,together with improved SWDA and CMOD4 algorithms, could offer high quality wind vector.