Development of Methods for Measuring Ocean Wavelengths by Radar Altimeters

为了通过数据处理来确定海洋波长，我们需要知道海浪和海浪的原始散射数据。假设海浪用Pierson-Moskowitz谱来描述，我们用线谱来近似它。一旦定义了谱并给出了海浪的有效波高H_(1/3)和波长L_(1/3)，我们就可以将海浪表示为一些非周期函数的和。通过计算近似海浪散射的电磁波脉冲，我们可以得到高度计接收到的脉冲序列，并确保该脉冲序列具有与SkyLab和SEASAT相似的第一和第二统计数据。因此，计算机模拟了H&lt；1/3&gt；和L；1/3&gt；的每个海浪的脉冲序列，并建立了H&lt；1/3&gt；=2.56-4.56m和L；1/3&gt；海浪的SkyLab和Seasat的脉冲序列数据库；=25.6-91.4米。现尝试将该数据库扩展到其他高度计和海浪。利用该数据库，得到了变量L 1/3和常数H 1/3的平均返回脉冲波形。结果表明，在无噪声的情况下，由于从平均值接收的脉冲功率的波动，L 1/3可以在5米精度内确定。当海面为均匀高斯随机场时，假设海面为均匀高斯随机场，当海面为均匀高斯随机场时，利用随机表面的概率密度，可以直接利用随机表面的概率密度计算平均回波脉冲波形。这一结果明确了平均脉冲波形与随机表面之间的关系。

To determine ocean wavelengths by data processing, we need to know both of ocean waves and raw scattering data from ocean waves. Assuming that ocean waves are characterized by the Pierson-Moskowitz spectrum, we approximate the spectrum by using line spectra. Once defining the spectra and giving the significant waveheight H_<1/3> and wavelength L_<1/3> of the ocean wave, we can express the ocean wave as the sum of some aperiodic functions. By calculating electromagnetic wave pulses scattered from the approximate ocean wave, we can obtain the pulse train received with altimeters and make sure that the train has the first and second statistics similar to those of SKYLAB and SEASAT.The pulse train has therefore been simulated by computer for each ocean wave with the parameters of H_<1/3> and L_<1/3> ; and we have the database of the pulse train of SKYLAB and SEASAT for ocean waves of H_<1/3>=2.56-4.56m and L_<1/3>=25.6-91.4m. We now try the extension of the database to other altimeters and ocean waves.Using the database, the mean return pulse-waveforms have been obtainde for variable L_<1/3> and constant H_<1/3>, and show that if there is no noise, the L_<1/3> may be determined within 5m accuracy because of the fluctuation of received pulse power from the mean. If noise is added to the fluctuation and the standard deviation of received power is assumed to be 3dB,the resolution of L_<1/3> is reduced to 15m for both altimeters of SKYLAB and SEASAT.Development of the method based on pulse correlation is a forthcoming study.When ocean surfaces are assumed to be a homogeneous Gaussian random field, we can calculate the mean return pulse-waveform directly by using the probability density of random surfaces through the law of large numbers. This result makes clear the relation of the mean pulse waveforms and random surfaces.