Wave effects on the retrieved wind field from the advanced scatterometer (ASCAT)
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摘要: 为改善反演效果, 本文研究海浪对散射计风场反演精度的影响. 首先, 收集同步的ASCAT散射计数据和NdBC浮标数据, 并将浮标风速统一转换成海面10 m高度风速. 其次, 比较ASCAT和浮标的风速和风向. 再次, 利用 ASCAT和浮标风速、风向的误差建立的与各种海浪参数的函数关系, 来分析海浪对风场反演的影响. 涉及的海浪参数包括主波波长(dpd)、有效波高(swh)、平均波长(apd)以及主波波向和风向的夹角(angle). 关于误差的计算, 先将各种海浪参数分为多个数值区间, 再对照各区间将同步数据划分为多个子数据集, 进而通过计算各子数据集的均方根误差(RMSE)或平均绝对误差(MAE), 建立起误差同各海浪参数的函数关系. 最后, 基于误差分析方法确定ASCAT风场反演的最佳海浪条件. 研究结果表明, 海浪参数与反演风速的RMSE以及反演风向的MAE均存在一定的相关关系. 同时, 最佳海浪条件以dpd, swh, apd和angle的形式提出.Abstract: To improve retrieval accuracy, this paper studies wave effects on retrieved wind field from a scatterometer. First, the advanced scatterometer (ASCAT) data and buoy data of the National data Buoy Center (NdBC) are collocated. Buoy wind speed is converted into neutral wind at 10 m height. Then, ASCAT data are compared with the buoy data for the wind speed and direction. Subsequently, the errors between the ASCAT and the buoy wind as a function of each wave parameter are used to analyze the wave effects. Wave parameters include dominant wave period (dpd), significant wave height (swh), average wave period (apd) and the angle between the dominant wave direction (dwd) and the wind direction. Collocated data are divided into sub-datasets according to the different intervals of each wave parameter. A root mean square error (RMSE) for the wind speed and a mean absolute error (MAE) for the wind direction are calculated from the sub-datasets, which are considered as the function of wave parameters. Finally, optimal wave conditions on wind retrieved from the ASCAT are determined based on the error analyses. The results show the ocean wave parameters have correlative relationships with the RMSE of the retrieved wind speed and the MAE of the retrieved wind direction. The optimal wave conditions are presented in terms of dpd, swh, apd and angle.
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Key words:
- advanced scatterometer /
- ASCAT /
- wind field /
- wave effects /
- wave parameters
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