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Open AccessArticle

A Neural Network-Based Rain Effect Correction Method for HY-2A Scatterometer Backscatter Measurements

1
School of Geographical Sciences, Guangzhou University, Guangzhou 510006, China
2
School of Geography and Planning, Sun Yat-Sen University, Guangzhou 510275, China
3
National Satellite Ocean Application Service, Beijing 100081, China
*
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(10), 1648; https://doi.org/10.3390/rs12101648
Received: 24 April 2020 / Revised: 15 May 2020 / Accepted: 19 May 2020 / Published: 21 May 2020
(This article belongs to the Section Ocean Remote Sensing)
The backscattering coefficients measured by Ku-band scatterometers are strongly affected by rainfall, resulting in a systematic error in sea surface wind field retrieval. In rainy conditions, the radar signals are subject to absorption by the raindrops in their round-trip propagation through the atmosphere, while the backscatter of raindrops raises the echo energy. In addition, raindrops give rise to roughness by impinging the ocean surface, resulting in an increase in the echo energy measured by a scatterometer. Under moderate wind conditions, the comprehensive impact of rainfall causes the wind speeds retrieved by the scatterometer to be higher than their actual values. The HY-2A scatterometer is a Ku-band, pencil-beam, conically scanning scatterometer. To correct the systematic error of the HY-2A scatterometer measurement in rainy conditions, a neural network model is proposed according to the characteristics of the backscatter coefficients measured by the HY-2A scatterometer in the presence of rain. With the neural network, the wind fields of the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis data were used as the reference to correct the deviation in backscatter coefficients measured by the HY-2A scatterometer in rainy conditions, and the accuracy in wind speeds retrieved using the corrected backscatter coefficients was significantly improved. Compared with the cases of wind retrieval without rain effect correction, the wind speeds retrieved from the corrected backscatter coefficients by the neural network show a much lower systematic deviation, which indicates that the neural network can effectively remove the systematic deviation in the backscatter coefficients and the retrieved wind speeds caused by rain. View Full-Text
Keywords: microwave scatterometer; backscatter coefficient; rainfall effect; neural network model microwave scatterometer; backscatter coefficient; rainfall effect; neural network model
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MDPI and ACS Style

Xie, X.; Wang, J.; Lin, M. A Neural Network-Based Rain Effect Correction Method for HY-2A Scatterometer Backscatter Measurements. Remote Sens. 2020, 12, 1648.

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