Emissivity Measurements of Foam-Covered Water Surface at L-Band for Low Water Temperatures

Remote Sensing

En-Bo Wei²  Shu-Bo Liu²  Zhen-Zhan Wang⁴  Xiao-Lin Tong¹  Shuai Dong¹  Bin Li⁴  Jing-Yi Liu⁴  Raphael M. Kudela³ 

[1] University of Chinese Academy of Sciences, Beijing 100039, China; E-Mails:;Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; E-Mail:;Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China; E-Mail;Centre for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China; E-Mails:

关键词: sea foam layer;    microwave emissivity;    L-band;    sea surface salinity and temperature;   

DOI  :  10.3390/rs61110913

来源: mdpi

【 摘 要 】

For a foam-covered sea surface, it is difficult to retrieve sea surface salinity (SSS) with L-band brightness temperature (1.4 GHz) because of the effect of a foam layer with wind speeds stronger than 7 m/s, especially at low sea surface temperature (SST). With foam-controlled experiments, emissivities of a foam-covered water surface at low SST (−1.4 °C to 1.7 °C) are measured for varying SSS, foam thickness, incidence angle, and polarization. Furthermore, a theoretical model of emissivity is introduced by combining wave approach theory with the effective medium approximation method. Good agreement is obtained upon comparing theoretical emissivities with those of experiments. The results indicate that foam parameters have a strong influence on increasing emissivity of a foam-covered water surface. Increments of experimental emissivities caused by foam thickness of 1 cm increase from about 0.014 to 0.131 for horizontal polarization and 0.022 to 0.150 for vertical polarization with SSS increase and SST decrease. Contributions of the interface between the foam layer and water surface to the foam layer emissivity increments are discussed for frequencies between 1 and 37 GHz.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.