Sea surface roughness (SSR) is measurable from spaceborne synthetic aperture radar (SAR) that also expressed in normalized radar cross section (NRCS). This work aims to identify the relationship between NRCS and oceanic chlorophyll-a (Chl-a) concentration using satellite data in Yilan Bay, Taiwan. Marine biological activity signifies the Chl-a concentration floating on the sea surface can alter SSR where Chl-a is located. Optical satellites usually cannot provide Chl-a concentration images due to cloudy weather and night time. The SSR images provided by SAR can usually help solving this issue. As change in sea surface temperature (SST) can affect SSR, the SSR is first corrected by SST and then compared with Chl-a concentration to find the relationship between the two. An area of interest was chosen between 24.72 and 24.78°N, as this area is close to the mouth of the Lanyang River and the fronts are also easily noticeable. To avoid the influence of wind, the satellite images used in this study were selected during the wind speed under 2 m s^-1 measured by the weather station at Gueishan Island near Yilan Bay. The results show that NRCS directly proportionally to SST. The NRCS after SST correction is compared with Chl-a concentration derived from the Geostationary Ocean Color Imager, showing a good negative correlation. The coefficient of determination can reach 0.78. This study discovered that 1 mg m^-3 of oceanic Chl-a suppresses Bragg scattering, producing NRCS of around -16.7 dB with a -0.34 dB/mg m^-3 NRCS to Chl-a ratio. Since the images taken by SAR, Chl-a and SST used in this study are somewhat different in time, if images taken at the same time can be obtained, the estimation errors should be better than the results presented in this study. Sea surface roughness (SSR) is measurable from spaceborne synthetic aperture radar (SAR) that also expressed in normalized radar cross section (NRCS). This work aims to identify the relationship between NRCS and oceanic chlorophyll-a (Chl-a) concentration using satellite data in Yilan Bay, Taiwan. Marine biological activity signifies the Chl-a concentration floating on the sea surface can alter SSR where Chl-a is located. Optical satellites usually cannot provide Chl-a concentration images due to cloudy weather and night time. The SSR images provided by SAR can usually help solving this issue. As change in sea surface temperature (SST) can affect SSR, the SSR is first corrected by SST and then compared with Chl-a concentration to find the relationship between the two. An area of interest was chosen between 24.72 and 24.78°N, as this area is close to the mouth of the Lanyang River and the fronts are also easily noticeable. To avoid the influence of wind, the satellite images used in this study were selected during the wind speed under 2 m s^-1 measured by the weather station at Gueishan Island near Yilan Bay. The results show that NRCS directly proportionally to SST. The NRCS after SST correction is compared with Chl-a concentration derived from the Geostationary Ocean Color Imager, showing a good negative correlation. The coefficient of determination can reach 0.78. This study discovered that 1 mg m^-3 of oceanic Chl-a suppresses Bragg scattering, producing NRCS of around -16.7 dB with a -0.34 dB/mg m^-3 NRCS to Chl-a ratio. Since the images taken by SAR, Chl-a and SST used in this study are somewhat different in time, if images taken at the same time can be obtained, the estimation errors should be better than the results presented in this study. Sea surface roughness (SSR) is measurable from spaceborne synthetic aperture radar (SAR) that also expressed in normalized radar cross section (NRCS). This work aims to identify the relationship between NRCS and oceanic chlorophyll-a (Chl-a) concentration using satellite data in Yilan Bay, Taiwan. Marine biological activity signifies the Chl-a concentration floating on the sea surface can alter SSR where Chl-a is located. Optical satellites usually cannot provide Chl-a concentration images due to cloudy weather and night time. The SSR images provided by SAR can usually help solving this issue. As change in sea surface temperature (SST) can affect SSR, the SSR is first corrected by SST and then compared with Chl-a concentration to find the relationship between the two. An area of interest was chosen between 24.72 and 24.78°N, as this area is close to the mouth of the Lanyang River and the fronts are also easily noticeable. To avoid the influence of wind, the satellite images used in this study were selected during the wind speed under 2 m s^-1 measured by the weather station at Gueishan Island near Yilan Bay. The results show that NRCS directly proportionally to SST. The NRCS after SST correction is compared with Chl-a concentration derived from the Geostationary Ocean Color Imager, showing a good negative correlation. The coefficient of determination can reach 0.78. This study discovered that 1 mg m^-3 of oceanic Chl-a suppresses Bragg scattering, producing NRCS of around -16.7 dB with a -0.34 dB/mg m^-3 NRCS to Chl-a ratio. Since the images taken by SAR, Chl-a and SST used in this study are somewhat different in time, if images taken at the same time can be obtained, the estimation errors should be better than the results presented in this study.