Evaluation of Biological Films to Sea Surface Roughness Observed by Sar

The images of the sea surface roughness observed by PALSAR on ALOS over the Philippine Archipelagos were studied with other opportunities of satellite observations including MODIS and other measurement to understand an imaging mechanism by SAR. The Tabulas Strait and the Mindanao Sea, which are connecting the Pacific and the South China Sea and blocking the North Equatorial Current, were selected to study the physical and biological contribution to the sea surface roughness observed by SAR. The data from MODIS on TERRA and AQUA were refereed as a semi-synchronized observation and the reanalysis wind data from NCEP were refereed as the observation on the same day. The intensity of sea surface roughness is represented as the power spectrum in the frequency domain from each specific region, where the roughness is modulated by the wind, the upwelling, the rain, and the surface film associated with biological activities. Although the chlorophyll-a concentration observed by MODIS is not the direct estimate of the surface film, the chlorophyll-a concentration would be refereed to represent the surface film as the zooplankton being expected proportional to chlorophyll-a concentration and the associated products as a result of the surface film being expected proportional. The wind direction and speed from the NCEP data set were applied to analyze the contribution to the sea surface roughness, which has a positive contribution against the surface film. The power spectrum obtained from the different texture patterns in the sea surface roughness observed by SAR exhibited the different intensities in the frequency domain. The correlation plots between the power spectrum at the certain frequency and the chlorophyll-a concentration showed a good relationship, where the negative correlation was observed as the increase of chlorophyll-a concentration. The reduction of surface roughness by the surface film associated with the biological activities were confirmed under a limited a wind speed .