EVALUATION OF MODIS OCEAN COLOR PRODUCTS FOR COASTAL APPLICATIONS: A CASE STUDY IN LIAN, BATANGAS

摘要

Field validation activities are important in the assessment and evaluation of satellite data. A field validation from March 15 to 17, 2016 was done in the coastal waters of Lian, Batangas, located in the north western part of the country. The activity includes a total of 27 sampling points where radiance values and chlorophyll-a concentration from filtration and fluorometry were measured. The chlorophyll-a concentration distribution of the samples ranges in the mesotrophic levels, particularly from 0.1 to 0.37 mg/m~3. In situ chlorophyll-a concentration varies linearly with Aqua MODIS level 2 chlorophyll-a product, with a coefficient of determination of 0.2421. Maximum band ratio (MBR) values for Aqua MODIS level 2 remote sensing reflectance (Rrs) were further compared with the MBR of ground-measured Rrs. The bands considered in the maximum band ratio are centered at 443, 489 and 547 nm based on the OCI algorithm used by MODIS. The two variables have a linear relationship with an R~2 of 0.5635. The atmospheric correction applied in converting L1 to L2 products highly accounts for the significant difference between the Rrs values, and subsequently in the chlorophyll-a concentration of the satellite data and the in situ measurements.