Corrections to the Calibration of MODIS Aqua Ocean Color Bands Derived From SeaWiFS Data

The National Aeronautics and Space Administration ocean color products of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua have been reprocessed in 2009. This paper describes the changes to the calibration approach for MODIS Aqua. Due to a significant downward trend in the operational MODIS Aqua water-leaving radiances at 412 nm, the previous calibration approach was no longer sufficient. The new approach uses SeaWiFS water-leaving radiances to adjust the temporal trends of the radiometric calibration of MODIS Aqua bands at 412 and 443 nm. The adjustments to the temporal trends at the beginning of the scan are minor but are significant around nadir and at the end of scan (up to 5% at 412 nm and up to 1% for 443 nm). The remaining five bands (488 to 678 nm) are adjusted with regard to their scan-angle dependence only; no temporal correction is necessary. There is no indication that the sensor polarization sensitivity needs to be modified for MODIS Aqua.