The retrieval of oceanic inherent optical properties based on semianalytical algorithm during the red ride

In optical buoy experiments in the Zhujiang River mouth regions, the time series of biooptical data of the red tide were obtained.Using these data, retrieving inherent optical parameters of the red tide were carried out with a semianalytical algorithm, and the model was tested, validated and modified with in situ data. (1) In the retrieval of inherent optical properties at major satellite ocean color bands (412, 443, 490, 510, 560, 620 and 665 nm)with r_rs and QAA(quasianalytical algorithm), the errors for total absorption coefficient a_t and particle backscattering coefficient b_bp at 490~665 nm are less than 25%. The errors for a_t and b_bp at 443 nm are about 8%~32%, and about 31%~57% at 412 nm.The error ranges for phytoplankton pigment absorption a_ph, detritus and colored dissolved organic matter absorption a_dg are 32%~157% and 59%~80%, respectively. Comparing retrieval result by different reference wavelengths (555 and 640 nm) of QAA, it is found that with the exception of 490 and 510 nm, QAA-640 is better than QAA-555 at other bands, especially at 412 and 443 nm. (2) QAA is modified by in situ data. Modified QAA-555 model derives better a_t and b_bp. The errors decrease by 1%~11%. Modified QAA-640 returns better a_t and b_bp at 412, 620 and 665 nm. For a_ph and a_dg, the accuracy of retrieval results has no significant improvement. With the exception of 412 and 443 nm, the modified QAA-555 is better than the modified QAA-640. (3)Using QAA to retrieve a_ph and a_dg from in situ measured a_t, the errors are less than 24%; when adding 20% errors to the in situ a_t, the retrieval error for a_dg has no significant changes(＜33%), but the errors of a_ph fluctuate in the range of 58%~241% at 560~665 nm.