Pre-launch sensitivity study for GOCI-II aerosol retrieval

Geostationary Ocean Color Imager-II (GOCI-II), a unique ocean color imager in geostationary orbit, is planned to be launched in 2019 onboard GEO-KOMPSAT-2B (GK-2B) satellite. GOCI-II has 13 channels in UV, VIS and NIR including a panchromatic channel compared to 8 bands of GOCI. In terms of aerosol property retrieval, GOCI-II has two major advantages compared to GOCI. First, the inclusion of UV band centered at 380 nm is advantageous to retrieve radiative absorptivity of aerosol over darker surface reflectance than visible band. Second, the spatial resolution of GOCI-II is doubled to 250 m, compared to 500 m for GOCI, which allows us to mask smaller scale clouds and retrieve the aerosol optical properties in better accuracy.

In this study, we evaluate the information content in GOCI-II aerosol retrieval and compare it to that in GOCI. The GOCI-II observation system is simulated using a radiative transfer model, the linearized pseudo-spherical vector discrete ordinate radiative transfer (VLIDORT). Then, we calculate the degree of freedom for signal (DFS) based on the optimal estimation approach. The information content analysis results show the increases in DFS for GOCI-II measurements. Particularly, it is found that UV band utilization with the previous GOCI spectral bands shows higher increase of the DFS than any other visible and NIR channels. To simulate GOCI-II retrieval results prior to launch based on these results, GOCI-II aerosol retrieval based on a multi-channel algorithm is performed using GOCI and 380 nm channel of other satellite as proxy data.