Skill assessment of a spectral ocean-atmosphere radiative model

OASIM spectrally-integrated surface irradiance had root mean square (RMS) difference = 20.1 W m− 2 (about 11%), bias = 1.6 W m− 2 (about 0.8%), regression slope = 1.01 and correlation coefficient = 0.89, when compared to 2322 in situ observations. OASIM had the lowest bias of any of the global data products evaluated (ISCCP-FD, NCEP, and ISLSCP II), and the best slope (nearest to unity). It had the second best RMS, and the third best correlation coefficient. OASIM total surface irradiance compared well with ISCCP-FD (RMS = 20.7 W m− 2; bias = − 11.4 W m− 2, r = 0.98) and ISLSCP II (RMS = 25.2 W m− 2; bias = − 13.8 W m− 2; r = 0.97), but less well with NCEP (RMS = 43.0 W m− 2; bias = − 22.6 W m− 2; r = 0.91). Comparisons of OASIM photosynthetically available radiation (PAR) with PAR derived from SeaWiFS showed low bias (− 1.8 mol photons m− 2 d− 1, or about 5%), RMS (4.25 mol photons m− 2 d− 1, or about 12%), near unity slope (1.03) and high correlation coefficient (0.97). Coupled with previous estimates of clear sky spectral irradiance in OASIM (6.6% RMS at 1 nm resolution), these results suggest that OASIM provides reasonable estimates of surface broadband and spectral irradiance in the oceans, and can support studies on ocean ecosystems, carbon cycling, and heat exchange.