Generating a High-Resolution Time-Series Ocean Surface Net Radiation Product by Downscaling J-OFURO3

Abstract

The ocean surface net radiation (<inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula>) characterizing ocean surface radiation budget is a key variable in ocean climate modeling and analysis. In this study, a downscaling scheme was developed to generate a high-resolution (0.05°) time-series (2002–2013) daily ocean surface <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula> from the third-generation Japanese Ocean Flux Data Sets with Use of Remote-Sensing Observations (J-OFURO3) at 0.25° based on the Advanced Very-High-Resolution Radiometer (AVHRR) top-of-atmosphere (TOA) observations (AVH021C) and other ancillary information (Clearness Index and cloud mask). This downscaling scheme includes the statistical downscaling models and the residual correction post-processing. A series of angle-dependent downscaling statistical models were established between the daily ocean surface <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula> in J-OFURO3 and the AVHRR TOA data, and then, the residual correction was conducted to the model estimates <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula>_AVHRR_est to obtain the final downscaled data set <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula>_AVHRR. Validation against the measurements from 57 moored buoy sites in six ocean observing networks shows the high accuracy of the downscaled estimates <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula>_AVHRR_est with a <inline-formula> <tex-math notation= LaTeX >$R^{2}$ </tex-math></inline-formula> of 0.88, RMSE of 23.44 <inline-formula> <tex-math notation= LaTeX >$\\text{W}\\cdot \\text{m}^{-2}$ </tex-math></inline-formula>, and bias of <inline-formula> <tex-math notation= LaTeX >$-0.14\\,\\,\\text{W}\\cdot \\text{m}^{-2}$ </tex-math></inline-formula> under all-sky condition. The results of the spatio-temporal analysis in <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula>_AVHRR and intercomparison with Cloud and the Earth’s Radiant Energy System (CERES) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) products also indicated that the superior of the <inline-formula> <tex-math notation= LaTeX >$R_{n}$ </tex-math></inline-formula>_AVHRR with more detailed information especially in the hot spot regions, such as central tropical Pacific (warming pool), Atlantic and Equatorial Eastern Indian Ocean (EIO).