Publications

Sundararaman, HKK; Shanmugam, P; Nagamani, PV (2023). Robust extension of the simple sea-surface irradiance model to handle cloudy conditions for the global ocean using satellite remote sensing data. ADVANCES IN SPACE RESEARCH, 71(3), 1486-1509.

Abstract
Sea-surface solar radiation (abbreviated as photosynthetically available radiation, PAR) in the visible wavelength (400-700 nm) is an essential parameter to estimate marine primary productivity and understanding phytoplankton dynamics, upper ocean physics and bio-geochemical processes. Although many remote-sensing models were developed to estimate daily PAR (DPAR) from ocean colour data, these models often produce biases in the DPAR products under cloudy-sky and complex atmospheric conditions due to the lack of parameterization to deal with the cloud cover conditions and insufficient in-situ DPAR data. This study presents an Extended Sea -surface Solar Irradiance Model (ESSIM) for estimating DPAR over the global ocean. The ESSIM uses the direct and diffuse components from the Simple sea-surface Solar Irradiance Model (SSIM) along with a new parameter to handle cloudy conditions. The ESSIM pro-duced DPAR products with greater accuracy under both clear and cloudy conditions. Its performance was tested on the time-series MODIS-Aqua images and compared with the concurrent in-situ data and the results from two global models. Results showed that the DPAR values produced by ESSIM agree with in-situ data better than the global models for all-sky conditions (with a mean relative error of 11.267 %; a root mean square error of 5.563 Em-2day-1; and a mean net bias of 2.917 Em-2day-1). The ESSIM performed slightly better than the SSIM for clear conditions and the Frouin's Operational Algorithm (FOA) for all-sky conditions. As the new parameterization accounts for cloudy conditions, the ESSIM produced more accurate results for cloud cover conditions across latitudes (up to 60 degrees). The time-series Level-3 binned MODIS-Aqua data (global gridded) also demonstrated that the ESSIM improved the accu-racy of DPAR products and produced spatially and temporally consistent DPAR products over the global ocean regardless of the sea-sons and sky conditions. (c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

DOI:
10.1016/j.asr.2022.10.009

ISSN:
1879-1948