Radiometric products determined from fixed-depth and continuous in-water profiles collected at a coastal site characterized by moderately complex waters have been compared to investigate differences and limitations of the applied methods. Within the 412-683 nm spectral interval, comparison results exhibit uncertainties in the range of 2-4%, 3-5% and 2% for the subsurface radiometric values of upwelling radiance, Lun, upward irradiance, Eun, and downward irradiance, Edn, all normalized with respect to the above water downward irradiance. The related spectral biases are in the range of -2-1% for Lun, 2-3% for Eun and lower than 0.5% for Edn. Derived products like the irradiance reflectance, R, Q-factor at nadir, Q, and the normalized water leaving radiance, LWN, exhibit spectral uncertainties in the range of 4-6%, 2-3% and 2-4%. The related spectral biases are in the range of 1-3%, 2-3% and -2-1%. An evaluation of results as a function of the diffuse attenuation coefficient, indicates a general decrease with Kd(490) of the uncertainty and bias for most of the quantities investigated. Exceptions are Edn and Kd because an increase of Kd reduces the perturbations due to wave effects on downward irradiance measurements. An evaluation of the perturbing effects due to the presence of optical stratifications in the extrapolation interval, which lead to a non linear decrease with depth of log-transformed radiometric measurements, shows an expected increase in uncertainty and bias specifically evident for Ku, Eun, Kl, Lun and derived quantities like R, Q and LWN. Overall results, supported by a t-test analysis, indicate the possibility of using moorings in moderately complex coastal waters to determine LWN with a slightly higher uncertainty with respect to that achievable with continuous profiling systems.
ZIBORDI Giuseppe;
BERTHON Jean-Francois;
DALIMONTE Davide;
2009-03-30
AMER METEOROLOGICAL SOC
JRC42734
0739-0572,
http://ams.allenpress.com/perlserv/?request=get-toc&issn=1520-0426&volume=26&issue=1,
http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F2008JTECHO619.1,
https://publications.jrc.ec.europa.eu/repository/handle/JRC42734,
10.1175/2008JTECHO619.1,
