Journal cover Journal topic
Ocean Science An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 2.539 IF 2.539
  • IF 5-year value: 3.129 IF 5-year
    3.129
  • CiteScore value: 2.78 CiteScore
    2.78
  • SNIP value: 1.217 SNIP 1.217
  • IPP value: 2.62 IPP 2.62
  • SJR value: 1.370 SJR 1.370
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 48 Scimago H
    index 48
  • h5-index value: 32 h5-index 32
Volume 11, issue 5 | Copyright
Ocean Sci., 11, 779-788, 2015
https://doi.org/10.5194/os-11-779-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 02 Oct 2015

Research article | 02 Oct 2015

Estimation of upward radiances and reflectances at the surface of the sea from above-surface measurements

Ø. Kleiv1, A. Folkestad1,a, J. Høkedal2, K. Sørensen1, and E. Aas3 Ø. Kleiv et al.
  • 1Norwegian Institute for Water Research, Gaustadalleen 21, 0349 Oslo, Norway
  • 2Narvik University College, Lodve Langes gt. 2, 8505 Narvik, Norway
  • 3Department of Geosciences, University of Oslo, Gaustadalleen 21, 0349 Oslo, Norway
  • anow at: Rolls-Royce Marine Propulsion, Sjøgata 98, 6065 Ulsteinvik, Norway

Abstract. During 4 field days in the years 2009–2011, 22 data sets of measurements were collected in the inner Oslofjord, Norway. The data consist of recordings of spectral nadir radiances in air and water as well as spectral downward irradiance in air. The studied wavelengths are 351, 400, 413, 443, 490, 510, 560, 620, 665, 681, 709 and 754 nm.

The water-leaving radiance and the reflected radiance at the sea surface have been obtained from the measured nadir radiances in air and water, where the latter radiance has been extrapolated upwards to the surface. For comparison we present a simpler and much faster method that determines the water-leaving and reflected radiances solely from above-surface measurements of upward nadir radiance and downward irradiance. This new method is based on an assumption about similarity in spectral shape of the radiance reflected at the surface, and it makes use of the small ratio between water-leaving and reflected radiances at 351 and 754 nm in the Oslofjord.

A comparison between the quantities determined by the two mentioned methods shows that the average relative deviations between their results are less than or equal to 15 % for the reflected radiance, at the studied wavelengths. The average relative deviation of the water-leaving radiance at 560 nm is 24 %. These results are obtained for a cloudiness range of 1–8 oktas (12.5–100 %) and solar zenith angles between 37 and 51°. We consider these to be acceptable uncertainties for a first check of satellite products in the inner Oslofjord.

Publications Copernicus
Download
Short summary
A method which determines the radiance reflectance at the surface as well as the water-leaving and reflected radiances solely from the measurements of upward nadir radiance and downward irradiance in air is presented. A comparison between this method and in situ measurements shows that the average relative deviations between their results are less than or equal to 15% for the reflected radiance, at the studied wavelengths.
A method which determines the radiance reflectance at the surface as well as the water-leaving...
Citation
Share