Ws. Pegau et al., ABSORPTION AND ATTENUATION OF VISIBLE AND NEAR-INFRARED LIGHT IN WATER - DEPENDENCE ON TEMPERATURE AND SALINITY, Applied optics, 36(24), 1997, pp. 6035-6046
We have measured the absorption coefficient of pure and salt water at
15 wavelengths in the visible and near-infrared regions of the spectru
m using WETLabs nine-wavelength absorption and attenuation meters and
a three-wavelength absorption meter. The water temperature was varied
between 15 and 30 degrees C, and the salinity was varied between 0 and
38 PSU to study the effects of these parameters on the absorption coe
fficient of liquid water. In the near-infrared portion of the spectrum
the absorption coefficient of water was confirmed to be highly depend
ent on temperature. In the visible region the temperature dependence w
as found to be less than 0.001 m(-1)/degrees C except for a small regi
on around 610 The same results were found for the temperature dependen
ce of a saltwater solution. After accounting for index-of-refraction e
ffects, the salinity dependence at visible wavelengths is negligible.
Salinity does appear to be important in determining the absorption coe
fficient of water in the near-infrared region. At 715 nm, for example,
the salinity dependence was -0.00027 m(-1)/PSU. Field measurements su
pport the temperature and salinity dependencies found in the laborator
y both in the near infrared and at shorter wavelengths. To make estima
tes of the temperature dependence in wavelength regions for which we d
id not make measurements we used a series of Gaussian curves that were
fit to the absorption spectrum in the visible region of the spectrum.
The spectral dependence on temperature was then estimated based on mu
ltiplying the Gaussians by a fitting factor. (C) 1997 Optical Society
of America.