ABSORPTION AND ATTENUATION OF VISIBLE AND NEAR-INFRARED LIGHT IN WATER - DEPENDENCE ON TEMPERATURE AND SALINITY

Citation
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
Citations number
33
Categorie Soggetti
Optics
Journal title
ISSN journal
00036935
Volume
36
Issue
24
Year of publication
1997
Pages
6035 - 6046
Database
ISI
SICI code
0003-6935(1997)36:24<6035:AAAOVA>2.0.ZU;2-7
Abstract
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.