An experimental model of the solar‐stimulated fluorescence of chromophoric dissolved organic matter

We present an experimental model of CDOM solar‐stimulated fluorescence. Three‐dimensional fluorescence spectra of natural waters were used to determine the solar‐stimulated emission as a function of depth in the water column. Inclusion of the wavelength‐dependent fluorescence quantum yield provides emission values in absolute units of photons s −1 cm −2 5 nm −1 . Attenuation of light in the water column was also modeled, allowing determination of total upwelled emission. The upwelled fluorescence is compared to irradiance reflectance calculated from a semianalytical model. The fluorescence contribution to reflectance in the blue‐green to green region can be as high as 70% for blackwater but is rapidly reduced by the introduction of scattering particles. Except for blackwaters, CDOM fluorescence does not significantly affect irradiance reflectance ratios commonly used in remote‐sensing applications. In water with moderate amounts of CDOM (absorption coefficient at 355 nm ≥0.5 m −1 ), fluorescence will dominate water Raman scattering as a secondary influence on the light field in the green spectral region.