Effects of molecular and particle scatterings on the model parameter for remote-sensing reflectance

Abstract

For optically deep waters, remote-sensing reflectance (r(rs)) is traditionally expressed as the ratio of the backscattering coefficient (b(b)) to the sum of absorption and backscattering coefficients (a + b(b)) that multiples a model parameter (g, or the so-called f'/Q). Parameter g is further expressed as a function of b(b)/(a + b(b)) (or b(b)/a) to account for its variation that is due to multiple scattering. With such an approach, the same g value will be derived for different a and b(b) values that provide the same ratio. Because g is partially a measure of the angular distribution of upwelling light, and the angular distribution from molecular scattering is quite different from that of particle scattering; g values are expected to vary with different scattering distributions even if the b(b)/a ratios are the same. In this study, after numerically demonstrating the effects of molecular and particle scatterings on the values of g, an innovative r(rs) model is developed. This new model expresses r(rs) in two separate terms: one governed by the phase function of molecular scattering and one governed by the phase function of particle scattering, with a model parameter introduced for each term. In this way the phase function effects from molecular and particle scatterings are explicitly separated and accounted for. This new model provides an analytical tool to understand and quantify the phase-function effects on r(rs), and a platform to calculate r(rs) spectrum quickly and accurately that is required for remote-sensing applications.

Diffuse attenuation coefficient of downwelling irradiance: An evaluation of remote sensing methods

“…In this strategy, the values of the absorption, a, and backscattering, b b , coefficients are most essential to the determination of both apparent optical properties of interest to our study, R rs and K d (wavelength notation suppressed). When the values of a and b b are known, along with boundary conditions, R rs and K d can be calculated from semianalytical models [Lee et al, 2004Sathyendranath and Platt, 1997]. In remote sensing applications by satellite imagery, R rs is determined from satellite measurements.…”

Analyzing the effects of particle size on remotely sensed spectra: a study on optical properties and spectral similarity scale of suspended particulate matters in water

“…(14), b bs a λ c s a R rs a a w λ a s λ b bw λ − 0.051 b bw λ 0.051 − R rs a : With Eqs. (11) and (14), we have Eq. (15):…”

“…The IOPs parameters of water can be written as a product of component concentrations and the specific absorption coefficient or specific scattering coefficient [1]. Apart from SPM concentration, particle size is another important impact factor in IOPs for case 2 water [10,11]. The particle size of SPM in case 2 water influences the penetration of incident light into the water.…”

Validation and Calibration of QAA Algorithm for CDOM Absorption Retrieval in the Changjiang (Yangtze) Estuarine and Coastal Waters

“…Moreover, it is inappropriate to regard parameters of this equation (i.e., g 0 and g 1 ) as constants. These parameters are associated with the solar zenith angle and water properties, and vary with water composition scattering properties [62]. Consequently, g 0 and g 1 have influence on b b (λ), when using QAA, it will further affect the inversion accuracy of a(λ).…”

“…Consequently, g 0 and g 1 have influence on b b (λ), when using QAA, it will further affect the inversion accuracy of a(λ). Lee et al [62] partitioned and weighted parameter g according to the molecular (water itself) and particulate contributions to the backscattering coefficient. In this study, however, this approach was not exploited.…”