Asymmetrical spectral curvature algorithms: oceanic-constituents sensitivities

Abstract

The asymmetrical spectral curvature algorithm for Morel case 1 waters has been characterized by application of the semianalytical radiance model of ocean color to post-Coastal Zone Color Scanner (CZCS) sensor bands. Results of the study suggest that the [L (490)/L (443)][L (490)/L (555)] asymmetrical spectral curvature algorithm has a higher pigment-retrieval sensitivity than does the [L (490)/L (443)][L (490)/L (510)] curvature algorithm that was initially identified for pigment recovery. When this [L (490)/L (443)][L (490)/L (555)] algorithm was highlighted for study, it was found to (a) xhibit pigment-retrieval sensitivity that is intermediate to the [L (443)/L (555)] and the [L (510)/L (555)] CZCS-type radiance-ratio algorithms, (b) have less sensitivity to nonabsorbing particulate backscatter (NAB) than the [L (443)/L (555)] radiance ratio, (c) display remarkable insensitivity to the absorption of dissolved organic material (DOM), and (d) possess a NAB invariance point at an algorithm value of ∼1.8 (corresponding to a pigment concentration of ∼0.35 mg/M(3)). At this invariance point the [L (490)/L (443)][L (490)/L (555)] algorithm is insensitive to a wide concentration range of coccolith-like backscatterers in addition to being insensitive to DOM. The dual DOM and NAB insensitivity of the algorithm at a specific curvature value and chlorophyllous-pigment concentration suggests that such invariance points should be further studied for possible use in (1) the validation of other chlorophyllouspigment algorithms or model inversions and (2) the computation of other inherent optical properties.