Abstract: From multi-spectral exit radiance emerging from the ocean water, the 3D Chlorophyll concentration is reconstructed. The inverse problem as an optimization problem and iteratively solved by the meta-heuristics Ant Colony Optimization, using the radiative transfer equation as direct model solved by the LTSN method. An objective function is given by the square di?erence between computed and experimental radiances at every iteration. It was included an intrinsic regularization scheme that pre-selects candidate solutions at every iteration based on their smoothness, quanti ?ed by the 2nd order Tikhonov norm. An additional information is also used to compute the inverse solution: the concavity of the Chlorophyll pro?le that is veri?ed by means of its second derivative [2]. For considering an ocean surface divided in several sub-domains (as pixels in an image), there will be a signi?cant amount of computation to be performed. The demand for high processing power is addressed with the use of grid computing to speed up the inversion process. A grid infrastructure was built to perform the inversion for each pixel, managing a queue of independent jobs submitted to three clusters spread over Brazil. The OurGrid middleware [1] was used to manage these jobs. Keywords: Inverse hidrologic optics, Chlorophyll concentration, bio-optical models, grid computing.

References

[1] OurGrid. http://www.ourgrid.org/.

[2] R.P. Souto, V.C.F. Barbosa, H.F. de Campos Velho, S. Stephany (2007): Determining Chlorophill Concentration in O?-shore Sea Water from Multispectral Radiances by Using Second Devirtive Criterion and Ant Colony Meta-Heuristic. Inverse Problems, Desing and Optimization Symposium (IPDO-2007), Vol. 1, pp. 341–348. Miami (FL), USA.