Morel and Maritorena^{3} also present a model for diffuse attenuation given by Display Formula
$Kd=Kw+\chi Ce,$(9)
where $Kw$ is the diffuse attenuation from pure seawater, and $\chi $ and $e$ are parameters that vary with wavelength. These three parameters are available in tables.^{5} It is occasionally convenient to have approximations to the tabulated values, and we have done this by piecewise polynomial fits. These are Display Formula$Kw=\u221281.373033+0.98491411\lambda \u22120.0047381508\lambda 2+1.1334476\xd710\u22125\lambda 3\u22121.3491818\xd710\u22128\lambda 4+6.3969794\xd710\u221212\lambda 5,350\u2264\lambda <515Kw=907.42423\u22126.729768\lambda +0.01871207\lambda 2\u22122.311898\xd710\u22125\lambda 3+1.07099\xd710\u22128\lambda 4,515\u2264\lambda <605,Kw=\u22121419.824+8.654027\lambda \u22120.01970537\lambda 2+1.985801\xd710\u22125\lambda 3\u22127.46716\xd710\u22129\lambda 4,605\u2264\lambda <665,Kw=\u22121373.958+6.150477\lambda \u22129.177511\xd710\u22123\lambda 2+4.56626263\xd710\u22126\lambda 3,665\u2264\lambda \u2264700,$(10)
Display Formula$\chi =\u221211.5717+0.0982478\lambda \u22122.72055\xd710\u22124\lambda 2+2.48741\xd710\u22127\lambda 3,350\u2264\lambda <415,\chi =\u22126.22839+0.05027291\lambda \u22121.440342\xd710\u22124\lambda 2+1.769267\xd710\u22127\lambda 3\u22127.919928\xd710\u221211\lambda 4,415\u2264\lambda <675,\chi =\u22121.5063+5.44393\xd710\u22123\lambda \u22124.64286\xd710\u22126\lambda 2,675\u2264\lambda \u2264700,$(11)
Display Formula$e=4.06652\u22120.0151677\lambda +1.65361\xd710\u22125\lambda 2,350\u2264\lambda <400,e=1.26402\u22127.31889\xd710\u22123\lambda +2.27559\xd710\u22125\lambda 2\u22122.08551\xd710\u22128\lambda 3,400\u2264\lambda <580,e=0.799443\u22121.40758\xd710\u22123\lambda +1.86375\xd710\u22126\lambda 2,400\u2264\lambda <675,e=\u221212.6864+0.0429771\lambda \u22123.42857\xd710\u22125\lambda 2,675\u2264\lambda \u2264700.$(12)