UNDERWATER RADIATION MEASUREMENTS: CONSEQUENCES OF AN INCREASED UV-B RADIATION - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 188

giving the k d coefficients. According to equation 1 there is a linear dependence between
k d and Z(10%) or Z(1%)

Z(10%) = -ln(0.10)/k d = 2.30/k d (2)

Z(1%) = -ln(0.01)/k d = 4.60/k d (3)

where k d is the mean vertical attenuation between the surface and the depth Z(10%),
respectively Z(1%).

Figure 3. Downward irradiance at 305 nm (upper curve), 320 nm, 340 nm and 380 nm (lower curve)
relative to surface irradiance as a function of depth. Measured in Samnanger Fjord, Norway
(60° 13' N, 05° 37' E).

For the example given in Figure 3, k d varied from 2.6 (305 nm) to 0.7 (380 nm)
and the corresponding 1% depth values are given in Table 1.

Table 1. Diffuse attenuation coefficient and corresponding 1% depth for data shown in Figure 3

k d [m -1 ]

wavelength [nm] Z(1%) [m]

305 2.6 1.8

320 1.9 2.4

340 1.4 3.3

380 0.7 6.6