Mineral dust absorption
This is a follow up of TM5 issue #338.
In the current TM5 code we use 0.0011 for the imaginary part of the refractive index of mineral dust at 550 nm, which is based on a revision made at some point in ECHAM (Stier et al., ACP, 2005). Recent aircraft measurements (Denjean et al., ACP, 2006) give a range between 0.0001 and 0.0046 for Saharan dust with a mean value of 0.003. This is higher than the value currently used in TM5, but is still lower than the range from OPAC (0.006 to 0.008) and the value 0.055 used in earlier versions of ECHAM (Kinne et al., JGR, 2003).
It would be worthwhile to do some tests with imaginary part as a function of wavelength scaled by a fixed ratio 0.003 / 0.0011.