On 07 Aug 2003 00:07:22 GMT, (TudorHgh) wrote:

It's caused by Rayleigh scattering,
snip
Nothing whatsoever to do with Saharan dust, which is too large
to cause Rayleigh scattering.

Are you saying that none of the Saharan particles are small enough to
cause this effect?

I would have thought that at the end of a Saharan dust spell, such as
occurred yesterday, the final particles to settle out of suspension
would be the finest particles which, if small enough, could have
contributed to the observed discolouration. Even today,
http://forecast.uoa.gr/MODEL_OUTPUT/dload/000.gif
there are dusty areas quite near to the UK and I'd expect some fine
dust still to be up there. But are the particles small enough?

--
Dave