Sub-Roman Britain (Cavalry etc)

[Alanus]

how effective is a composite say during a wet summer?
can it be used in fog or light rain?
i know tombstones of roman soldiers here in the west tend to show recurve composites

any idea why the english and welsh and the vikings (and probably the franks.slavs and saxons) also used large self bows and continued to do so?every invading nomadic (steppe ie huns and avars) group that came into europe had composites.
is there a different reason(s) for the poor performance of the avars against the west?-when arguably they were one of the most advanced steppe groups (besides the mongols)who invaded europe.

I would think that localized tradition influenced which type of bow was used. In the extreme west, the self bow was used since the stone age, and it continued in use after the steppe influence to the Roman army had faded. The requirements needed to make a self bow were easier, and the materials were less complicated. What we really would like to know is how long the composite bow was used in Britain.