corioles force/rossby number

I have the equation for the rossby number as: u/(f*L) where u = velocity and f = coriolis frequency. I know L = length scale in the abstract, but what would it specifically be if you are trying to figure out the coriolis force on a boat at sea? what # would L be?

thanks.

Re: corioles force/rossby number

If there is a "coriolis force" on the boat to begin with, the boat must be moving in a circle (perhaps moving around the earth as the earth turns toward the east). So the reasonable "length" would be the radius of that circle (in the case of the boat moving with the earth, that would be the distance from the boat to the earth's axis at the same latitude).