Questions about some roughness and drag coefficient.

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Dear all:
I have recently run a simulation use the WRF-ROMS-SWAN coupled model successfully, i want to plot the surface roughnenss in the ocean_his file, but it turned out to be a constant, is that normal？also, i find that the there are two drag coefficients include linear and quadratic coefficient, their numerical values differs a lot, what do they mean? i am not a expert in it and i am confused why they are constant too? it is really beyond my comprehension. thank you all very much !!!
Jan,
yours sincerely.