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CdT: $C_{dT}$

If the roughness at the lid is zero (i.e. z0T=0) then the drag coefficient at the lid is given by this constant, otherwise the drag coefficient is calculated with the rough wall relationship. Use of no-slip boundary conditions for the top cell is specified by setting CdT=-1.

C_{dT} = \left[\frac{1}{\kappa}\ln\left(\frac{1}{2}\frac{\Delta z_{top}}{z_{0T}}\right)\right]^{-2} .

where $\Delta z_{top}$ is the thickness of the top cell (in meters) and $\kappa=0.4$ is the von Karman constant.