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wetdry: Boolean

Different time-stepping schemes are used for horizontal scalar advection when wetting and drying occur (vertical advection always uses the $\theta$ method). To guarantee consistency with continuity, the $\theta$ method must be used for scalar advection. This is formally first-order accurate in time, so results are more accurate when second-order Adams-Bashforth is used if there is no wetting and drying. Therefore, the wetdry Boolean is set according to:
(0): No wetting and drying, employ AB2 for horizontal scalar advection
(1): Wetting and drying: employ $\theta$-method for horizontal scalar advection.
Depending on the stratification at the surface and the grid size it is often desirable to employ wetdry = 1 so as to ensure consistency with continuity and avoid spurious oscillations in the temperature and salinity fields.