Sensitivity tests and model parameterization

Idealized process-oriented river plume studies with the HYCOM
Sensitivity tests and model parameterization

Different mechanisms that change the vertical and horizontal structure of the buoyant plumes are investigated with the BOX domain. Experiments that are similar to the 20m deep flat bottom case in the previous link (Dynamics of river plumes) but with enhanced vertical mixing inside the estuary are performed. Enhanced vertical mixing is produced by increasing the downward penetration of the river inflow (river parameterization) and by increasing the overall vertical mixing inside the estuary via the vertical mixing scheme (larger background salt diffusivity)

DESCRIPTION:
Left: Surface salinity snapshots of the plume development under two different vertical mixing conditions inside the estuary, after 60 days. When we increase the downward penetration of the river inflow, the plume becomes less fresh at the surface, indicating that river water are being mixed downward. That enhances the gravitational circulation inside the estuary, promoting the development of a larger buoyant plume. The offshore bulge has grown in size, with a stronger coastal current that also presents more meanders. When we increase the overall mixing inside the estuary, the plume shape changes drastically, with no development of an offshore bulge and a wider coastal current.
 
Right: Vertical salinity cross-shore sections (y = 0km) from the same experiments. When we increase the downward penetration of the river inflow, the buoyant plume goes deeper at the river source, in contrast to the plume that does not have additional mixing (Dynamics of river plumes).
A deeper plume is also produced when we increase the overall mixing inside the estuary.