The parameterization of processes which are not explicitly resolved by an ocean model constitute subgridscale parameterizations. In many ways, the area of subgridscale (SGS) parameterizations is the most challenging, and frustrating, endeavor in oceanography. Many oceanographers would wish nothing more than to ignore the issue, while others are obsessed with it. Its importance from a pragmatic modeling perspective rests largely on the crucial part such parameterizations play in determining the physical integrity of the numerical solutions. Fundamentally, ``good'' parameterizations often (but not always) come only after understanding the process which is to be parameterized. For a very educational and entertaining summary of certain SGS parameterization issues as of 1989, the reader is encouraged to read Holloway's lectures from the Les Houches School (Holloway, 1989). These lectures place some perspective on the SGS affair.
MOM provides a large number of SGS parameterizations. Fundamentally, the large number reflects the broad spectrum of processes present in the ocean requiring parameterization in a finite sized ocean model. Additionally, it manifests the diverse requirements within the ocean modeling community whose goals are far from uniform. Unfortunately, this state of affairs can be intimidating and confusing to many researchers wishing to use MOM. The purpose of this and the following chapters is to provide an overview of the options. The hope is to reduce the intimidation and thence to allow for a more informed choice of the options suitable for each researcher's particular needs.
The present chapter focuses on the options in MOM associated with vertical processes. Most notably, options for representing convection and parameterizing mixed layer processes are described.