# Planetary Boundary Layer (PBL) Group

## Surface Layer Parameterizations

### Parameterizations

Parameterizations are mathematical simplifications of physical processes.
The term *parameterization* usually refers to a simple
mathematic formula expressing some desired variable in terms of other
parameters of the system that are known through measurement or are
"realized" within a model. Parameterizations are normally used when a
variable is of interest only internally to a model, or the process is
so complicated it can only be practically represented statistically,
or we lack an essential measured property and must estimate it from
properties that are measured.

To place this concept in perspective, consider the way weather and climate models compute "forecasts". This is done by time integrations of rate equations (i.e., expressions of conservation) for the relevant variables. For example, atmospheric temperature is forecast by dividing the atmosphere into gridboxes and computing the time evolution of the average temperature within each box based on a number of variables including wind vector and the turbulent transport of heat. Whereas the wind vector can be calculated from models or measured directly, the turbulent transport of heat must be estimated by some equation approximating the motion of the atmosphere under those conditions.

Parameterizations are developed through high resolution observation and model validation. ETL has developed parameterizations for turbulent and radiative fluxes at the surface. For a more detailed discussion of our work see, Introduction to ETL Surface Flux Parameterizations.

- Radiative Flux Parameterizations

- Turbulent Flux Parameterizations (The COARE Algorithm)

- Sea Spray Parameterizations

The development of parameterizations furthers our understanding and modeling of weather and climate systems involving the complex interfaces between the oceans and atmosphere and ocean, ice and atmosphere regions.