Vertical Resolution and Coordinates


Properly depicting the vertical structure of the atmosphere leads to better forecasts by Numerical Weather Prediction Models.  To successfully understand this vertical structure, the model must have an appropriate vertical coordinate to lead to better resolution and thus better forecasts.  Numerical Weather Prediction models produce these forecasts by computing the average over these coordinate surfaces, rather than on the surface itself.  At this point, one familiar with forecasting models might ask: "Why not use pressure and height surfaces, as they are used in most maps anyway?"  The reason that these surfaces are not used in Numerical Weather Prediction is because they cause much confusion at the ground.  Therefore, other surfaces have been developed and used in the vertical.  Some of the most popular surfaces used in many of the current models are the Sigma, Eta, and Theta surfaces(UCAR, 2000).  These will be the surfaces we will focus our attention to in this webpage, describing each vertical coordinate system,  giving examples of models from coordinate systems, and making an evaluation of the coordinate types.
Description of Vertical Coordinate Systems