The method used to derive the boundary conditions must guard against the introduction of severe changes in model variables along the boundaries. Model resolution is usually defined as the distance between grid points in the model and is of primary interest to modelers and operational forecasters. In general, increased model resolution allows for definition of smaller scale features. In data rich areas, this increased resolution allows for more accurate depiction of small scale phenomena. For example, a model with a horizontal resolution of 125 km can resolve only horizontal phenomena of 500 km or greater.
Vertical resolution defines the resolution between the earth's surface and the top of the model.
In many cases vertical resolution is variable. For example, a model with 21 vertical levels may have 7 levels in the region below the 850-hPa level. In this case, processes in the boundary layer will be much better represented than if the levels were evenly spaced in the vertical. The MVOI is a method for producing a dynamically consistent blending of observations and model forecasts for use as initial conditions for forecast models. The simplest procedure is to interpolate the coarse mesh variables to the fine mesh boundaries at each time step of the coarse mesh.