BAROCLINIC BOUNDARY

Common Remarks

Baroclinicity means that in the atmosphere surfaces of constant pressure intersect surfaces of constant temperature (or density), implying that on a surface of constant pressure there exists a temperature gradient. Consequently a horizontal stream on a pressure surface causes a change in temperature.
In general the atmosphere is in a baroclinic state. But there are self contained areas with stronger baroclinicity like i.e. fronts. This is also true for the CM under discussion, the Baroclinic Boundary.
Baroclinicity is represented in this manual with help of indicative model parameter fields:

• High gradient in equivalent thickness
• High gradient in ThetaE or ThetaW
• Thermal front parameter

The second word in the title of this CM is "Boundary". This is understood to be a boundary of a synoptic system (i.e. height contours at upper levels, e.g. 500 hPa) such as an upper level trough or an Upper Level Low. Consequently, a Baroclinic Boundary cloud is not situated at typical locations for frontal cloudiness, i.e. at the leading side of a trough.
Furthermore Baroclinic Boundaries are distinguished from stationary fronts and air mass boundaries.

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