Thermal boundary Layer (TBL) development and maintenance depends on two factors: (i) convectively produced turbulence caused by solar heating of the surface and internal redistribution of heat under the cap of the stable layer, and (ii) mechanically produced turbulence originating from the vertical wind speed shear and the surface roughness. The figure given below shows the various physical processes involved in the TBL growth.

Traditionally, two distinct approaches have been taken to predict the development of the thermal boundary layer: (i) theoretical approach and (ii) experimental studies.

Experimental studies usually involve the determination of temperature profiles with time of day using direct or indirect (remote) sensing techniques. Direct sensing devices such as mini-sondes or thermocouples are used to record temperature variation with height while indirect methods may involve surface-based remote sensors such as acoustic radar to detect the TBL height.

The theoretical approach may be classified into three groups:

Empirical formulae,

Analytical solutions,

Numerical models

One layer models,

Higher order closure models.

The prediction of the boundary layer height (H) as a function of time of day and time of year is based on the solution of the appropriate conservation equations relating both the heat flux and the temperature jump across the inversion layer to the height of the TBL.

A comparison between calculated (using the analytical model) and observed TBL heights is shown in figure below. The TBL heights were obtained from minisonde data using single theodolite or double theodolite.

The TBL heights depends on time of year and time of day. This is evident from the heat flux profiles given in the following figure.