Soil Temperature Equation Bases on Ambient Air Temperature

[SilverGhost]

I'm looking for soil temperatures, ranging from 0-3 meters into the ground, for different parts of South America and Africa. Is there an equation that can calculate this based on the ambient air temperature? Things such as soil properties, pressure, etc can all be looked up or assumed, I'm just unable to find an equation.

Thanks
MechArmy

 

[CarlB]

http://soilphysics.okstate.edu/software/SoilTemperature/document.pdf

http://soil.scijournals.org/cgi/content/full/68/3/784