def METHOD_NAME(P,PB,T,QVAPOR,ELEVATION):
	'''Calculation of Sea-level pressure.
	Calling sequence:  WRF_SLP = SLP(P,PB,T,QVAPOR,ELEVATION)
	where P,PB,T,QVAPOR are WRF 3D variables and ELEVATION is 
	the VAPOR variable indicating the elevation in meters above sea level.
	Result is a 2D variable with same horizonal extents as input variables.''' 