large_scale_condensation Module

Parametrization of large-scale condensation

Large-scale condensation is modelled as a relaxation of humidity to a sigma-dependent threshold value $RH(\sigma)$. $$\frac{\partial q}{\partial t} = -\frac{q - RH(\sigma) q_{sat}}{\tau_{lsc}},$$ where $\tau_{lsc}$ is the relaxation timescale. The temperature tendency is computed as the resultant latent heating, $$\frac{\partial T}{\partial t} = - \frac{L}{c_p} \frac{\partial q}{\partial t}.$$ Precipitation is diagnosed as all the moisture lost to condensation falling out of the atmospheric column in the timestep, $$P = -\frac{1}{g} \sum_{k=2}^N \Delta p \frac{\partial q}{\partial t}.$$

Contents

Variables

trlsc rhlsc drhlsc rhblsc

Subroutines

get_large_scale_condensation_tendencies

Variables

Type	Visibility	Attributes		Name		Initial
real,	private,	parameter	::	trlsc	=	4.0	Relaxation time (in hours) for specific humidity
real,	private,	parameter	::	rhlsc	=	0.9	Maximum relative humidity threshold (at sigma=1)
real,	private,	parameter	::	drhlsc	=	0.1	Vertical range of relative humidity threshold
real,	private,	parameter	::	rhblsc	=	0.95	Relative humidity threshold for boundary layer

Subroutines

public subroutine get_large_scale_condensation_tendencies(psa, qa, qsat, itop, precls, dtlsc, dqlsc)

Compute large-scale condensation and associated tendencies of temperature and moisture

Arguments

Type	Intent	Optional	Attributes		Name
real,	intent(in)			::	psa(ix,il)	Normalised surface pressure [p/p0]
real,	intent(in)			::	qa(ix,il,kx)	Specific humidity [g/kg]
real,	intent(in)			::	qsat(ix,il,kx)	Saturation specific humidity [g/kg]
integer,	intent(inout)			::	itop(ix,il)	Cloud top diagnosed from precipitation due to convection and large-scale condensation
real,	intent(out)			::	precls(ix,il)	Precipitation due to large-scale condensation
real,	intent(out)			::	dtlsc(ix,il,kx)	Temperature tendency due to large-scale condensation
real,	intent(out)			::	dqlsc(ix,il,kx)	Specific humidity tendency due to large-scale condensation