GFS gwdc Main

This subroutine is the parameterization of convective gravity wave drag based on the theory given by Chun and Baik (1998) [17] modified for implementation into the GFS/CFS by Ake Johansson(Aug 2005). More...

Detailed Description

Argument Table

local_name	standard_name	long_name	units	rank	type	kind	intent	optional
im	horizontal_loop_extent	horizontal loop extent	count	0	integer		in	F
ix	horizontal_dimension	horizontal dimension	count	0	integer		in	F
km	vertical_dimension	number of vertical layers	count	0	integer		in	F
lat	latitude_index_in_debug_printouts	latitude index in debug printouts	index	0	integer		in	F
u1	x_wind	zonal wind	m s-1	2	real	kind_phys	in	F
v1	y_wind	meridional wind	m s-1	2	real	kind_phys	in	F
t1	air_temperature	mid-layer temperature	K	2	real	kind_phys	in	F
q1	water_vapor_specific_humidity	mid-layer specific humidity of water vapor	kg kg-1	2	real	kind_phys	in	F
deltim	time_step_for_physics	physics time step	s	0	real	kind_phys	in	F
pmid1	air_pressure	mid-layer pressure	Pa	2	real	kind_phys	in	F
pint1	air_pressure_at_interface	interface pressure	Pa	2	real	kind_phys	in	F
dpmid1	air_pressure_difference_between_midlayers	difference between mid-layer pressures	Pa	2	real	kind_phys	in	F
qmax	maximum_column_heating_rate	maximum heating rate in column	K s-1	1	real	kind_phys	in	F
ktop	vertical_index_at_cloud_top	vertical index at cloud top	index	1	integer		in	F
kbot	vertical_index_at_cloud_base	vertical index at cloud base	index	1	integer		in	F
kcnv	flag_deep_convection	flag indicating whether convection occurs in column (0 or 1)	flag	1	integer		in	F
cldf	cloud_area_fraction	fraction of grid box area in which updrafts occur	frac	1	real	kind_phys	in	F
grav	gravitational_acceleration	gravitational acceleration	m s-2	0	real	kind_phys	in	F
cp	specific_heat_of_dry_air_at_constant_pressure	specific heat of dry air at constant pressure	J kg-1 K-1	0	real	kind_phys	in	F
rd	gas_constant_dry_air	ideal gas constant for dry air	J kg-1 K-1	0	real	kind_phys	in	F
fv	ratio_of_vapor_to_dry_air_gas_constants_minus_one	rv/rd - 1 (rv = ideal gas constant for water vapor)	none	0	real	kind_phys	in	F
pi	pi	ratio of a circle's circumference to its diameter	radians	0	real	kind_phys	in	F
dlength	characteristic_grid_length_scale	representative horizontal length scale of grid box	m	1	real	kind_phys	in	F
lprnt	flag_print	flag for debugging printouts	flag	0	logical		in	F
ipr	horizontal_index_of_printed_column	horizontal index of column used in debugging printouts	index	0	integer		in	F
fhour	forecast_time	forecast hour	h	0	real	kind_phys	in	F
utgwc	tendency_of_x_wind_due_to_convective_gravity_wave_drag	zonal wind tendency due to convective gravity wave drag	m s-2	2	real	kind_phys	out	F
vtgwc	tendency_of_y_wind_due_to_convective_gravity_wave_drag	meridional wind tendency due to convective gravity wave drag	m s-2	2	real	kind_phys	out	F
tauctx	instantaneous_x_stress_due_to_gravity_wave_drag	zonal stress at cloud top due to convective gravity wave drag	Pa	1	real	kind_phys	out	F
taucty	instantaneous_y_stress_due_to_gravity_wave_drag	meridional stress at cloud top due to convective gravity wave drag	Pa	1	real	kind_phys	out	F
errmsg	error_message	error message for error handling in CCPP	none	0	character	len=*	out	F
errflg	error_flag	error flag for error handling in CCPP	flag	0	integer		out	F

GFS Convective GWD Scheme General Algorithm

Parameterizing subgrid-scale convection-induced gravity wave momentum flux for use in large-scale models inherently requires some information from subgrid-scale cumulus parameterization. The methodology for parameterizing the zonal momentum flux induced by thermal forcing can be summarized as follows. From the cloud-base to cloud-top height, the effect of the momentum flux induced by subgrid-scale diabatic forcing is not considered because subgrid-scale cumulus convection in large-scale models is only activated in a conditionally unstable atmosphere. Below the cloud base, the momentum flux is also not considered because of the wave momentum cancellation.

The formulation of the momentum flux at the cloud top that can be broken in the upper atmosphere is similar to that of the surface drag of mountain waves by using the nonlinearity factor of thermally induced waves that is analogous to the inverse Frounde number in mountain waves. A vertical profiles of redistributed momentum flux above the cloud top can be approximated either by specifying a functional form or by using the wave saturation hypothesis in terms of the Richardson number criterion. The formulation of the minimum Richardson number including wave impact is similar to that in the mountain wave case.

GFS Convective GWD Scheme Detailed Algorithm

Functions/Subroutines
subroutine	gwdc::gwdc_run (im, ix, km, lat, u1, v1, t1, q1, deltim, pmid1, pint1, dpmid1, qmax, ktop, kbot, kcnv, cldf, grav, cp, rd, fv, pi, dlength, lprnt, ipr, fhour, utgwc, vtgwc, tauctx, taucty, errmsg, errflg)