Mass and mass-fluxes

Task

task	description
task	mass fluxes and surface pressures

Content versions

The content version is an attribute in hdf files.

content version	description
10	initial number (march 2003)
11	debugged: first sp field was constant (sep 2003)

Surface pressure and horizontal flux

file	param	description	unit	levels	from	time res. (hr)	grib code	hor. comb.	vert. comb	Comments
uvsp	ps	surface pressure at begin time interval	Pa	1	sh	21,03,09,15	160	area average	-
	pu	eastward flux during time interval	kg/s	1:lm	sh	[21,03],..	158	sum	sum	dimension(0:im,1:jm,lm) !
	pv	northward flux during time interval	kg/s	1:lm	sh	[21,03],..	159	sum	sum	dimension(1:im,0:jm,lm) !
	ps	surf. press. at end (=begin new interval)	Pa	1:lm	sh	21	160	area average	-

Surface pressures and fluxes are computed from spectral log surface pressure, vorticity, and divergence.

Surface pressure fields and fluxes completly define mass and mass change during time intervals [21,3], [3,9], [9,15], [15,21]. The first surface pressure is valid for the start of the intervals and can be used to compute the initial mass distribution. The fluxes are average values during the time interval, and are computed such that the mass distribution at the end of the time interval matches with the surface pressure. Since the end surface pressure is provided to, a file contains 5 surface pressure fields.

Surface pressures are defined on a 2D grid. The u-fluxes are defined for all east/west boundaries of a rectangular grid, thus for each latitude row one value more than the number of cells. Idem for v-fluxes:

           real          ::  ps(im,jm)
           real          ::  pu(0:im,jm,lm)
           real          ::  pv(im,0:jm,lm)

Vertical flux

file	param	description	unit	levels	from	time res. (hr)	grib code	hor. comb.	vert. comb	Comments
w	pw	downward flux throuh bottom of a layer	kg/s	1:lm	sh	[21,03],..	157	sum	bottom	used for matching of zoom grids with parent

Valid during time intervals [21,3], [3,9], [9,15], [15,21]. The vertical fluxes are used to balance the horizontal fluxes with the observed surface pressures. Could be computed from the sp/pu/pv too, and are therefore not required for TM. However, they are used in the preprocessing to match fine with coarse grids.

Surface pressure

file	param	description	unit	levels	from	time res. (hr)	grib code	hor. comb.	vert. comb	Comments
spm	ps	surface pressure at tmid	Pa	1	sh	00,06,12,18	160	area average	-	computed from LNSP, thus not (ps(tmin)+ps(tplus)/2; used for matching zoom grids

Valid for mid of time intervals.

Used to compute mass averages during the preprocessing.

Related material

• [Segers et al., 2002]: paper with description of how to compute mass fluxes from spectral fields;
• [Segers, 2001]: extensive research notes, including manipulation of spectral fields;
• [Bregman et al., 2001]: experiments showed errors in vertical transport.
• [Bregman et al., 2003]: paper over use of new fluxes