Heres another person trying to do staggered grids in CF.
I forgot what we decided was the right way to do it.
------- Forwarded Message
>To: support-idv at unidata.ucar.edu
>cc: rsignell at usgs.gov
>From: Rich Signell <rsignell at yahoo.com>
>Subject: how to handle staggered U & V in IDV?
>Organization: UCAR/Unidata
>Keywords: 200410081020.i98AK8UE000709
I have U and V fields from a model that uses a
Arakawa-C grid, with U values at the left and right of
a grid cell, and V values at the top and bottom. In
the NetCDF file, therefore, U and V have different
dimensions (different by 1), and different coordinate
variables (lat_u, lon_u, lon_v, lat_v).
It would be great to have a formula that averages the
U & V values to the grid point centers so that we can
create displays with co-located velocity. Is this
possible?
Here's what my file looks like:
netcdf feb2003_short {
dimensions:
ocean_time = UNLIMITED ; // (1 currently)
s_rho = 20 ;
eta_u = 60 ;
xi_u = 159 ;
eta_v = 59 ;
xi_v = 160 ;
eta_rho = 60 ;
xi_rho = 160 ;
tracer = 2 ;
s_w = 21 ;
eta_psi = 59 ;
xi_psi = 159 ;
variables:
short u(ocean_time, s_rho, eta_u, xi_u) ;
u:scale_factor = -1.191449e-005f ;
u:add_offset = 0.0627047f ;
u:coordinates = "lat_u lon_u" ;
short v(ocean_time, s_rho, eta_v, xi_v) ;
v:scale_factor = -1.155427e-005f ;
v:add_offset = -0.1354672f ;
v:coordinates = "lat_v lon_v" ;
short salt(ocean_time, s_rho, eta_rho, xi_rho) ;
salt:scale_factor = -0.0006029948f ;
salt:add_offset = 19.75863f ;
salt:coordinates = "lat_rho lon_rho" ;
short temp(ocean_time, s_rho, eta_rho, xi_rho) ;
temp:scale_factor = -0.0003902203f ;
temp:add_offset = 11.19728f ;
temp:coordinates = "lat_rho lon_rho" ;
double Akk_bak ;
Akk_bak:long_name = "background vertical mixing
coefficient for turbulent energy" ;
Akk_bak:units = "meter2 second-1" ;
double Akp_bak ;
Akp_bak:long_name = "background vertical mixing
coefficient for length scale" ;
Akp_bak:units = "meter2 second-1" ;
double Akt_bak(tracer) ;
Akt_bak:long_name = "background vertical mixing
coefficient for tracers" ;
Akt_bak:units = "meter2 second-1" ;
double Akv_bak ;
Akv_bak:long_name = "background vertical mixing
coefficient for momentum" ;
Akv_bak:units = "meter2 second-1" ;
double Cs_r(s_rho) ;
Cs_r:long_name = "S-coordinate stretching curves at
RHO-points" ;
Cs_r:units = "nondimensional" ;
Cs_r:valid_min = -1. ;
Cs_r:valid_max = 0. ;
Cs_r:field = "Cs_r, scalar" ;
double Cs_w(s_w) ;
Cs_w:long_name = "S-coordinate stretching curves at
W-points" ;
Cs_w:units = "nondimensional" ;
Cs_w:valid_min = -1. ;
Cs_w:valid_max = 0. ;
Cs_w:field = "Cs_w, scalar" ;
double Falpha ;
Falpha:long_name = "Power-law shape barotropic
filter parameter" ;
double Fbeta ;
Fbeta:long_name = "Power-law shape barotropic filter
parameter" ;
double Fgamma ;
Fgamma:long_name = "Power-law shape barotropic
filter parameter" ;
double M2nudg ;
M2nudg:long_name = "2D momentum nudging/relaxation
inverse time scale" ;
M2nudg:units = "day-1" ;
double M3nudg ;
M3nudg:long_name = "3D momentum nudging/relaxation
inverse time scale" ;
M3nudg:units = "day-1" ;
double Tcline ;
Tcline:long_name = "S-coordinate surface/bottom
layer width" ;
Tcline:units = "meter" ;
double Tnudg(tracer) ;
Tnudg:long_name = "Tracers nudging/relaxation
inverse time scale" ;
Tnudg:units = "day-1" ;
double Znudg ;
Znudg:long_name = "free-surface nudging/relaxation
inverse time scale" ;
Znudg:units = "day-1" ;
double Zob ;
Zob:long_name = "bottom roughness" ;
Zob:units = "meter" ;
double Zos ;
Zos:long_name = "surface roughness" ;
Zos:units = "meter" ;
double angle(eta_rho, xi_rho) ;
angle:long_name = "angle between xi axis and east" ;
angle:units = "degree" ;
double dstart ;
dstart:long_name = "time stamp assigned to model
initilization" ;
dstart:units = "days since 0000-01-01 00:00:00" ;
dstart:calendar = "365.25 days in every year" ;
double dt ;
dt:long_name = "size of long time-steps" ;
dt:units = "second" ;
double dtfast ;
dtfast:long_name = "size of short time-steps" ;
dtfast:units = "second" ;
double el ;
el:long_name = "domain length in the ETA-direction"
;
el:units = "meter" ;
double f(eta_rho, xi_rho) ;
f:long_name = "Coriolis parameter at RHO-points" ;
f:units = "second-1" ;
f:field = "coriolis, scalar" ;
double gamma2 ;
gamma2:long_name = "Slipperiness parameter" ;
gamma2:units = "nondimensional" ;
double h(eta_rho, xi_rho) ;
h:long_name = "bathymetry at RHO-points" ;
h:units = "meter" ;
h:field = "bath, scalar" ;
h:coordinates = "lat_rho lon_rho" ;
double hc ;
hc:long_name = "S-coordinate parameter, critical
depth" ;
hc:units = "meter" ;
double lat_rho(eta_rho, xi_rho) ;
lat_rho:long_name = "latitude of RHO-points" ;
lat_rho:units = "degree_north" ;
lat_rho:field = "lat_rho, scalar" ;
double lat_u(eta_u, xi_u) ;
lat_u:long_name = "latitude of U-points" ;
lat_u:units = "degree_north" ;
double lat_v(eta_v, xi_v) ;
lat_v:long_name = "latitude of V-points" ;
lat_v:units = "degree_north" ;
float latent(ocean_time, eta_rho, xi_rho) ;
latent:units = "Watts meter-2" ;
latent:negative = "upward flux, cooling" ;
latent:positive = "downward flux, heating" ;
latent:time = "ocean_time" ;
latent:field = "latent heat flux, scalar, series" ;
double lon_rho(eta_rho, xi_rho) ;
lon_rho:long_name = "longitude of RHO-points" ;
lon_rho:units = "degree_east" ;
lon_rho:field = "lon_rho, scalar" ;
double lon_u(eta_u, xi_u) ;
lon_u:long_name = "longitude of U-points" ;
lon_u:units = "degree_east" ;
double lon_v(eta_v, xi_v) ;
lon_v:long_name = "longitude of V-points" ;
lon_v:units = "degree_east" ;
float lwrad(ocean_time, eta_rho, xi_rho) ;
lwrad:units = "Watts meter-2" ;
lwrad:negative = "upward flux, cooling" ;
lwrad:positive = "downward flux, heating" ;
lwrad:time = "ocean_time" ;
lwrad:field = "longwave radiation, scalar, series" ;
double mask_psi(eta_psi, xi_psi) ;
mask_psi:long_name = "mask on psi-points" ;
mask_psi:option_0 = "land" ;
mask_psi:option_1 = "water" ;
double mask_rho(eta_rho, xi_rho) ;
mask_rho:long_name = "mask on RHO-points" ;
mask_rho:option_0 = "land" ;
mask_rho:option_1 = "water" ;
mask_rho:option(0) = "land" ;
mask_rho:option(1) = "water" ;
double mask_u(eta_u, xi_u) ;
mask_u:long_name = "mask on U-points" ;
mask_u:option_0 = "land" ;
mask_u:option_1 = "water" ;
mask_u:option(0) = "land" ;
mask_u:option(1) = "water" ;
double mask_v(eta_v, xi_v) ;
mask_v:long_name = "mask on V-points" ;
mask_v:option_0 = "land" ;
mask_v:option_1 = "water" ;
mask_v:option(0) = "land" ;
mask_v:option(1) = "water" ;
int navg ;
navg:long_name = "number of time-steps between
time-averaged records" ;
int ndtfast ;
ndtfast:long_name = "number of short time-steps" ;
int nhis ;
nhis:long_name = "number of time-steps between
history records" ;
int nrst ;
nrst:long_name = "number of time-steps between
restart records" ;
nrst:cycle = "only latest two records are
maintained" ;
int nsta ;
nsta:long_name = "number of time-steps between
stations records" ;
int ntimes ;
ntimes:long_name = "number of long time-steps" ;
int ntsavg ;
ntsavg:long_name = "starting time-step for
accumulation of time-averaged fields" ;
double ocean_time(ocean_time) ;
ocean_time:long_name = "averaged" ;
ocean_time:units = "seconds since 1968-05-23
00:00:00 UTC" ;
ocean_time:calendar = "365.25 days in every year" ;
ocean_time:field = "time, scalar, series" ;
ocean_time:axis = "T" ;
double pm(eta_rho, xi_rho) ;
pm:long_name = "curvilinear coordinate metric in XI"
;
pm:units = "meter-1" ;
pm:field = "pm, scalar" ;
double pn(eta_rho, xi_rho) ;
pn:long_name = "curvilinear coordinate metric in
ETA" ;
pn:units = "meter-1" ;
pn:field = "pn, scalar" ;
double rdrg ;
rdrg:long_name = "linear drag coefficient" ;
rdrg:units = "meter second-1" ;
double rdrg2 ;
rdrg2:long_name = "quadratic drag coefficient" ;
rdrg2:units = "nondimensional" ;
double rho0 ;
rho0:long_name = "mean density used in Boussinesq
approximation" ;
rho0:units = "kilogram meter-3" ;
double s_rho(s_rho) ;
s_rho:long_name = "S-coordinate at RHO-points" ;
s_rho:units = "nondimensional" ;
s_rho:valid_min = -1. ;
s_rho:valid_max = 0. ;
s_rho:field = "sc_r, scalar" ;
s_rho:standard_name = "ocean_s_coordinate" ;
s_rho:positive = "up" ;
s_rho:formula_terms = "s: s_rho eta: zeta depth: h
a: theta_s b: theta_b depth_c: hc" ;
double sc_w(s_w) ;
sc_w:long_name = "S-coordinate at W-points" ;
sc_w:units = "nondimensional" ;
sc_w:valid_min = -1. ;
sc_w:valid_max = 0. ;
sc_w:field = "sc_w, scalar" ;
float sensible(ocean_time, eta_rho, xi_rho) ;
sensible:units = "Watts meter-2" ;
sensible:negative = "upward flux, cooling" ;
sensible:positive = "downward flux, heating" ;
sensible:time = "ocean_time" ;
sensible:field = "sensible heat flux, scalar,
series" ;
float shflux(ocean_time, eta_rho, xi_rho) ;
shflux:units = "Watts meter-2" ;
shflux:negative = "upward flux, cooling" ;
shflux:positive = "downward flux, heating" ;
shflux:time = "ocean_time" ;
shflux:field = "surface heat flux, scalar, series" ;
char spherical ;
spherical:long_name = "grid type logical switch" ;
spherical:option_T = "spherical" ;
spherical:option_F = "Cartesian" ;
float sustr(ocean_time, eta_u, xi_u) ;
sustr:units = "Newton meter-2" ;
sustr:time = "ocean_time" ;
sustr:field = "surface u-momentum stress, scalar,
series" ;
float svstr(ocean_time, eta_v, xi_v) ;
svstr:units = "Newton meter-2" ;
svstr:time = "ocean_time" ;
svstr:field = "surface v-momentum stress, scalar,
series" ;
float swrad(ocean_time, eta_rho, xi_rho) ;
swrad:units = "Watts meter-2" ;
swrad:negative = "upward flux, cooling" ;
swrad:positive = "downward flux, heating" ;
swrad:time = "ocean_time" ;
swrad:field = "shortwave radiation, scalar, series"
;
double theta_b ;
theta_b:long_name = "S-coordinate bottom control
parameter" ;
theta_b:units = "nondimensional" ;
double theta_s ;
theta_s:long_name = "S-coordinate surface control
parameter" ;
theta_s:units = "nondimensional" ;
double tnu2(tracer) ;
tnu2:long_name = "Laplacian mixing coefficient for
tracers" ;
tnu2:units = "meter2 second-1" ;
float ubar(ocean_time, eta_u, xi_u) ;
ubar:units = "meter second-1" ;
ubar:time = "ocean_time" ;
ubar:field = "ubar-velocity, scalar, series" ;
ubar:coordinates = "lat_u lon_u" ;
float vbar(ocean_time, eta_v, xi_v) ;
vbar:units = "meter second-1" ;
vbar:time = "ocean_time" ;
vbar:field = "vbar-velocity, scalar, series" ;
vbar:coordinates = "lat_v lon_v" ;
double xl ;
xl:long_name = "domain length in the XI-direction" ;
xl:units = "meter" ;
float zeta(ocean_time, eta_rho, xi_rho) ;
zeta:units = "meter" ;
zeta:time = "ocean_time" ;
zeta:field = "free-surface, scalar, series" ;
zeta:coordinates = "lat_rho lon_rho" ;
// global attributes:
:type = "ROMS/TOMS averages file" ;
:title = "ROMS/TOMS 2.0 - Adriatic Sea low-res test
grid K-Omega run" ;
:var_info = "varinfo.dat" ;
:rst_file = "river48_new/adria03_rst.nc" ;
:avg_file = "river48_new/adria03_avg.nc" ;
:sta_file = "river48_new/adria03_sta.nc" ;
:flt_file = "river48_new/adria03_flt.nc" ;
:grd_file = "adria02_grid2.nc" ;
:ini_file = "adria02_init2.nc" ;
:frc_file_01 =
"/bag_data3/adriatic/coarse_input/lami_wind_frc.nc" ;
:frc_file_02 =
"/bag_data3/adriatic/coarse_input/lami_bulk_frc.nc" ;
:frc_file_03 =
"/bag_data3/adriatic/coarse_input/lami_cloud_frc.nc" ;
:frc_file_04 =
"/bag_data3/adriatic/coarse_input/lami_swrad_frc.nc" ;
:frc_file_05 =
"/bag_data3/adriatic/coarse_input/tidal_frc.nc" ;
:frc_file_06 =
"/bag_data3/adriatic/coarse_input/adria48_rivers.nc" ;
:fpos_file = "adria02_floats.in" ;
:spos_file = "adria02_sta.in" ;
:history = "Fri Oct 8 05:20:59 2004: ncap -s
u=pack(u);v=pack(v);salt=pack(salt);temp=pack(temp)
feb2003_short.nc new.nc\n",
"Fri Oct 8 04:45:33 2004: ncks -x -v AKs,AKt,AKv
feb2003_cf.nc new.nc\n",
"Mon Oct 4 21:03:14 2004: ncks -A feb2003b.nc
feb2003b.nc_CF.nc\n",
"Thu Sep 23 09:23:39 2004: ncra -F -d
ocean_time,140,168 adria03_avg.nc feb2003.nc\n",
"ROMS/TOMS, Version" ;
:tiling = "002x001" ;
:CPP_options = " ANA_BSFLUX, ANA_BTFLUX, ANA_FSOBC,
ANA_M2OBC, ANA_RAIN, ANA_SSFLUX, ASSUMED_SHAPE,
AVERAGES, AVERAGES_AKS, AVERAGES_AKT, AVERAGES_AKV,
AVERAGES_FLUXES, BULK_FLUXES, DIURNAL_SRFLUX,
DJ_GRADPS, DOUBLE_PRECISION, EAST_FSCHAPMAN,
EAST_M2FLATHER, EAST_M3RADIATION, EAST_TRADIATION,
FLOATS, KANTHA_CLAYSON, LONGWAVE, MASKING, MIX_GEO_TS,
MY25_MIXING, NONLIN_EOS, NORTHERN_WALL, N2S2_HORAVG,
_OPENMP, POWER_LAW, PROFILE, K_GSCHEME, RADIATION_2D,
!RST_SINGLE, SALINITY, SOLVE3D, SOUTHERN_WALL,
SPLINES, SSH_TIDES, STATIONS, TS_A4HADVECTION,
TS_A4VADVECTION, TS_DIF2, TS_PSOURCE, UV_ADV, UV_COR,
UV_U3HADVECTION, UV_PSOURCE, UV_TIDES, VAR_RHO_2D,
WESTERN_WALL," ;
:Conventions = "CF-1.0" ;
:gridid = "Adria 01" ;
:CPP-options = "DCOMPLEX, DBLEPREC, NCARG_32,
PLOTS," ;
}
=====
Rich Signell
work: rsignell at usgs.gov
home: rsignell at umich.edu
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Received on Sat Oct 09 2004 - 09:05:06 BST
