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To learn about what's going on, see About the Archive Site.
On Thu, 15 Aug 2002, Unidata Support wrote:
>
> ------- Forwarded Message
>
> >To: address@hidden
> >From: Tony Eckel <address@hidden>
> >Subject: handling thinned grids
> >Organization: University of Washington
> >Keywords: 200208142238.g7EMc5K14065 Japanese Met Agency thinned grids
> >gribtonc
>
> Hello,
>
> I was wondering if you might know how to handle thinned lat/lon grids.
> I am trying to use gribbed global data from the Japanese Meteorological
> Agency and the data is thinned by row as you head toward the poles (to
> conserve space). Do you have a routine that can convert such data into
> a regular lat/lon grid (i.e., fill in the thinned part), and write back
> out to either grib or NETCDF?
Tony,
Sorry for the late reply, I've been on vacation. I don't know anything
about Japanese Met Agency thinned grids but gribtonc does work with
thinned grids. It uses the -q flag to do the interpolation of the grids, a
entry from the LDM pqact.conf file would look like this:
# AVN model on thinned grids, interpolated to global 5.0 x 2.5 regular
grid
HRS ^H.[I-P]... KWB. (..)(..).*(/mAVN|/mSSIAVN)
PIPE /usr/local/ldm/decoders/gribtonc
-q "lin,dlat=2.5,dlon=5.0" etc/avn-x.cdl
data/GRIB/(\1:yy)(\1:mm)\1\2_avn-x.nc
I'll include the avn-x.cdl too.
As I stated, it depends if the grid follows the "regular" conventions,
etc.
The decoders page is located at:
http://www.unidata.ucar.edu/packages/decoders/
You might get some hints from the Seachable archives on the page using
thinned or quasi keywords.
Robb...
>
> Thanks for any help you can provide.
>
> Tony Eckel
> (206)-543-9144
> address@hidden
> 408 Atmospheric Sciences - Geophysics Bldg
> University of Washington
> Box 351640
> Seattle, WA 98195-1640
>
>
> ------- End of Forwarded Message
>
>
===============================================================================
Robb Kambic Unidata Program Center
Software Engineer III Univ. Corp for Atmospheric Research
address@hidden WWW: http://www.unidata.ucar.edu/
===============================================================================
netcdf avn-x { // 126 Wave, 18 Layer Spectral Model Aviation Run
// on expanded quasi-regular "thinned" grids
dimensions:
record = UNLIMITED ; // (reference time, forecast time)
level = 12 ;
lat = 73 ; // latitude
lon = 73 ; // longitude
lpdg = 1 ; // boundary layer levels
fhg = 2 ; // fixed height above ground levels
sigma = 1 ; // sigma level
datetime_len = 21 ; // string length for datetime strings
nmodels = 3 ; // both AVN and SSIAVN models
accum = 2 ; // time range for accumulations
nav = 1 ; // For navigation. Variables that use
// this dimension define a mapping between
// (lat, lon) indices and (lat, lon) coords.
nav_len = 100 ; // max string length for navigation strings
variables:
double reftime(record) ; // reference time of the model
reftime:long_name = "reference time" ;
reftime:units = "hours since 1992-1-1" ;
double valtime(record) ; // forecast time ("valid" time)
valtime:long_name = "valid time" ;
valtime:units = "hours since 1992-1-1" ;
:record = "reftime, valtime" ; // "dimension attribute" -- means
// (reftime, valtime) uniquely
// determine record
char datetime(record, datetime_len) ; // derived from reftime
datetime:long_name = "reference date and time" ;
// units YYYY-MM-DD hh:mm:ssZ (ISO 8601)
float valtime_offset(record) ; // derived as valtime-reftime
valtime_offset:long_name = "hours from reference time" ;
valtime_offset:units = "hours" ;
float level(level) ;
level:long_name = "level" ;
level:units = "hectopascals" ;
:lpdg = "lpdg_bot, lpdg_top" ; // (lpdg_bot, lpdg_top) uniquely
// determines lpdg
float lpdg_bot(lpdg) ;
lpdg_bot:long_name = "bottom level of boundary layer between 2
levels at specified pressure differences from ground to levels" ;
lpdg_bot:units = "hectopascals" ;
float lpdg_top(lpdg) ;
lpdg_top:long_name = "top level of boundary layer between 2
levels at specified pressure differences from ground to levels" ;
lpdg_top:units = "hectopascals" ;
float fhg(fhg) ; // fixed height above ground
fhg:long_name = "fixed height above ground" ;
fhg:units = "meters" ;
float sigma(sigma) ; // fixed height above ground
sigma:long_name = "sigma level" ;
sigma:units = "" ; // dimensionless
long model_id(nmodels) ;
model_id:long_name = "generating process ID number" ;
// The following lat and lon coordinate variables are redundant,
// since the navigation variables provide the necessary information.
// The extra information is included here for human readability.
float lat(lat) ;
lat:long_name = "latitude" ;
lat:units = "degrees_north" ;
float lon(lon) ;
lon:long_name = "longitude" ;
lon:units = "degrees_east" ;
// navigation variables all use nav dimension
char nav_model(nav, nav_len) ; // navigation parameterization
nav_model:long_name = "navigation model name" ;
int grid_type_code(nav) ;
grid_type_code:long_name = "GRIB-1 GDS data representation
type" ;
char grid_type(nav, nav_len) ;
grid_type:long_name = "GRIB-1 grid type" ;
char grid_name(nav, nav_len) ;
grid_name:long_name = "grid name" ;
int grid_center(nav) ;
grid_center:long_name = "GRIB-1 originating center ID" ;
int grid_number(nav) ;
grid_number:long_name = "GRIB-1 catalogued grid numbers" ;
grid_number:_FillValue = -9999 ;
char i_dim(nav, nav_len) ;
i_dim:long_name = "longitude dimension name" ;
char j_dim(nav, nav_len) ;
j_dim:long_name = "latitude dimension name" ;
int Ni(nav) ;
Ni:long_name = "number of points along a latitude circle" ;
int Nj(nav) ;
Nj:long_name = "number of points along a longitude circle" ;
float La1(nav) ;
La1:long_name = "latitude of first grid point" ;
La1:units = "degrees_north" ;
float Lo1(nav) ;
Lo1:long_name = "longitude of first grid point" ;
Lo1:units = "degrees_east" ;
float La2(nav) ;
La2:long_name = "latitude of last grid point" ;
La2:units = "degrees_north" ;
float Lo2(nav) ;
Lo2:long_name = "longitude of last grid point" ;
Lo2:units = "degrees_east" ;
float Di(nav) ;
Di:long_name = "Longitudinal direction increment" ;
Di:units = "degrees" ;
float Dj(nav) ;
Dj:long_name = "Latitudinal direction increment" ;
Dj:units = "degrees" ;
byte ResCompFlag(nav) ;
ResCompFlag:long_name = "resolution and component flags" ;
// end of navigation variables
float P_maxwind(record, lat, lon) ;
P_maxwind:long_name = "pressure at maximum wind" ;
P_maxwind:units = "Pa" ;
P_maxwind:_FillValue = -9999.f ;
P_maxwind:navigation = "nav" ;
float P_trop(record, lat, lon) ;
P_trop:long_name = "pressure at tropopause" ;
P_trop:units = "Pa" ;
P_trop:_FillValue = -9999.f ;
P_trop:navigation = "nav" ;
float P_msl(record, lat, lon) ;
P_msl:long_name = "pressure reduced to MSL" ;
P_msl:units = "Pa" ;
P_msl:_FillValue = -9999.f ;
P_msl:navigation = "nav" ;
float P_sfc(record, lat, lon) ;
P_sfc:long_name = "pressure at surface" ;
P_sfc:units = "Pa" ;
P_sfc:_FillValue = -9999.f ;
P_sfc:navigation = "nav" ;
float RH(record, level, lat, lon) ;
RH:long_name = "relative humidity" ;
RH:units = "percent" ;
RH:_FillValue = -9999.f ;
RH:navigation = "nav" ;
float T(record, level, lat, lon) ;
T:long_name = "temperature" ;
T:units = "degK" ;
T:_FillValue = -9999.f ;
T:navigation = "nav" ;
float T_maxwind(record, lat, lon) ;
T_maxwind:long_name = "temperature at maxwind" ;
T_maxwind:units = "degK" ;
T_maxwind:_FillValue = -9999.f ;
T_maxwind:navigation = "nav" ;
float T_trop(record, lat, lon) ;
T_trop:long_name = "temperature at tropopause" ;
T_trop:units = "degK" ;
T_trop:_FillValue = -9999.f ;
T_trop:navigation = "nav" ;
float T_sigma(record, sigma, lat, lon) ;
T_sigma:long_name = "temperature" ;
T_sigma:units = "degK" ;
T_sigma:_FillValue = -9999.f ;
T_sigma:navigation = "nav" ;
float Z(record, level, lat, lon) ;
Z:long_name = "geopotential height" ;
Z:units = "gp m" ;
Z:_FillValue = -9999.f ;
Z:navigation = "nav" ; // georeference info
float Z_maxwind(record, lat, lon) ;
Z_maxwind:long_name = "geopotential height at maxwind" ;
Z_maxwind:units = "gp m" ;
Z_maxwind:_FillValue = -9999.f ;
Z_maxwind:navigation = "nav" ;
float Z_trop(record, lat, lon) ;
Z_trop:long_name = "geopotential height at tropopause" ;
Z_trop:units = "gp m" ;
Z_trop:_FillValue = -9999.f ;
Z_trop:navigation = "nav" ;
float T_lpdg(record, lpdg, lat, lon) ;
T_lpdg:long_name = "temperature in boundary layer" ;
T_lpdg:units = "degK" ;
T_lpdg:_FillValue = -9999.f ;
T_lpdg:navigation = "nav" ;
float RH_lpdg(record, lpdg, lat, lon) ;
RH_lpdg:long_name = "relative humidity in boundary layer" ;
RH_lpdg:units = "percent" ;
RH_lpdg:_FillValue = -9999.f ;
RH_lpdg:navigation = "nav" ;
float u_lpdg(record, lpdg, lat, lon) ;
u_lpdg:long_name = "u-component of wind in boundary layer" ;
u_lpdg:units = "meters/second" ;
u_lpdg:_FillValue = -9999.f ;
u_lpdg:navigation = "nav" ;
float v_lpdg(record, lpdg, lat, lon) ;
v_lpdg:long_name = "v-component of wind in boundary layer" ;
v_lpdg:units = "meters/second" ;
v_lpdg:_FillValue = -9999.f ;
v_lpdg:navigation = "nav" ;
float u(record, level, lat, lon) ;
u:long_name = "u-component of wind" ;
u:units = "meters/second" ;
u:_FillValue = -9999.f ;
u:navigation = "nav" ;
float u_maxwind(record, lat, lon) ;
u_maxwind:long_name = "u-component of wind at max wind" ;
u_maxwind:units = "meters/second" ;
u_maxwind:_FillValue = -9999.f ;
u_maxwind:navigation = "nav" ;
float u_trop(record, lat, lon) ;
u_trop:long_name = "u-component of wind at tropopause" ;
u_trop:units = "meters/second" ;
u_trop:_FillValue = -9999.f ;
u_trop:navigation = "nav" ;
float v(record, level, lat, lon) ;
v:long_name = "v-component of wind" ;
v:units = "meters/second" ;
v:_FillValue = -9999.f ;
v:navigation = "nav" ;
float v_maxwind(record, lat, lon) ;
v_maxwind:long_name = "v-component of wind at max wind" ;
v_maxwind:units = "meters/second" ;
v_maxwind:_FillValue = -9999.f ;
v_maxwind:navigation = "nav" ;
float v_trop(record, lat, lon) ;
v_trop:long_name = "v-component of wind at tropopause" ;
v_trop:units = "meters/second" ;
v_trop:_FillValue = -9999.f ;
v_trop:navigation = "nav" ;
float u_fhg(record, fhg, lat, lon) ;
u_fhg:long_name = "u-component of wind at fixed height above
ground" ;
u_fhg:units = "meters/second" ;
u_fhg:_FillValue = -9999.f ;
u_fhg:navigation = "nav" ;
float v_fhg(record, fhg, lat, lon) ;
v_fhg:long_name = "v-component of wind at fixed height above
ground" ;
v_fhg:units = "meters/second" ;
v_fhg:_FillValue = -9999.f ;
v_fhg:navigation = "nav" ;
float RH_fhg(record, fhg, lat, lon) ;
RH_fhg:long_name = "relative humidity at fixed height above
ground" ;
RH_fhg:units = "percent" ;
RH_fhg:_FillValue = -9999.f ;
RH_fhg:navigation = "nav" ;
float T_fhg(record, fhg, lat, lon) ;
T_fhg:long_name = "temperature at fixed height above ground" ;
T_fhg:units = "degK" ;
T_fhg:_FillValue = -9999.f ;
T_fhg:navigation = "nav" ;
float PRECIP(record, lat, lon) ;
PRECIP:long_name = "total precipitation over accumulation
interval" ;
PRECIP:units = "kg/m2" ;
PRECIP:_FillValue = -9999.f ;
PRECIP:navigation = "nav" ;
float PRECIP_accum_times(record, accum) ;
PRECIP_accum_times:long_name = "precipitation accumulation
interval" ;
PRECIP_accum_times:units = "hours" ;
PRECIP_accum_times:_FillValue = -9999.f ;
float precip_cn(record, lat, lon) ;
precip_cn:long_name = "convective precipitation over
accumulation interval" ;
precip_cn:units = "kg/m2" ;
precip_cn:_FillValue = -9999.f ;
precip_cn:navigation = "nav" ;
float precip_cn_accum_times(record, accum) ;
precip_cn_accum_times:long_name = "convective precipitation
accumulation interval" ;
precip_cn_accum_times:units = "hours" ;
precip_cn_accum_times:_FillValue = -9999.f ;
float omega(record, level, lat, lon) ;
omega:long_name = "pressure vertical velocity" ;
omega:units = "Pa/s" ;
omega:_FillValue = -9999.f ;
omega:navigation = "nav" ; // georeference info
float absvor(record, level, lat, lon) ;
absvor:long_name = "absolute vorticity" ;
absvor:units = "1/s" ;
absvor:_FillValue = -9999.f ;
absvor:navigation = "nav" ;
// global attributes:
:history = "created by gribtonc from HRS broadcast" ;
:title = "NMC Global Product Set" ;
:Conventions = "NUWG" ;
:version = 0.0 ; // still just a draft
data:
level = 1000, 850, 700, 600, 500, 400, 300, 250, 200, 150, 100, 70 ;
lpdg_bot = 0 ;
lpdg_top = 30 ;
fhg = 2, 10 ;
sigma = 0.9950 ;
model_id = 77, 81, 96;
// Navigation
nav_model = "GRIB1" ;
grid_type_code = 0 ;
grid_type = "Latitude/Longitude" ;
grid_name = "Global 5.0 x 2.5 degree grid" ;
grid_center = 7 ; // NMC
grid_number = 255 ; // from expanding thinned grids
i_dim = "lon" ;
j_dim = "lat" ;
Ni = 73 ;
Nj = 73 ;
La1 = -90.0 ;
Lo1 = -30.0 ;
La2 = 90.0 ;
Lo2 = 240.0 ;
Di = 5.0 ;
Dj = 2.5 ;
ResCompFlag = 128 ;
lon = -30, -25, -20, -15, -10, -5, 0, 5, 10, 15, 20, 25,
30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85,
90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145,
150, 155, 160, 165, 170, 175, 180,-175,-170,-165,-160,-155,
-150,-145,-140,-135,-130,-125,-120,-115,-110,-105,-100, -95,
-90, -85, -80, -75, -70, -65, -60, -55, -50, -45, -40, -35, -30 ;
lat = -90.0,-87.5,-85.0,-82.5,-80.0,-77.5,-75.0,-72.5,
-70.0,-67.5,-65.0,-62.5,-60.0,-57.5,-55.0,-52.5,
-50.0,-47.5,-45.0,-42.5,-40.0,-37.5,-35.0,-32.5,
-30.0,-27.5,-25.0,-22.5,-20.0,-17.5,-15.0,-12.5,
-10.0, -7.5, -5.0, -2.5, 0.0, 2.5, 5.0, 7.5,
10.0, 12.5, 15.0, 17.5, 20.0, 22.5, 25.0, 27.5,
30.0, 32.5, 35.0, 37.5, 40.0, 42.5, 45.0, 47.5,
50.0, 52.5, 55.0, 57.5, 60.0, 62.5, 65.0, 67.5,
70.0, 72.5, 75.0, 77.5, 80.0, 82.5, 85.0, 87.5, 90.0 ;
}