[ncl-talk] problem with GPCP data grid
Dennis Shea
shea at ucar.edu
Sun Jan 27 19:45:41 MST 2019
The nlat and nlon are dimension names that refer to sizes.This is a
"standard grid" [ie: "rectilinear grid"]. In my opinion, this is a *poorly
structured netCDF file.*
--
%> ncdump -h gpcp_cdr_v23rB1_y2018_m08.nc
or
%> ncl_filedump gpcp_cdr_v23rB1_y2018_m08.nc
--
dimensions:
*nlat = 72*
*nlon = 144*
t*ime = 1*
...
float *time(time)*
float *latitude(nlat)*
float* longitude(nlon)*
float *precip(nlat,nlon)*
-------------------------------
What is really desired is
float *latitude(latitude)*
float* longitude(longitude)*
float *precip(latitude,longitude) *or, better
* precip(time,latitude,longitude) *
Variables structured like *latitude(latitude) are *called * "coordinate
variables
<https://www.unidata.ucar.edu/software/netcdf/workshops/2011/datamodels/NcCVars.html>".
*Please read.
-----------------------------
latitude = f->latitude ; latitude(nlat)
latitude!0 = "latitude" ; "nlat" ==> "latitude"
latitude&latitude= latitude ; assign coordinate latitude values
printVarSummary(latitude) ; latitude(latitude)
longitude = f->longitude ; longitude(nlon)
longitude!0 = "longitude" ; "nlon" ==> "longitude"
longitude&longitude= longitude ; assign coordinate longitude
values
printVarSummary(longitude) ; longitude(longitude)
precip = f->precip ; precip(nlat,nlon) ; (0,1)
precip!0 = "latitude" ; name dimensions
precip!1 = "longitude"
precip&latitude = latitude ; assign values to named dimension
precip&longitude = longitude
printVarSummary(precip)
On Sun, Jan 27, 2019 at 7:09 AM Barry Lynn <barry.h.lynn at gmail.com> wrote:
> Hello:
>
> I believe that this is a standard grid. Latitude(nlat) just means that
> the variable name is latitude and there are nlat points.
>
> It can be useful to use ncl and use PrintVarSummary after extracting the
> variable you want to look at from the file.
>
> For example:
>
> lon = a->longitude
>
> printVarSummary(lon)
>
> On Sun, Jan 27, 2019 at 3:39 PM victor <mashibo321 at 126.com> wrote:
>
>> I need some help with GPCP monthly data grid.
>> The grid of data seems unusual. When I do ncdump -h, it output like
>> below. I don't know how to deal with something like "latitude(nlat)"?
>> Should I need to regriding? What should I do if I want to reshape the
>> data to an usual one?
>> ...
>> variables:
>> float latitude(nlat) ;
>> latitude:long_name = "Latitude" ;
>> latitude:standard_name = "latitude" ;
>> latitude:units = "degrees_north" ;
>> latitude:valid_range = -90.f, 90.f ;
>> latitude:missing_value = -9999.f ;
>> latitude:bounds = "lat_bounds" ;
>> float longitude(nlon) ;
>> longitude:long_name = "Longitude" ;
>> longitude:standard_name = "longitude" ;
>> longitude:units = "degrees_east" ;
>> longitude:valid_range = 0.f, 360.f ;
>> longitude:missing_value = -9999.f ;
>> longitude:bounds = "lon_bounds" ;
>> float time(time) ;
>> time:long_name = "time" ;
>> time:standard_name = "time" ;
>> time:units = "days since 1970-01-01 00:00:00 0:00" ;
>> time:calendar = "julian" ;
>> time:axis = "T" ;
>> float lat_bounds(nlat, nv) ;
>> lat_bounds:units = "degrees_north" ;
>> lat_bounds:comment = "latitude values at the north and south
>> bounds of each pixel." ;
>> float lon_bounds(nlon, nv) ;
>> lon_bounds:units = "degrees_east" ;
>> lon_bounds:comment = "longitude values at the west and east
>> bounds of each pixel." ;
>> float time_bounds(nv, time) ;
>> time_bounds:units = "days since 1970-01-01 00:00:00 0:00" ;
>> time_bounds:comment = "time bounds for each time value" ;
>> float precip(nlat, nlon) ;
>> precip:long_name = "NOAA Climate Data Record (CDR) of Monthly
>> GPCP Satellite-Gauge Combined Precipitation" ;
>> precip:standard_name = "precipitation amount" ;
>> precip:units = "millimeters/day" ;
>> precip:coordinates = "longitude latitude time" ;
>> precip:valid_range = 0.f, 100.f ;
>> precip:cell_methods = "precip: mean" ;
>> precip:missing_value = -9999.f ;
>> float precip_error(nlat, nlon) ;
>> precip_error:long_name = "NOAA CDR of GPCP Satellite-Gauge
>> Combined Precipitation Error" ;
>> precip_error:units = "millimeters/day" ;
>> precip_error:coordinates = "longitude latitude" ;
>> precip_error:valid_range = 0.f, 100.f ;
>> precip_error:missing_value = -9999.f ;
>> ...
>>
>>
>>
>>
>>
>>
>> --
>> ------------------------------------------------------------------------
>> Shibo Ma(马世波)
>> Graduate Student
>> Department of Atmospheric and Oceanic Sciences
>> School of Physics, Peking University
>> No. 209 Chengfu Road, Beijing, China
>> Email: mashibo321 at 126.com
>> Tel : +86 18810507714
>> ------------------------------------------------------------------------
>>
>>
>>
>>
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk at ucar.edu
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>
>
> --
> Barry H. Lynn, Ph.D
> Senior Associate Scientist, Lecturer,
> The Institute of the Earth Science,
> The Hebrew University of Jerusalem,
> Givat Ram, Jerusalem 91904, Israel
> Tel: 972 547 231 170
> Fax: (972)-25662581
>
> C.E.O, Weather It Is, LTD
> Weather and Climate Focus
> http://weather-it-is.com
> Jerusalem, Israel
> Local: 02 930 9525
> Cell: 054 7 231 170
> Int-IS: x972 2 930 9525
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at ucar.edu
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20190127/f24ce72d/attachment.html>
More information about the ncl-talk
mailing list