[ncl-talk] lat,lon not accurately generated by NCL

[Craig Mattocks]

Hi Guoqing,

Here's the NCEP/WMO GRIB2 documentation:

http://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/

specifically Table 3.2 - Shape of the Reference System:

http://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table3-2.shtml

You are describing the difference between setting Section 3, Octet 15 to 0 (MM5/WRF) vs. 6 (NDFD grids).

You can modify specific octets in a grib2 file using wgrib2:

wgrib2 -set_byte 3 15 6 oldFile.grb2 -grib_out newFile.grb2

changes Section 3, Octet 15 to the value 6 (Earth assumed spherical, radius = 6,371,229.0 m).

Craig

> On Fri, 3 Aug 2018 11:26:17 -0600 Guoqing Ge - NOAA Affiliate <guoqing.ge at noaa.gov> wrote:
> 
> I still hope there is a direct option to easily set earth radius in NCL just as in WGRIB2.