[ncl-talk] plot spatial distribution of BELD3 data, NetCDF data online
Rick Brownrigg
brownrig at ucar.edu
Thu Feb 7 08:41:00 MST 2019
Hi Xiaoming,
Please let's keep this conversation on the ncl_talk, unless we really need
to take it offline.
Are you familiar with Proj4? Playing around with that, I tried:
$ proj +proj=lcc +lon_0=-90 +lat_0=40 +lat_1=30 +lat_2=60
-90 40 <---input
0.00 0.00 <----returned value
This is a specification for a lambert conformal projection, with parameters:
+lon_0=-90 longitude at center of projection
+lat_0=40 latitude at center of projection
+lat_1=30 1st standard parallel
+lat_2=60 2nd standard parallel
I enter the lon/lat pair -90 40 and get back 0 0 in units of meters, which
checks out as the center of the projection.
So, the inverse "de-projection" using the XORG/YORG values in your file
yields:
$ invproj +proj=lcc +lat_0=40 +lat_1=30 +lat_2=60 +lon_0=-90 -f "%.6f"
-1296000 -1404000 <---- input
-102.797916 26.266793 <---returned value
Which I can believe -102.7/26.2 is the lower-left corner of tile #9, just
eyeing the tilemap
That all said, I'm still not certain you are going to get good alignment
across your area-of-interest just by specifying LL/UR corners, due to the
distortion inherent to the lamber conformal. If you find that to be the
case, the "native grids" approach I mentioned previously may be required.
Hope that helps...
Rick
On Thu, Feb 7, 2019 at 7:48 AM Hu, Xiaoming <xhu at ou.edu> wrote:
> Rick
>
> Thanks for your reply, I think I agree with all your interpretation.
>
> I tried to plot Juniper for tile 9 in this map:
> https://www.cmascenter.org/sa-tools/documentation/4.2/html/smoke_bio_inputs.html
> using
> http://www.caps.ou.edu/micronet/temp/forJianPing/plot_xhu_BELD3_Juniper.ncl
> The data is at
> http://www.caps.ou.edu/micronet/temp/forJianPing/b3_a.tile9.nzero.ncf
>
> Based on my current technique, I need
> ; res at mpLeftCornerLatF = lat2d(0,0)
> ; res at mpLeftCornerLonF = lon2d(0,0)
> to plot accurately to match tile 9 in
> https://www.cmascenter.org/sa-tools/documentation/4.2/html/smoke_bio_inputs.html
>
> I wonder if you have a solution.
>
> I am ccing to Dennis if he'd like to give it a try.
>
> Thanks a lot
> Xiaoming
>
> On 2/7/19 8:32 AM, Rick Brownrigg wrote:
>
> Hi Xiaoming,
>
> Yes, NCL could interpret this -- in principle -- but not without more
> information. The data appear to be in a projected coordinate space. See
> the examples at
>
> http://ncl.ucar.edu/Applications/native.shtml
> <https://urldefense.proofpoint.com/v2/url?u=http-3A__ncl.ucar.edu_Applications_native.shtml&d=DwMFaQ&c=qKdtBuuu6dQK9MsRUVJ2DPXW6oayO8fu4TfEHS8sGNk&r=W32uvgk4VvmL2B6mi-37Lg&m=Rm0xpdrfxUY-YcoOdw7qGfGdEQxejDWnG_-7sJ75n0k&s=n80Mqz4HlpboRb4qhkfzNfZbPlcC7HtYajvc66OEtFA&e=>
>
> The precise cartographic projection parameters are not immediately evident
> from the metadata given above, although we can make some guesses (it would
> be better to know for certain!).
>
> These parameters:
> :XCENT = -90. ;
> :YCENT = 40. ;
> :XORIG = -1296000. ;
> :YORIG = -1404000. ;
> :XCELL = 1000. ;
> :YCELL = 1000. ;
>
> XCELL/YCELL affirm the data are at 1 1km spacing. The XCENT/YCENT and
> XORIG/YORIG give the correspondence between the projected and geographical
> spaces for the geographical location 90W/40N, a central location in North
> America.
>
> These parameters:
>
> :P_ALP = 30. ;
> :P_BET = 60. ;
> :P_GAM = -90. ;
>
> Looking at some of the maps at the EPA site you reference, these could
> very well be projection parameters for a Lambert Conformal projection, with
> P_ALP/P_BET being more commonly referred to as "standard parallels" and
> P_GAM being the "standard meridian". The values look quite right for North
> America, but again all of this is conjecture.
>
> Hope this helps...
> Rick
>
> On Thu, Feb 7, 2019 at 5:08 AM xiaoming Hu <yuanfangcan at hotmail.com>
> wrote:
>
>> I try to plot spatial distribution of BELD data from
>> https://www.epa.gov/air-emissions-modeling/biogenic-emissions-landuse-database-version-3-beld3
>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.epa.gov_air-2Demissions-2Dmodeling_biogenic-2Demissions-2Dlanduse-2Ddatabase-2Dversion-2D3-2Dbeld3&d=DwMFaQ&c=qKdtBuuu6dQK9MsRUVJ2DPXW6oayO8fu4TfEHS8sGNk&r=W32uvgk4VvmL2B6mi-37Lg&m=Rm0xpdrfxUY-YcoOdw7qGfGdEQxejDWnG_-7sJ75n0k&s=Ye9wZ_kUZae0pNvfQ_2QtXtPV5s87-kpy-5IXyYyuqM&e=>
>>
>> the NetCDF files don't provide latitude/longitude, only with information
>> of
>> :P_ALP = 30. ;
>> :P_BET = 60. ;
>> :P_GAM = -90. ;
>> :XCENT = -90. ;
>> :YCENT = 40. ;
>> :XORIG = -1296000. ;
>> :YORIG = -1404000. ;
>> :XCELL = 1000. ;
>> :YCELL = 1000. ;
>> :VGTYP = -9999 ;
>> :VGTOP = -9.e+36f ;
>> :VGLVLS = 0.f, 0.f ;
>> :GDNAM = "BELD3_TILE9 " ;
>>
>> It there anyway NCL could interpret this ?
>>
>> Thanks
>> Xiaoming
>>
>>
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>>
>
>
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