[Met_help] [rt.rap.ucar.edu #59668] History for Point Stat: using NetCDF gridded forecast data
John Halley Gotway via RT
met_help at ucar.edu
Fri Jan 4 11:39:19 MST 2013
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Initial Request
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Hi there
I have a question regarding point_stat input format.
I know that for accumulated precipitation in grid_stat, I can make my NetCDF forecast files look like the PCP_Combine output and run it successfully. However, I was wondering if the same thing would work for point_stat when verifying non-accumulated variables (temperature, MSLP) in a netCDF forecast file against point observations (netCDF output produced by ascii2nc)? I am trying to decide whether to convert my forecasts to GRIB for point_stat, or whether I can just process the forecast netCDF files in a similar manner to what I've done for grid_stat accumulated precipitation.
I notice the User's Guide says that "The gridded model field to be verified must be in GRIB-1 format or in the NetCDF format that is output by the Pcp-Combine tool" so I wasn't sure if it would actually be possible for variables other than accumulated precipitation - thought I'd check before I went ahead with trying to convert it!
Thanks
Malcolm Nunn
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Complete Ticket History
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Subject: Re: [rt.rap.ucar.edu #59668] Point Stat: using NetCDF gridded forecast data
From: John Halley Gotway
Time: Wed Dec 19 12:34:34 2012
Malcolm,
Yes, that should work fine. However, the caveats when using NetCDF
files in point-stat are that the following 2 features won't work:
- It doesn't know the pressure for each forecast field, so you
won't be able to verify a range of pressure levels. Meaning, it won't
do vertical interpolation of forecast values to the pressure
level of the observation.
- It won't rotate wind fields from being grid-relative to earth-
relative, and it won't be able to derive wind speed from U and V
components.
But if you are simply comparing, for example, gridded 2-meter
temperature to point observations of 2-meter temperature, using NetCDF
should be fine.
Thanks,
John
On 12/18/2012 08:25 PM, Malcolm.Nunn at csiro.au via RT wrote:
>
> Tue Dec 18 20:25:13 2012: Request 59668 was acted upon.
> Transaction: Ticket created by Malcolm.Nunn at csiro.au
> Queue: met_help
> Subject: Point Stat: using NetCDF gridded forecast data
> Owner: Nobody
> Requestors: Malcolm.Nunn at csiro.au
> Status: new
> Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=59668 >
>
>
> Hi there
>
> I have a question regarding point_stat input format.
>
> I know that for accumulated precipitation in grid_stat, I can make
my NetCDF forecast files look like the PCP_Combine output and run it
successfully. However, I was wondering if the same thing would work
for point_stat when verifying non-accumulated variables (temperature,
MSLP) in a netCDF forecast file against point observations (netCDF
output produced by ascii2nc)? I am trying to decide whether to convert
my forecasts to GRIB for point_stat, or whether I can just process the
forecast netCDF files in a similar manner to what I've done for
grid_stat accumulated precipitation.
>
> I notice the User's Guide says that "The gridded model field to be
verified must be in GRIB-1 format or in the NetCDF format that is
output by the Pcp-Combine tool" so I wasn't sure if it would actually
be possible for variables other than accumulated precipitation -
thought I'd check before I went ahead with trying to convert it!
>
> Thanks
> Malcolm Nunn
>
------------------------------------------------
Subject: RE: [rt.rap.ucar.edu #59668] Point Stat: using NetCDF gridded forecast data
From: Malcolm.Nunn at csiro.au
Time: Wed Dec 19 15:32:06 2012
Thank you.
And the essential information that needs to be added to
the NetCDF files is just the grid information in the global
attributes?
Cheers
Malcolm
-----Original Message-----
From:
John Halley Gotway via RT [mailto:met_help at ucar.edu]
Sent: Thursday,
20 December 2012 6:35 AM
To: Nunn, Malcolm (CMAR, Aspendale)
Subject: Re: [rt.rap.ucar.edu #59668] Point Stat: using NetCDF gridded
forecast data
Malcolm,
Yes, that should work fine. However, the
caveats when using NetCDF files in point-stat are that the following 2
features won't work:
- It doesn't know the pressure for each
forecast field, so you won't be able to verify a range of pressure
levels. Meaning, it won't do vertical interpolation of forecast
values to the pressure level of the observation.
- It won't rotate
wind fields from being grid-relative to earth-relative, and it won't
be able to derive wind speed from U and V components.
But if you
are simply comparing, for example, gridded 2-meter temperature to
point observations of 2-meter temperature, using NetCDF should be
fine.
Thanks,
John
On 12/18/2012 08:25 PM,
Malcolm.Nunn at csiro.au via RT wrote:
>
> Tue Dec 18 20:25:13 2012:
Request 59668 was acted upon.
> Transaction: Ticket created by
Malcolm.Nunn at csiro.au
> Queue: met_help
> Subject:
Point Stat: using NetCDF gridded forecast data
> Owner:
Nobody
> Requestors: Malcolm.Nunn at csiro.au
> Status: new
> Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=59668
> >
>
>
>
Hi there
>
> I have a question regarding point_stat input format.
>
> I know that for accumulated precipitation in grid_stat, I can make
my NetCDF forecast files look like the PCP_Combine output and run it
successfully. However, I was wondering if the same thing would work
for point_stat when verifying non-accumulated variables (temperature,
MSLP) in a netCDF forecast file against point observations (netCDF
output produced by ascii2nc)? I am trying to decide whether to convert
my forecasts to GRIB for point_stat, or whether I can just process the
forecast netCDF files in a similar manner to what I've done for
grid_stat accumulated precipitation.
>
> I notice the User's Guide
says that "The gridded model field to be verified must be in GRIB-1
format or in the NetCDF format that is output by the Pcp-Combine tool"
so I wasn't sure if it would actually be possible for variables other
than accumulated precipitation - thought I'd check before I went ahead
with trying to convert it!
>
> Thanks
> Malcolm Nunn
>
------------------------------------------------
Subject: RE: [rt.rap.ucar.edu #59668] Point Stat: using NetCDF gridded forecast data
From: John Halley Gotway
Time: Wed Dec 19 15:51:34 2012
Malcolm,
I'm cutting-and-pasting info below from a similar MET-Help question
from
the past. The grid definition attributes depend on the type project
being
used.
Give it a shot and then try to use it in one of the MET tools. If you
get
an error, just send me the NetCDF file and I can tell you where the
issue
lies.
Thanks,
John
> netcdf ex_latlon {
> dimensions:
> lat = 60 ;
> lon = 120 ;
> variables:
> float lat(lat, lon) ;
> lat:long_name = "latitude" ;
> lat:units = "degrees_north" ;
> lat:standard_name = "latitude" ;
> float lon(lat, lon) ;
> lon:long_name = "longitude" ;
> lon:units = "degrees_east" ;
> lon:standard_name = "longitude" ;
> float APCP_01(lat, lon) ;
> APCP_01:name = "APCP_01" ;
> APCP_01:long_name = "Total precipitation" ;
> APCP_01:level = "A1" ;
> APCP_01:units = "kg/m^2" ;
> APCP_01:_FillValue = -9999.f ;
> APCP_01:init_time = "20050807_110000" ;
> APCP_01:init_time_ut = 1123412400 ;
> APCP_01:valid_time = "20050807_120000" ;
> APCP_01:valid_time_ut = 1123416000 ;
> APCP_01:accum_time = "010000" ;
> APCP_01:accum_time_sec = 3600 ;
>
> // global attributes:
> :FileOrigins = "File ex_latlon.nc generated
20120726_134701 UTC
on host rambler by the MET pcp_combine tool" ;
> :MET_version = "V4.0" ;
> :MET_tool = "pcp_combine" ;
> :RunCommand = "Addition: 1 files." ;
> :Projection = "LatLon" ;
> :lat_ll = "25.000000 degrees_north" ;
> :lon_ll = "-130.000000 degrees_east" ;
> :delta_lat = "0.500000 degrees" ;
> :delta_lon = "0.500000 degrees" ;
> :Nlat = "60 grid_points" ;
> :Nlon = "120 grid_points" ; }
>
> Here's what's required:
>
> - The dimensions should be named lat and lon.
> - The lat and lon variables are actually not used by MET, but it's
fine
if they're
present.
> - The variable attributes should contain the "name" and "level"
attributes. In this example "A1" means that this is precip
accumulated
over 1 hour.
> - The variable attributes should contain timing information:
init_time_ut,
valid_time_ut, and accum_time_sec for the initialization and valid
times in
unixtime (date +%s) and the accumulation interval as a number of
seconds.
> - The global attributes should contain "MET_version" so that MET
knows
how to
parse the projection information.
> - The global attributes for a lat/lon projection are: Projection,
lat_ll, lon_ll, delat_lat, delta_lon, Nlat, and Nlon (pretty
self-explanatory).
>
> Give that a shot and just let me know if you get stuck.
>
> <URL: https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=59668 >
>
> Thank you.
> And the essential information that needs to be added to the NetCDF
files
> is just the grid information in the global attributes?
>
> Cheers
> Malcolm
>
> -----Original Message-----
> From: John Halley Gotway via RT [mailto:met_help at ucar.edu]
> Sent: Thursday, 20 December 2012 6:35 AM
> To: Nunn, Malcolm (CMAR, Aspendale)
> Subject: Re: [rt.rap.ucar.edu #59668] Point Stat: using NetCDF
gridded
> forecast data
>
> Malcolm,
>
> Yes, that should work fine. However, the caveats when using NetCDF
files
> in point-stat are that the following 2 features won't work:
> - It doesn't know the pressure for each forecast field, so you
won't be
> able to verify a range of pressure levels. Meaning, it won't do
> vertical interpolation of forecast values to the pressure level of
the
> observation.
> - It won't rotate wind fields from being grid-relative to
> earth-relative, and it won't be able to derive wind speed from U and
V
> components.
>
> But if you are simply comparing, for example, gridded 2-meter
temperature
> to point observations of 2-meter temperature, using NetCDF should be
fine.
>
> Thanks,
> John
>
> On 12/18/2012 08:25 PM, Malcolm.Nunn at csiro.au via RT wrote:
>>
>> Tue Dec 18 20:25:13 2012: Request 59668 was acted upon.
>> Transaction: Ticket created by Malcolm.Nunn at csiro.au
>> Queue: met_help
>> Subject: Point Stat: using NetCDF gridded forecast data
>> Owner: Nobody
>> Requestors: Malcolm.Nunn at csiro.au
>> Status: new
>> Ticket <URL:
https://rt.rap.ucar.edu/rt/Ticket/Display.html?id=59668
>> >
>>
>>
>> Hi there
>>
>> I have a question regarding point_stat input format.
>>
>> I know that for accumulated precipitation in grid_stat, I can make
my
>> NetCDF forecast files look like the PCP_Combine output and run it
>> successfully. However, I was wondering if the same thing would work
for
>> point_stat when verifying non-accumulated variables (temperature,
MSLP)
>> in a netCDF forecast file against point observations (netCDF output
>> produced by ascii2nc)? I am trying to decide whether to convert my
>> forecasts to GRIB for point_stat, or whether I can just process the
>> forecast netCDF files in a similar manner to what I've done for
>> grid_stat accumulated precipitation.
>>
>> I notice the User's Guide says that "The gridded model field to be
>> verified must be in GRIB-1 format or in the NetCDF format that is
output
>> by the Pcp-Combine tool" so I wasn't sure if it would actually be
>> possible for variables other than accumulated precipitation -
thought
>> I'd check before I went ahead with trying to convert it!
>>
>> Thanks
>> Malcolm Nunn
>>
>
>
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