From andrew.kren at noaa.gov Sat Jun 1 14:15:22 2024 From: andrew.kren at noaa.gov (Andrew Kren - NOAA Federal) Date: Sat, 1 Jun 2024 16:15:22 -0400 Subject: [ncl-talk] Converting a polar stereographic netcdf to lat/lon Message-ID: Hi there, I am not sure I am asking the right question, but here goes. I am reading noaa stage IV precipitation data, found here: https://water.noaa.gov/resources/downloads/precip/stageIV/2024/06/01/ The new data has been transformed to a polar stereographic grid. When I did an ncl_filedump on the netcdf file, the variables were x, y and not lat/lon. The x, y values are random positive/negative numbers, which I'm guessing is some non lat/lon projection. My question is, is there a way in NCL to convert this file so that the variables are in lat/lon coordinates? Or is this something I need to do outside ncl? Thanks for any help! -- Andrew Kren Meteorologist NOAA's National Weather Service Raleigh Forecast Office 1005 Capability Drive, Suite 300 Raleigh, North Carolina 27606 voice: 919-326-1035 mailto: andrew.kren at noaa.govhttp://www.weather.gov/rah -------------- next part -------------- An HTML attachment was scrubbed... URL: From meier-fleischer at dkrz.de Mon Jun 3 07:18:17 2024 From: meier-fleischer at dkrz.de (Karin Meier-Fleischer) Date: Mon, 3 Jun 2024 15:18:17 +0200 Subject: [ncl-talk] Converting a polar stereographic netcdf to lat/lon In-Reply-To: References: Message-ID: Hi Andrew, you can remap the data using gdal or cdo for instance. I prefer using cdo and in the following the way to do it with cdo is described. 1. get grid description from input file 2. change the units of x and y coordinate variable from 'Meter' to 'm' 3. generate the grid description file for the output data on regular lonlat grid for Puerto Rico area 4. remap the input file Sounds difficult but it isn't. 1. get the input file grid description cdo griddes nws_precip_wytd_20240601_pr.nc > gridfile.txt 2. edit the gridfile.txt and change Meter to m gridtype? = projection gridsize? = 42025 xsize???? = 205 ysize???? = 205 xname???? = x xlongname = "x coordinate of projection" xunits??? = "m" yname???? = y ylongname = "y coordinate of projection" yunits??? = "m" xfirst??? = 4943283.5160097 xinc????? = 4762.5 yfirst??? = -6236964.62846119 yinc????? = -4762.5 grid_mapping = crs grid_mapping_name = polar_stereographic straight_vertical_longitude_from_pole = -105. false_easting = 0. standard_parallel = 60. false_northing = 0. latitude_of_projection_origin = 90. earth_radius = 6367470. proj4 = "+proj=stere +lat_0=90 +lat_ts=60 +lon_0=-105 +x_0=0 +y_0=0 +a=6367470 +b=6367470 +units=m +no_defs" crs_wkt = 'PROJCS["NOAA_HRAP_Grid", GEOGCS["GCS_NOAA_HRAP",??????? DATUM["D_NOAA_HRAP", SPHEROID["Sphere",6367470,0.0]??????? ], PRIMEM["Greenwich",0.0], UNIT["Degree",0.0174532925199433]??? ], PROJECTION["Polar_Stereographic"], PARAMETER["false_easting",0.0], PARAMETER["false_northing",0.0], PARAMETER["central_meridian",-105.0], PARAMETER["latitude_of_origin",60.0],??? UNIT["meter",1.0]]' esri_pe_string = 'PROJCS["NOAA_HRAP_Grid", GEOGCS["GCS_NOAA_HRAP",??????? DATUM["D_NOAA_HRAP", SPHEROID["Sphere",6367470,0.0]??????? ], PRIMEM["Greenwich",0.0], UNIT["Degree",0.0174532925199433]??? ], PROJECTION["Stereographic_North_Pole"], PARAMETER["false_easting",0.0], PARAMETER["false_northing",0.0], PARAMETER["central_meridian",-105.0], PARAMETER["standard_parallel_1",60.0],??? UNIT["meter",1.0]]' 3. generate output grid descption file grid_lonlat.txt gridtype? = lonlat gridsize? = 31122 xsize???? = 182 ysize???? = 171 xname???? = lon xlongname = "longitude" xunits??? = "degrees_east" yname???? = lat ylongname = "latitude" yunits??? = "degrees_north" xfirst??? = -70.6 xinc????? = 0.05 yfirst??? = 13.78 yinc????? = 0.05 4. remap the data cdo -remapbil,grid_lonlat.txt -setgrid,gridfile.txt nws_precip_wytd_20240601_pr.nc outfile.nc Hope this will help you, Karin Am 01.06.24 um 22:15 schrieb Andrew Kren - NOAA Federal via ncl-talk: > Hi there, > > I am not sure I am asking the right question, but here goes. I am > reading noaa stage IV precipitation?data, found here: > https://water.noaa.gov/resources/downloads/precip/stageIV/2024/06/01/ > > The new data has been transformed to a polar stereographic grid. When > I did an ncl_filedump on the netcdf file, the variables were x, y and > not lat/lon. The x, y values are random positive/negative numbers, > which I'm guessing is some non lat/lon projection. My question is, is > there a way in NCL to convert this file so that the variables are in > lat/lon coordinates? Or is this something I need to do outside ncl? > > Thanks for any help! > > -- > Andrew Kren Meteorologist NOAA's National Weather Service Raleigh > Forecast Office 1005 Capability Drive, Suite 300 Raleigh, North > Carolina 27606 voice: 919-326-1035 mailto: > andrew.kren at noaa.govhttp://www.weather.gov/rah > > _______________________________________________ > ncl-talk mailing list > ncl-talk at mailman.ucar.edu > List instructions, subscriber options, unsubscribe: > https://mailman.ucar.edu/mailman/listinfo/ncl-talk -------------- next part -------------- An HTML attachment was scrubbed... URL: