Extract data from GRIB/NetCDF for a specific location and time

Much of the data provided by the Copernicus Atmosphere Monitoring Service (CAMS), the Copernicus Climate Change Service (C3S), and by meteorological centres like ECMWF comes in GRIB or NetCDF format.

In this example we work with the  ERA5 dataset, hourly surface pressure (sp) for the month 2010-08, in GRIB and NetCDF format, as specified in this data retrieval script:

#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer
server = ECMWFDataServer()
server.retrieve({
    "class": "ea",
    "dataset": "era5",
    "date": "2010-08-01/to/2010-08-31",
    "expver": "1",
    "levtype": "sfc",
    "param": "134.128",
    "stream": "oper",
    "time": "00/to/23/by/1",
    "type": "an",
    # ----- For GRIB version, specify target file name ------
    "target": "e5-sp-201008xx.grib",
    # ----- For NetCDF version, specify grid, format and target file name ------
    "grid": "0.5/0.5",
    "format": "netcdf",
    "target": "e5-sp-201008xx.nc",
 })

This script retrives a GRIB file 'e5-sp-201008xx.grib' and a NetCDF file 'e5-sp-201008xx.nc'.

See also: How to download ERA5 data via the ECMWF Web API

Looking up data values in GRIB

We want to look up the surface pressure (sp) data value for 2010-08-05 00:00, at the model point closest to lon=7.36 lat=43.89.

Install ECMWF ecCodes, then look up the data value with the grib_ls command:

grib_ls -l 43.89,7.36,1 -w dataDate=20100805,dataTime=0000 -p shortName e5-sp-201008xx.grib

Output:

...
shortName    value 
sp          88510       
...
Input Point: latitude=43.89  longitude=7.36
Grid Point chosen #3 index=84109 latitude=43.98 longitude=7.50 distance=15.11 (Km)
...

Looking up data values in NetCDF

We want to look up the surface pressure (sp) data value for 2010-08-05 00:00, at the model point closest to lon=7.36 lat=43.89.

Install CDO, then look up the data value:

cdo -outputtab,lon,lat,date,time,value -selyear,2010 -selmonth,08 -selday,05 -seltime,00:00 -remapnn,lon=7.36_lat=43.89 e5-sp-201008xx.nc

Output:

#   lon    lat       date     time    value 
...
  7.36  43.89  2010-08-05 00:00:00  88360.6 
...

Notes

The results from the GRIB and NetCDF versions are slightly different, because the GRIB data is in the original grid and resolution, whil eteh NetCDF data was regridded interpolated

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