I'm trying to access the data in a GRIB2 file at a specific longitude and latitude. I have been following along with this tutorial () approximately 2:52 but my GRIB file is formatted differently to the example and uses different variables
import xarray as xr import pygrib ds=xr.open_dataset('testdata.grb2', engine='cfgrib', filter_by_keys={'typeOfLevel': 'heightAboveGround', 'topLevel':2}) ds This prints:
<xarray.Dataset> Dimensions: (latitude: 361, longitude: 720) Coordinates: time datetime64[ns] ... step timedelta64[ns] ... heightAboveGround float64 ... * latitude (latitude) float64 90.0 89.5 89.0 ... -89.0 -89.5 -90.0 * longitude (longitude) float64 0.0 0.5 1.0 1.5 ... 358.5 359.0 359.5 valid_time datetime64[ns] ... Data variables: t2m (latitude, longitude) float32 ... sh2 (latitude, longitude) float32 ... r2 (latitude, longitude) float32 ... I then try to use imshow to index along the latitude and longitude (t2m?) dimension using:
t0_ds = ds.isel(t2m={200,200}) which gives this error:
ValueError: Dimensions {'t2m'} do not exist. Expected one or more of Frozen({'latitude': 361, 'longitude': 720}) Obviously there is an error in the way I'm using isel but I have tried many variations and I can't find much information about this particular error
1 Answer
You can access the closest datapoint to a specific latitude/longitude using:
lat = #yourlatitude lon = #yourlongitude ds_loc = ds.sel(latitude = lat, longitude = lon, method = 'nearest') isel is used to access point by index, ie:
ds_loc = ds.isel(latitude = 200) will return a subset along the 200th latitude value.
