Python satellite swath data

Software requirements:

• Python 3

• numpy

• xarray

• matplotlib

• cartopy

Example script

satellite_swath_data.py

#!/usr/bin/env python
# coding: utf-8
'''
DKRZ example

EUMETSAT IASI swath data

Data
      Satellite swath data, 3-hourly

Variable
      BT_OBS - Observed brightness temperature

Content

- read satellite data
- create the plot
- save as PNG data

-------------------------------------------------------------------------------
2023 copyright DKRZ licensed under CC BY-NC-SA 4.0
               (https://creativecommons.org/licenses/by-nc-sa/4.0/deed.en)
-------------------------------------------------------------------------------
'''
import xarray as xr
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.cm as cm
import cartopy.crs as ccrs
import cartopy.feature as cfeature

def main():

    # Data path.
    infile = '../../data/IASI_004_200907170300-200907170600.nc'
    
    # Name of the output file.
    plotfile = "plot_IASI_EUMETSAT_original"
    
    # Select channel to be used.
    chan = 2
    
    # Read the data.
    ds = xr.open_dataset(infile)
    print(ds.BT_OBS)
    
    # Read the data of channel 2 of the BT_OBS variable.
    var = ds.BT_OBS[:,chan]
    print(var.values.min(), var.values.max())
    
    # Read the coordinates.
    lat = ds.LAT
    lon = ds.LON
    
    # Define value levels.
    levels = np.arange(220.,300.,2.)
    nlevels = levels.shape
    
    # Create the scatter plot
    plt.switch_backend('agg')

    projection = ccrs.PlateCarree()
    
    fig, ax = plt.subplots(figsize=(16,8), subplot_kw={"projection":projection})
    
    ax.set_global()
    ax.add_feature(cfeature.LAND, facecolor='wheat')
    ax.add_feature(cfeature.OCEAN, facecolor='white')
    ax.add_feature(cfeature.COASTLINE)
    ax.set_title('EUMETSAT IASI Observed brightness temperature',
                  fontsize=16,
                  fontweight='bold',
                  y=1.1)
    
    gl = ax.gridlines(xlocs=range(-180,181,15),
                      ylocs=range(-90,91,15),
                      color='gray',
                      linestyle='dotted',
                      draw_labels=True)
    
    plot = ax.scatter(x=lon.values, y=lat.values,
                      c=var.values,
                      s=0.1,
                      vmin=220.,
                      vmax=300.,
                      cmap='jet',
                      transform=ccrs.PlateCarree())
    
    cbar = plt.colorbar(plot, shrink=0.7)
    
    plt.savefig(plotfile, bbox_inches='tight', facecolor='white')
    

if __name__ == '__main__':
    main()

Plot result