4.13. MERSI-LL L1B Reader

The FY-3E MERSI-LL Level 1B reader operates on Level 1B (L1B) HDF5 files.

The files come in four varieties; band data and geolocation data, both at 250m and 1000m resolution. Files usually have the following naming scheme:

tf{start_time:%Y%j%H%M%S}.FY3E-X_MERSI_1000M_L1B.{ext}

This reader’s default resampling algorithm is ewa for Elliptical Weighted Averaging resampling. The --weight-delta-max parameter is set to 40 and the --weight-distance-max parameter is set to 1.

The frontend can be specified with the polar2grid.sh command using the mersi_ll_l1b frontend name. The MERSI-LL frontend provides the following products:

Product Name	Description	Central Wavelength (um)
1	Channel 1 Day/Night Radiance Band	0.709
2	Channel 2 Brightness Temperature Band	3.80
3	Channel 3 Brightness Temperature Band	4.05
4	Channel 4 Brightness Temperature Band	7.20
5	Channel 5 Brightness Temperature Band	8.55
6	Channel 6 Brightness Temperature Band	10.8
7	Channel 7 Brightness Temperature Band	12.0
histogram_dnb	Histogram Equalized DNB Band	N/A
adaptive_dnb	Adaptive Histogram Equalized DNB Band	N/A

4.13.1. Command Line Arguments

usage: polar2grid.sh -r mersi_ll_l1b -w <writer> [-h]

Examples:

$POLAR2GRID_HOME/bin/polar2grid.sh -r mersi_ll_l1b -w geotiff -h

polar2grid.sh -r mersi_ll_l1b -w geotiff --list-products -f tf2019259173245.FY3E-X_MERSI*.HDF

polar2grid.sh -r mersi_ll_l1b -w geotiff -p 1 2 3 4 6 7 -f tf2019233172521.FY3E-X_MERSI_0250M_L1B.HDF tf2019233172521.FY3E-X_MERSI_1000M_L1B.HDF tf2019233172521.FY3E-X_MERSI_GEOQK_L1B.HDF tf2019233172521.FY3E-X_MERSI_GEO1K_L1B.HDF

polar2grid.sh -r mersi_ll_l1b -w geotiff -p 1 2 -g lcc_fit -f ../mersi/tf2019259173245.FY3E-X_MERSI*.HDF

polar2grid.sh -r mersi_ll_l1b -w hdf5 -p 3 4 5 --grid-configs ${HOME}/my_grid.yaml -g shanghai seoul -f ../data/*.HDF

polar2grid.sh -r mersi_ll_l1b -w binary --sza-threshold=90  -p 1 -f tf2019226095418.FY3E-X_MERSI_*.HDF