###	GRACE observations of changes in Antarctic land ice mass relative to the 2002 average

###	Data accessed from https://grace.jpl.nasa.gov/data/get-data/jpl_global_mascons on 2026-03-06
    GRACE/GRACE-FO Monthly Mass Grids - Global mascons (JPL RL06.3_v04). https://grace.jpl.nasa.gov/data/get-data/jpl_global_mascons
    
##  Data description
    A multiband Geotiff with each band representing the annual change in Antarctic ice mass relative to the 2002 average (GRACE start), smoothed for visualisation and clipped to Antarctic land mask
     
###	Processing steps:

    1.  Download .nc file from https://grace.jpl.nasa.gov/data/get-data/jpl_global_mascons and store in cwd/input
    
    2.  Run 02_extract_tif.py from working directory (cwd):
        2a) Reads monthly liquid water equivalent thickness (lwe_thickness) values from cwd\.nc
        2b) Applies .nc internal land mask (land_mask) to retain only Antarctic land ice signals
        2c) Converts units from cm to metres water equivalent (m w.e.)
        2d) Crops dataset to latitudes south of 60°S
        2e) Calculates the mean 2002 baseline across all 2002 months and derives anomalies relative to this baseline
        2f) Aggregates anomalies into yearly rasters representing cumulative mass change since 2002
        2g) Reprojects to EPSG:3031, resamples to 5 km resolution for cleaner visualisation
        2h) Applies Gaussian smoothing (~100 km) for visualisation
        2i) Masks output to Antarctic land ice extent polygon in cwd\input
        2j) Writes a multiband Cloud Optimized GeoTIFF (COG) to cwd\output where each band represents annual mass change relative to 2002