README for Mass_Balance_GIC structure

Dataset name:
Mass_Balance_GIC

Description:
Mass_Balance_GIC is a MATLAB structure containing regional glacier and ice cap (GIC) mass-balance time series derived from the mean of three GRACE/GRACE-FO mascon solutions: JPL, CSR and GSFC. The three mascon products were resampled to a common 0.5° × 0.5° latitude-longitude grid before regional integration.

The data are organized for 16 glacier regions. Each element of the structure corresponds to one glacier region.

Grid definition:
The global and regional grid is arranged as:

Latitude:
89.75 : -0.5 : -89.75

Longitude:
-179.75 : 0.5 : 179.75

Mask definition:
Regional masks were constructed from Randolph Glacier Inventory version 7.0 (RGI v7.0) outlines expanded by a 1° buffer. These buffered masks were used to reduce truncation of the spatially smoothed GRACE/GRACE-FO mascon signal over small or fragmented glacierized regions.

Time coverage:
The time series span April 2002 to October 2024 at monthly resolution. Missing GRACE/GRACE-FO months, including the inter-mission gap, are represented by NaN values.

Structure fields:

1. regions_RGI
   Description:
   Name or identifier of each RGI glacier region.
   
2. LatRange
   Description:
   Latitude range used for extracting each regional subset from the global 0.5° grid.
   Unit:
   degrees north.
   Ordering:
   Descending latitude order, consistent with the global grid.

3. LonRange
   Description:
   Longitude range used for extracting each regional subset from the global 0.5° grid.
   Unit:
   degrees east.
   Ordering:
   Longitudes are expressed in the range -179.75° to 179.75°.

4. mask_grids_1_degree_buffer
   Description:
   Regional glacier mask constructed from RGI v7.0 outlines with a 1° buffer.
   Content:
   Mask grid for each region on the common 0.5° × 0.5° grid.
   Notes:
   Grid cells inside the buffered glacier region are retained; cells outside the mask are excluded or set to NaN.

5. time_series_grids_cm
   Description:
   Masked gridded GRACE/GRACE-FO mass-anomaly time series for each glacier region.
   Unit:
   centimetres equivalent water height (cm EWH).
   Notes:
   This field contains the gridded time series after applying the regional glacier/buffer mask. Values outside the mask are NaN.

6. time_series_Gt
   Description:
   Regionally integrated GRACE/GRACE-FO glacier mass-anomaly time series.
   Unit:
   gigatonnes (Gt).
   Notes:
   This is the final regional mass-anomaly time series obtained by integrating the masked gridded fields over each glacier region.

Data source:
The mass-balance time series are based on the average of the JPL, CSR and GSFC GRACE/GRACE-FO mascon solutions. Each product was first processed onto the same 0.5° × 0.5° global grid and then averaged to reduce solution-specific noise and processing-centre dependence.

Units:
- time_series_grids_cm: cm equivalent water height
- time_series_Gt: Gt
- LatRange and LonRange: degrees

Missing values:
NaN values indicate grid cells outside the regional glacier/buffer mask or missing GRACE/GRACE-FO monthly observations.

Recommended use:
Use time_series_Gt for regional glacier mass-balance analyses, trend estimation and comparison among RGI regions. Use time_series_grids_cm for spatial diagnostics within each buffered glacier region. Use mask_grids_1_degree_buffer to identify the grid cells included in each regional integration.

Important notes:
1. The Greenland and Antarctic peripheral glacier regions were excluded where their GRACE/GRACE-FO signals could not be robustly separated from adjacent ice-sheet mass changes.
2. The 1° buffer was applied to reduce loss of spatially smoothed GRACE/GRACE-FO mascon signal near fragmented or small glacierized regions.