APS3 NetCDF Data File Notes
The format of ACCESS NetCDF files has undergone significant changes with APS3. NetCDF files now contain much richer metadata that is intended to be broadly compliant with CF 1.6 conventions while maintaining backward compatibility with the APS2 format.
Richer Metadata
NetCDF field variables now include the following additional attributes:
| New Variable Attribute | Convention | Example Value |
|---|---|---|
| standard_name | CF-1.6 | air_pressure_at_sea_level |
| coordinates | CF-1.6 | forecast_reference_time |
| grid_mapping | CF-1.6 | latitude_longitude |
| cell_methods | CF-1.6 | time: mean |
| bounds (for coordinate vars) | CF-1.6 | time_bnds |
| coverage_content_type | ACDD-1.3 | modelResult |
| um_stash_source | N/A | m01s16i222 |
| marsParam | N/A | 228202 |
New supporting variables (e.g. "forecast_reference_time", "latitude_longitude", "time_bnds", "lat_bnds" etc) have also been added in accordance with the CF conventions.
The following global NetCDF attributes have been added:
| New Global Attribute | Convention | Example Value |
|---|---|---|
| title | CF-1.6 | ACCESS-Global Model Forecast |
| institution | CF-1.6 | Australian Bureau of Meteorology |
| summary | ACDD-1.3 | Global Numerical Weather Prediction Data |
| license | ACDD-1.3 | Bureau Express Licence |
| date_created | ACDD-1.3 | 2019-10-22T02:32:43 |
| standard_name_vocabulary | ACDD-1.3 | CF Standard Name Table v67 |
| stash_vocabulary | N/A | http://reference.metoffice.gov.uk/um/stash |
Other Changes
- The following NetCDF fields have been renamed or replaced:
| APS2 NetCDF Variable Name | Units | APS3 Name | Units | Change Note |
|---|---|---|---|---|
| accum_conv_prcp | kg m-2 | accum_conv_rain | kg m-2 | Renamed, field determined to be a rainfall quantity |
| accum_ls_prcp | kg m-2 | accum_ls_rain | kg m-2 | Renamed, field determined to be a rainfall quantity |
| accum_evap_sea | kg m-2 | av_evap_sea | kg m-2 s-1 | Replaced, accum_evap_sea field values were invalid |
| z0 | m | sfc_rough_len | m | Renamed/Replaced, see NWP Data Notes |
- The units of the "prob_vis_5km_ppt" field have been fixed from "m" to "1".
- Subsurface level-depth metadata values (i.e. values in the "soil_lvl" NetCDF variable) were found to be incorrect in APS2 and have been corrected in APS3 to the following: 0.1, 0.35, 1, 3 (m). An accompanying cell boundary variable (soil_lvl_bnds) has also been provided. The description of temperature on soil levels field(s) have also been clarified as representing an average layer temperature (now reflected also in the cell_methods = "soil_lvl: mean" metadata).
- Legacy "accum_value" variable attribute metadata values are now accurate but it is recommended users ignore this metadata and leverage CF compliant cell_methods and time bounds metadata instead.
- "missing_value" and "_FillValue" variable attributes are now only defined for fields that actually contain missing values.
- "valid_min" and "valid_max" variable attributes values better represent the actual min/max field value bounds.
- The 962.5hPa level value in the "lvl" variable in pressure-level files is no longer rounded to the nearest integer.