IDY25403: single-level "mask" fields
A number of raw and post-processed NWP products are available as outputs from the Australian Community Climate Earth-System Simulator (ACCESS) suite of Numerical Weather Prediction models which are run routinely by the Bureau of Meteorology's National Meteorological & Oceanographic Centre (NMOC). This document describes the content of the ACCESS-C PERTH (version APS0) IDY25403.mask.surf.YYYYMMDDHH.HHH.surface series of products.
An overview of the scientific and technical details of the ACCESS models can be found in NMOC's Operations Bulletin 83 http://www.bom.gov.au/nwp/doc/bulletins/apob83.pdf
If you require further information or assistance about ACCESS NWP products contact the Bureau's Registered User Services section.
Model summary
ACCESS-C PERTH covers the Perth/Southwest WA domain, has a resolution of about 5 km and is run twice per day (00Z and 12Z basetimes) out to a forecast hour of +36. This model is nested in the ACCESS-R model and consists of only a forecast component.
NWP data filename convention
All NWP files in this product series have names that conform to the following convention:
IDY25403.mask.surf.YYYYMMDDHH.HHH.surface.grb or IDY25403.mask.surf.YYYYMMDDHH.HHH.surface.nc
where
| YYYYMMDDHH | Base-date of model run in UTC time. YYYY = year, MM = month, DD = day, HH = hour |
|---|---|
| HHH | Forecast hour. A FHR of 000 is the analysis time-step. |
Horizontal grid geometries
Resolution
[Lon x Lat]
|
Domain limits
[W to E, N to S (Lon x Lat grid points)]
|
GRIB parameters
[code.table]
|
|---|---|---|
| 0.050 by 0.050 | 112.000 to 119.950, -28.050 to -37.000 (160 x 180) | All |
Please note that
- Latitude values in GRIB and NetCDF files are ordered North to South while longitude values are ordered West to East.
- Longitudes always lie in the range 0.0 to 360.0 degrees. Longitudes can be transformed to lie between -180 and +180 degrees by subtracting 360 degrees from any longitude values greater than 180.
Time steps
- Forecast hours of single-level fields:
- 0
Parameters
Single-level fields
| Par | NetCDF var | Steps | Units | Description |
|---|---|---|---|---|
| 172.228 | lnd_mask | All | 0/1 | Land mask |
Explanation of steps column terms
| All | Parameter available at all time-steps |
|---|---|
| fhr... | Parameter available from fhr onward |
Appendix A - Notes on specific NWP file-formats
GRIB-1
ACCESS data in GRIB-1 format is defined relative to the Bureau's local GRIB tables. A copy of these tables in plain-text format is available for download from the ACCESS NWP web data interface.
Local extensions are also present in the GRIB-1 message headers. The following tables summarise these.
Section 1 octet Value Remarks 29-30 Stash ID 16-bit UM STASH ID. 31 4V offset Number of hours from start of 4V assimilation window to nominal analysis time. 19 P1 period of time Be aware that currently this is sometimes being set incorrectly for averaged, accumulated and max/min quantities (at certain timesteps only).
APS0 Model name GeneratingProcessIdentifier (ID of model) ACCESS-G 1 ACCESS-T 10 ACCESS-R 20 ACCESS-A 30 ACCESS-VT 50 ACCESS-SY 54 ACCESS-BN 58 ACCESS-AD 62 ACCESS-PH 66 ACCESS-TC 80 ACCESS-O3 90
NetCDF
- ACCESS NetCDF files aim to be broadly compliant with CF 1.4 conventions (http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html)
- NetCDF data is of the "classic format" variant (compatible with the unidata NetCDF library version 3.6.x+)
- Please ignore the accum_value metadata value. This parameter is not always set correctly for non-instantaneous fields.
- Longitudes in the NetCDF files lie in the range [0.0 degrees, 360.0 degrees]. The NetCDF files somewhat misleadingly describe the valid range attribute for this dimension as -180 to +360.
Appendix B - Extended Field Descriptions
Extended description of single-level fields
| Par | NetCDF var | Detailed description |
|---|---|---|
| 172.228 | lnd_mask | Land mask (takes the value 1 if any land is in the grid box, otherwise 0). [0/1] |
Please note:
- Fields in the above tables are listed in the same order as shown in the Parameters section of this document.
- The nature of fields can not always be deduced easily from their NetCDF variable names. It is always safest to refer to the detailed description of a parameter.