ACCESS-PH: single-level "group2" 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 National Operations Centre (NOC). This document describes the content of the ACCESS-C PERTH (version APS3) IDY25403.APS3.group2.slv.YYYYMMDDHH.HHH.surface and IDY25423.APS3.group2.slv.YYYYMMDDHH.HHH.surface series of products.

For background information about ACCESS please refer to the top-level ACCESS NWP technical data documentation page.

If you require further information or assistance about ACCESS NWP products contact the Bureau's Real-time Data Services Section.

Model summary

ACCESS-C PERTH covers the Perth/Southwest WA domain, has a resolution of about 1.5 km and is run four times per day (00Z, 06Z, 12Z & 18Z basetimes) out to a forecast hour (HHH) of +36 (+42 for 18Z). This model is nested in the ACCESS-G model and consists of both an assimilation and forecast component.

NWP data filename convention

All NWP files in this product series have names that conform to the following convention:

IDY25403.APS3.group2.slv.YYYYMMDDHH.HHH.surface.grb2 or IDY25403.APS3.group2.slv.YYYYMMDDHH.HHH.surface.nc4 or

IDY25423.APS3.group2.slv.YYYYMMDDHH.HHH.surface.grb2 or IDY25423.APS3.group2.slv.YYYYMMDDHH.HHH.surface.nc4


YYYYMMDDHHBase-date of model run in UTC time. YYYY = year, MM = month, DD = day, HH = hour
HHHForecast hour. A HHH of 000 is the analysis time-step.

Horizontal grid geometries

[IDY code]
[Lon x Lat]
Domain limits
[W to E, S to N (Lon x Lat grid points)]
[NC Vars]
0.013 by 0.013 112.000 to 124.028, -37.000 to -26.970 (892 x 744) All
0.013 by 0.013 112.000 to 124.028, -37.000 to -26.970 (892 x 744) 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 to 36 by 1


The following fields are included in this product series. Note that the "G2 d.c.n" table column refers to a field's GRIB2 'discipline'.'parameterCategory'.'parameterNumber' metadata. For more information see GRIB2 format notes.

Single-level fields

G2 d.c.n NetCDF var Steps G2 Units NC Units Description
0.2.22 wndgust10m All m s-1 m s-1 10m wind gust
0.1.6 accum_evap All kg m-2 kg m-2 Accumulated evaporation from land soil surface
0.1.206 av_evap_sea 1... kg m-2 s-1 kg m-2 s-1 Average rate of evaporation over open sea
0.6.32 fog_fraction All Numeric 1 Fog fraction
0.6.5 hi_cld All % 1 High cloud cover
0.19.0 vis_precip All m m Horizontal visibility (incl precip)
0.6.3 low_cld All % 1 Low cloud cover
0.6.4 mid_cld All % 1 Middle cloud cover
0.3.18 abl_ht All m m Planetary boundary layer height
0.1.3 precwtr All kg m-2 kg m-2 Precipitable water
2.0.3 soil_mois All kg m-2 kg m-2 Soil moisture content in a layer

Explanation of steps column terms

AllParameter available at all time-steps
All but stepsParameter available at all time-steps except as specified
hhh...Parameter available from fhr onward

Notes on specific NWP file-formats

For technical notes about the GRIB2 encoding of ACCESS data, please refer to GRIB2 format notes. For technical notes about the NetCDF4 encoding of ACCESS data, please refer to NetCDF format notes.

Appendix A - Extended Field Descriptions

Extended description of single-level fields

G2 d.c.n NetCDF var Detailed description
0.2.22 wndgust10m Maximum three second wind speed (wind gust) at 10m above ground level. [m s-1]
0.1.6 accum_evap Accumulated evaporation from land soil surface. [kg m-2]
0.1.206 av_evap_sea Time-averaged rate of evaporation over open sea. [kg m-2 s-1]
0.6.32 fog_fraction Estimated fog fraction at 1.5m above ground level. Please note that this diagnostic has not be tuned for Australian conditions and does not include dynamic atmospheric particulate densities, which is an important part of the algorithm used to generate this field. At this stage this field is considered experimental and should be used with due caution. [1]
0.6.5 hi_cld High cloud cover, calculated under maximum overlap assumption between ICAO 500hPa and 150hPa levels (5574m and 13608m above mean sea level). [1]
0.19.0 vis_precip Estimated horizontal visibility at approximately 1.5m above ground level, including reduction due to precipitation. Calculated similarly to grib code 20.229. At this stage this field is considered experimental and should be used with due caution. [m]
0.6.3 low_cld Low cloud cover, calculated under maximum overlap assumption between ICAO 1000hPa and 800Pa levels (111m and 1949m above mean sea level). [1]
0.6.4 mid_cld Middle cloud cover, calculated under maximum overlap assumption between ICAO 800hPa and 500Pa levels (1949m and 5574m above mean sea level). [1]
0.3.18 abl_ht Height above ground level of the top of the planetary boundary layer (i.e. boundary layer depth). [m]
0.1.3 precwtr Total column precipitable water. [kg m-2]
2.0.3 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 1 (surface to 0.1m depth). [kg m-2]

Please note:

  • Fields in the above tables are listed in the same order as shown in the Parameters section of this document.
  • Units in the above table refer to NetCDF fields. In some cases the GRIB2 equivalent field has had values scaled/offset to convert to SI units for WMO GRIB2 compliance.
  • 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.
  • All accumulated fields are accumulated from the start of the model assimilation window. Hence any of these fields can be non-zero at the model base-time (which is a time-step at the center of the assimilation window).