ACCESS-PH: Pressure (all-lvls) "pop-flds" 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.pop-flds.all-lvls.YYYYMMDDHH.HHH.pressure 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:



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

[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

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.

Vertical levels

Pressure-levels (hPa):
10, 20, 30, 50, 70, 100, 150 to 275 by 25, 300 to 750 by 50, 800 to 950 by 25, 962, 975, 985, 990, 995, 1000

Time steps

Forecast hours of multi-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.

Multi-level fields

G2 d.c.n NetCDF var Steps G2 Units NC Units Description
0.3.5 geop_ht All gpm gpm Geopotential height above msl
0.2.3 merid_wnd All m s-1 m s-1 Meridional wind
0.1.1 relhum All % % Relative humidity w.r.t. water
0.0.0 air_temp All K K Temperature
0.2.2 zonal_wnd All m s-1 m s-1 Zonal wind

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 multi-level fields

G2 d.c.n NetCDF var Detailed description
0.3.5 geop_ht Geopotential height of level (m above the geoid). [gpm]
0.2.3 merid_wnd Meridional (V) component of the wind velocity. [m s-1]
0.1.1 relhum Relative humidity. Calculated as 100*water_vapour_pressure/saturation_partial_pressure_of_water_vapour where the the saturation partial pressure of water vapour represents the saturation vapour pressure over liquid water for temperatures above the triple point, over ice for temperatures 20 degrees below the triple point, and a linear combination of the two for temperatures in-between. Values over 100% represent supersaturated conditions (typically in the upper troposphere where it is not uncommon to find atmospheric air to be supersaturated with respect to ice). [%]
0.0.0 air_temp Air temperature. [K]
0.2.2 zonal_wnd Zonal (U) component of the wind velocity. [m s-1]

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.
  • The geoid surface is at approximately mean sea level.