ACCESS-G: single-level "group4" 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-G (version APS3) IDY25000.APS3.group4.slv.YYYYMMDDHH.HHH.surface and IDY25006.APS3.group4.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-G covers a global domain, has a resolution of about 12 km and is run four times per day (00Z, 06Z, 12Z & 18Z basetimes) out to a forecast hour (HHH) of +240 (+84 for 06Z and 18Z). This model 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:

IDY25000.APS3.group4.slv.YYYYMMDDHH.HHH.surface.grb2 or IDY25000.APS3.group4.slv.YYYYMMDDHH.HHH.surface.nc4 or

IDY25006.APS3.group4.slv.YYYYMMDDHH.HHH.surface.grb2

where

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

Variant
[IDY code]
Resolution
[Lon x Lat]
Domain limits
[W to E, S to N (Lon x Lat grid points)]
Parameters
[NC Vars]
IDY25000
 0.176 by 0.117 0.088 to 359.912, -89.941 to 89.941 (2048 x 1536) All
IDY25006
 0.176 by 0.117 64.951 to 184.482, -64.980 to 16.934 (681 x 700) 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 240 by 1

Parameters

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
0.1.48 accum_conv_rain All kg m-2 kg m-2 Accumulated convective rainfall
0.1.14 accum_conv_snow All kg m-2 kg m-2 Accumulated convective snowfall
0.1.47 accum_ls_rain All kg m-2 kg m-2 Accumulated large scale rainfall
0.1.15 accum_ls_snow All kg m-2 kg m-2 Accumulated large scale snowfall
0.3.1 av_mslp All Pa Pa Average mean sea level pressure
0.2.3 av10v All m s-1 m s-1 Average meridional wind at 10m
0.0.0 av_temp_scrn All K K Average screen level air temperature
0.1.0 av_qsair_scrn All kg kg-1 kg kg-1 Average screen level specific humidity
0.2.18 av_vwnd_strs All N m-2 N m-2 Average surface meridional wind stress
0.2.17 av_uwnd_strs All N m-2 N m-2 Average surface zonal wind stress
0.6.1 av_ttl_cld All % 1 Average total cloud coverage
0.2.2 av10u All m s-1 m s-1 Average zonal wind at 10m
2.0.13 canopy_wtr_cont All kg m-2 kg m-2 Canopy water content
0.3.0 conv_cldbse_pres All Pa Pa Convective cloud-base pressure
0.3.0 conv_cldtop_pres All Pa Pa Convective cloud-top pressure
2.0.0 lnd_mask All 1 1 Land mask
0.1.0 qsair_scrn All kg kg-1 kg kg-1 Screen level specific humidity
2.0.3 soil_mois All kg m-2 kg m-2 Soil moisture content in a layer
2.0.3 soil_mois All kg m-2 kg m-2 Soil moisture content layer 2
2.0.3 soil_mois All kg m-2 kg m-2 Soil moisture content layer 3
2.0.3 soil_mois All kg m-2 kg m-2 Soil moisture content layer 4
2.3.18 soil_temp All K K Soil temperature in a layer
2.3.18 soil_temp All K K Soil temperature layer 2
2.3.18 soil_temp All K K Soil temperature layer 3
2.3.18 soil_temp All K K Soil temperature layer 4
0.0.10 lat_hflx All W m-2 W m-2 Surface latent heat flux
0.2.18 vwnd_strs All N m-2 N m-2 Surface meridional wind stress
0.3.0 sfc_pres All Pa Pa Surface pressure
2.0.1 sfc_rough_len All m m Surface roughness length for momentum
0.0.11 sens_hflx All W m-2 W m-2 Surface sensible heat flux
0.2.17 uwnd_strs All N m-2 N m-2 Surface zonal wind stress
0.3.5 topog All gpm gpm Topography height above msl

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
0.1.48 accum_conv_rain Accumulated total convective rainfall amount at the surface. [kg m-2]
0.1.14 accum_conv_snow Accumulated total convective snow amount that falls to the surface. [kg m-2]
0.1.47 accum_ls_rain Accumulated total large-scale rain amount at the surface. It does not include a convective contribution. [kg m-2]
0.1.15 accum_ls_snow Accumulated total large-scale snow amount that falls to the surface. It does not include a convective contribution. [kg m-2]
0.3.1 av_mslp Time-averaged atmospheric pressure at mean sea level. [Pa]
0.2.3 av10v Time-averaged meridional (V) component of the wind velocity at 10m above ground level. [m s-1]
0.0.0 av_temp_scrn Time-averaged atmospheric temperature at 1.5m above ground level (screen level). Calculated by integrating the similarity equations from the surface to 1.5m. [K]
0.1.0 av_qsair_scrn Time-averaged atmospheric specific humidity at 1.5m above ground level (screen level). Calculated by integrating the similarity equations from the surface to 1.5m (surface value taken as saturated specific humidity at the surface temperature). [kg kg-1]
0.2.18 av_vwnd_strs Time-averaged north-south (meridional) component of the surface stress. [N m-2]
0.2.17 av_uwnd_strs Time-averaged east-west (zonal) component of the surface stress. [N m-2]
0.6.1 av_ttl_cld Time-averaged total cloud coverage calculated with a maximum-random overlap assumption. [1]
0.2.2 av10u Time-averaged zonal (U) component of the wind velocity at 10m above ground level. [m s-1]
2.0.13 canopy_wtr_cont Quantity of water held in the canopy. [kg m-2]
0.3.0 conv_cldbse_pres Atmospheric pressure at the convective cloud base. [Pa]
0.3.0 conv_cldtop_pres Atmospheric pressure at the convective cloud top. [Pa]
2.0.0 lnd_mask Land mask (takes the value 1 or -1 if any land is in the grid box, otherwise 0). [1]
0.1.0 qsair_scrn Atmospheric specific humidity at 1.5m above ground level (screen level). Calculated by integrating the similarity equations from the surface to 1.5m (surface value taken as saturated specific humidity at the surface temperature). [kg kg-1]
2.0.3 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 1 (surface to 0.1m depth). [kg m-2]
2.0.3 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 2 (0.10m to 0.35m depth). [kg m-2]
2.0.3 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 3 (0.35m to 1.00m depth). [kg m-2]
2.0.3 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 4 (1.00m to 3.00m depth). [kg m-2]
2.3.18 soil_temp Mean soil/land-ice temperature within soil layer 1 (surface to 0.1m depth). [K]
2.3.18 soil_temp Mean soil/land-ice temperature within soil layer 1 (0.10m to 0.35m depth). [K]
2.3.18 soil_temp Mean soil/land-ice temperature within soil layer 1 (0.35m to 1.00m depth). [K]
2.3.18 soil_temp Mean soil/land-ice temperature within soil layer 1 (1.00m to 3.00m depth). [K]
0.0.10 lat_hflx Latent heat flux at the surface (upward outgoing radiation values are positive). [W m-2]
0.2.18 vwnd_strs The north-south (meridional) component of the surface stress. [N m-2]
0.3.0 sfc_pres Atmospheric pressure at the surface. [Pa]
2.0.1 sfc_rough_len Surface roughness length for momentum in air. A constant of integration in the logarithmic wind profile. In this diagnostic, the effective roughness of subgrid model orography has been neglected. [m]
0.0.11 sens_hflx Surface sensible heat flux. This represents the exchange of heat between the surface and the air by motion of air; also called “turbulent” heat flux. [W m-2]
0.2.17 uwnd_strs The east-west (zonal) component of the surface stress. [N m-2]
0.3.5 topog Height of topography (above the geoid). [gpm]

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