IDY25200: single-level "group3" 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-A (version APS0) IDY25200.group3.slv.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-A covers the Australian 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 of +48. This model is nested in the ACCESS-R 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:

IDY25200.group3.slv.YYYYMMDDHH.HHH.surface.grb or IDY25200.group3.slv.YYYYMMDDHH.HHH.surface.nc

where

YYYYMMDDHHBase-date of model run in UTC time. YYYY = year, MM = month, DD = day, HH = hour
HHHForecast 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]
0.110 by 0.110 95.000 to 169.690, 4.730 to -55.000 (680 x 544) 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 48 by 1

Parameters

Single-level fields

Par NetCDF var Steps Units Description
213.228 av_lwsfcdown All W m-2 Average downwards longwave radiation at the surface
214.228 av_swsfcdown All W m-2 Average downwards shortwave radiation at the surface
212.228 av_netlwsfc All W m-2 Average net longwave radiation at surface
211.228 av_netswsfc All W m-2 Average net shortwave radiation at surface
215.228 av_olr All W m-2 Average outgoing longwave radiation
221.228 av_lat_hflx All W m-2 Average surface latent heat flux
222.228 av_sens_hflx All W m-2 Average surface sensible heat flux
047.228 av_sfc_sw_dif All W m-2 Average surface shortwave diffuse radiation flux
115.228 av_sfc_sw_dir All W m-2 Average surface shortwave direct radiation flux

Explanation of steps column terms

AllParameter 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
213.228 av_lwsfcdown Time-averaged downward flux of longwave radiation at the ground or ocean surface. [W m-2]
214.228 av_swsfcdown Time-averaged downward flux of shortwave radiation at the ground or ocean surface. [W m-2]
212.228 av_netlwsfc Time-averaged net downward (total downward minus upward) radiative longwave flux at the surface (ground or ocean). [W m-2]
211.228 av_netswsfc Time-averaged net downward (total downward minus upward) radiative shortwave flux at the surface (ground or ocean). [W m-2]
215.228 av_olr Time-averaged longwave radiation flux leaving the top of the atmosphere. [W m-2]
221.228 av_lat_hflx Time-averaged latent heat flux at the surface (upward outgoing radiation values are positive). [W m-2]
222.228 av_sens_hflx Time-averaged sensible heat flux at the surface (upward outgoing radiation values are positive). [W m-2]
047.228 av_sfc_sw_dif Time-averaged downward diffuse shortwave radiation flux at the surface. [W m-2]
115.228 av_sfc_sw_dir Time-averaged downward direct shortwave radiation flux at the surface. [W m-2]

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.