IDY25400: 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 of Meteorology's National Meteorological & Oceanographic Centre (NMOC). This document describes the content of the ACCESS-C VICTAS (version APS0) IDY25400.group4.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-C VICTAS covers the Victoria/Tasmania 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:

IDY25400.group4.slv.YYYYMMDDHH.HHH.surface.grb or IDY25400.group4.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]
0.050 by 0.050 139.000 to 150.950, -34.050 to -46.000 (240 x 240) 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

Parameters

Single-level fields

Par NetCDF var Steps Units Description
143.228 accum_conv_prcp All kg m-2 Accumulative convective precipitation
239.228 accum_conv_snow All kg m-2 Accumulative convective snowfall
142.228 accum_ls_prcp All kg m-2 Accumulative large scale precipitation
240.228 accum_ls_snow All kg m-2 Accumulative large scale snowfall
202.228 av_mslp All Pa Average mean sea level pressure
234.228 av10v All m s-1 Average meridional wind at 10m
200.228 av_temp_scrn All K Average screen level air temperature
253.228 av_qsair_scrn All kg kg-1 Average screen level specific humidity
225.228 av_vwnd_strs All N m-2 Average surface meridional wind stress
224.228 av_uwnd_strs All N m-2 Average surface zonal wind stress
217.228 av_ttl_cld 3... 0-1 Average total cloud coverage
233.228 av10u All m s-1 Average zonal wind at 10m
087.128 canopy_wtr_cont All kg m-2 Canopy water content
089.128 conv_cldbse_pres 3... Pa Convective cloud-base pressure
090.128 conv_cldtop_pres 3... Pa Convective cloud-top pressure
126.228 fric_vel All m s-1 Friction velocity
172.228 lnd_mask All 0/1 Land mask
211.229 vis_prob All 0-1 Probability of horizontal visibility < 5km
109.128 z0 All m Roughness length
081.128 qsair_scrn All kg kg-1 Screen level specific humidity
140.128 soil_mois All kg m-2 Soil moisture content layer 1
171.128 soil_mois All kg m-2 Soil moisture content layer 2
184.128 soil_mois All kg m-2 Soil moisture content layer 3
237.128 soil_mois All kg m-2 Soil moisture content layer 4
139.128 soil_temp All K Soil temperature layer 1
170.128 soil_temp All K Soil temperature layer 2
183.128 soil_temp All K Soil temperature layer 3
236.128 soil_temp All K Soil temperature layer 4
147.128 lat_hflx All W m-2 Surface latent heat flux
181.128 vwnd_strs All N m-2 Surface meridional wind stress
134.128 sfc_pres All Pa Surface pressure
146.128 sens_hflx All W m-2 Surface sensible heat flux
180.128 uwnd_strs All N m-2 Surface zonal wind stress
156.228 topog All m Topography height

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
143.228 accum_conv_prcp Accumulated total convective rainfall amount at the surface. [kg m-2]
239.228 accum_conv_snow Accumulated total snow amount that falls to the surface. [kg m-2]
142.228 accum_ls_prcp Accumulated total large-scale rain amount at the surface. It does not include a convective contribution. [kg m-2]
240.228 accum_ls_snow Accumulated total large-scale snow amount that falls to the surface. It does not include a convective contribution. [kg m-2]
202.228 av_mslp Time-averaged atmospheric pressure at mean sea level. [Pa]
234.228 av10v Time-averaged meridional (V) component of the wind velocity at 10m above-ground-level. [m s-1]
200.228 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]
253.228 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]
225.228 av_vwnd_strs Time-averaged north-south (meridional) component of the surface stress. [N m-2]
224.228 av_uwnd_strs Time-averaged east-west (zonal) component of the surface stress. [N m-2]
217.228 av_ttl_cld Time-averaged total cloud coverage calculated with a maximum-random overlap assumption. [0-1]
233.228 av10u Time-averaged zonal (U) component of the wind velocity at 10m above- ground-level. [m s-1]
087.128 canopy_wtr_cont Quantity of water held in the canopy. [kg m-2]
089.128 conv_cldbse_pres Atmospheric pressure at the convective cloud base. [Pa]
090.128 conv_cldtop_pres Atmospheric pressure at the convective cloud top. [Pa]
126.228 fric_vel Friction velocity (a scalar measure of the magnitude of the surface stress). [m s-1]
172.228 lnd_mask Land mask (takes the value 1 if any land is in the grid box, otherwise 0). [0/1]
211.229 vis_prob Probability of horizontal visibility at approximately 1.5m above-ground- level being less than 5 km. 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. [0-1]
109.128 z0 Roughness length. [m]
081.128 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]
140.128 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 1 (surface to 0.1m depth). [kg m-2]
171.128 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 2 (0.10m to 0.25m depth). [kg m-2]
184.128 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 3 (0.25m to 0.65m depth). [kg m-2]
237.128 soil_mois Total (frozen and unfrozen) soil moisture content in soil layer 4 (0.65m to 2.00m depth). [kg m-2]
139.128 soil_temp Soil/land-ice temperature in soil layer 1 (surface to 0.1m depth). [K]
170.128 soil_temp Soil/land-ice temperature in soil layer 1 (0.10m to 0.25m depth). [K]
183.128 soil_temp Soil/land-ice temperature in soil layer 1 (0.25m to 0.65m depth). [K]
236.128 soil_temp Soil/land-ice temperature in soil layer 1 (0.65m to 2.00m depth). [K]
147.128 lat_hflx Latent heat flux at the surface (upward outgoing radiation values are positive). [W m-2]
181.128 vwnd_strs The north-south (meridional) component of the surface stress. [N m-2]
134.128 sfc_pres Atmospheric pressure at the surface. [Pa]
146.128 sens_hflx Surface sensible heat flux (upward outgoing radiation values are positive) [W m-2]
180.128 uwnd_strs The east-west (zonal) component of the surface stress. [N m-2]
156.228 topog Height of topography (above the geoid). [m]

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.
  • 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.