Summary
The archive provides hindcasts on a 5km grid over Australia (the same grid as the AWAP data; Jones et al. 2009). The hindcasts have been calibrated using the quantile-quantile mapping approach (see appendix C for full details of the method). This calibration means that the hindcasts can be used to generate products or to drive applications tools directly without the need for any model bias correction.
Location
The archive can be accessed in two ways:
- Direct access for users with a login at the National Computing Infrastructure (NCI), location:
/g/data2/ub7/access-s1/hc/calibrated_5km_v3/
- Through an OPeNDAP data server, location: http://dapds00.nci.org.au/thredds/catalog/ub7/access-s1/hc/calibrated_5km_v3/catalog.html
Archive format
The data is NetCDF4 format. Each file contains the output for all gridpoints, for one ensemble member starting on a specified start date and for a specific variable (e.g. rainfall). Each file contains all the lead times available. For example a file with daily data will contain data each day through the full forecast (217 days), a monthly mean file will contain values each month throughout the forecast (7 months).
The location and name of each output file is as follows:
{location}/{system}/{var}/{period}/{ensemble}/{type}_{var}_{YYYYMMDD}_{ensemble}.nc
| Descriptor | Description | Options |
|---|---|---|
| system | The component of the model | atmos - atmospheric fields |
| var | variable | pr - rainfall
tasmin - minimum daily air surface air temperature tasmax - maximum daily air surface air temperature vprp_09 - 9am vapour pressure vprp_15 - 3pm vapour pressure wind_speed - surface wind speed rsds - incoming solar radiation evap - daily evaporation Full details of the variables is given in appendix A |
| period | The time averaging period of the data | daily - daily data
monthly - monthly average of the daily values |
| ensemble | Ensemble number | e01 ...e11 - ensembles 1 to 11
emn - ensemble mean |
| type | Describes the type of field
Derived from period and system |
da5 - daily mean atmospheric (containing values each day)
ma5 - monthly mean atmospheric (containing values each month) |
| YYYYMMDD | The start date of the hindcast | Hindcasts available are over the period 1990-2012 |
Note that the monthly rainfall is given as the average daily rainfall for the month, not the monthly rainfall.
Climatologies corresponding to each file are also available with the format:
{location}/{system}/{var}/{period}/clim_1990-2012/{type}_{var}_clim{MMDD}.nc
The climatology is the average of each hindcast for a given start day and month (e.g. 1st Jan) over the hindcast period (e.g. 1990-2012) and averaged across all 11 ensemble members. This climatology can be used to create anomalies by subtracting the climatology from the forecast.
The data is available on the AWAP data grid (see appendix B for full grid details).
Accessing the data
The data is available directly on the NCI infra-structure in NetCDF format. The data can also be accessed through the OPeNDAP server, which allows small sub-sets of the data to be accessed efficiently. The OPeNDAP server can be accessed directly using a range of tools including Python, R, Matlab. See here.
Appendix A: Variables available
Atmospheric Variables (including land surface)
| NetCDF name | Description | Units |
|---|---|---|
| pr | Daily rainfall | mm/day |
| tasmax | Maximum daily surface temperature | °C |
| tasmin | Minimum daily surface temperature | °C |
| rsds | Daily solar radiation | W/m2 |
| wind_speed | Daily average near surface wind speed | m/s |
| vprp_09 | 9am Surface vapour pressure | hPa |
| vprp_15 | 3pm Surface vapour pressure | hPa |
| evap | Daily evaporation | mm/day |
Appendix B: Spatial Grids
Domain covering Australia (44.5°S - 10°S ; 112°E - 156.25°E) on the AWAP analyses grid (Jones et al. 2009; http://www.bom.gov.au/jsp/awap/)
| Latitude: 691 | 0.05° | grid spacing Latitude of first grid box (centre) = 44.5°S |
| Longitude: 886 | 0.05° | grid spacing Longitude of first grid box (centre) = 112°E |
Appendix C: Method for quantile-quantile matching
This gives a brief outline of the method used to be referred to until a research paper is written.
The calibration of the hindcast data is carried out as follows:To calibrate the data for a given variable, location, leadtime, year
- create a training data set by using 22 of the 23 years (leave out the year of the data we wish to calibrate)
- extract an 11 day window of data around the leadtime (centred for all other than the first and last 5 days)
- for both the model hindcast data and the AWAP data
- order both the model (22years*11ens*11days) and the observations (23years*11days)
- work out where the data-to-calibrate lies within the model hindcast training data set
- eg 56.3%
- find the data at that same percentile (eg 56.3%) for the observations
If the data-to-calibrate is outside the model data training data (ie has a new maximum or minimum) then
we extrapolate using the following formula:
calibrated value = raw value * (observed max / model max)
or
calibrated value = raw value * (observed min / model min)