POAMA-2 (version M24) is the current operational seasonal prediction system run by Bureau operations. This system forms the basis for the Bureau operational El Niño forecasts and the monthly and seasonal climate outlook, as well as a range of other products. In addition, a suite of trial and research forecast products from this version are available on this web site.
POAMA-2 has several features that have led to significant improvements in skill on both multi-week and seasonal time scales. These include:
- A new state-of-the-art assimilation system for using ocean observations,
- A multi-model approach using three different configurations of the model (the 33-member ensemble is made up of 11 member ensembles from each model configuration),
- A new state-of-the-art ensemble generation method that generates coupled bred vectors to initialise the forecasts (unique to M24 version),
- Some products utilise a time-lagged ensemble to increase the ensemble size and in so doing provide more reliability.
Real-time forecasts from POAMA-2 are produced every week by running a 33 member ensemble starting at 00Z each Sunday and Thursday.
The real-time system is supported by a comprehensive set of hind-casts using exactly the same system as used for real-time forecasts. This hind-cast set is used to calibrate the real-time forecasts and assess the skill of the forecast system. These consist of a 33-member ensemble starting on the 1st, 6th, 11th, 16th, 21st and 26th of each month from 1981 to 2011.
Full details of POAMA-2 are provided in Hudson et al. 2013 (Monthly Weather Review; POAMA version P2M) and key features are summarised in the table below.
Table: The POAMA-2 system
|Atmospheric model||BAM (BMRC atmospheric model, version 3.0)
T47 horizontal resolution, 17 vertical levels
|Ocean model||ACOM2 (Australian Community Ocean Model, version 2.0)
Resolution: 2° in the zonal direction; in the meridional direction it is 0.5° at the equator and gradually increases to 1.5° near the poles. 25 vertical levels
|Atmosphere/land data assimilation||ALI (Atmosphere Land Initialisation Scheme; Hudson et al. 2011)|
|Ocean data assimilation||PEODAS (POAMA Ensemble Ocean Data Assimilation System; Yin et al. 2011)|
|Ensemble generation||33 ensemble members
Multi-model (3 atmospheric model versions, Hudson et al. 2013)
Ocean and atmosphere perturbations from a coupled breeding scheme (Hudson et al. 2013)
|Hindcast configuration||33 ensemble members generated on the 1st, 6th, 11th, 16th, 21st and 26th of the month out to 270 days (hindcast period used for calibration is 1981-2010)|
|Real-time configuration||33 ensemble members generated every Sunday and Thursday out to 270 days|