Monitoring the SAM
/The SAM has retreated into negative territory this week, although it is forecast to recover to neutral phase for the remainder of the month. Climatologists expect the SAM to become entrenched in positive phase through summer, in line with the La Nina signal. Until this occurs with some consistency, it is difficult for farmers in NSW and S Qld to get too optimistic with hopes for a fairytale wet La Niña summer.
Antarctic Oscillation or SAM values (20 Nov)
Recent research by Hendon et al, (2014) at the Centre for Australian Weather and Climate Research found the Southern Annular Mode to be the leading mode of circulation variability through parts of inland eastern Australia where cotton is grown; particularly in the spring planting period.
A positive SAM has been proven to increase moisture supply into fronts and troughs forming in eastern Australia. The chart provided by Climate Prediction Center (US) shows the most recent observations of the SAM or (AAO).
A negative SAM traditionally leads to a dry westerly circulation pattern through eastern Australian cropping areas.
BOM researchers Lim and Hendon (2013) found the SAM has the strongest connection with El-Niño Southern Oscillation in October and November – whereby the SAM is influenced most by El Niño or La Niña conditions.
Growers and advisors are encouraged to monitor the phases of the SAM together with seasonal forecasting, multi-week and short term weather models during planting. A short cartoon explaining the SAM can be found HERE.