The daily AAO index is constructed by projecting the daily (00Z) 700mb height anomalies poleward of 20°S onto the loading pattern of the AAO. Please note that year-round monthly mean anomaly data have been used to obtain the loading pattern of the AAO (Methodology). Since the AAO has the largest variability during the cold season, the loading pattern primarily captures characteristics of the cold season AAO pattern.
The daily AAO index is shown for the past 120 days. Each daily value has been standardized by the standard deviation of the monthly AAO index from 1979-2000.