Danielle C. Verdon

Long-term behaviour of ENSO: interactions with the PDO over the past 400 years inferred from paleoclimate records

This study uses proxy climate records derived from paleoclimate data to investigate the long-term behaviour of the Pacific Decadal Oscillation (PDO) and the El Nino Southern Oscillation (ENSO). During the past 400 years, climate shifts associated with changes in the PDO are shown to have occurred with a similar frequency to those documented in the 20th Century. Importantly, phase changes in the PDO have a propensity to coincide with changes in the relative frequency of ENSO events, where the positive phase of the PDO is associated with an enhanced frequency of El Nino events, while the negative phase is shown to be more favourable for the development of La Nina events.

Multi-decadal variability of forest fire risk - eastern Australia

This study investigates the influence that the El Nino/Southern Oscillation (ENSO) and the Inter-decadal Pacific Oscillation (IPO) have on long term daily weather conditions pertinent to high forest fire danger in New South Wales, Australia. Using historical meteorological data for 22 weather stations to compute the daily value of McArthur’s Forest Fire Danger Index (FFDI), it is shown that a strong relationship exists between climate variability, on a range of time scales, and forest fire risk. An investigation into the influence of ENSO on fire risk demonstrates that the proportion of days with a high, or greater than high, fire danger rating is markedly increased during El Nino episodes. More importantly, this study also shows that the already significantly enhanced fire danger associated with El Nino events was even further increased during El Nino events that occurred when the IPO was negative. The potential to use simple indices of climate variability to predict forest fire risk is therefore demonstrated to be significant.

Influence of Indian Ocean sea surface temperature variability on southwest Western Australian winter rainfall

[1] Southwest Western Australia (SWWA) has experienced a significant drop in winter rainfall during the past three decades, the cause of which is still subject to considerable speculation and debate. This prolonged drought has heavily impacted on water resources in the state, the predicted continuation of which is of major concern to the people of Western Australia. In this paper, the possible influence of sea surface temperature (SST) variability occurring over parts of the Indian Ocean on SWWA rainfall variability is explored. The results of our statistical analyses show that winter rainfall (May to October) in SWWA is lower in years when warm SSTs dominate the southern and tropical western Indian Ocean, compared to years when cool anomalies are present in the same region. In addition, a step change that can be detected in the SST anomalies in the southern and tropical western Indian Ocean occurring around 1970 happens to coincide with a similar sharp reduction in SWWA rainfall. It is suggested that the possible association between the Indian Ocean SST anomalies and observed variability of SWWA rainfall may be utilized, at a minimum, as possible diagnostic tools in the evaluation of global climate model outputs, in this way constraining the uncertainties in their predictions.