Assessing Climate Variability using Extreme Rainfall and Temperature Indices

Abstract

Future climate change is generally believed to lead to an increase in climate variability and in the frequency and intensity of extreme events. Extreme
climate events such as floods and dry spells have significant impacts on
society. As noted by the Bureau of Meteorology, Canada, to examine whether such extremes have changed over time a variety of extreme climate indices can be defined, such as the number of days per year which exceed, or fail to exceed, fixed thresholds. However, since people tend to adapt to their local climate, a threshold considered extreme in one part of Australia could be considered quite normal in another. To overcome this problem, thresholds based on percentile values have been defined by the Bureau of Meteorology, Canada. In this present study, three indices of extreme rainfall were examined: the number of events above an extreme threshold (extreme frequency); the average intensity of rainfall from extreme events
(extreme intensity); and the proportion of total rainfall from extreme events (extreme percent). The same exercise was repeated using daily temperature
values over the same time period. The aim was to assess whether the island
was already experiencing variability in its climate pattern, as such an information would be very useful for decision making.

Keywords: Climate change, Rainfall Variability, Extreme Rainfall Indices