Trend analysis of drought using standard precipitation index (SPI) in Victoria, Australia

Trend analysis is conducted using nonparametric trend tests (Mann-Kendall and Spearman's rho) for five selected meteorological stations in Victoria. For the drought analysis, the Standardized Precipitation Index (SPI) was applied to 3 month and 12 month time scales using monthly mean precipitation data for the time series of over 60 years. The computed SPI values for both time scales showed statistically significant downward trend for all stations. To compare one time period to another, the series were then subdivided into two 33 year periods. For the 3 month basis, three out of five stations showed significant decreasing trends. In contrast, for the 12 month time scale, the results showed downward trends for all stations illustrating conditions becoming drier over the last thirty three years (1977-2010). These results could be associated with the consequences of climate change as it is postulated that droughts would become more common in the future.