A review and modelling results of the simulated response of deforestation on climate extremes in eastern Australia

摘要

The native vegetation cover in Australia has been modified extensively since the advent of European population. This was paralleled by increases in mean surface temperatures, decreases in mean rainfall and persistence of long-lasting and severe droughts, especially in eastern Australia. The purpose of this article is twofold: (1) to review the simulated response of deforestation on Australian droughts in light of the physics of land-surface processes, (2) to provide further analysis of the modelling results from the CSIRO Mark 3 Atmospheric Global Climate Model (AGCM) to quantify the changes in Australian droughts from the pre-European to modern-day land cover conditions. The simulated response for the austral summer for the modern-day period showed (1) a shift in the tails of the probability distribution functions of rainfall and temperature towards drier and warmer conditions, (2) a decrease in average rainfall between ～4-12%, (3) a reduction in average soil moisture by ～40%, (4) an increase dry spells by ～3-4 days, (5) a decrease in cumulative wet day rainfall between 10 and 25 mm day~(-1), (6) an increases in drought duration by ～6-12 consecutive days and an increase in drought severity by ～4-8%, (7) an average warming of ～0.4-3.6 ℃, and an increase in dry spells by ～6-9 days for the 1982/83 EI Nino event. These changes were statistically significant at the 95% confidence level using the non-parametric bootstrapping procedure. The simulated changes in atmospheric variables indicate that deforestation has been a contributing factor to the observed increases in drought severity and duration in eastern Australia.