Land surface albedo and vegetation feedbacks enhanced the millennium drought in south-east Australia.

In this study, we have examined the ability of a regional climate model (RCM) to simulate the extended drought that occurred throughout the period of 2002 through 2007 in south-east Australia. In particular, the ability to reproduce the two drought peaks in 2002 and 2006 was investigated. Overall, the RCM was found to reproduce both the temporal and the spatial structure of the drought- related precipitation anomalies quite well, despite using climatological seasonal surface characteristics such as vegeta- tion fraction and albedo. This result concurs with previous studies that found that about two-thirds of the precipitation decline can be attributed to the El Niño–Southern Oscillation (ENSO). Simulation experiments that allowed the vegetation fraction and albedo to vary as observed illustrated that the intensity of the drought was underestimated by about 10 % when using climatological surface characteristics. These results suggest that in terms of drought development, capturing the feedbacks related to vegetation and albedo changes may be as important as capturing the soil moisture–precipitation feedback. In order to improve our modelling of multi-year droughts, the challenge is to capture all these related surface changes simultaneously, and provide a comprehensive description of land surface–precipitation feedback during the droughts development.

Figure 10. The bivariate joint probability distribution of the albedo change and precipitation change in the (a) 2002 drought (2002–2000) and (c) the 2006 drought (2006–2005). The change to this relationship caused by the addition of vegetation changes in the WRF_BOTH experiment is shown in (b) and (d), respectively.