Preferential formation of cumulus clouds over native vegetation in southwest Australia

In the GMS visible channel imagery for 3rd of January 1999, the approximately wedge shaped brighter region along the southwestern coast in Figure 1 is the agricultural region while the darker region to the east is the native vegetation area. At 0900 LST, 3 January 1999, some large scale clouds are observed near the northern boundary of the scene shown in Figure 1, over the native vegetation. However other regions are completely clear. By 1400 LST, fair weather cumulus is observed forming along the northern regions and also in the vicinity of the Bunny Fence, on the native vegetation side (Figure 2). In another hour (1500 LST) wide spread cumulus cloud formation is observed over the native vegetation with the western extend of the cloud field coinciding with the Bunny Fence (Figure 3). This phenomenon of enhanced cloud formation over native vegetation area is a visible signature of land use impacting atmospheric processes. Agriculture in southwest Australia is mainly on rain fed. Thus, observations of decreasing trend in rainfall and preferential cloud formation over native vegetation has motivated research into understanding the role of land use change on regional climate of this region. A series of field experiments, called the Bunny Fence Experiment (buFex), have examined the role of land use change on the preferential formation of clouds over native vegetation. These experiments did indeed find that the darker surface and increased surface roughness associated with native vegetation result in enhanced heat flux in to the atmosphere, increasing the possibility of formation of clouds, especially during summer time. Note that satellite images also show cloud patterns where increased vigor of cloud development is observed along the bunny fence (Figure 4) and occasionally during winter time clouds are found to form preferentially over the agricultural areas (Figure 5).