SEMINAR: Land use change suppresses precipitation

In the southwest of Western Australia, the large scale replacement of native perennial vegetation with agriculture based on winter growing annual species has lead to a significant change in the surface albedo and roughness. This has resulted in a diurnally averaged shortwave radiative forcing of approximately -7 W m-2 and a redistribution of the surface energy balance. These land use changes impact directly on cloud climatology, through preferential enhancement of cumulus cloudiness and cumulus cloud properties. Over the agricultural area, there is an enhanced production of atmospheric aerosols, leading to a higher number of cloud condensation nuclei, an increase in cloud droplet number, and a reduction in cloud droplet size. Though more water vapour was available over the agriculture land, the liquid water content was higher within the clouds over the natural vegetation, where the droplets are larger and more likely to precipitate.