Assessing the hydroclimatic impacts of expanding a large inland lake in Australia

The radiative and thermal properties of the land surface are associated with its moisture content. It is necessary to advance our understanding about how changes in the exchange of water and energy fluxes between land and atmosphere shape the regional hydroclimate. This study employs the Community Earth System Model (CESM) with water tracer enabled to simulate atmospheric responses to a “wetter” Australia with inland water expanses (or hypothetical lakes) of different extents. Perturbations in land surface water lead to increased latent heat flux, ranging from 79.21 to 97.98 W/m 2 , which corresponds with significant surface cooling effects (e.g., an average decrease of 1.87 K in near surface air temperature). Results also show that the process of moisture recycling strengthens as more inland areas are “wet- ted” in model simulations. However, significant increases in precipitation are identified only in the simulation replacing the current land surface condition by a hypothetical lake covering one-third of the Australian continent. Wet- ting a relatively smaller extent of the dry inland would witness any resultant rainfall increases being balanced out by moisture divergence from surface cooling. On the contrary, wetting a significant portion of the land continuously changes large-scale circulation patterns, which may then modulate the moisture divergence induced by surface cooling and thus contribute to the precipitation increase. More efforts including, but not limited to, ensemble simulations would be needed to further validate the interactions between land and atmosphere revealed in this study. • Atmosphere responds differently to land surface perturbations of different scales. • Water tracers are used to quantify the changes in precipitation recycling. • Surface cooling by inland water can stabilize the atmosphere and suppress rainfall. • Inundating one-third of Australia would significantly increase regional rainfall. • Large-scale circulations may modulate moisture divergence to increase rainfall.