The La Plata river basin in southern South America is a “hot-spot” for land-atmosphere interactions. The region has a strong positive feedback between soil moisture and precipitation, in part because most of the precipitation in this part of the world originates predominantly from continental evapotranspiration. However, changes in the land surface modify the surface fluxes of latent and sensible heat and can affect continental-scale precipitation by 1) changing the amount of moisture available for precipitation (moisture recycling) or by 2) modifying the thermal structure of the atmosphere, and consequently affecting the atmospheric circulation and resulting large-scale precipitation (thermodynamics/dynamics). However, it is unclear how land surface variability and change affect the hydroclimate of the LPRB region, or how the atmospheric response can be attributed to moisture recycling vs. thermodynamic/dynamic effects of the land surface on the atmosphere. In this work, we quantify these relative contributions using the Weather Research and Forecast (WRF) model with new water vapor tracing capabilities.
Results/Conclusions
Using the WRF with tracers, we quantify moisture recycling in the basin. The high spatial resolution of our simulations allows us to track the moisture sources for individual mesoscale convective systems which contribute to approximately 95% of the precipitation in the region. These events cannot be captured using coarse resolution models. Furthermore, our experimental design allows us to indirectly evaluate the thermodynamic/dynamic effects. We find that this new methodology allows us to untangle the complex eco-climate feedbacks at the continental scale.