The role of land surface physics on land-atmosphere interactions and convective precipitation during the North American Monsoon season

Land surface processes are essential components of land-atmosphere interactions in regions of complex terrain and have the potential to affect convective rainfall formation. However, hydrologic processes in mountain regions are not well understood, and the superimposed impacts of topography, soil, and vegetation on land-atmosphere interactions have not been comprehensively quantified. In the North American Monsoon (NAM) region, the monsoon onset accompanied by dramatic vegetation greening adds spatial and temporal variability to local and regional ecohydrologic processes. The recently released WRF-Hydro modeling system has the capability of representing high-resolution hydrologic processes and land-atmosphere interactions. This fully coupled model system can be used to decipher complex interactions during the monsoon season and would provide valuable insight for the operational weather prediction. In this study, we present a detailed land surface model intercomparison between the offline WRF-Hydro and tRIBS, which has been applied to our study area and intensively verified against various datasets, including ground observations and remotely-sensed land surface products. The comparison will be conducted at two sub-basins within the Rio Sonora River system (~21000km2), including a mid-size basin (~90km2) and a large basin (~3800km2). The temporal and spatial patterns of hydrologic variables produced by the offline WRF-Hydro simulation with intermediate resolution (1km) and the high resolution (~100m) tRIBS simulation may be different, depending on the mean states of the two models. However, we expect to see consistent hydrologic response from the two models when fed with comparable inputs and meteorological forcings. Meanwhile, leaf-on and leaf-off simulations will be conducted with both models to inspect the impact of dynamic vegetation greening on ecohydrologic processes, in addition to terrain characteristics and soil properties. Once we have built our confidence in the offline land surface model, we will conduct fully-coupled simulations over the Rio Sonora River System to inspect the upscaled impact of land surface processes on mountain-valley circulation. Lastly, we will diagnose key variables and threshold values for the development of convective precipitation in mountainous regions.