The Principal Investigator will study the role of mesoscale land-atmosphere interactions - both their control by large-scale meteorological conditions and their aggregate impact at large scales. The goal is to determine the impact of the scale interactions on warm season convective precipitation in the continental U.S. with a focus on links between soil moisture and rainfall. The underlying hypothesis is that nonlinear interactions between scales may be a source of important feedbacks that might help control the joint evolution of the land and atmosphere. The methodological approach is to use a state-of-the-art, high-resolution, coupled land-atmosphere modeling system to investigate the following primary research questions:
o How do precipitation systems driven by large-scale dynamics scale down to mesoscale heterogeneity in soil moisture and surface fluxes, and what is the evolution of this heterogeneity over monthly to seasonal timescales? o How does this evolving mesoscale surface heterogeneity scale up to influence convective clouds and precipitation at larger scales, and how important is the aggregate impact of these mesoscale effects over a larger-scale region? o Can we identify feedbacks between the large-scale and mesoscale processes? o How do these downscaling and upscaling processes and feedbacks vary intraseasonally, as a function of synoptic dynamical regime? o How do these downscaling and upscaling processes and feedbacks vary interannually, as a function of variations in hydrological regime (e.g., dry vs. wet years)?
The results of this investigation are expected to contribute to a more unified picture of land-atmosphere coupling across spatial scales from mesoscale to synoptic, and across timescales from hourly to seasonal. Improved understanding of the factors that control continental rainfall is crucial for applications such as managing water resources and planning for weather-related emergencies. Furthermore, estimating changes in regional climate and hydrology resulting from the combined influence of changing atmospheric composition and natural or anthropogenic land cover change will require improved representations of land-atmosphere interactions in models.
