"Coupling between the land and atmosphere: new insights from models and observations"

Strong coupling exists between the land surface and atmospheric boundary layer (ABL). Therefore, modeling and prediction of state variables at or near the land surface, such as temperature, humidity, or vegetation biomass, requires a full understanding of the state of the ABL. However, modeling the ABL is difficult because it is turbulent, and because surface fluxes are heterogeneous. Due to these difficulties, models often exhibit substantial biases at the land surface, precisely where predictions are most relevant to humanity. In this talk, I will present results from high-resolution simulations of an idealized ABL, which demonstrate that large-scale turbulent motions contribute significantly to turbulent fluxes at the land surface, contrary to existing theory used in climate model parameterizations. This demonstrates that the land surface and the ABL are more tightly coupled than previously thought. I will also present results using new soil moisture observations from NASA’s Soil Moisture Active Passive (SMAP) mission. I use these observations to globally map regions in which soil moisture-precipitation feedbacks can occur; and to estimate a key land-atmosphere coupling parameter used in climate models, related to water-limited evapotranspiration. I will discuss these results in the context of future challenges and opportunities for understanding land-atmosphere interactions. [Background readings: 1 2 3]