Parameterization of Extremely Heterogeneous Land-Surface Processes

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Land surface is a key component of the climate system, as land-surface processes influence the exchanges of energy, mass and momentum between the atmosphere, biosphere and lithosphere. Over the past decades, a number of international research programs and field campaigns have been carried out focusing on these processes, and numerous land-surface schemes have been developed, which are now an essential part of weather and climate models. While homogeneous land-surface processes are now fairly well understood, heterogeneous land-surface processes remain to be elucidated and adequately parameterized. I propose to divide land surfaces into the three heterogeneity categories: homogenous (HC-I for heterogeneity category I), moderate heterogeneous (HC-II) and extremely heterogeneous (HC-III) land surfaces. This project focuses on the parameterization of HC-III land-surface processes when both the aggregation and dynamic effect are significant, as exemplified by the land surface of a complex terrain. We plan to develop a new HC-III land-surface parameterization scheme via a combination of the mosaic approach, accounting for static heterogeneity, with a new treatment of aerodynamic transfer over complex terrains, accounting for dynamic heterogeneity. We will conduct atmosphere-and-land-surface coupled large-eddy simulation over a ragged site of the southeastern Tibetan Plateau to generate data for comparison with the new scheme. The tested scheme component will then build into the Community Land Model. This project tackles a very challenging problem and the outcomes will be of great relevance to improved weather prediction and climate projection.