Parameterization of Extremely Heterogeneous Land-Surface Processes

陆面是气候系统的一个重要组成部分，因为陆面过程影响着大气层、生物圈和岩石圈之间的能量、质量和动量的交换。在过去的几十年里，针对这些过程开展了许多国际研究计划和实地活动，并开发了许多陆面方案，这些方案现在是天气和气候模型的重要组成部分。虽然同质陆面过程现在已被很好地理解，但异质陆面过程仍有待阐明和充分参数化。我建议将地表分为三个非均质类别：均质(HC-I为非均质I类)、中度非均质(HC-II)和极不均质(HC-III)。本项目的重点是当聚集和动力效应都很显著时，HC-III陆面过程的参数化，例如复杂地形的陆面。我们计划开发一个新的HC-III陆面参数化方案，通过马赛克方法的组合，考虑静态非均质性，以及一个新的处理复杂地形上的空气动力转移，考虑动态非均质性。我们将在青藏高原东南部的一个凹凸不平的地区进行大气-陆面耦合大涡模拟，以产生与新方案比较的数据。然后，测试后的方案组件将被构建到社区土地模型中。该项目解决了一个非常具有挑战性的问题，其结果将与改进天气预报和气候预测密切相关。

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.