Scale dependent impact of dynamic vegetation heterogeneity on heat and moisture fluxes at the blending height

大气模式采用陆面模式和大气边界层(ABL)通量参数化之间的接口。通过表层方案，动量、热量和水汽通量在地面和最低大气模式层之间交换。在该方法中，引入了一个混合高度，其中非均匀陆地表面上的通量在网格尺度上被视为均匀的。在最低大气模式层内假定的这个高度，就会发生向ABL参数化的过渡。然而，对于非均匀植被上的允许对流(CP)模式模拟(网格尺度&lt；3公里)，低模式层可能低于混合高度，从而导致模拟通量的误差。大气模拟中的一个主要挑战是在不稳定、稳定和中性条件下，在不同风向平流的情况下，对非均匀动态植被和ABL之间的界面进行参数化。因此，我们的目标是根据植被异质性和状态以及大气框架条件来识别混合高度，并量化植被异质性对混合高度处能量通量的影响。这些结果将被用来在这一水平上得出具有代表性的、与尺度相关的通量，用于陆地-大气(L-A)反馈研究和湍流参数化。从CP到大尺度涡旋模拟的WRF-NoahMP-Gecros模式模拟将与Lafo和MOL-Rao站点的观测结果进行比较，以确定CP模拟的混合高度和有效植被粗糙度参数，这取决于大气框架条件。模拟将通过横切工作组(CCWG)-MME嵌入多模型实验(MME)。非均质性对L-A反馈强度的影响将被研究，并将促进对地面与大气之间以及大气边界层内交换过程的理解。这些模型结果和三维观测数据的协同作用将被用来研究动态植被异质性对混合高度能量通量的尺度依赖性影响。本项目涉及LAFI的主要目标2、3、4、S和E。它参加了CCWG-MME和CCWG-DL。模拟是与P6、P8和P9项目合作进行的。P2将为模型初始化提供叶面积指数和植被覆盖率。将使用来自P1-P5的拉菲观测数据进行模型评估。

Atmospheric models employ an interface between the land surface model and the atmospheric boundary layer (ABL) flux parameterization. Via a surface layer scheme, momentum, heat and moisture fluxes are exchanged between the surface and the lowest atmospheric model layer. In this approach a blending height is introduced where the surface fluxes above a heterogeneous land surface are considered as homogeneous at the grid scale. At this height assumed within the lowest atmospheric model layer, the transition to the ABL parameterization takes place. However, for convection permitting (CP) model simulations (grid scale < 3 km) over heterogeneous vegetation, the lower model layers can be below the blending height leading to errors in the simulated fluxes. A major challenge in atmospheric modelling is to parameterize the interface between heterogeneous dynamic vegetation and ABL in unstable, stable and neutral conditions with advection from different wind directions. Accordingly, our objectives are the identification of the blending height in dependence of vegetation heterogeneity and states and of atmospheric framing conditions and the quantification of the impact of vegetation heterogeneity on the energy fluxes at the blending height. The results will be used to derive representative, scale-dependent fluxes at this level for land-atmosphere (L-A) feedback studies and turbulence parameterizations. WRF-NoahMP-Gecros model simulations from the CP to large eddy simulation scales will be compared with observations at LAFO and MOL-RAO sites to identify the blending height and effective vegetation roughness parameters for CP simulations in dependence of atmospheric framing conditions. The simulations will be embedded in the Multi Model Experiment (MME) via the Cross Cutting Working Group (CCWG)-MME. The impact of heterogeneity on the strength of L-A feedback will be investigated and the understanding of exchange processes between the surface and the atmosphere as well as within the ABL will be advanced. The synergy of these model results and 3D observational data will be used to study the scale dependent impact of dynamic vegetation heterogeneity on energy fluxes at the blending height. This project addresses the LAFI main objectives 2, 3, 4, S and E. It participates in CCWG-MME and CCWG-DL. Simulations are performed in collaboration with the projects P6, P8 and P9. P2 will provide leaf area index and vegetation cover fractions for model initialization. LAFI observations from P1-P5 will be used for model evaluation.