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Exploring Boundary-Layer Processes Over Complex Terrain: Insights and Implications

This article delves into the intricacies of the planetary boundary layer (PBL) and its behavior over complex terrain. We explore the effects of irregular landscape features on PBL structure, methods for observing these dynamics, and the insights provided by current models. Key topics include energy and mass exchanges, surface-layer flux measurements, and the roles of diverse ecosystems and urban environments. We also discuss outstanding challenges in PBL research and modeling, offering a comprehensive understanding of its fundamental processes and interactions.

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Exploring Boundary-Layer Processes Over Complex Terrain: Insights and Implications

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Presentation Transcript

  1. Observations and Models of Boundary-Layer Processes Over Complex Terrain • What is the planetary boundary layer (PBL)? • What are the effects of irregular terrain on the basic PBL structure? • How do we observe the PBL over complex terrain? • What do models tell us? • What is our current understanding of the PBL and what are the outstanding problems to be addressed?

  2. Modeling the PBL Over Complex TerrainIssues and Applications

  3. Planetary boundary layer 1 km Height (m) • Energy and mass exchanges at ground • ---interactions among soil science, hydrological cycles • (ground and air), ecosystems, and atmosphere. • Canopy • Terrain • Heterogeneous surfaces • Clouds/fog • Urban environment, air pollution

  4. Surface heterogeneity • Leaf stomatal control • Soil properties • Induced circulations • Internal boundary layer Internal boundary layer fully adjusted

  5. Convective Internal Boundary Layers

  6. Schematic diagrams of potential temperature profiles after changes in surface temperature (heat flux). (a) development of an advective inversion after a hot-cold transition (b) growth of a CIBL after a cold- Hot transition (c) structure of a CIBL at longer fetch. Kaimal & Finnigan, 1994

  7. Effects of Heterogeneity on Flux Measurement in the Surface Layer Horst and Weil (1994, JTECH) show via modeling studies how far upstream surface fluxes originate that are measured via eddy correlation from a tower in the SL. This is known as the flux “footprint.” This is an important issue in flux measurement over heterogeneous terrain.

  8. Note strong effect of stability on required fetch for flux measurement

  9. Homogeneous

  10. Heterogeneous l/zi ~ 9

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