Micrometeorology and Ecology

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1 Monique Y. Leclerc Thomas Foken Footprints in Micrometeorology and Ecology With Contributions by M. J. Savage and M. Gockede 4^1 Springer

2 1 History and Definition Micrometeorological Measurements Towards the Footprint Definition Footprint Modeling Validation of Footprint Models 12 References 15 2 Surface-Layer Properties and Parameterizations Atmospheric Boundary Layer and Scales Turbulence Parameterization Flux-Gradient Similarity Profile Functions Above the Canopy Profile Functions in the Canopy Roughness Sublayer Power Laws Dispersion Profiles Relevance of Profile Parameterizations in Footprint Models Internal Boundary Layers Mechanical Internal Boundary Layer Thermal Internal Boundary Layer Blending Height Concept Modeling Concepts Diffusion Model Lagrangian Higher-Order Model 52 Closure Model Large-Eddy Simulation Model Averaging Surface Characteristics Averaging Using Effective Parameters Flux-Averaging Models in Inhomogeneous Terrain 59 References 62 ix

3 X 3 Classification of Footprint Models Analytical Footprint Models The Schuepp et al. (1990) Approach The Schmid and Oke (1990) approach The Family of Horst and Weil's (1992) Analytical Solution Analytical Solutions Based on Lagrangian Models Lagrangian Simulations The Leclerc and Thurtell (1990) Approach The Sabelfeld-Rannik Approach The Kljun et al. (2002) 3D Backward Lagrangian Footprint Model Higher-Order Closure Footprint Models Large-Eddy Simulation Models Hybrid Footprint Models LES-Driven Lagrangian Stochastic Models LES-Embedded Lagrangian Stochastic Models: The Steinfeld et al. (2008) Approach Higher-Order Closure-Driven Lagrangian Simulation References 98 4 Footprint Studies Footprint in the Atmospheric Boundary Layer Tall Tower Footprints The Influence of Coriolis Forces on Footprint Flux Footprints in the Convective Boundary Layer Footprint in the Roughness Sub-Layer of Plant Canopies In-Canopy Footprints Flux Footprint in Canopy Over Hills Influence of Contrasting Adjoining Surfaces on Footprints Role of Contrasting Thermal Land Surfaces on Fluxes and Footprints Role of Clearcuts on Forest Fluxes/Footprints Footprints in the Presence of a Transition from the Forest Leading Edge Flux Footprints Over Complex Topography in Forests Emissions of Odor and Reactive Trace Gas Fluxes Using the Flux Footprint Method Footprints in Urban Areas 137 References 140

4 xi 5 Model Validation Model Validation Against Other Models Model Validation and Comparison Against Experimental Data Model Validation with Natural Tracers Classification of the Comparison Results 153 References Land Surface: Coupled Footprints Grid Schema of Surface Characteristics Determination of Surface Characteristics Roughness Length Remote-Sensing Data Coupling Footprint Results with Surface Information 169 References Application of Footprint Models to Different Measurement Techniques Profile Technique Profile Technique with Three and More Measuring Levels Profile Technique with Two Measuring Levels Accuracy and Footprint Issues for Profile Technique Eddy-Covariance Technique Basics of the Eddy-Covariance Method ID Eddy-Covariance Method Generalized Eddy-Covariance Method (3D) Quality Control of Eddy-Covariance Data Scintillometer Technique Airborne Measurement Technique 190 References Practical Applications of Footprint Techniques Selection of Flux Measurement Sites Interpretation of Flux Data Footprint Climatology Covering the Area of Interest Footprint-Dependent Data Quality Control Upscaling Point Measurements Using Footprint Models Additional Practical Application Air Pollution Application and Trace Gas Fluxes Wind-Energy Application 215

5 xii 8.5 Easily Applicable Footprint Models Limits of Footprint Application 218 References Looking Forward to the Next Generation of Footprint Models References 228 Glossary 231 About the Authors 235 Index 237

Footprint Modelling for Flux Towers

College of Science Swansea University Footprint Modelling for Flux Towers Natascha Kljun*, Eva van Gorsel *Email: n.kljun@swansea.ac.uk / Swansea University, UK Footprint Estimates wind Footprint Estimates