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Transport in the Atmosphere-Vegetation-Soil Continuum

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Contents

Preface

1 The Atmosphere-Vegetation-Soil System

1.1 Introduction

1.2 Conservation of Energy and Mass

1.2.1 Water Balance

1.2.2 Energy Balance

1.2.3 The Link: Evapotranspiration

1.2.4 Simplified Balances

Atmosphere

Soil

Vegetation

Integration

1.3 Modes of Transport of Energy and Mass

1.4 Setup of the Book

2 Available Energy: Net Radiation and Soil Heat Flux

2.1 Introduction

2.2 Net Radiation

2.2.1 Interaction between Radiation and the Atmosphere

Scattering

Absorption

2.2.2 Downwelling Shortwave Radiation

Extinction: General

Extinction: Scattering and Absorption

Impact of the Atmosphere on Radiation Reaching the Surface

Global Radiation

2.2.3 Reflected Shortwave Radiation

Bidirectional Reflectance Distribution Function

Albedo

2.2.4 Downwelling Longwave Radiation

2.2.5 Emitted (and Reflected) Longwave Radiation

2.2.6 Net Radiation: Sum of Components

2.2.7 Measurement of Net Radiation

2.3 Soil Heat Flux

2.3.1 Bare Soil

2.3.2 Heat Transport in Soils

2.3.3 Thermal Properties of Soils

2.3.4 Semi-infinite Homogeneous Soil with Sine-Wave at the Surface

Soil Temperature

Soil Heat Flux

2.3.5 Force-Restore Method

2.3.6 Vegetated Surfaces

2.3.7 Measurement of Soil Heat Flux

2.3.8 Snow and Ice

Snow Cover

Soil Freezing

2.4 Summary

3 Turbulent Transport in the Atmospheric Surface Layer

3.1 Introduction

3.2 Characteristics of Turbulent Diffusivities

3.3 Turbulence

3.3.1 Qualitative Description

3.3.2 Intermezzo: Conserved Quantities, Scalars and Vectors

3.3.3 Statistical Description of Turbulence

Reynolds Decomposition

Statistics of a Single Variable

Statistics of Two Variables

3.3.4 Buoyancy

3.3.5 Turbulent Kinetic Energy

3.4 Turbulent Transport

3.4.1 Mean Vertical Flux Density

3.4.2 Eddy-Covariance Method

3.4.3 The Atmospheric Surface-Layer and the Roughness Sublayer

3.5 Similarity Theory

3.5.1 Dimensionless Gradients: Relevant Variables in MOST

3.5.2 Physical Interpretation of z/L and Its Relationship to the Richardson Number

3.5.3 Similarity Relationships for Gradients

3.5.4 Gradients and Profiles Under Neutral Conditions

3.5.5 Gradients and Profiles Under Conditions Affected by Buoyancy

3.5.6 Similarity Theory: Final Remarks

Other Scalars and Other Turbulence Statistics

Stability Parameters

Experimental Determination of Similarity Relationships: Spurious Correlations

Zero-Plane Displacement

Limiting Cases of Stability

Deviations from MOST

Conclusion

3.6 Practical Applications of Similarity Relationships

3.6.1 Fluxes from Observations at Two Levels

3.6.2 Fluxes from Observations at a Single Level in the Air and One at the Surface

Roughness Length: Concept

Roughness Length and Displacement Height: Values

Determination of the Fluxes

3.6.3 Analytical Solutions for the Integrated Flux–Gradient Relationships

3.6.4 Feedback Between Stability and the Sensible Heat Flux for Stable Conditions

3.6.5 The Schmidt Paradox

3.7 Summary

4 Soil Water Flow

4.1 Introduction

4.2 Field Water Balance

4.3 Hydraulic Head

4.3.1 Hydraulic Head of Groundwater

4.3.2 Hydraulic Head of Soil Water

4.3.3 Hydraulic Head of Water Vapour

4.4 The Soil Water Characteristic

4.5 Darcy’s Law

4.5.1 Saturated Soil

4.5.2 Unsaturated Soil

4.6 Richards’ Equation for Water Flow in Variably Saturated Soils

4.7 Soil Hydraulic Functions

4.8 Infiltration

4.8.1 Horton Infiltration Model

4.8.2 Green–Ampt Infiltration Model

4.9 Capillary Rise

4.10 Measurement of Soil Water Pressure Head

4.10.1 Piezometer

4.10.2 Tensiometer

4.11 Measurement of Soil Water Content

4.11.1 Gravimetric and Volumetric Soil Water Content

4.11.2 Measurement by Oven Drying

4.11.3 Measurement by Time Domain Reflectrometry

4.12 Measurement of Hydraulic Conductivity

4.13 Measurement of Root Water Uptake

4.14 Summary

5 Solute Transport in Soil

5.1 Introduction

5.2 Solute Flux through Soil

5.3 Convection–Dispersion Equation

5.4 Transport of Inert, Nonadsorbing Solutes

5.5 Transport of Inert, Adsorbing Chemicals

5.6 Reactions of Chemicals in Soil

5.7 Salinization of Root Zones

5.8 Pesticide Pollution of Groundwater

5.9 Residence Time in Groundwater

5.10 Simulation of Solute Transport

5.11 Summary

6 Vegetation: Transport Processes Inside and Outside of Plants

6.1 Functions of Water in the Plant

6.2 Root Water Uptake

6.2.1 Functions of Roots

6.2.2 Structure of the Root Tip

6.2.3 Physiology of Root Water Uptake

6.2.4 Modelling of Root Water Uptake

Microscopic Models

Macroscopic Models

6.3 Water Flow within the Plant

6.4 Transpiration, Photosynthesis and Stomatal Control

6.4.1 Transpiration

6.4.2 Photosynthesis

6.4.3 Stomatal Behaviour

6.4.4 CO2 Exchange at the Ecosystem Level

6.5 Dry Matter Production

6.6 Microclimate

6.6.1 Radiation

Shortwave Radiation

Longwave Radiation

6.6.2 Air Temperature

6.6.3 Wind Speed

6.6.4 Leaf Temperature

6.6.5 Dew

6.7 Rainfall Interception

6.8 Summary

7 Combination Methods for Turbulent Fluxes

7.1 Bowen Ratio Method

7.1.1 Sensible and Latent Heat Flux

7.1.2 Trace Gases

7.2 Penman–Monteith Equation

7.2.1 Penman Derivation

7.2.2 Penman–Monteith Derivation

7.2.3 Canopy Resistance

7.2.4 Analysis of Evapotranspiration from Different Surface Types

7.3 Derived Evapotranspiration Models

7.3.1 Equilibrium Evaporation

7.3.2 Priestley–Taylor Equation

7.3.3 Makkink Equation

7.4 Dewfall

7.5 Summary

8 Integrated Applications

8.1 Crop Water Requirements

8.1.1 Definitions of Terms and Units

8.1.2 Factors Affecting Evapotranspiration

8.1.3 Crop Factor Method: General Structure

8.1.4 Crop Factor Method: Penman–Monteith Equation for Eref

Reference Evapotranspiration: A Hypothetical Crop

Single-Crop Coefficient

Dual Crop Coefficient

Extra Crop Coefficients for Nonstandard Conditions

8.1.5 Crop Factor Method: Makkink Equation for Eref

8.2 Evapotranspiration Measurement: Lysimeters

8.3 Water Productivity at Field and Regional Scale

8.3.1 Introduction

8.3.2 Sirsa District

8.3.3 Modelling Tools

8.3.4 Measurements

8.3.5 Yield Gap

8.3.6 Crop Yields at Field Scale

8.3.7 Water Productivity at a Regional Scale

8.3.8 Scenario Analysis

8.3.9 Satellite Data Assimilation

8.4 Response to Heat Wave Conditions of the Energy and Water Balance of Grassland and Forests

8.4.1 Data

8.4.2 Energy Balance during Normal Summers

8.4.3 Energy Balance during Heat Wave Conditions

8.4.4 Temporal Development of the Energy and Water Balance

9 Integrated Models in Hydrology and Meteorology

9.1 SWAP

9.1.1 Introduction

9.1.2 Soil Water Flow

9.1.3 Top Boundary Condition Hydrology

9.1.4 Bottom Boundary Condition Hydrology

9.1.5 Lateral Drainage

9.1.6 Solute Transport

9.1.7 Heat Flow

9.1.8 Crop Growth

9.2. The Land-Surface in Atmospheric Models

9.2.1 The Role of LSMs in Atmospheric Models

9.2.2 General Structure of a LSM

9.2.3 Modelling of Vegetation

LSMs Without Vegetation (First Generation)

LSMs with Empirical Stomatal Control (Second Generation)

LSMs Based on Plant Physiology (Third Generation)

LSMs with Adaptive Vegetation (Fourth Generation)

9.2.4 Canopy Resistance

Jarvis–Stewart Approach

A–gs Approach

9.2.5 Surface Heterogeneity

9.2.6 Coupling to the Atmosphere and the Soil

Coupling to the Atmosphere

Coupling to the Soil

9.2.7 The Role of Observations

Appendix A Radiation

A.1 Radiation Laws

A.2 Solar Radiation: Instantaneous

A.3 Solar Radiation: Daily Values

Appendix B Thermodynamics and Water Vapour

B.1 Some Basic Thermodynamics

B.2 Hydrostatic Equilibrium

B.3 Potential Temperature

B.4 Measures of Water Vapour Content

B.5. Latent Heat of Vaporization

Appendix C Dimensional Analysis

C.1 Choose Relevant Physical Quantities

C.2 Make Dimensionless Groups

C.3 Do an Experiment

C.4 Find the Relationship between Dimensionless Groups

Appendix D Microscopic Root Water Uptake

D.1 Mass Balance Equation

D.2 General Solution of Matric Flux Potential Differential Equation

Appendix E Crop Factors for Use with Makkink Reference Evapotranspiration

Answers

Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

Chapter 9

List of Main Symbols

References

Index