1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Scope of the Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Overview of Existing Literature . . . . . . . . . . . . . . . . . . . . . . . 3

1.3 History of Wind Energy Generation. . . . . . . . . . . . . . . . . . . . . 3

1.4 Potential of Wind Energy Generation. . . . . . . . . . . . . . . . . . . . 4

1.5 Present Status of Wind Energy Generation . . . . . . . . . . . . . . . . 5

1.6 Structure of This Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 Wind Regimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.1 Global Circulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Driving Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.1 Hydrostatic Equation . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.2.2 Momentum Budget Equations for the Wind . . . . . . . . . . 12

2.3 Geostrophic Winds and Gradient Winds. . . . . . . . . . . . . . . . . . 14

2.4 Thermal Winds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.5 Boundary Layer Winds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.6 Thunderstorm Gusts and Tornados. . . . . . . . . . . . . . . . . . . . . . 18

2.7 Air Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.8 Thermal stratification of the air

2.8.1 The geostrophic drag law

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3 Vertical Profiles Over Flat Terrain. . . . . . . . . . . . . . . . . . . . . . . . 23

3.1 Surface Layer (Prandtl Layer) . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.1.1 Logarithmic Wind Profile . . . . . . . . . . . . . . . . . . . . . . 28

3.1.2 Power Law. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.1.3 Comparison Between Logarithmic and Power Law . . . . . 33

3.1.4 Vertical Wind Profile with Large Wind Speeds . . . . . . . 40

3.2 Profile Laws Above the Surface Layer. . . . . . . . . . . . . . . . . . . 40

3.2.1 Ekman Layer Equations . . . . . . . . . . . . . . . . . . . . . . . . 41

3.2.2 Inertial Oscillations in the Ekman Layer . . . . . . . . . . . . 42

3.2.3 Vertical Wind Profiles in the Ekman Layer . . . . . . . . . . 42

3.2.4 Unified Description of the Wind Profile for the Boundary Layer . . . . 43

3.3 Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.4 Diurnal Variations of the Wind Profile . . . . . . . . . . . . . . . . . . . 50

3.4.1 Vertical Profiles of the Weibull Parameters . . . . . . . . . . 51

3.4.2 Low Level Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

3.5 Internal Boundary Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

3.6 Wind and Turbulence Profiles Over Forests . . . . . . . . . . . . . . . 61

3.7 Winds in Cities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

3.7.1 Characteristics of Urban Boundary Layers . . . . . . . . . . . 63

3.7.3 Special Flow Phenomena in Urban Canopy Layers . . . . . 67

3.8 Summary for Flat Terrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
About the Author:

Stefan Emeis is a meteorologist. He received his PhD at the University of Bonn, Germany in 1985 and his habilitation at the University of Karlsruhe, Germany in 1994. He is currently a senior scientist and research group leader at the Institute of Meteorology and Climate Research at the Karlsruhe Institute of Technology in Garmisch-Partenkirchen, Germany and adjunct professor of meteorology at the University of Cologne, Germany. His research interests are the structure and turbulence of the atmospheric boundary layers, surface-based remote sensing of the atmosphere, the meteorological prerequisites for the usage of wind energy and all aspects of climate change.

He is the editor-in-chief of the scientific journal "Meteorologische Zeitschrift" and (co)author of more than 80 scientific papers and of several books.