17: Regional Winds
- Page ID
- 9644
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Each locale has a unique landscape that creates or modifies the wind. These local winds affect where we choose to live, how we build our buildings, what we can grow, and how we are able to travel. During synoptic high pressure (i.e., fair weather), some winds are generated locally by temperature differences. These gentle circulations include thermals, anabatic/katabatic winds, and sea breezes. During synoptically windy conditions, mountains can modify the winds. Examples are gap winds, boras, hydraulic jumps, foehns/chinooks, and mountain waves.
- 17.1: Wind Frequency
- This page examines wind-speed and direction frequencies, emphasizing their variability and analytical importance. It explains the Weibull distribution for mean wind speed estimation and introduces relative frequency for predicting wind patterns. The creation of wind roses for visualizing wind direction frequency is also discussed, particularly their aviation relevance for runway alignment.
- 17.2: Wind-Turbine Power Generation
- This page discusses wind turbine power generation, emphasizing the dependence on wind's kinetic energy, air mass, and wind speed. Theoretical power output is proportional to the cube of wind speed, with optimal efficiencies between 30% and 45%. Turbines are engineered for specific wind speed ranges, incorporating safety mechanisms for high winds. Betz's limit states maximum efficiency at around 59.
- 17.3: Thermally Driven Circulations
- This page covers various atmospheric circulation phenomena including thermals, anabatic winds, katabatic winds, and sea breezes. It explores how thermal updrafts arise from buoyancy and their mathematical relationships with temperature and pressure. Anabatic winds help gliders ascend, while katabatic winds descend due to temperature differences. Sea breezes are initiated by pressure variations between land and sea, affecting local weather and air quality.
- 17.4: Open-channel Hydraulics
- This page covers atmospheric layers with distinct temperature profiles and how they mimic water flows, applying hydraulic theory when compressibility is low. It introduces the Froude number to classify flow types—subcritical, critical, or supercritical—impacting wave speed and information travel in fluid dynamics.
- 17.5: Gap Winds
- This page covers cold air behavior in mountainous regions, particularly in winter, where it pools behind ranges and creates pressure differences leading to gap winds. It differentiates between short and long gap flows, discussing their dynamics and influences like temperature differences and valley geometry.
- 17.6: Coastally Trapped Low-level (Barrier) Jets
- This page discusses the Coriolis force and coastal mountain ranges' effects on low-level wind jets in the eastern Pacific. It explains the interaction of synoptic-scale low-pressure systems with mountains, creating stationary fronts and coastally trapped jets. These cold winds are shaped by pressure gradients and the Coriolis force, with specific jet core characteristics.
- 17.10: Downslope Winds
- This page examines winter downslope winds, particularly Bora and Foehn winds. Bora winds are cold, causing rapid descent and potential damage, resulting from strong upstream winds and mountain interactions. Foehn winds are warm and dry, emerging as air rises and cools on windward slopes, leading to precipitation, then warms and dries on the lee side.
- 17.11: Canopy Flows
- This page covers the dynamics of wind flows in forest and crop canopies, including measurement techniques for wind speed and calculation of parameters like displacement distance and roughness length. It also addresses the urban heat island effect, explaining how urban structures influence local wind patterns, temperatures, and cloud formation, particularly under light to moderate winds, leading to asymmetrical effects and the development of urban plumes.
- 17.12: Review
- This page covers the Weibull distribution for wind speed modeling and wind roses for wind direction representation. It explains how synoptic forcing influences local wind patterns, detailing both weak and strong scenarios, and highlights the characteristics of Bora and Foehn winds. Additionally, it examines how urban environments affect wind speed and temperature measurements, noting the alterations caused by urban structures and the urban-heat-island effect.
- 17.13: Homework Exercises
- This page provides a comprehensive exploration of meteorological concepts focusing on wind dynamics, including web-based activities and empirical investigations. It addresses problems related to atmospheric equilibrium, buoyancy, and temperature effects on wind patterns. The page also examines phenomena like mountain waves and Foehn winds, applying Bernoulli's equation and analyzing the impact of human activity on climate.
- 17.7: Mountain Waves
- This page covers mountain waves caused by stable air over hills, detailing wave types, effects on winds, and cloud formations like lenticular clouds, while introducing the Froude number for wave analysis. It also addresses wave drag and airflow stability. Additionally, it explains the calculation of a force component through motion equations, confirming a value of 3.5 x 10^-4 m·s^-1 and reinforcing the connection between this force and dynamics of motion.
- 17.8: Streamlines, Streaklines, and Trajectories
- This page explains streamlines, streaklines, and trajectories in flow dynamics. Streamlines indicate instantaneous flow directions and do not intersect, while streaklines arise from continuous tracer emissions and trajectories show the actual paths of air parcels. In stationary flow, all three coincide, but they differ in nonstationary flow due to factors like changing wind direction. Understanding these concepts is crucial for analyzing fluid movement across various scenarios.
- 17.9: Bernoulli's Equation
- This page covers fluid dynamics principles, including steady-state fluid flow and Bernoulli's equation, emphasizing energy conservation across different flow conditions. It explores the limitations of Bernoulli's equation in turbulent flows and the need for more comprehensive conservation equations. The text also addresses airflow dynamics at stagnation points, the effects of atmospheric pressure differences during severe weather, and the Venturi effect.