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Subtropical and Polar Jet Streams

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9topics build on this

1,776prerequisites beneath it

Thermal Wind Balance and the Relationship Between Temperature and Wind Planetary Wind Circulation Cells and Their Drivers→→Storm Track Dynamics and Climate

Core Idea

Jet streams are narrow bands of strong westerly winds (~100+ m/s) at upper levels, located where the thermal wind is strongest. The subtropical jet marks the poleward edge of the Hadley cell and subtropical anticyclones (~30° lat), while the polar jet forms at the baroclinic zone between mid and polar latitudes (~60° lat). Polar jet variability drives mid-latitude weather patterns and storm tracks.

Explainer

From the thermal wind relationship, you know that when a horizontal temperature gradient exists in the atmosphere, the geostrophic wind must change with height — the wind shear is proportional to the temperature contrast. From planetary circulation cells, you know that Earth's atmosphere organizes into distinct latitudinal bands: the Hadley cell in the tropics, the Ferrel cell in the midlatitudes, and the Polar cell at high latitudes. Jet streams are the dramatic consequence of combining these two ideas — they form where the strongest temperature gradients meet the deepest atmosphere, concentrating kinetic energy into remarkably narrow ribbons of fast-moving air.

The subtropical jet stream sits near 30° latitude at roughly 10–12 km altitude, right at the poleward boundary of the Hadley cell. Here, air that rose at the equator and flowed poleward in the upper troposphere has been steadily deflected eastward by the Coriolis force. By the time it reaches the subtropics, it has accumulated so much eastward momentum that it forms a concentrated wind maximum — often reaching 50–70 m/s. The subtropical jet is relatively steady in position and strength because the Hadley cell itself is thermally direct and persistent. It is strongest in winter, when the equator-to-pole temperature gradient steepens.

The polar jet stream forms near 50–60° latitude where cold polar air masses collide with warmer midlatitude air — the polar front. This is where the temperature gradient is sharpest in the lower and middle troposphere, and the thermal wind equation dictates that the strongest wind shear and therefore the strongest upper-level winds will concentrate here. Unlike the relatively stable subtropical jet, the polar jet is wild and variable. It meanders in great sinuous waves called Rossby waves, dipping south to bring Arctic air into temperate regions (troughs) and bulging north to carry warm air poleward (ridges). These undulations are the steering mechanism for midlatitude weather — extratropical cyclones form and travel along the jet, and the position of the jet determines whether a given region experiences warmth or cold, drought or rain.

The polar jet's behavior has enormous practical consequences. When the jet is strong and relatively zonal (flowing mostly west to east), weather systems move briskly across the midlatitudes, and no single pattern persists for long. When the jet weakens and becomes highly meridional (large north-south undulations), weather patterns stall — a blocking ridge can park over a region for weeks, producing heat waves and drought, while an adjacent deep trough delivers persistent cold and flooding. The jet stream's position also matters for aviation: flying with a strong jet stream tail wind can cut hours off a transatlantic flight, while flying against it extends travel time significantly. Understanding where the jets are and how they are behaving is the starting point for nearly all midlatitude weather forecasting.

Practice Questions 5 questions

Prerequisite Chain

Understanding Zero → The Number Zero → Counting to Five → Counting to 10 → One-to-One Correspondence → Counting a Set of Objects Up to 20 → Cardinality: The Last Number Counted → Matching Numerals to Quantities → Subitizing Small Quantities → Addition Within 10 → Making 10 as an Addition Strategy → Addition Within 20 → Doubles and Near Doubles → Doubles Facts Within 10 → Near Doubles Facts Within 20 → Mental Math Strategies for Addition → Mental Math: Adding and Subtracting Tens → Addition Within 100 → Repeated Addition as Multiplication → Multiplication as Equal Groups → Multiplication: Arrays → Basic Multiplication Facts (0s, 1s, 2s, 5s, 10s) → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Multiplication and Division Fact Families → Relationship Between Multiplication and Division → Division Facts as Inverse of Multiplication → Remainders and Quotients in Division → Division Word Problems → Multi-Step Word Problems → Solving Multi-Step Word Problems → Multiplication Word Problems → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Integers and the Number Line → Comparing and Ordering Integers → Absolute Value → Adding Integers → Subtracting Integers → Multiplying Integers → Dividing Integers → Unit Rates → Proportions → Percent Concept → Converting Between Fractions, Decimals, and Percents → Operations with Rational Numbers → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Sine, Cosine, and Tangent Ratios → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Iterated Integrals and Fubini's Theorem → Double Integrals in Cartesian Coordinates → Double Integrals in Polar Coordinates → Double Integrals in Polar Coordinates → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Work and Circulation → Line Integrals of Scalar and Vector Functions → Fundamental Theorem for Line Integrals → Conservative Vector Fields → Conservative Vector Fields and Potential Functions → Curl and Divergence of Vector Fields → Curl and Divergence → Divergence Theorem → Electric Flux and Divergence Theorem → Gauss's Law: Integral Form and Meaning → Solving Problems with Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → Postulates of Special Relativity → Time Dilation → Length Contraction → Lorentz Transformation → Relativistic Velocity Addition → Relativistic Momentum and Energy → Mass-Energy Equivalence and E=mc² → Photons as Particles with Energy and Momentum → Planck-Einstein Relation: Energy and Frequency → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → The Measurement Problem → Interpretations of Quantum Mechanics → Postulates of Quantum Mechanics → Observables and Quantum Operators → Commutators and Commutation Relations → Quantum Angular Momentum → Quantum Mechanical Treatment of Hydrogen → Solving the Schrödinger Equation for Hydrogen Atom → Quantum Numbers → Electron Configuration → Periodic Trends → Covalent Bonding → Electronegativity and Bond Polarity → Ionic Bonding → Lewis Structures → VSEPR Theory and Molecular Geometry → Molecular Geometry and Electron Pair Geometry → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Acid-Base Chemistry → Weak Acid Ionization → Weak Base Ionization → Acid and Base Strength: Ka, Kb, and Ionization → Leaving Groups and Nucleofugality → SN2 Substitution Reactions → SN1 Substitution Reactions → E1 Elimination Reactions → Alcohols and Ethers: Structure, Properties, and Nomenclature → Reactions of Alcohols → Aldehydes and Ketones: Structure and Reactivity → Oxidation Reactions in Organic Chemistry → Oxidation of Alcohols to Aldehydes and Ketones → Aldehyde and Ketone Structure and Nomenclature → Nucleophilic Addition to Aldehydes and Ketones → Carboxylic Acids and Their Derivatives → IUPAC Nomenclature of Carbonyls and Carboxylic Acids → IUPAC Nomenclature of Alkenes → Electrophilic Addition to Alkenes → Aromaticity and Benzene → Hückel Molecular Orbital Theory → Electronic Spectroscopy and the Franck-Condon Principle → Selection Rules for Electronic Transitions → Selection Rules in Molecular Spectroscopy → Electronic Transitions and Excited State Behavior → Beer–Lambert Law and Optical Absorbance → Calibration Strategies: External Standards, Internal Standards, and Standard Addition → UV–Vis Spectrophotometry → Asteroid Composition and Spectroscopic Properties → Meteorites as Planetary Samples → Planetary Accretion Chronology and Radiometric Age Constraints → Thermal Evolution of Terrestrial Planets → Planetary Magnetic Field Generation → Planetary Magnetospheres and Solar Wind Interaction → Radiation Belt Dynamics and Trapped Particle Systems → Ring Particle Dynamics and Collisional Evolution → Atmospheric Dynamics on Exoplanets → Atmospheric Stability and Convective Dynamics → Convective Instability Indices and Stability Analysis → Thermodynamic Diagrams and Atmospheric Sounding Analysis → Scale Analysis of Atmospheric Equations → Geostrophic Balance and Ageostrophic Flow → Thermal Wind Balance and the Relationship Between Temperature and Wind → Zonal and Meridional Atmospheric Circulation → Planetary Wind Circulation Cells and Their Drivers → Subtropical and Polar Jet Streams

Longest path: 219 steps · 1776 total prerequisite topics

Prerequisites (2)

Thermal Wind Balance and the Relationship Between Temperature and Windhard Planetary Wind Circulation Cells and Their Driverssoft

Leads To (1)

Storm Track Dynamics and Climatesoft