Unit 6: Global Systems

• Relaxation? • Questions on the Reading and Reading Guide • Turn in Reading (GWS) and Writing (Wind) • Pick up Global Wind Systems Packet • Global Wind Systems: • Pressure Centers • Convection Loops • Wind Patterns • Global Wind Systems Writing Assignment Cyclone Anticyclone

Northern Hemisphere

Southern Hemisphere Connection between upper & lower atmosphere flow

• Cyclone - low pressure • Near surface, circulation creates convergence • As air converges it rises near center

• Rising air cools, H2Og condenses, & may precipitate L • Anticyclone – high pressure • Outward flow near surface creates divergence • Draws air flow from above towards surface at center • Sinking air warms adiabatically, clear skies

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Clouds

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Clear skies Worksheet Section 1: Cyclones and , Questions #1-3 Divergence at surface → Convergence above Convergence at surface → Divergence above Convection Loops (Single Cell Model)

Videos

• https://www.youtube.com/channel/UCylCbuzRsB92Gc1l8ru6VIg/sear ch?query=circulation Worksheet Section 2: Global Wind Belts, Questions # 4-9

Hadley Cell • Circulation cells between equator and sub-tropics • Air rises due to intense heating in vicinity of declination • Low pressure at surface over equator (ITCZ) • Air pushes toward poles, deflected by coriolis • ~ 30°N & S air in upper atmosphere cools & sinks to surface • Sinking air → Subtropical high pressure belt Hadley Cell • Air returns to ITCZ through Trade • Trades deflected by • NE trades in northern hemisphere, • SE trades in southern hemisphere

Ferrel Cell (Midlatitudes)

• Subtropical highs lead to ~westerly winds at surface in midlatitudes • Polar lows around 60 degrees create another band of convergence, clouds, and precipitation • Polar jet stream: more ~westerly winds aloft around 60 degrees latitude • Coriolis force turns diverging air → westerly wind • 30-60° N & S – Mid-latitude • Weather systems move generally west-to-east

Polar Cell

• Another convergence band of low pressures (like ITCZ) around 60 degrees N and S • In upper atmosphere, winds continue poleward • Air subsides (descends to surface) in high-pressure areas near the poles • As surface air returns southward, it is deflected by Coriolis, causing Ferrel Cell Polar Cell

Key surface features: STH’s, , and ’s Mechanism Creating Polar Jet • Jet stream centered over polar front • Steep gradient in temperatures, and therefore, large PGF!

Hadley Cell Leads to…

• ITCZ/Doldrums/Equatorial Trough: zone of rising air, deep convection, intense precipitation • Subtropical Jet Stream: ~westerly winds aloft at strongest pressure gradient • Subtropical Highs: 2-4 (semi- )persistent cells that intensify and grow in summer • : (N/S)easterly winds at surface Ferrel Cell Leads to… • Midlatitude Westerlies • Convergence at Polar Front • Polar Jet Stream

Polar Cell Leads to… • Polar High Pressure Areas beyond 80 degrees latitude • Polar Easterlies Effects of High Pressure Centers over Oceans High Pressure Cells Around the U.S.

Hawaiian Bermuda High or High or Pacific High January Pressure Averages

Find on map: • ITCZ • Bermuda High • Hawaiian High • • • SH Subtropical Highs • SH Polar Front July Pressure Averages

Find on map: • ITCZ • Bermuda High • Hawaiian High • NH Subpolar Lows • SH Subtropical Highs • SH Polar Front Polar Highs

Subpolar Lows (Polar Front)

Subtropical Highs

Equatorial Lows (ITCZ)

Subtropical Highs

Subpolar Lows (Polar Front)

Polar Highs Global Wind Systems Writing Assignment

• Choose a place to examine (hopefully the location of your final project) • Locate your chosen place on the maps of average surface winds and pressures in January and July (Figure 9.5 in book or maps in this PPT) • Answer the following questions for your location: • What are the regions from which wind blows into your region? • What might the wind be bringing into your region? • When wind blows out of your region, what region does it blow into? • What might the wind be carrying out of your region? • What large-scale circulation patterns are responsible for these winds (Equatorial Lows? Subtropical Highs? Subpolar Lows? Westerlies? Tradewinds? Polar Easterlies?)