Global Winds It’s all about the open system, our atmosphere, trying to restore equilibrium, balance!! Obi-wan, I feel a disturbance in the force!!

For this reason, it’s warmer near the equator than at the poles. Climatic Variation & Seasons on Earth Uneven heating of Earth’s surface causes predictable latitudinal variation in climate. Why? - Angle of incidence… equator vs. poles North Pole Equator Earth South Pole Thus, radiation is more intense near the equator compared to the poles. For this reason, it’s warmer near the equator than at the poles.

Earth North Pole Equator South Pole Earth’s Seasons Tilt of the Earth’s axis towards or away from the sun creates the seasons When the north pole tilts toward the sun, it gets more radiation – more warmth during the summer SUMMER (Northern Hemisphere) North Pole Equator Earth When the north pole tilts toward the sun, the south pole tilts away So when it’s summer in the north, it’s winter in the south South Pole WINTER (Southern Hemisphere)

Earth North Pole Equator South Pole Earth’s Seasons Tilt of the Earth’s axis towards or away from the sun creates the seasons WINTER (Northern Hemisphere) When the north pole tilts away from the sun, it gets less radiation – So it’s colder during the winter North Pole Equator Earth South Pole When the north pole tilts away from the sun, the south pole tilts toward it… When it’s winter in the north, it’s summer in the south SUMMER (Southern Hemisphere)

Intense radiation at the equator warms the air Air cools as it rises, moisture condenses and falls as rain Warm air rises, collecting moisture Lots of rain in the tropics!

some of the rising air flows north some of the rising air flows south Rising air is now dry… some of the rising air flows north some of the rising air flows south Dry air descends at around 30º N …and at around 30º S Deserts Deserts The descending air flows N and S

What causes global wind patterns? Uneven heating of the earth causes less dense hot air to rise at equator = low pressure More dense cold air to sink at poles = high pressure Air moves from high P (poles) to low P (equator)

Paper strips activity

Non-Rotating Earth Model • On a hypothetical non-rotating planet with a smooth surface of either all land or all water, two large thermally produced cells would form.

Circulation on a Non-Rotating Earth Makes no sense without caption in book

Rotation of earth activity Pen and paper activity

Rotating Earth Model • If other effects were added to the global circulation model, the two-cell convection system would break down into smaller cells.

Global Winds!

Circulation on a Rotating Earth Makes no sense without caption in book

WIND BELTS Trade winds are two belts of winds that blow almost constantly from easterly directions and are located on the north and south sides of the subtropical highs. Westerlies are the dominant west-to-east motion of the atmosphere that characterizes the regions on the poleward side of the subtropical highs.

WIND BELTS Polar easterlies are winds that blow from the polar high toward the subpolar low. These winds are not constant like the trade winds. A polar front is a stormy frontal zone separating cold air masses of polar origin from warm air masses of tropical origin.

Make note of the location of borders of the convection cells. Interesting stuff happens at the boundaries between convection cells….. A Closer Look 60o Make note of the location of borders of the convection cells. 30o

There are 3 Main Climate Zones

Analyzing Evidence 60o N and S latitude mark the border between the temperate regions and the polar regions. It also marks the border between the 300 N and S latitude mark the border between the temperate regions and the tropical region. So…

Explanation So when the warm air rises at equator. As it approaches 30o N & S latitude some of the air must be cooling down so sinks.

Continued When its closer to the surface, the surface absorbs a lot of the sun’s energy so the air must warm up again and rises.

Continued Then when the air approaches 60o N & S latitude the some air cools down and so sinks again.

6 Convection Cells So we end up with 3 convection cells in each hemisphere.

What else is going on at the boundaries between convection cells ? Air rises, low pressure at Equator 60 N and S RESULT – can be cloudy, rainy weather Air sinks, high pressure at Poles 30 N and S RESULT – fair, nice weather

At 30 N and S…. up high – subtropical jetstream At surface – weak winds known as the horse latitudes Weird?? Why ‘horse latitudes’?

At 60 N and S…. At equator…. At surface, weak winds - doldrums Up high – POLAR JET STREAM !!! At equator…. At surface, weak winds - doldrums

Jet Stream High velocity Polar and subtropical jet stream winds are located in the lower tropopause Polar jet stream travels at 150-350 mph, ~ 4-7 miles up, 1-3 miles thick and 100-400 mi wide HUGE!!!

Two jets in each hemisphere Polar jet is stronger, lower Sub tropical jet is weaker, higher up

How does the jetstream affect our weather patterns? It controls how much polar air drops into the mid latitudes and how much mid-latitude air moves into the northern, polar areas. It moves with the seasons, more south in the winter and more north in the summer.

What are the other factors that affect the global wind patterns? besides Coriolis effect?

Land vs sea worksheet

Global Winds Influenced by Continents • The only truly continuous pressure belt is the subpolar low in the Southern Hemisphere. In the Northern Hemisphere, where land masses break up the ocean surface, large seasonal temperature differences disrupt the pressure pattern.

Global Winds Influenced by Continents • Monsoons are the seasonal reversal of wind direction associated with large continents, especially Asia. In winter, the wind blows from land to sea. In summer, the wind blows from sea to land.

We just learned this !!!  The difference is that at the Jersey Shore the land and sea breezes change according to __________ and ________ In Asia the land and sea breezes change according to _____________ and __________

Monsoon Photos Click here to learn more about monsoons…

Who needs this information? What occupations, etc.? Why?

Thinking back to people who need global wind info …. Why do meteorologists need the info? What is the difference between weather and climate??? Do global winds affect weather or climate?

There are 3 Main Climate Zones

“Air Pressure & Wind” High & Low Pressures

Pressure Centers and Winds Cyclones are centers of low pressure. (storms occur here) Anticyclones are centers of high pressure.  In cyclones, the pressure decreases from the outer isobars toward the center. In anticyclones, just the opposite is the case—the values of the isobars increase from the outside toward the center.

How are weather maps made? In cyclones, (L) the pressure decreases from the outer isobars toward the center. In anticyclones, (H) just the opposite is the case—the values of the isobars increase from the outside toward the center.

Pressure Differences Low Pressure system air coming up either cloud cover and precipitation or no clouds because no moisture High pressure system air coming down generally fair skies

H Wind and Pressure Relationships L 950 mb. 970 mb. 960 mb. 930 mb. H L WINDS ALWAYS MOVE FROM HIGH PRESSURE AREAS TO LOW PRESSURE AREAS!!!!!!!

Cyclonic and Anticyclonic Winds • When the pressure gradient and the Coriolis effect are applied to pressure centers in the Northern Hemisphere, winds blow: Counterclockwise around a low pressure area Clockwise around a high pressure area

Cyclonic and Anticyclonic Winds Makes no sense without caption in book

Pressure Centers and Winds  Weather and Air Pressure • Rising air is associated with cloud formation and precipitation, whereas sinking air produces clear skies.  Weather Forecasting • Weather reports emphasize the locations and possible paths of cyclones and anticyclones. • Low-pressure centers can produce bad weather in any season.

Identify the Wind Belts Makes no sense without caption in book Click on the link below to see the wind belts in action and answer some questions! http://meted.ucar.edu/hurrican/strike/orig/htc5_1.htm