Temperature, Air Pressure and Wind ES12a Temperature, Pressure and Wind I can label a diagram that demonstrates the interaction of Earth’s atmosphere and energy transfer (conduction, convection, and radiation). I can explain the reason for high and low pressure areas Identify and describe the direction of local winds (land and sea breezes). Identify and describe the direction of global winds (Tradewinds, Westerlies, Polar Easterlies, Doldrums, Jet stream) Read and interpret data from a thermometer and a barometer

Sun’s energy is transferred by: 1. Radiation A type of energy transfer in which energy moves in waves through space and the atmosphere.

Sun’s energy is transferred by: 2. Conduction A type of energy transfer in which vibrating molecules pass heat along to other vibrating molecules by direct contact (Air is in contact with the surface below it.)

Sun’s energy is transferred by: 3. Convection The movement of gases or liquids due to differences in density. As air is heated is becomes less dense and rises. As air is cooled is becomes more dense and sinks downward.

How much radiation reaches the surface? 50% reaches the Earth’s surface 25% absorbed by atmosphere on the way in 25% is reflected by clouds

Variations in Temperature Radiation from sun heats the earth unevenly. This is called differential heating. There are 3 main reasons why the earth is heated unevenly: 1. Latitude 2. Cloud and Ice Cover 3. Land-Water Heating Differences

Latitude and Angle of Incidence At the Equator, the rays hit the earth at 90°. They are very concentrated there. At higher latitudes, the rays hit the earth at a lower angle. The same amount of energy is spread out over a larger area=less heat per area

Cloud and Ice Cover More clouds and ice will reflect more radiation. When a surface reflects a lot of light is has a high albedo. Can you think of a surface that would have low albedo?

Nearness to a Body of Water Water has a very high specific heat capacity. We saw this in the Lab on Heating of Land vs. Water This means it can absorb lot if energy before it will heat up. Oceans and lakes take a long time to heat up and long time to cool down. This property helps water regulate the temperatures around the world.

Land-Water Temperatrue Controls

Measuring Temperature An instrument used to measure temperature is called a thermometer. Thermometers make use of a liquid’s ability to expand & contract.

Measuring Temperature What happens to a liquid when air temperature falls? The fluid contracts and it moves down the column.

Indicating Temp on Weather Map Scientists draw lines on weather maps that connect places with the same temperature. These lines (similar to contour lines) are called ISOTHERMS.

Complete the Isotherms and worksheet before continuing.

Part II: Air Pressure

What is Air Pressure? Atmospheric pressure = force of air pressing down on the Earth’s surface. Two factors influence whether air pressure will be HIGH or LOW: 1. Density of the air 2. Amount of Water Vapor present (We will do more with water vapor in the next section)

How pressure works

2 Factors affect Air Pressure Temperature Air Pressure Hot air Low density Air rises Low Pressure Cold Air High density Air sinks High Pressure Water Vapor content Air Pressure High Humidity Low Pressure Low humidity High Pressure What type of air will have the lowest pressure? What type of air will have the highest pressure?

Wind Blows from Hi to Low The sun’s energy is transferred by the wind and convection Wind is the horizontal flow of air from areas of high pressure towards regions of low pressure. Wind Blows from Hi to Low TEST QUESTIONs: What is the immediate cause of wind? What is the ultimate cause of wind?

Local Winds Generally move short distances and can blow in any map direction N, S, E, W (but always hi to low) Caused by geographic features (land, water) that produce temperature differences

Sea Breezes High pressure is created over the ocean during the day and low pressure over land due to uneven heating Air moves from the ocean to the land creating a sea breeze

Land Breezes Low pressure occurs over the ocean during the night and high pressure over land due to the uneven heating of earth This causes wind to move from the land to the ocean creating a land breeze

DYO-Draw your own Local Winds Label high and low pressure areas, draw wind direction arrows write the ‘name’ of the wind.

How do we measure Pressure? Use an instrument called a barometer. Two Types: Aneroid barometer Mercury barometer

Mercury barometer Aneroid barometer

Reading air pressure Read the larger ‘hand’ (like hand on a clock). __________________ The smaller hand is set by a person every three hours to see how the pressure changes over time.

Predicting weather using Barometric Pressure: High Pressure (anticyclone) fair weather Cool, dry air descends, clear skies Low Pressure (cyclone) Stormy, rain or snow Warm, moist air rises, cools, clouds form L

Jet Stream is the movement of Air at high altitudes. Think of it as a fast moving river of air.

READING ATMOSPHERIC PRESSURE Scientists connect areas on a weather map with the same air pressures. These lines are called ISOBARS Pressure Gradients describe how close isobars are together

Complete the back of your notes by drawing isobars!

The closer the isobars are to each other, the steeper the pressure change. The steeper the slope the faster the wind blows.

Three factors control speed and direction of the wind. 1. Pressure differences 2. Coriolis Effect 3. Friction

Coriolis Effect Earth rotating causes things to be sent off course. Northern Hemisphere – Right deflection Southern Hemisphere – Left deflection http://www.youtube.com/watch?v=_36MiCUS1ro https://www.youtube.com/watch?v=dt_XJp77-mk

Friction Friction resists the flow of air opposite to the direction of flow.

Pressure Centers High Pressure – “Anti-cyclone” Air moves down and out. Wind blows clockwise Weather – Clear, Sunny, AWESOME Low Pressure – “Cyclone” Air moves in and up Wind blows counter-clockwise Weather – Rainy, Cloudy, Dreary

jetstream https://www.youtube.com/watch?v=C_HiBj0teRY http://www.wunderground.com/maps/us/JetStream.html?

Local Winds

Global Atmospheric Circulation Model

Cyclones and Anticyclones http://media.pearsoncmg.com/bc/bc_0media_geo/interactiveanimations/018_CycAntiCyc_HS_GG_Stu.html?tru10#/Anticyclones