Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Atmosphere and Ocean Interact • Atmosphere: volume of gases, water vapor, and airborne particles that surround Earth • Water and gases are freely exchanged between atmosphere and ocean • Gases entering the atmosphere from the ocean affect climate • Gases entering the ocean from the atmosphere can affect sediment deposition, distribution of life, and physical characteristics of seawater (CO2) Atmosphere and Ocean Interact • Water evaporated from the ocean is moved by wind (mass movement of air) and affects both weather and climate • Weather: state of the atmosphere at a specific time and place – Sunny, rainy, cloudy, windy • Climate: long term averages of temperature and precipitation in a given area Composition of Atmosphere • Composed mainly of: – Nitrogen – 78% – Oxygen – 21% – Ar, CO2, Ne, He, CH4 – less than 1% • Water vapor can occupy as much as 4% of air’s volume – Mostly invisible as vapor - humidity – Can be visible as clouds or fog Density of Air • Density of air is influenced by temperature and water content • As air is heated, it expands, becomes less dense and rises – Warm air can also hold more vapor • As air is cooled, it shrinks, becomes more dense and sinks – Cold air holds less water vapor – as air cools, its water vapor condenses into clouds • If enough condensation takes place, you get precipitation Solar Heating and the Atmosphere • Atmospheric circulation is powered by sunlight – drives wind • 51% of solar energy is absorbed by Earth’s land and water Solar Heating and Latitude • Not all areas on Earth get the same amount of solar heating • Poles get less solar heating due to the amount of atmosphere the sunrays have to travel through and also due to reflection • Equator gets the most solar heating – direct sunrays, very little reflection Solar Heating and Latitude Solar Heating and Seasons • At different times of year, places get different amounts of solar energy • This is due to the 23.5 degree tilt of Earth’s rotational axis relative to the plane of its orbit around the sun Solar Heating and Circulation • The concentration of solar energy at the equator affects the atmosphere • Uneven solar heating causes convection currents to form – Air is heated at the equator, becomes less dense and rises to high altitude – The air then turns towards the poles – At the poles, the air is cooled, becomes more dense and sinks to the surface – The air then turns back to the equator • However, air does not travel directly north/south – it travels at an angle due to the Coriolis Effect Solar Heating and Circulation Coriolis Effect • What is it? – The apparent deflection of a moving object due to the rotation of the Earth • What does it cause? – Causes air masses and water to move in a clockwise direction in the N. Hemisphere and counterclockwise in the S. Hemisphere How Does the Coriolis Effect Work? • Each city moves at a rate of 15 degrees/hr • However, the cities move at diff speeds – Buffalo moves slower because it has to travel less distance in a 24 hr period than Quito How Does the Coriolis Effect Work? How Does the Coriolis Effect Work? • Imagine a massive moving object between the two cities – a cannonball shot north from Quito toward Buffalo • The cannonball would not only be traveling north, but it will also be traveling eastward at 1,668 km/hr (Quito’s eastward speed) • So, as it goes north, it also veers to the right (east) – clockwise direction • Will it land in Buffalo? – No – Buffalo doesn’t move at the same speed as Quito – The cannonball will land ahead of Buffalo since Buffalo moves at a slower rate How Does the Coriolis Effect Work? • Now take a second cannonball. Shoot it south from Buffalo to Quito. What will happen? • Not only will it travel south, it will veer to the right again (this time to the west or clockwise) at a speed of 1,260 km/hr. • Will it land in Quito? – No – Quito travels at a different speed – The cannonball will land behind Quito since Buffalo travels slower and the ball was moving at a slower rate Coriolis Effect Video • http://www.youtube.com/watch?v=mcPs_ OdQOYU • http://www.classzone.com/books/earth_sci ence/terc/content/visualizations/es1904/es1 904page01.cfm?chapter_no=visualization Coriolis Effect and the Atmosphere • The Coriolis Effect causes atmospheric circulation cells to form • Convection currents still play a huge role in the rising and sinking of air • However, due to the Coriolis Effect, the air is deflected eastward as is moves towards the poles – It turns to the right (clockwise) in the N. Hemisphere – It turns to the left (counter clockwise in the S. Hemisphere Circulation Cells in the Atmosphere • Due to changes in air density from precipitation and changes in temperature, air can’t travel all the way from the equator to the poles. • This causes air to sink at 3 latitudes: 30˚ N/S, 60˚ N/S, and at the poles Circulation Cells in the Atmosphere • There are 3 pairs of circulation cells • Hadley Cells – Occur from 0˚-30˚ N/S of the Equator • Ferrel Cells – Occur from 30˚-60˚ N/S • Polar Cells – Occurs above 60˚ N/S Atmospheric Circulation Cells Atmospheric Circulation Cells and Wind Patterns • At boundaries between circulation cells, air is moving vertically and surface winds are weak – Occur where the 2 Hadley cells meet – called the doldrums • Also known as the Intertropical Convergence Zone • Contributes to the success of tropical rain forests – Also occurs where the Hadley and Ferrel cells meet – called the horse latitudes • Contributes to desert-like climates Atmospheric Circulation Cells and Wind Patterns • Within each cell, there is dependable surface winds that blow almost constantly • Trade winds (aka – the easterlies) – Surface winds of the Hadley cells – Centered at 15˚N and 15˚S – Winds move toward the equator • Westerlies – Surface winds of the Ferrel cells – Centered at 45˚N and 45˚S Atmospheric Circulation Cells and Wind Patterns Monsoons • A monsoon is a pattern of wind circulation that changes with the season • Areas subject to monsoons generally have wet summers and dry winters • What causes monsoons? – In the spring, land heats more rapidly than the adjacent ocean. – The air above the land becomes warmer and rises – Relatively cool air flows from the ocean to the land to replace the warm air that had risen – Continued heating causes this humid air to rise, condense, and form clouds and rain Sea Breezes and Land Breezes • Small, daily mini-monsoons • Morning sunlight doesn’t warm the ocean as much as the land • The warmer inland rocks transfer heat to the air, which expands and rises, creating a zone of low atmospheric pressure over the land; cooler air from over the sea then moves toward land sea breeze • Situation reverses after sunset land breeze Sea Breezes Cool air descends Warm air ascends Land warmer than sea; breeze flows onshore Storms • Storms are regional atmospheric disturbances characterized by strong winds accompanied by precipitation • Cyclones – huge rotating masses of lowpressure air in which winds converge and ascend – Tropical cyclones – originate in the tropics and travel poleward – Extratropical cyclones – originate in the Ferrel cells (“extra” means outside) Storms and Air Masses • Cyclones form between or within air masses – Air mass – a large body of air with uniform temperature, humidity, and density • Air that pauses over land or water tends to take on the characteristics of the surface below – i.e. cold, dry land causes the air to become cold and dry Storms and Air Masses • Air masses can move within or between circulation cells, however, air masses cannot mix with each other due to density differences • When 2 air masses meet, the denser air slides under the lighter air mass, lifting the lighter one and causing its air to expand and cool causing water vapor to condense • The boundary between air masses is called a front Extratropical Cyclones • Form at the boundary between the Polar and Ferrel cells – the polar front • Occur mainly in the winter when temperature and density differences are more pronounced • Turns counter clockwise in the N. Hemisphere and clockwise in the S. Hemisphere Extratropical Cyclones Tropical Cyclones • Great masses of warm, humid, rotating air • Occur in all tropical oceans except the equatorial S. Atlantic • Large tropical cyclones are called a variety of names depending on origin: – – – – Hurricanes – N. Atlantic and E. Pacific Typhoons – W. Pacific Tropical cyclones – Indian Ocean Willi-willis – near Australia • Winds must reach 74mph in order to be called a hurricane – About 100 reach this status every year! Tropical Cyclones Tropical cyclones develop in zones of high humidity and warm air over sea surfaces with temperatures above 26ºC (79ºF), which are shown in red in the satellite image above. Origins/Paths of Tropical Cyclones As tropical storms move westward on the trade winds, they veer northward towards the poles and then hit land or move out to the ocean going eastward, where the storms die. Hurricanes • May be up to 620 miles in diameter • Can be over 9 miles high • The eye (or center) of the hurricane can be 8-10 miles in diameter • Forms between 10˚ and 25˚ latitude in both hemispheres where the water is warm and the atmosphere is both warm and humid Hurricanes Rising winds exit from the storm at high altitudes. The calm central eye usually is about 24 kilometers (15 miles) wide. Gales circle the eye at speeds of up to 320 kilometers (200 miles) per hour. Moist surface winds spiral in towards the center of the storm Rotation of Hurricanes • Rotate counterclockwise in the N. Hemisphere • Rotate clockwise in the S. Hemisphere • Does this mean the that Coriolis effect does not apply to tropical cyclones? NO – The opposite rotation is caused by the Coriolis deflection of winds approaching the center of a low pressure area from great distance – In the N. Hemisphere, the approaching air is deflected rightward, which causes the storm to spin counter clockwise Rotation of Hurricanes Hurricane Katrina - 2005 Hurricane Katrina - 2005 Katrina 25 ft storm surge Hurricane Ike - 2008 Ike Aftermath – Galveston, TX 15-20 ft storm surge Storm Damage • Three types • Wind • Rain • Storm Surge = mass of waves driven by storm winds • Which is the biggest problem? • Storm surge Storm Surges • Abrupt bulge or dome of water driven ashore by a hurricane • The dome becomes bigger as the surge enters shallower water – The only way for the water to go is up • Bigger storms = bigger storm surges • All of this water does not come ashore as one wave. Instead, it rushes on land in what looks like a series of large waves or sometimes looks like high tide is moving in rapidly Storm Surges http://www.nhc.noaa.gov/surge/animations/hurricane_stormsurge.swf