Climate Variability

Question 1

describe surface atmospheric pressure

Answer 1

• high pressure –> weight of the air is relatively large
• low pressure –> weight of the air is relatively small
• if temp of air is colder than the surrounding –> dense air –> high pressure
• if temp of air is warmer than the surrounding –> light air –> low pressure

Question 2

describe relationship between warm air and low surface pressure

Answer 2

surrounding air moves to low pressure –> pushes surface air up –> rising motion

Question 3

describe relationship between cold air and high surface pressure

Answer 3

air will move out to lower pressure zones –> air will sink to replace the diverging air –> winds

Question 4

low pressures associated with __

Answer 4

rising motion, condensation, rain

Question 5

high pressures associated with ____

Answer 5

sinking motion, dry, sunny conditions

Question 6

describe the southern oscillation

Answer 6

pressure high over the eastern pacific –> low over the maritime continent

Question 7

describe non el Nino conditions

Answer 7

• trade winds blow strongly across pacific from east to west
• generates upwelling along the equator across most of pacific –> piles up warm water in the west
• thermocline is deep in west and shallow in east
• equatorial upwelling brings colder water to the surface along the equator in the east
• east-west contrast in sea surface temp sets up an atmospheric flow w/low pressure & rising motion in the west with warm temps
• low temps, high pressure and sinking in the east
• surface winds blow from high to low pressure, east to west

Question 8

describe conditions during El Nino

Answer 8

• trade winds reduced, warm water above the thermocline flows eastward
• upwelling goes down bc trade winds are weaker
• sea surface temps become warmer in central and eastern equatorial pacific where thermocline deepens
• surface pressures drop –> rising motion & rain in central and eastern pacific
• no longer a strong surface pressure contrast from east to west –> trade winds reduced