Atmosphere Part 2

What are interannual climate variations

Changes in climate patterns that occur over multiple years

What are three major interannual climate oscillations

ENSO in the equatorial Pacific and PDO in the North Pacific and NAO in the North Atlantic

What does ENSO stand for

El Niño Southern Oscillation

What is ENSO

A recurring variation in tropical Pacific trade winds and ocean temperatures and atmospheric pressure

Where was El Niño first observed

Off the coast of Peru around Christmas

How frequently does El Niño generally occur

Approximately every 3 to 5 years with variable timing

What drives the different phases of ENSO

Changes in the strength of equatorial trade winds

What happens to Pacific surface water under normal ENSO conditions

Trade winds push warm surface water westward toward Indonesia

How does the thermocline differ across the equatorial Pacific under normal conditions

It is deeper in the western Pacific and shallower in the eastern Pacific

Why does upwelling occur in the eastern equatorial Pacific

Trade winds push surface water westward allowing cold deep water to rise

Why is the eastern Pacific highly productive under normal conditions

Upwelling supplies cold nutrient-rich water to surface organisms

What are normal atmospheric conditions in the western equatorial Pacific

Warm water causes strong evaporation and rising air and heavy rainfall near Indonesia

What are normal atmospheric conditions in the eastern equatorial Pacific

Cooler surface water supports higher pressure and relatively dry conditions

What happens to trade winds during El Niño

They weaken and allow warm surface water to spread eastward

How does El Niño change Pacific atmospheric pressure and rainfall

Low pressure and heavy rainfall shift eastward toward the central or eastern Pacific

How does El Niño affect the eastern Pacific thermocline

The thermocline deepens in the east and becomes more level across the Pacific

Why does El Niño suppress eastern Pacific upwelling

A deeper thermocline reduces the supply of cold nutrient-rich water to the surface

How does El Niño affect fisheries off South America

Reduced nutrient upwelling lowers primary productivity and can cause fishery declines

How do sea surface temperatures change during El Niño

The central and eastern equatorial Pacific become unusually warm

What happens to trade winds during La Niña

They become stronger than normal

How does La Niña change the distribution of warm Pacific water

More warm surface water accumulates in the western Pacific

How does La Niña affect eastern Pacific upwelling

Stronger trade winds increase upwelling of cold nutrient-rich water

How does La Niña affect eastern Pacific productivity

Increased nutrient supply generally supports higher primary productivity

How does La Niña affect atmospheric pressure and rainfall

The east-west pressure contrast strengthens and heavy rainfall shifts farther west

How do El Niño and La Niña differ

El Niño has weak trades and reduced eastern upwelling while La Niña has strong trades and enhanced eastern upwelling

How can El Niño influence winter weather in the United States

The North Pacific jet stream can shift south bringing wetter southern conditions and warmer northern conditions

Why is ENSO difficult to predict

Its timing and intensity vary and depend on complex ocean-atmosphere feedbacks

How have ENSO predictions improved

More observations and better climate models improve forecasts

How does land differ from ocean in heat capacity

Land has lower heat capacity and warms or cools faster

How do land and ocean influence atmospheric temperatures differently

Land transfers temperature changes to the atmosphere faster while oceans moderate temperature changes

What factors define land climate zones

Seasonal temperature variation and precipitation patterns

Where are seasonal temperature changes generally greatest

At high latitudes and in continental interiors

Why do coastal areas often have milder climates than inland areas

Nearby ocean water changes temperature slowly and moderates the air

How do prevailing winds affect coastal climates

Winds from the ocean moderate temperatures while winds from land can produce greater extremes

What is the difference between weather and climate

Weather describes short-term atmospheric conditions while climate describes long-term patterns

What causes weather to vary

Changes in heating and evaporation and precipitation and air movement and friction

What characterizes a high-pressure weather system

Sinking air with generally dry conditions and clear skies

What characterizes a low-pressure weather system

Rising air with cloud formation and precipitation and possible storms

What is the pressure gradient force

The force that drives air from higher pressure toward lower pressure

How does Coriolis affect winds around pressure systems

It deflects moving air to the right in the Northern Hemisphere and left in the Southern Hemisphere

How do winds rotate around pressure systems in the Northern Hemisphere

Counterclockwise around lows and clockwise around highs

How do winds rotate around pressure systems in the Southern Hemisphere

Clockwise around lows and counterclockwise around highs

What conditions are required for hurricane formation

Warm ocean water above about 26 degrees Celsius and a low-pressure disturbance and sufficient Coriolis force

Why do hurricanes generally form away from the equator

Coriolis force is too weak near the equator to support organized rotation

How does a hurricane develop

Warm moist air rises into a low-pressure center and condensation releases heat that strengthens the storm

What are the eye and eyewall of a hurricane

The eye is the relatively calm center while the eyewall contains the strongest winds and storms

How do hurricanes typically travel in the tropical North Atlantic

Trade winds initially push them westward and many later curve northward

What causes hurricanes to strengthen or weaken

They gain energy over warm water and weaken over cooler water or land

What is storm surge

Abnormal coastal water rise driven mainly by hurricane winds and often the most destructive hurricane hazard

What causes daytime sea breezes and nighttime land breezes

Daytime land heating draws ocean air inland while nighttime land cooling sends air toward the ocean

How does coastal fog form near upwelling regions

Warm moist air moves over cold surface water and cools until water vapor condense