Atmosphere, Seasons & Circulation

Atmosphere, Seasons & Circulation

Ms. Levensailor

Ocean and AtmosphereInteract with each other.

Water evaporated from the ocean enters the atmosphere.

This impacts climates on land.Atmosphere is composed of:

Nitrogen (78%) Oxygen (21%)Water vapor (1%)

Atmospheric MovementMoves in response

to:Uneven solar

heatingEarth’s rotation

Solar heating of Earth varies with latitude.

Solar Heating & SeasonsSolar heating varies

with seasons

Large Scale Atmospheric CirculationWarm air rises and cool air sinks.

Warm air expands and becomes less dense.Cool air contracts and becomes more dense.

Convection currents: circular current of air.

Convection CurrentsIf uneven solar

heating was the only factor in Earth’s air circulation it would look like this

Earth’s Rotation Plays a RoleCoriolis effect: eastward rotation of Earth

on its axis deflects the moving air or water away from its initial course.

Coriolis effect:Northern Hemisphere: curve is to the right

(clockwise)Southern Hemisphere: curve is to the left

(counterclockwise)

Coriolis Effect Influences the movement of air in

atmospheric circulation cells.Air rising from the equatorial region moves

poleward and is gradually deflected eastward.Turns right in the Northern Hemisphere.Turns left in the Southern Hemisphere.

Coriolis Effect on Air CellsCirculation cells are

large circuits of air.There are 3 cells in

each hemisphere:Hadley cellsFerrel cellsPolar cells

Atmospheric Circulation Cells generate large

scale surface wind patterns.

Trade winds (easterlies) centered at 15° N and 15° S latitudes.Surface winds of the

Hadley cells. Westerlies centered at

45° N and 45° S.Surface winds of the

Ferrel cells.

Circulation of the Ocean

Mass flow of Ocean WaterKnown as ocean currents.Driven by wind and gravity!Surface currents: wind-driven movement of

ocean water at or near the ocean’s surface.Thermohaline currents: slow, deep

currents that affect the bulk of seawater below the surface.Depends on density differences as a result of

temperature and salinity.

Surface Currents10% of the water in the ocean is involved in

surface currents.Water flowing horizontally in the upmost 400

meters.Responsible force: WIND!

Surface winds form global patterns within latitude bands.

Northern Hemisphere surface currents flow to the right.

Southern Hemisphere surface currents flow to the left.

Continents block continuous flow and creates a circular pattern (GYRE).

Ocean Layers & Gyre

Ekman SpiralA body of water can be

thought of as a set of layers.Top layer driven by wind.Each layer below is moved

by friction. Moving at a slower speed

and at an angle to the layer immediately above it.

Horizontal movements in a layered water column.Each layer moving in a

slightly different direction.

Seawater flows in 6 surface circuits2 in the Northern

Hemisphere.4 in the Southern

Hemisphere.

Antarctic Circumpolar is not a gyre.

Direction of currents

Boundary CurrentsWestern Boundary Currents: Gulf stream

Narrow, fast, deep currents.Move warm water poleward.

Eastern Boundary Currents: California currentCarry cold water equatorwardShallow and broad.