FW 4421 Week 9

Causes of polward heat transport

Air mass exchange, storm systems, ocean circulation

Advection

movement of an air mass from one place to another

Cold air advection

Occurs when the wind transports colder air into a previously warmer area

Warm air advection

Occurs when the wind transports warmer air into a previously colder area

Coriolis Effect

Earth’s rotation causes the equator to move faster than higher latitudes

Effects of the Coriolis effect

Subtropical jet stream from the Hadley cell to move west to east and produce westerlies

Weather system tracks

Clockwise in the N hemisphere and counter clockwise in the S hemisphere

Isobars

Lines that show high and low pressures

Pressure ridges

High pressure systems caused by taller atmosphere over that land surface; air descending usually associated with clear sky conditions

Troughs

Low pressure systems caused by shorter atmosphere over that land surface; air rising usually causes clouds to form

Geostrophic winds

Idealized winds that move parallel to isobars

Westerly winds

Mid-latitudes, west

Trade winds

Tropical latitudes, east

Polar easterlies

Polar latitudes, east

Coriolis effect dist.

Smaller at the equator, larger at mid-high lats

Jet Streams

Narrow bands of strong wind that generally blow from west to east across Earth at intersections of storm cells

Polar jet stream

Stronger because stronger Coriolis force and greater radiation imbalance

Subtropical jet stream

Weaker

zonal flow

west to east component of westerlies motion

Meridional flow

North-south component of westerlies motion

Jet stream motion

closer to the equator in winter and closer to the poles during the summer because of changes in the thermal gradient across each hemisphere

Jet stream strength oscillations

stronger during winter due to a greater thermal gradient across latitudes

Jet stream eccentricity

Associated with meridional flow, can cause parts of colder or warmer air above or below to break off

Rossby waves

Propogate in mid latitudes spawning cyclones and anticyclones as large air masses detach

Synoptic weather

Weather on scales of days to weeks; caused by Rossby waves

Internal forcing mechanisms

Variability in atmospheric circulation, ocean circulation, Atmosphere-ocean interactions

External forcing mechanisms

Volcanoes, GHG, Milankovitch cycles

ENSO acronym

El Nino Southern Oscillation

Length of ENSO phases

a few months to a few years

Normal/neutral ENSO conditions

Warm Western Pacific Cold Eastern Pacific

El Nino

Tradewinds weaken and sea surface temps rise across much of the Pacific ocean

La Nina

Tradewinds are enhanced and cold deep water is advected upwards cooling Pacific sea surface temps

El Nino shifts

much more energy and water vapor is convected into the Hadley Cell making this cell larger than usual; this brings more rain to the Western US and tends to shift the sub-tropical and Polar Jet streams further northward

Walker circulation cell

Southern oscilaltion of air that circulates zonally within the tropics between Indoneasia and South America