Circulations Flashcards
what is the single celled circulation model?
- strong heating at the equator
- air expands upwards, diverges toward the poles, descends, and flows back toward the equator
- winds blowing along longitudes meriodonal winds (north-south)
- winds moving long latitudinal zones (east-west)
what are the three distinct cells in the 3-cell model? which cell is in which latitdues?
- Hadley cell: tropics and subtropics
- ferrel cell: mid latitudes
- polar cell: Polar regions
which cell is considered not a ‘real’ cell?
Ferrel cell - it exists due to the Hadley and Polar cells, not a heating cell
In a polar cell, air moves from a subpolar low to a polar high due to ____?
temperature
Three cell model works best to describe ___?
surface winds
The Hadley cell begins at the ____?
equator with the intertropical convergence zone
What is the ICTZ band? It changes positions with the ___?
- A zone of strong local heating that causes air to expand upward and diverge toward the poles.
- Changes positions with the seasons, following the suns movement back and forth across the equator.
At ___ latitude, air in the Hadley cell sinks to form the subtropical highs, large bands of high surface pressure
20-30 degrees
How are northeast trade winds formed vs southeast trade winds
- in the northern hemisphere, the pressure gradient force directs surface air from the subtropical highs to the ICTZ. The Coriolis force deflects the air slightly to the right to form the northeast trade winds.
- In the southern hemisphere, the northward moving air from the subtropical high is deflected to the left to create the southeast trade winds.
in the upper troposphere
- Higher pressure gradient is where the air is ___?
- Temperature decreases from the ____ to the _____?
- the gradient of the height contours is largest in the hemisphere experiencing ___?
- cold
- from the equator to the poles
- winter
Name the four upper troposphere winds
- westerly winds
- polar front and jet streams
- troughs and ridges
- Rossby waves
for gradient winds, wind flows ___ to height contours?
parallel (toward the east in the NH mid-latitudes)
why do wind speeds increase with height?
because the pressure gradient force is stronger at higher latitudes
What is a polar front?
a sharp boundary between warm mid-latitude air and cold polar air
In a polar front, why does the slope of the pressure surface increase?
Because of the abrupt horizontal temperature change.
With steep, sloping pressure surfaces, there is a strong PGF, resulting in the polar jet stream situated near the tropopause.
What are jet streams?
Areas of high-elevation winds that form along boundaries between adjacent pressure cells.
- “rivers” of air, usually 9-12km above sea level
Where are the four main streams located?
- 2 located above the tropics (subtropical jet streams)
- 2 where the polar fronts occur (polar jet streams)
Where do troughs occur? Where in North America does it occur?
the middle troposphere where the 500 mb height contours dip equator-ward
- the zone of lower pressure over the central part of NA, giving rise to a wave-like air flow
What are Rossby waves?
- large wave like wind flow that follows the pattern of ridges and troughs
Do Rossby waves remain in a fixed position?
Yes, but they also migrate east to west and can transport warm air from subtropical regions to high latitudes or cold polar air to low latitudes
divergence vs convergence
- divergence draws air upward, causing adiabatic cooling
- convergence forces air downward, inhibiting cloud formation
List the 5 major wind systems
- Monsoons
- Foehn, chinook, Santa ana
- Katabatic-anabatic
- Sea-land breeze
- Valley and mountain breeze
