Module 9 (Atmospheric Circulations)

What are the four scales of atmospheric motion, in order of increasing size and duration? The last two are sometimes combined into one scale. Be familiar with examples of each.

1. Microscale: few meters, few seconds, swaying branches, smoke from fire, etc.

2. Mesoscale: few km, min, hr, as long as. a day. thunderstorms, tornadoes, small tropical storms

3. Synoptic scale: hundreds-thousands of km², days weeks. Weather map scale, circulations of a city, cyclones and anticyclones

4. Planetary/global scale: entire earth, weeks, centuries, long waves in westerlies

What is wind shear?

changes in wind speed/direction in short distances

What is a dust devil? What atmospheric conditions allow it to form?

on a hot dry day, ground air becomes unstable, causes heated air to rise and wind blowing past an obstruction can twist the rising air forming a rotating cloumn. .

Air rises lifting sand, dust, leaves, etc.

How is a dust devil different from a tornado?

forms differently, not as damaging. Tornadoes form from severe thunderstorms

How can heating and cooling produce a thermal circulation?

warm air rises and cooler sinks, which creates

How does a sea breeze form during the day? Is it an onshore or offshore wind?

pressure gradient, contrasts between difference in temp between land and water.

During day it is onshore wind.

How does a land breeze form at night? Is it an onshore or offshore wind?

Calmer waters heated, recersed, offshore wind.

In addition to convection, what promotes afternoon thunderstorm development over interior Florida during summer?

onshore winds from both sides enhance and uplift ths development and rainfall

How do upslope and downslope mountain breezes form?

mountain slopes heat up creating low pressure regions

air density difference is produced next to and air away from mountain, this creates upslope winds during day

and slopes cool down by radiation at night creating high pressure regions, resulting in downslope winds at night

What is a monsoon? In what part of the world is the monsoon common?

a wind system that changes direction seasonally

winter: air over land colder that over water

summer: air over land is warmer that water

Where and when does the North American Monsoon occur? What weather is associated with it?

southerwestern US where spring and early summer are hot and dry.

THS, rainfall, floodings, etc.

What are katabatic winds? Give examples including Santa Ana and Diablo Winds.

downslope wind (katiabatic)

elevated plateau, cool air flows downslope, increase in pressure temp too

Santa Ana: warm dry winds go down near santa ana and east LA. low pressure over water and high over mohave result in high winds in fall

Diablo winds: NE winds blow from MT diablo, and east of bay area,

What is the single-cell model of global circulation?

one circulation, warm waters at wquator colder near poles. war air

What are the major features associated with the three-cell model of global circulation?

Hadley, ferrel and polar regions

Why do all the deserts on Earth occur near 30 N&S latitudes?

winds come down to surface from hadley cell winds leading to high pressure regions leading to deserts from warm and dry wind.