Chapter 5 - Atmospheric Pressure Flashcards
(29 cards)
What is Atmospheric Pressure?
Changes in temperature leads to changes in pressure causing wind
Force exerted by weight of gas molecules on portion of Earth’s surface
3 Factors influencing atmospheric pressure
- Greater density
- Greater temperature
- Vertical movement of air
Generalizations of surface pressure
High surface pressure = descending air (cold air)
Low surface pressure = ascending air (warm air)
What is pressure gradient
Horizontal pressure change. a “slope”
winds going from high pressure to low pressure.
What is Coriolis force?
Deflection of wind due to earth’s rotation.
Northern Hemisphere: deflecs to its right
Southern Hemisphere: deflects to its left
What is friction?
Drag of Earth’s surface. Slows winds and reduces coriolis effect
What is wind speed and the type of gradients?
Determined primarily by pressure gradient.
Steep gradients generate faster wind speeds
Gentle gradients generate slower wind speeds
What is an anticyclone?
-HIGH PRESSURE
-sinking air (cold air)
-surface DIVERGENCE
-clear skies
what is a cyclone?
-LOW PRESSURE
-rising air (warm air)
-surface CONVERGENCE
-clouds, storms
What are Hadley cells? and explain.
Tropical convection cells situated on either side of equator.
-warm air rises, air cools, air shifts poleward as antitrade winds (cool air)
-air descends around 30n/s forming high pressure
-diverging air from 30n/s known as trade winds (warm air)
What are the 4 components of general circulation?
- Intertropical Convergence Zone (ITCZ)
- Trade Winds
- Subtropical Highs
- Westerlies
What is a subtropical high?
-Always near 30N/S
-descending air from hadley cells
Why is sth located over ocean basins?
Warm air from land rises (low pressure) and descends on the ocean (high pressure)
What is a trade wind?
-Winds coming out of sth
-anticyclone
-between 25n/s
-wind is dry and warm from sth
What is Intertropical Convergence Zone (ITCZ)?
Zone of convergence of trade winds
Why is the ITCZ more pronounced over land?
- Land gets more heat compared to water
- as a result, warm air rises
- and clouds form
What is a sea breeze? and explain
Daytime onshore winds
-water heats slowly during the day (because water is 5x slower to heat up)
-wind flows from higher pressure to low
(water being high pressure because it’s cooler)
(land being low pressure because it’s warmer)
What is a land breeze? and explain
Night time offshore winds
-land cools off faster at night
-water takes 5x longer to cool
-land becomes high pressure (because it’s cooler)
-water becomes low pressure (because it’s warmer)
What is Foehn/Chinook winds?
Downslope winds develop from pressure gradients over mountain barriers
Wind on the backside of the mountain.
Wind is warmer.
What is a leeward flow?
Backside of the mountains. Flow is warm and dry (low pressure)
What is windward?
Front of the mountain, cooler air (high pressure)
What is santa ana winds?
Opposite of chinook winds.
Typically happens in mid latitudes (west to east)
Winds go from east to west (temporarily happens)
What is el nino?
Temperature of the ocean and how the environment reacts to it.
-Eastern pacific water gets abnormally warm -> warm air rises -> storms and rains
What is La Nina
Cooling of waters off South America
-Eastern pacific water gets cooler -> cool air sinks -> no rain = droughts
