Week 8 Weather & Climate Change (10/15-10/17) Flashcards
What is the Adiabatic Lapse Rate?
- rate at which air cools when decompressed
- no actual heat gets exchanged in or out of material
- same amount of heat (expansion)
What is latent heat?
change in physical state without change temperature
Where does a cloud have a relative humidity of 100%?
bottom
What is dew point?
- ground temperature
- coldness condenses water out of atmosphere
What is dry adiabatic lapse rate?
more pressure = hotter
less pressure = colder
What is wet adiabatic lapse rate?
- condensing water out of the air
- latent heat of evaporation involved
Name low clouds
nimbostratus, stratus (across sky, layer), stratocumulus, cumulus, cumulonimbus (storm)
name mid clouds
altostratus, altocumulus
name high clouds
cirrocumulus, cirrostratus (ring around sun/moon), cirrus, anvil
what does nimbo mean?
- convecting to the point it can make rain
- convects high enough that condensation rains out
What is relative humidity?
amount of moisture the air is holding compared to how much it could hold
* more than 100% = rain
What determines how much water the air can hold?
- temperature
- cold= less
- hot= more
Daily variation in relative humidity
low temperature= higher relative humidity
high temperature= lower relative humidity
* since warm air can hold more water relative humidity goes down because water is occupying the space
what is an isobars?
- barometric pressure
- lines connecting equal pressures
what is a bar?
atmospheric pressure
In what direction does net flow move?
- direction of lower isobar
- parallel to isobars
- higher up b/c Coriolis force
What is pressure gradient force?
wind moving from high to low pressure
What increases wind force?
- isobar distance from each other
- more wind= close
- less wind= far apart
- less gradient between
Where is there no wind?
centers of highs and lows
*air circles around
What is the Coriolis effect?
- the reason why wind doesn’t move straight from high to low
- not a force
- Inertia going in one direction while something else is turning under it
What is the ITCZ?
- it moves with the seasons
- spring/fall = equator
- summer/winter = 23.5 N & 23.5 S
- where the sun shines directly
- moves rainy place
- rising air
- productive ecosystems
What is hadley cell?
- hot air at it rises from equator
- cools and rains
- falls at subtropics (30, 60 N & S)
- warm and dry
where is the tropopause highest?
tropics
What is a polar front
- sinking air a cold pole
- rising air at 30
- zone close to 60 degrees
- sharp temperature contrasts
- imperfect mixing
- northern latitudes
what is a jet stream?
- narrow zones of relatively high-speed winds embedded in the westerlies
- polar and subtropical
What is a cyclonic flow?
- counterclockwise around a low
- storms, rain
- hurricanes
What is an anticyclonic flow?
- clockwise around a high
- sunny
what does an up jet do?
warm weather
What does a down jet do?
cold weather
When does a sea/land breeze happen?
during the day:
- land heats up so much during the day that it rises
- water has a huge heat capacity
- cold air replaces it
at night:
- land radiates heat (clear sky) cools
- hot water compared to land
- warm air moves in to replace
How far do sea/land breezes go?
one troposphere ~10km
What is a monsoon?
sea breeze on steroids
When does a monsoon occur?
- winter= dry counterclockwise
- summer= wet clockwise
- heating of high-altitude land
- shoots air up
What is Earth’s radiative balance?
- 45% absorbed by surface
- 70% heat lost to space
- 30% reflected to space
- 25% absorbed by atmosphere
How do GHGs trap heat?
- triatomic atoms are excited by infrared
- relaxes and re-emits radiation
- goes in every direction, including down
What does the sun do in terms of radiation?
massive radiation flux of short-wave visible radiation
* a million times greater
What does the Earth do in terms of radiation?
small radiation flux of long-wave infrared radiation
Describe a positive feedback loop with GHGs.
warm air w/ CO2 => evaporates water and holds vapor => more GHG warming
Describe negative feedback with heat.
radiation is proportional to the fourth power of its temperature
* some warming= more radiated
Describe a feedback with clouds.
- high clouds reflect solar radiation (increase albedo cooling ground)
- low clouds absorb more infrared warming the ground
List negative feedbacks
- marine biological pump
- CO2 fertilization helps plants grow
List positive feedbacks
- polar albedo
- increase water vapor
- methane from melting permafrost
- air conditioners: burning coal to generate electricity–> coal goes to CO2 –> warms atmosphere –> use more air conditioner
What is El Nino?
- warmer water
- winter: extended pacific jet stream amplified by storm track (across south USA)
- drier than usual in SA
What is La Nina?
- upwelling of cold water
- cold air falling down (no rain)
- dry conditions
- reduces atmospheric shear: more hurricanes
- wetter than usual in SA
- winter: extended polar jet stream (begins at Alaska goes to MA)
What is the Bergeron process?
- supercooled air: relative humidity is more than 100%
- will form a nucleus
- condenses sub-solidus
* settling velocity faster than turbulence –> fall as rain (have to beat convection currents
What is the collision-coalescence process?
- same sized drops don’t collide bc they are moving at the same speed
- big drops don’t touch the small ones bc of air escape flow
- big drops can break up
what is a warm front?
- warm air moves to cool air
- cool air is denser so warm air rises above it
- the warm air cools as it rises causing rain
What is a cold front?
pushes warm air out of the way to cold heights with so much force that it rains intensely
What is orographic lifting?
- moving air across a mountain
- jungle on one side desert on the other
What causes thunderstorms?
rapid rising air causes turbulence leading to ionic formation in the air that leads to static charges developing
* separation of charges in the atmosphere
How do tornadoes happen?
- thunderstorm is moved sideways
- wind shear on the ground
- horizontal, narrow spinning of wind
- associated with cold fronts
- funnels of high winds
- move SW to NE
Why do tornadoes only occur in the USA?
- there are no oceans between the tropical Gulf of Mexico and Arctic Ocean
- polar air masses and tropical wet air masses lead to cyclogenesis that gets sheared
When do tornadoes occur during the year?
summer because hot
What are hurricanes?
- big low-pressure area
- fueled by hot seawater
- evaporates ->rises-> condenses (heats surrounding air) -> spins
- gets its energy from latent heat
- can’t be sheared
How are hurricanes formed?
- warm ocean from ITCZ
- low pressure surface, winds converge, use cyclonic rotation
- surface winds transfer heat from ocean to air causing evaporation (cause moist air convergence over the low)
- rain releases latent heat (more heating) deepening surface LOW (positive feedback)
* evaporation cools water
Where can you find hurricanes?
north atlantic, east pacific
where can you find typhoons?
north pacific
where can you find cyclones?
south pacific
What forms at low latitudes?
storms
