// lecture 15 Flashcards
real mean meridional circulations
- mostly one cell from summer to winter hemisphere in solstice seasons.
- in annual mean, southern hemisphere cell is larger.
- ITCZ is in NH most of the time.
hadley cell engine
- latent energy is converted to potential energy in ITCZ clouds.
- potential energy moves poleward in upper Hadley circulation.
- sun evaporates water.
- air sinks as radiative cooling removes energy.
- dried air returned to surface layer.
- water vapor moves toward equator in trade wins.
why do we have jet streams?
because of angular momentum conservation.
angular momentum equation
AM = mass * speed * moment arm
speed
AM/(mass * distance)
poleward flow conserving angular momentum gives
westerly winds: same direction as planet.
speed of dirt at equator due to rotation of Earth
2pi radians per day * 6370 km = 465 m/s = 1040 mph
earth’s angular moment cycle
- from earth to atmosphere in Easterlies
- from atmosphere to earth in Westerlies
the earth must have bands of Easterly (tropics) and Westerly (midlatitudes) zonal mean winds so that
the momentum balance can be maintained. otherwise the atmosphere would slow down or speed up and no maintain a steady climate.
a monsoon climate
is usually in the tropics. it has a rainy and dry season, usually with a change in wind direction.
Sahara: Ghardai, Algeria 32 N
dry with oasis, springs, but almost no rain.
Agadez and Tanout, Niger 16 N
sahel region, sparse grass and bush, summer rain.
Bondo, Zaire 4 N
congo basin rainforsest.
aridity
mostly subtropics and downwind of mountains.
sinking motion in the subtropics causes
deserts to be common in those latitudes.
the equator
is wetter.
the ocean
- massive: the mass of the atmosphere equals that of about 10 meters of ocean; 30 ft down the pressure is double the surface pressure. ~4000 m deep.
- dark: absorbs a lot of solar radiation.
- wet evaporates to provide source of moisture for land hydrology.
- absorbs and emits important chemicals, e.g. CO2.
atmopshere is ___ at the ____ and the ocean is ____ at the _____
hot, bottom; hot, top
takes a lot of energy to change ocean
temp. compared to land. so the seasonal cycle of surface temp. over ocean is small compared to land.
density of saltwater depends on
salinity and temp.
salinity
salt content in parts per thousand.
fresh water has its maximum density at
4 degrees C
