GEO 155 TEST 3

 tropics differ from the rest of the world for two reasons

solar energy is similar through the year and across the region

the Coriolis effect is weak

The weather of the middle latitudes comes from

Coriolis effect combined with the change in temperature between the equator and the poles

 temperature gradient

 rate at which temperature changes, here with latitude. It is largest in the middle latitudes.

Differences in temperature produce

differences in pressure

 equator-to-pole temperature gradient is what starts the winds

start winds = coliolis turns

greatest at winter

jet stream

 band of strong winds at high altitude

created by the equator-to-pole temperature gradient

thats why flying from LA to NYC takes less time, west to east

fastest happens at 30 N

 One knota

little more than one mile per hour. 100 knots is about 115 miles per hour

 jet stream during different temps

 temperature gradient produces differences in pressure at a given height

warm air = high column

DIFFERNECE WITH TEMP = SAME PRESSURE

jet stream with difference in temp

warm goes to cold at the poles

A difference in temperature makes a difference in column height, which makes a difference in pressure at a given height.

colioris moves from west to east

A stronger temperature gradient makes a stronger pressure gradient, and a stronger pressure gradient makes stronger winds.

hadley cells

30°N - deserts, dry air

20 N - ITCZ , storms

subtropical jets

formed by jet stream

strong winds

found at hadley cell

he temperature gradient makes a pressure gradient, which makes west-to-east winds high in the troposphere.

straight

polar-front jets

boundary between warmer air in the middle latitudes and colder air farther north

50-60 N

he temperature gradient makes a pressure gradient, which makes west-to-east winds high in the troposphere.

wavy shape

hot and cold air

balance each other out , depends on the lattitude

geostrophic winds

middle latitudes the stronger Coriolis effect

do the same job as hadley cells - turn hot and cold

strength of the Coriolis effect

the Hadley cell or pressure systems carry the heat: weak in the tropics, stronger in the middle latitudes.

energy at hadley cells

carries energy away from the tropics at 30 N - 30 S

Highs and lows pick it up there and carry it farther north.

Intertropical Convergence Zone

trade winds from the equator

Air then flows away from the equator to the north and south, sinks near 30°, and flows back toward the equator.

heaviest rains
The ITCZ follows the latitude where the sun is strongest,

If Earth did not rotate

 air would simply move from the tropics to the poles, with no highs and lows and a much simpler pattern of winds.

circulation

 how solar energy is spread over the planet, and Earth's rotation.

winds exist because of

temperature difference between the equator and the pole, combined with the change in the Coriolis effect with latitude.

tropics

solar energy is fairly constant through the year, so most of the tropics have a wet and a dry season instead of a winter and a summer.

 the Coriolis effect is weak in the tropics. This is the main reason the tropics are different.

average temp is 70

planet and energy

not in balance , causes global warming

more energy is at the equator

less energy is at towards the pole

42 degrees is the goldilocsk

energy is carried by

 the atmosphere, through the winds, and the ocean, through currents

Absolute humidity

the actual amount of water vapor in the air. It can be measured

always less than or equal to saturation humidity.

changed by weather systems bring in moister or drier air

grams cubic square

as air rises - AH doesnt change. water stays

Saturation humidity

maximum amount of water vapor the air can contain. It is calculated, not measured.

depends on temp

as air cools SH drops , AH stays because of temp

rises about 7% per °C of warming, sometimes a little less.

 Relative humidity =

absolute humidity ÷ saturation humidity

humidity of 50% means the air holds half the maximum water vapor it could hold

daily cycle based on temp

high relative humidity = cool

tells us when clouds form

at 100% = saturated

condensation

removes the water vapor

happens at AH

droplets are suspended in the air at first and do not necessarily fall , no WV

releases energy , warm air

clouds

suspended droplets

RH at 100

cimmulus clouds - High pressure , no precipitation

have flat bases - condensation begins at the same height everywhere across the sky

dry adiabatic lapse rate

cooling rate of 10 °C per km

Adiabatic means the parcel neither gains nor loses heat from outside it, for example from sunlight

Lapse rate means how the temperature of air changes with height

dry air

 unsaturated, with relative humidity below 100%

Above the cloud base

air is saturated

is at 100% relative humidity, and condensation is occurring

Condensation releases energy and warms the air, saturated rising air cools more slowly

saturated air

Saturated air cools about 5 °C per km.

air that holds the maximum possible amount of water vapor

water vapor

 content is highest near the equator and lowest toward the pole

the balance between evaporation and precipitation

carried around the world by the global circulation of winds

precipitation

holds about 8 to 9 days of precipitation. Water does not stay in it for long.

result of condensation

middle latt = 2 mm

happens at ITCZ

rises more slowly, about 1 to 3% per °C.

also increases with evaporation on average as the world warms

water in the atmosphere

constant

evaporation and condensation are about equal

difference between precipitation and evaporation

positive = more precipation than evaporation

 P minus E is positive in the middle and high latitudes, from about 40° to the pole in both hemispheres.

P minus E is negative in the subtropics, where evaporation peaks.

P minus E is positive again near the equator, around the intertropical convergence zone.

Where P minus E is positive, more energy is released by water vapor than stored in it, and the air gains energy.
 Where P minus E is negative, the place loses energy to evaporation.

stable atmosphere

air tends to stay at its own height

air in a stable atmosphere is pushed upward, it does not keep rising. It turns back and returns to its starting height.

Air pushed a little downward in a stable atmosphere also returns to its starting height

unstable atmosphere

air given a small push upward does not return to its starting height. It keeps rising by itself

Air that keeps rising cools, its relative humidity rises to 100%, and clouds and precipitation can form

Most precipitation, and thunderstorms in particular, happens when the atmosphere has become unstable

Moist adiabatic lapse rate

 5 °C per km. Saturated rising air cools more slowly because condensation releases heat.

 Environmental lapse rate

 the rate of temperature change with height observed at a given time. It is measured, not calculated, and changes with the weather.

Weather balloons measure — albany

Stable

 the environmental lapse rate is less than 5 °C per km, below both the moist and the dry rate

unstable

the environmental lapse rate is greater than 10 °C per km.

conditionally unstable

the environmental lapse rate is between 5 and 10 °C per km.

means the atmosphere is unstable only if the rising air is saturated

turated parcel cools more slowly because condensation releases heat and warms the air.

Above the cloud base the conditionally unstable air keeps rising, and water vapor keeps condensing out of it.

Low, flat, gray overcast clouds

stable

common during winter

clouds form a thin layer close to the ground and do not rise high into the atmosphere

- Instability matters

because it is how precipitation forms.

tower cloud

unstable

An unstable or conditionally unstable atmosphere gives tall cumulus clouds and thunderstorm clouds that rise high above the ground.

- In the tropics, clouds like this form almost every da

enviormnetla lapse rate

thunderstorms later in day

 form in the afternoon and sometimes continue overnight. The daily change in the temperature profile explains why.

At night, solar radiation drops to zero and the ground cools as it loses heat to space.

- The ground and the lowest air cool more than the air above, so the environmental lapse rate gets smaller.

- The atmosphere almost always becomes more stable overnight.

thunderstorms in the morning

During the day the sun heats the ground, which becomes warmer than the air above it.

- The environmental lapse rate gets bigger, so the atmosphere becomes less stable.

- This is why thunderstorms usually form in the afternoon

air rising surface

surface heating, mountains and low pressure system

Surface heating raises the environmental lapse rate. If it rises from 9 to 11 °C per km, conditionally unstable air becomes unstable, whatever its humidity. destablizes

air rising mountain

up bc of landscape

Clouds and precipitation often form on the side of the mountain facing the wind.

- Water is squeezed out of the air as it rises, so the air reaching the far side is dry.

rain shadow

The side of the mountain away from the wind is often very dry.

air during convergence

Low pressure systems are associated with rising air, clouds and precipitation

RH goes up, condesnes and makes rain

Dew point

measure of how humid the air is. higher = more humid

 higher in the south and lower in the north

dew point gradient follows temperature

Warmer places have more evaporation, so their air holds more water vapor

 low-pressure system

starts with the jet stream, high-altitude winds that can reach 100 to 200 miles per hour.

jet stream is wavy. It turns south, then north, then south again, in waves that go around the world.

when winds aloft starts the process

convergence

winds coming together

divergence

winds seperating

rise from below to replace the air that spreads out.

rising air with low pressure

air goes towards , coriolis turns cc

Both reduce the temperature gradient

Jet stream winds are caused by

emperature gradients, so there is a feedback loop.

starts the low. The low's winds make sharper temperature gradients. Those sharper gradients strengthen the jet stream winds above the low.

- The low forms where the jet turns north, because the winds diverge aloft there and encourage air to rise.

- This is a positive feedback: the low strengthens over time.

ENSO

 El Niño and La Niña together

Air rises if it is warmer than the air around it and sinks if it is colder.

It is not caused by human activity and for the most part is not related to climate change.

Earth's climate is set up and has existed for a long time. Its variability sits on top of human-caused global warming.

happens mostly at the tropics, changes the wweather

warm area is caused by

el nino

warms the eastern tropical Pacific, off South America. It cools the western tropical Pacific, near Indonesia, the Philippines and Australia.

warm west and cool east

make temp gradient , drives winds

brings thunderstorms

sinking air brings

HP Clear skies

El Nino and La nina happen

3-7 years

El Niño starts when something weakens the trade winds.

weak trade winds

- With weaker trade winds, less warm water is held in the west, so warm water moves east.

- The eastern tropical Pacific becomes warmer than normal, and the western tropical Pacific becomes relatively cooler than normal.

warmer eastern Pacific shifts where air rises — middle of asia and SA

postive feedback with wind

trade wind weakens —> warm water moves east and themoceline flattens —> east warms —> rising air and rain move east

El nino and weather

El Niño starts, it builds on itself. ffects weather around the world, mostly by moving where rain falls.

Warms the eastern tropical Pacific, and that reduces the number of hurricanes that form in the Atlantic.

The trade winds are now much weaker than normal, letting warm water from the west move east toward South America.

La nina

La Niña the trade winds get stronger

Stronger winds strengthen the west-to-east temperature difference, which strengthens the winds further.

- Stronger trade winds push warm water west more strongly, so more cold water rises in the eastern Pacific and it becomes colder than normal.

years raise the risk of drought there.

surface heating

 which increases the environmental lapse rate and makes the atmosphere less stable.

mountain

blowing against a mountain, which forces the air to rise on one side of the mountain.

convergence

 as around a low-pressure system, which forces air to rise.

front

both cold and warm fronts, cold air sinks underneath and the warmer air rises above it.

Rising air generates precipitation.