Atmosphere Flashcards
Monsoons
shift in winds that often causes a very rainy season or a very dry season
The winds shift because the temperature of the land and the temperature of the water are different as seasons change. For example, at the beginning of summer, the land warms up faster than bodies of water.
Monsoon winds always blow from cold to warm. In the summer, warm air rising off the land creates conditions that reverse the direction of the wind.
In Southern Asia:
In January the high pressure over the
land produces dry winds. Air flows
towards the ITCZ.
In July, the position of the ITCZ
moves north. The Low pressure over the land causes winds to flow off the ocean.
= heavy rainfall
warm front
surface low pressure systems have fronts associated
boundary between two air masses that contain different temperature, wind, and moisture properties.
cold front
cold air advances and displaces the warm air since cold air is more dense (heavier) than warm air
Where the two air masses meet, convergence often occurs which can result in upward motion of air parcels. If air contains enough moisture = rain
If the air also is unstable, thunderstorms can develop as well.
tornadoes
only form when a thunderstorm has a particular combination of winds
Air rising in a thunderstorm can begin to spin when it is affected by winds blowing it in different directions. It starts to rise and is pushed to the side by wind
The spinning air near the ground speeds up as it is drawn inward toward its axis of rotation.
during supercell thunderstorms, but not all supercell thunderstorms produce tornadoes.
Usually, the rotating air near the ground doesn’t rotate fast enough for a tornado to form.
classification: enhanced fujita scale
hurricanes
suck heat from tropical waters to fuel = weaken when they move over areas with cooler ocean water.
= While a hurricane is over warm water it will continue to grow.
storms form over the ocean, often beginning as a tropical wave = air that rises needs to be warm and moist so that it forms the clouds of the storm
When humid air is flowing upward at a zone of low pressure over warm ocean water, the water is released from the air, as creating the clouds of the storm.
weather system moves westward across the tropics, warm ocean air rises into the storm, forming an area of low pressure underneath. This causes more air to rush in. The air then rises and cools, forming clouds and thunderstorms.
Up in the clouds, water condenses and forms droplets, releasing even more heat to power the storm.
= needs the winds outside the storm to be light: not strong enough to disrupt it.
tropical depression
hurricanes: Atlantic ocean
typhoons - tropical cyclones in other parts of the world.
characteristics:
HURRICANE = Wind speed greater than 64 knots (74 mph)
TROPICAL STORM = Wind speeds between 35 and 64 knots (40 - 73 mph)
TROPICAL DEPRESSION = Wind speeds between 20 and 34 knots (23 - 39 mph)
TROPICAL DISTURBANCE = Thunderstorms with light cyclonic circulation
== As a storm grows, it goes through a series of stages.
First, it starts as a tropical disturbance. Then, with cyclonic circulation and faster wind speeds, it becomes a tropical depression. If the wind keeps getting faster it becomes a tropical storm and then a hurricane if winds are more than 74 miles per hour.
rain
little crystals of ice accumulate in the clouds
The ice crystals grow larger as more
water is evaporated.
= gravity makes them fall back to the
ground
– they melt
snow
accumulation of packed ice crystals
forms when tiny ice crystals in clouds stick together to become snowflakes.
If enough crystals stick together, they’ll become heavy enough to fall to the ground.
While it can be too warm to snow, it cannot be too cold to snow.
= can occur even at incredibly low temperatures
most heavy snowfalls occur when there is relatively warm air near the ground
hail
supercooled water, which is refrozen in the atmosphere, before falling back to the ground as a sizable ice ball
formed when updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere.
sleet
ice crystals drop from the clouds and drop through a warm layer of air which is relatively close to the ground = They melt
Closer to the ground there’s a very cold layer
which freezes the water once again into small
particles
= snowflakes only partially melt when they fall through a shallow layer of warm air
= slushy drops refreeze as they next fall through a deep layer of freezing air above the surface + reach the ground as frozen rain drops that bounce on impact.
low pressure
air rises
clouds + precipitation
Those near the equator tend to be high energy due to strong ground heating (convectional)
tornadoes/ hurricanes
fast moving, with plenty of cloud cover that reduces diurnal temperature range, strong winds and high rainfall.
high pressure
air sinks
no clouds + no wind
clear skies
= Sinking air is compressed = warms up + its relative humidity falls below saturation
trapped dust particles + cold
nights = dew, frost, fog or smog are common
pollution retained
clouds
condensation by itself does not cause precipitation (rain, snow, sleet, hail). The moisture in clouds must become heavy enough to succumb to gravity and return to earth’s surface.
form when the invisible water vapor in the air condenses into visible water droplets or ice crystals.
For this to happen, the parcel of air must be saturated = unable to hold all the water it contains in vapor form, so it starts to condense into a liquid or solid form.
There is no difference between fog and clouds other than altitude.
The Four Core Types of Clouds
-Cirro-form (latin for curl of hair)
Composed of ice crystals, cirro-form clouds are whitish and hair-like. There are the high, wispy clouds to first appear in advance of a low-pressure area such as a mid-latitude storm system or a tropical system such as a hurricane.
- Cumulo-form
detached clouds, they look like white fluffy cotton balls.
They show vertical motion or thermal uplift of air taking place in the atmosphere. They are usually dense in appearance with sharp outlines. The base of cumulus clouds are generally flat and occurs at the altitude where the moisture in rising air condenses.
-Strato-form (latin for layer)
broad and fairly wide spread appearing like a blanket. They result from non-convective rising air and tend to occur along and to the north of warm fronts. The edges of strato-form clouds are diffuse.
-Nimbo-form (latin for rain)
rainy cloud category which combined the three forms Cumulo + Cirro + Stratus. The vast majority of precipitation occurs from nimbo-form clouds and therefore these clouds have the greatest vertical height.
jet stream
strong wind
follows the sun
= it shifts toward the equator as winter progresses. Therefore, the polar region expands and the temperate region moves toward the equator.
= In summer, the Tropical Region expands shifting the temperate region toward the poles while the polar region shrinks.
follow the boundaries between hot and cold air.
high clouds
cirrus
cirrocumulus
cirrostratus
