Test 2 Flashcards
What is a Hadley Cell?
A convection cell in the atmosphere due to differential heating of the surface.
At the equator, air is _____ (rising/falling)
rising
Where is the ITCZ?
The low-pressure belt near the equator, at the solar declination
What does ITCZ stand for?
Inter-tropical convergence zone
The tradewinds converge where?
At the equator
The ITCZ has what kind of weather?
light winds with heavy precipitation
30* North and South is known as the _____ latitudes
horse
In the horse latitudes, air is ____
descending
30* N and S are _____ pressure belts
high
Which winds diverge at the horse latitudes?
Westerlies and trade winds
What is the weather like within the horse latitudes?
light winds with low precipitation. Dry.
60* North and South are known as the ______
Polar front
The polar fronts are ____ pressure belts
low
Air ______ at the polar fronts
rises
What winds converge at the polar fronts?
Easterlies and westerlies
What is the weather like at the polar fronts?
light winds, moderate precipitation
Why don’t the polar fronts have as much precipitation as the ITCZ?
It is much colder, and cold air can’t hold as much moisture
At 90* N and S, air is _____
sinking
90* N and S are known as the Polar _____
high
The polar high is a ____ pressure area
high
What winds diverge at the polar highs?
easterlies
What is the weather like at the polar highs?
dry conditions
What are the jet streams?
High velocity currents of air in the upper troposphere
How high are the jet streams in the air?
9-15 km in altitude
How fast are the winds in the jet streams?
More than 100 kt
What direction do the jet streams flow?
West to east
How many jet streams are there?
4
What are the two sets of jet streams called?
Polar jets and subtropical jets
Where are the polar jets located?
60* N and S
Where are the subtropical jets located?
30* N and S
The ITCZ moves with what?
the seasons
The change of the ITCZ’s location is more distinguished over _____ than _____ because water doesn’t change temperatures as quickly.
Land than water
The ITCZ is responsible for _____ in the tropics and subtropics
monsoons
The ITCZ creates semi-permanent _________
high and low pressure sectors
In a low pressure center, the air is _____
rising
Low pressure centers are termed _____
cyclones
A cyclone is characterized by what?
converging, rotating winds
In the northern hemisphere, cyclones spin ____
counterclockwise
In a high pressure center, the air is _____
sinking
High pressure centers are termed ____
anti-cyclones
anti-cyclones are characterized by what?
Diverging, rotating winds
Air masses are what?
large, 3-dimensional bodies of air in the atmosphere
Air masses have consistent ____ at all levels?
temperature and humidity conditions
Air masses develop where?
over “source areas”
What are source areas?
Broad areas of the earth’s surface that have rather homogeneous conditions
As an air mass moves over a source area, what happens?
they take on the characteristics of the area
What are the 8 air mass classifications?
Maritime arctic, maritime polar, maritime tropical, maritime equatorial, continental arctic, continental polar, continental tropical, continental equatorial.
What is a front?
A boundary between two air masses with different characteristics and densities.
A front is named for what?
The advancing air mass
The less dense air mass in a front is _____
pushed upwards
A front creates a ______ at the surface.
low pressure area
As a cold front approaches, temperatures are _____
stable and warm
As a cold front approaches, cumulus clouds develop into _____
cumulonimbus clouds
As a cold front approaches, what is the precipitation like?
Heavy precipitation, short duration
As a cold front approaches, what kind of weather is there?
lightning, t-storms, tornado, hail
As a cold front approaches, pressure ____
drops
As a cold front passes, temperatures ____
drop
As a cold front passes, what happens to the clouds?
they clear out
As a cold front passes, winds do what?
shift directions
As a cold front passes, pressure _____
rises
When a warm air mass moves into the area of a colder air mass, what happens to the warm air?
It is pushed aloft
A warm front that moves into the area of a colder air mass creates what kind of slope?
gentle slope
As a warm front approaches, temperatures are _____
stable and cold
As a warm front approaches, air pressure _____
drops
As a warm front approaches, _____ clouds form how far in front of the air mass?
cirrus, 500 miles in front
Why do the clouds form so far in front of a warm front?
because of the gentle slope
Cirrus clouds get ____ as a warm front approaches.
thicker
What is the progression of cirrus clouds when a warm front approaches?
cirrus, cirrostratus, altostratus, stratus, nimbostratus, and sometimes fog.
Clouds are _____ as warm front approaches
lowering
As a warm front approaches, what is the precipitation like?
Moderate to ight precipitation, long duration
As the warm front passes, temperatures…
warm rapidly
As a warm front passes, clouds and precipitation ____
clear
As a warm front passes, winds _____
shift direction
As a warm front passes, air pressure _____
rises
During a stationary front, a warm air mass is
sitting next to a cold air mass with neither advancing
Weather with a stationary front is _____
highly variable
In a stationary front, there can be clouds and precipitation if there is _____
any convergence of winds
What is an occluded front?
When cold air moves faster than warm air mass and catches up to it.
In an occluded front, what happens to a warm air mass?
it gets pushed completely aloft and out of the way
What is the weather like in an occluded front?
mixture of cold front and warm front weather
What are the clouds like in an occluded front?
cumulus and cumulonimbus mixed with stratus and nimbostratus.
What is the precipitation like in an occluded front?
heavy precipitation and slowly lightens
What is a dry line also known as?
Dew point front
What causes a dry line?
When a dry air mass moves into the area of a humid air mass of the same temperature
What happens in a dry line?
The dry air mass is pushed upwards
A dryline is pushed _____ during the day
eastward
A dryline is pushed _____ during the night.
westward
What kind of atmosphere does a dryline create?
extremely unstable
What kind of clouds does a dryline create?
Very large cumulonimbus
What else does a dryline create?
Supercells, very strong thunderstorms and tornadoes.
Behind a dryline, what are common?
dust storms.
Where do midlatitude cyclones form?
between 30 and 70 degrees latitude
In what zone do midlatitude cyclones form?
In westerlies zone
What speed do midlatitude cyclones travel?
20-40 mph
What is the wind speed of a midlatitude cyclone?
30-40 kt
When are midlatitude cyclones most intense?
in winter
What are responsible for the day-to-day weather we experience?
midlatitude cyclones
What does a midlatitude cyclone start as?
A stationary front
What triggers the bend in a stationary front?
Rossby waves in the jet stream
As the jet stream comes out of a rossby wave, what happens?
it diverges and pulls air up from below, creating a low pressure center, cold front, and warm front
Once a cold front and warm front are created, what happens?
The cold air mass catches up to the warm air mass and creates an occluded front
What happens to an occluded front as it grows in size?
it continues growing until the entire warm air mass is pushed aloft, shutting down clouds and precipitation
What is the weather associated with a warm front approaching in a mid-latitude cyclone?
Temp steady, pressure drops, nimbostratus clouds, steady continuous rain, south-southeast winds
What is the weather associated with a warm front passing?
Temp rising, pressure increasing then steady, cumulus clouds, no precip, south-southwest winds
What is the weather associated with a cold front approaching?
Temp rising and steady, pressure drops, cumulonimbus clouds, thunderstorms, south-southwest winds
What is the weather associated with a cold front passing?
temp drops, pressure rises, clouds clear, no precip, north-northwest winds
What alternates with cyclones?
mid-latitude anticyclones
What kind of weather does an anticyclone have?
None! No fronts
Anticyclones do what to the air?
pushes it away
As the jet stream ______ a rossby wave, it _____ and creates a high pressure center
enters, converges and pushes air down
As air sinks in the high pressure center, what happens?
it compresses in volume and warms adiabatically
Within the anti-cyclone, relative humidity _____, causing what?
decreases, causing clear and dry conditions
The problem with anticyclones, is that they _____
block cyclones from moving in.
What is a tropical cyclone?
A low pressure center characterized by converging rotating winds that form between 5* and 20* latitude
What direction do tropical cyclones move in?
east-west direction
tropical cyclones are ______ of a mid-latitude cyclone
half the size
How many air masses do tropical cyclones span?
one
What kind of fronts do tropical cyclones have?
None
A tropical cyclone moves at what speed?
20-40 mph
What is the first component of hurricane formation?
Large area of warm sea surface temperatures over 80*F
Warm water acts as a ____ for hurricanes?
fuel source
What is the second component of hurricane formation?
Convergence of surface winds
What does the convergence of surface winds do?
Concentrates clouds and precipitation in one area, starts rotation, organizes the storm, creates tropical waves
What is the line of low pressure known as?
trough
What is the third component of hurricane formation?
Conditions in the atmosphere which promote strong convection.
What does strong convection allow?
allows the cyclone to grow in size
Two things that can promote strong convection are what?
a) Strong temperature gradient and b) weak upper-level winds in the atmosphere.
Usually, weak upper winds in the atmosphere occur during what?
la nina
What is the first stage of tropical cyclone development?
Tropical disturbance
What is a tropical disturbance?
A mass of storms with a slight rotation.
During a tropical disturbance, winds rotate at what speed?
20-34 kt
What is the second stage of hurricane development?
Tropical depression
What is a tropical depression?
An increase in wind speeds to 20-34 kt and better organized.
What is the third stage of a tropical cyclone?
Tropical storm
What are the characteristics of a tropical storm?
Increase in size, wind speeds between 34-64 kt, no eye, increased organization, given a name
Why are the tropical storms named?
for tracking purposes
What is stage 4 of hurricane formation?
Hurricane
What are the characteristics of a hurricane?
wind speeds exceed 64kt, large well organized storm, eye
Why was 2013 a low hurricane year?
Unfavorable atmospheric conditions over the gulf of mexico
What are the parts of a hurricane?
Center, eye wall, spiral rain bands
What is the center of a hurricane?
The eye
What are the characteristics of the eye of a hurricane?
low pressure center, very calm, light winds
What are the spiral rain bands?
bands of clouds and precipitation moving out from the eye wall with increased intensity towards the eye.
What is the eye wall?
Ring of intense storms that rotate around the eye with the most rain and fastest winds
What are the hazards of a tropical cyclone?
1) Strong winds covering large areas
2) Hurricane-spawned tornadoes
3) Heavy rainfall
4) Storm surge
What part of the hurricane has the strongest winds, and why?
The northeast corner, because the wind speed and the speed of the hurricane moving north are added together
The average hurricane produces how many gallons of rainfall each day?
1 trillion gallons
Hurricanes cause extensive floods far inland when what?
They get stuck on a topographic barrier
What causes a storm surge?
Winds pushing a bulge of water that is lifted up by the low pressure center
What causes the most fatalities?
storm surge
What 3 things cause the height of a storm surge?
Wind speeds, fetch, and shape of the coast
What is fetch?
Distance of open water the storm travels over
Fetch: The longer the duration of the storm at a specific size, the ______
higher the surge it is going to be
A _____ shaped sea floor can increase the size of the surge
gently sloped
Bays and inlets do what?
Funnel the storm surge and increase height
What is the scale used to measure the magnitude of a hurricane event?
The Saffir-Simpson scale
What is the Saffir-Simpson scale based on?
the maximum sustained wind speed at the time of observation
What is the wind speed of a category 1 hurricane?
64-82KT
What is the wind speed of a category 2 hurricane?
83-95 kt
What is the wind speed of a category 3 hurricane?
96-112 kt
What is the wind speed of a category 4 hurricane?
113-136 kt
What is the wind speed of a category 5 hurricane?
> 136 kt
What are thunderstorms?
small, convective storms that produce thunder and lightning
What are thunderstorm cells composed of?
1 updraft, 1 downdraft, a single cumulonimbus cloud
What is an updraft?
warm, moist air rising
What is a downdraft?
cold, drier air falling
What is lightning?
The discharge of electricity from a cloud
What is the first step of lightning?
Two types of ice are present
What are the two types of ice that must be present for lightning to form?
crystals and hailstones
What occurs within the cloud between the two types of ice?
They rub against each other and create a static charge, making the hail negatively charged and the crystals positive
What is the second step of the formation of lightning?
Hail sinks to the bottom and crystals rise to the top, making the cloud like a battery.
What is the third step of lightning formation?
Ground becomes positively charged
What is the fourth step of lightning formation?
Charges in the cloud become unbalanced
What does the cloud send down to look for positive charges?
A “stepped leader”
What is a stepped leader?
A small tendril of electrons with a negative charge
What is stepped 5 of the formation of lightning?
Ground sends up a streamer
What is a streamer?
a positively charged tendril
What is step 6 of the formation of lightning?
stepped leader and streamer connect, electricity discharged as a “return stroke”
What is thunder?
The sound produced by lightning
What causes thunder?
Lightning very quickly heats the atmosphere to very high temperatures, causing the rapid expansion of air.
What is step 1 of the thunderstorm life cycle?
Cumulus stage
What occurs during the cumulus stage?
A cumulus cloud grows vertically with an updraft. Expands in volume and warms adiabatically. RH increases. Condensation level lifts above 0*F isotherm, bergeron process
What is step 2 of the thunderstorm life cycle?
The mature stage
What happens during the mature stage?
Falling precipitation creates a cool downdraft. Top of the cloud spreads into a anvil. Most intense part of the storm
What direction is the anvil pointing on a cumulonimbus cloud?
The direction the storm is moving
What is step 3 of the thunderstorm life cycle?
Dissipating stage
What occurs during the dissipating stage?
The downdraft strengthens and updraft weakens. Downdraft spreads out and cuts off the updraft, making precipitation end. Cloud evaporates from the bottom-up
What are the types of thunderstorms?
single-cell thunderstorm, multicell thunderstorm, squall, supercell thunderstorm
What must a severe thunderstorm do?
At least one of the following: create hail >= 1 in, winds > 50 kt, or create tornado
What is a single cell thunderstorm composed of?
1 cumulonimbus cloud with one updraft and one downdraft
How long does a single cell storm last?
20-30 min
What kind of weather does a single cell storm produce?
small hail, heavy rains, thunder and lightning
What is a multicell thunderstorm composed of?
Multiple cumulonimbus clouds that move together as a single unit with multiple updrafts and downdrafts
In a multicell, the downdraft of one cell does what?
creates a new updraft in another
What kind of weather comes from a multicell?
larger hail, stronger winds, weak tornadoes
What is a squall?
A line of thunderstorm cells along a cold front
What kind of weather might we see in a squall?
large hail, heavy rain, weak tornadoes, strong winds
What might you see in a squall’s clouds?
a shelf cloud
What is a shelf cloud?
A cloud that slopes down and away from leading edge of the squall
What does a shelf cloud mean?
shit is about to get real. strongest part of the storm
What is a supercell?
a massive group of thunderstorm cells rotating and moving as one
What does a supercell interact with to begin rotating?
upper-level winds
What weather might you see in a supercell?
very large hail, huge tornadoes, winds >90 kt
What is a tornado?
A rapidly rotating column of air around an intense low pressure center
In the northern hemisphere, most tornadoes spin which direction?
counter-clockwise
What direction do most tornadoes move?
southwest to northeast
What is the average length of a tornado’s path?
7 km
When are tornadoes most common?
spring and early summer
What is the first step of tornado formation?
convergence or crossing of warm low level winds with cooler upper level winds
What is step 2 of tornado formation?
air between upper and lower winds create wind shear (spinning)
What is step 3 of tornado formation?
Updraft of thunderstorm lifts spinning tube into a vertical position. Called mesocyclone
What is step 4 of tornado formation?
Precipitation wraps around mesocyclone
What is step 5 of tornado formation?
Downdraft wraps around mesocyclone, pulling and stretching it. rotation speed increases. when it touches ground, it’s a tornado.
What is climate?
long-term statistics of atmospheric conditions that are calculated over decades, centuries, and millenniums
What is more predictable, weather or climate?
climate
Why do we classify climates?
to simplify and organize data about a complex system and to compare climates.
What is the koppen climate classification based on?
annual and monthly temperature and precipitation data
What seasons does the koppen climate classification consider?
summer and winter
What is the A group?
tropical humid
What is the C group?
mild mid-latitude
What is the D group?
severe mid-latitude
What is the E group?
polar climates
What is the B group?
dry climates
What is the H group?
highland climates
What does the second letter in the koppen classification mean?
seasonal precipitation patterns
What does the third letter in the koppen classification mean?
seasonal temperature patterns
What is a climate system?
A series of interconnected spheres exchanging matter and energy
What are the 5 spheres of the climate system?
1) atmosphere 2) cryosphere 3) hydrosphere 4) geosphere 5) biosphere
What is climate change?
change in the statistics of a climate that lasts at least 10 years
What is climate change initiated by?
A forcing mechanism
What is a forcing mechanism?
A process that initiates a climate change in the system.
What is a feedback mechanism?
Processes in the climate system that alter a climate change already underway
What is positive feedback?
Processes that enhance a change already underway
What is negative feedback?
processes that suppress a change already underway, decreasing impact
What are long-term climate forcers?
things that do not operate on human timescales. Take billions of years
What are some forcing mechanisms?
1) solar cycle 2) ocean oscillations, 3) Volcanic activity 4) anthropogenic climate forcing
The solar cycle operates on an _____ cycle
11 year
What are the symptoms of a solar cycle?
sunspots and faculae
A high number of solar symptoms means what?
more solar activity
What are ocean oscillations?
fluctuations in sea surface temperature and pressure centers over oceans
What do volcanoes release?
dust/ash and SO2.
Aerosols do what to sunlight?
reflect sunlight and have a cooling impact on climate
What is anthropogenic climate forcing?
the unintended side effects of humans on the climate
What are the two was humans effect the climate?
a) land degradation b) changing chemical composition of the atmosphere
What are the greenhouse gases that humans have increased in the atmosphere?
CO2, Methane, Nitrous Oxide, Ozone, Manmade gases
