Download Unit 6 Notes Part 2

Unit 6: Atmosphere Part 2 Notes
Chapter 16: Weather
I.
II.
16.1: Weather and the Atmospheric Water
a. What is Weather and Climate?
i. __________________________ is what is going on in the atmosphere at a particular
place at a particular time.
ii. Weather can change rapidly
iii. A location’s weather depends on:
1. Air temperature, air pressure, fog, humidity, cloud cover, precipitation, wind
speed and direction
2. These are directly related to the amount of energy that is in the system and
where that energy is
3. The ultimate source of energy is the ________________
iv. _________________________ is the average of a region’s weather over time
v. The climate for a particular place is steady and changes only very slowly
vi. Climate is determined by many factors including:
1. The angle of the Sun, the likelihood of cloud cover, and the air pressure
b. Humidity:
i. The amount of ___________________________________ in the air in a particular spot.
ii. Relative Humidity – the percentage of water vapor a certain volume of air is holding
relative to the maximum amount it can contain.
iii. If the humidity today is 80%, it means that the air contains 80% of the total amount of
water it can hold at that air temperature.
iv. Since ________________________ air can hold more water than cold air, raising or
lowering temperature can change air’s relative humidity.
v. _________________________________________ - the temperature when air becomes
saturated with water
c. Clouds:
i. Clouds have a big influence on weather:
1. By preventing solar radiation from reaching the ground
2. By absorbing warmth that is re-emitted from the ground
3. As the source of precipitation
ii. When there are no clouds, there is less insulation:
1. Cloudless days can be extremely hot
2. Cloudless nights can be very cold
iii. Clouds form when air reaches its dew point
iv. Water vapor is not visible unless it condenses to become a cloud
d. Fog:
i. A cloud located at or near the ground
ii. When humid air near the ground cools below its dew point, fog is formed
e. Precipitation:
i. An extremely important part of weather
ii. The most common precipitation comes from clouds:
1. Rain and snow
2. Sleet is less common
16.2: Changing Weather:
a. Introduction:
i. The weather in a location often depends on what type of air mass is over it
ii. Another key factor is whether the spot is beneath a front, the meeting place of two air
masses.
b. Air Mass and Air Mass Formation:
i. Air Mass – a batch of air that has nearly the same __________________________ and
________________________
ii. Forms over a large region (a source region), in high pressure zones, most commonly
formed in polar and tropical regions
iii. Moves across temperate zones so the middle latitudes are prone to having interesting
weather
iv.
c. Air Mass Movement:
i. Air masses are _____________________ pushed along by high-level winds
1. When it moves over a new region, it shares its temperature and humidity with
that region
ii. Storms arise if the air mass and the region it moves over have different characteristics
iii. In general, cold air masses tend to flow toward the ___________________________
and warm air masses tend to flow toward the __________________
1. This is one of the many processes that act towards balancing out the planet’s
temperature
d. Fronts:
i. Where two air masses meet
ii. The two air masses have different ___________________________ and do not easily
mix
1. One air mass is lifted above the other, creating a low pressure zone
2. If the air lifted is moist, there will be condensation and precipitation
3. Winds are common at a front
iii. Fronts are the main cause of stormy weather
iv. With a cold front and warm fronts, the air mass at the leading edge at the front gives
the front its name
III.
1. Example: A cold front is right at the leading edge of moving cold air, and a warm
front marks the leading edge of the warm air
e. Stationary Front:
i. The air masses do not move
ii. Could become stationary if is blocked by mountains
iii. May bring days of rain, drizzle, or fog
iv. Winds usually blow parallel to the front, but in opposite directions
v. After several days the front may break apart
f. Cold Fronts:
i. When a cold air mass takes the place of a warm air mass
ii. The denser, cold air pushes up the arm air causing the air pressure to decrease
iii. At the front a line of rain showers, snow showers, and thunderstorms with blustery
winds
iv. ________________ line – a line of severe thunderstorms forms along a cold front
v. Behind the front is a __________________ air mass
vi. The weather at a cold front varies with season
g. Warm Fronts:
i. A warm air mass slides over a cold air mass
ii. Less dense air moves over the colder, denser air, the atmosphere is relatively
____________________
iii. The transition from cold air to warm air takes place over a long distance, so the first
signs of changing weather appear long before the front is actually over you
iv. Initially the air is cold, the cold air mass is above you and the warm air mass is above it
v. High circus clouds make the transition from one air mass to the other
h. Occluded Front:
i. Usually forms around a low pressure system
ii. Starts when a cold front catches up to a warm front
iii. The air masses, in order from front to back, are cold, warm, and then cold again
iv. Coriolis Effect curves the boundary where the two fronts meet towards the poles
v. _________________________ and shifting winds are typical
16.3: Storms:
a. Introduction:
i. Weather happens every day but only some days have storms
ii. The effect of storms also varies depending on weather may strike a populated area of a
natural landscape
iii. Hurricane Katrina is a good example; since the flooding after the storm severely
damaged New Orleans, while a similar storm in an unpopulated area would have done
little damage
b. Thunderstorms:
i. Extremely common – most drop a lot of rain on a small area quickly, but some are
severe and highly damaging
ii. From when ground temperature are high, ordinarily in the __________________
afternoon or early evening in spring and summer.
iii. Birth of a thunderstorm:
1. As water vapor ________________________ to form a cloud, the latent heat
makes the air in the cloud warmer than the air outside the cloud
2. This starts a downdraft, and soon there is a convection cell within the cloud
3. The thunderstorm is mature and it produces gusty winds, lightning, heavy
precipitation, and hail
iv. Death of a thunderstorm:
1. Convection shuts down – without ________________________ water vapor
does not condense, no latent heat is present, and the thunderhead runs out of
energy
v. With severe thunderstorms:
1. The warm air gives the convection cell more energy
2. Can cause lots of damage because of high winds, flooding, intense hail, and
tornadoes
vi. Thunderstorms can form individually or in a _________________ line along a cold front
vii. So much energy collects in cumulonimbus clouds that a huge release of electricity
occurs (aka ______________________________)
viii. Lightning heats the air so that it expands explosively, creating thunder
1. Sound waves travel much more slowly so a thunder clap may come many
seconds after the lightning is spotted.
c. Tornadoes (aka Twisters):
i. Fierce products of severe thunderstorms
1. As air in a thunderstorm rises, the surrounding air races to fill the gap, forming a
funnel
ii. Can last a few seconds to several hours
iii. Forms at the ___________________ of severe thunderstorms
1. Lines of theses thunderstorms form in the spring where a ______________
maritime tropical (mT) and continental polar (cP) air masses meet.
iv. April 2011:
1. The deadliest set of tornado strikes in 25 years
2. Had many factors to encourage tornado formation:
a. Meeting of the mT and cP air masses
b. Jet stream was blowing strongly from the west
3. Results more than 150 tornadoes reported thought the day
v. Meteorologist can only predict tornado danger over a very wide region
vi. No one can tell exactly where and when a tornado will touch down
vii. The exact path is unknown because tornado movement is not very predictable
viii. The intensity of tornadoes is measured on the Fujita Scale – which assigns a value based
on ______________ speed and damage
F Scale
(km/hr)
(mph)
Damage
64-116
40-72
Light-tree branches
fall and chimneys
may collapse
117-180
73-112
Moderate – mobile
homes, autos pushed
aside
181-253
113-157
Considerable – roofs
torn off houses, large
trees uprooted
254-332
158-206
Severe – houses torn
apart, trees
uprooted, cars lifted
333-419
207-260
Devastating – houses
leveled, cars thrown
420-512
261-318
>512
>318
Incredible –
structures fly, cars
become missiles
Maximum tornado
wind speed
d. Cyclones:
i. Can be the most intense storms on Earth
ii. A system of winds rotating counterclockwise in the Northern Hemisphere around a
_____________ pressure system
iii. Two types of cyclones:
1. Middle Latitude (mid-latitude) cyclones – the main course of winter storms in
the middle latitudes
2. Tropical Cyclones – aka hurricanes
iv. An anticyclone is the opposite of a cyclone – winds rotate clockwise in the N.
Hemisphere around a center of _______________ pressure.
e. Mid – Latitude Cyclones:
i. Sometimes called extratropical cyclones, form at the ______________ front when the
temperature difference between two air masses is large
ii. Mid-latitude cyclones are especially fierce in the mid-Atlantic and New England states
where they are called __________________________ - because they come from the
northeast.
f. Hurricanes:
i. Tropical cyclones have many names:
1. ______________________________ - North Atlantic, Eastern Pacific Ocean
2. Typhoons – Western Pacific Ocean
3. Tropical Cyclone – Indian Ocean
4. Willi-Willi’s – Australia
ii. Hurricanes arise in the tropical latitudes in summer and autumn when the surface
temperature are 820F or higher
iii. The warm air rises and forms a low pressure cell known as a topical
________________________
iv. Thunderstorms materialize around tropical depressions
v. Hurricane are huge with high winds
1. Exception is the calm eye of the storm – where air is rising upward
vi. Rainfall can be as high as 1” per hour
vii. The release of latent heat generates enormous amounts of ___________________
1. Nearly the total annual electrical power consumption of the US from ONE storm
viii. Hurricanes can also generate tornadoes
ix. Move with the prevailing winds – they originate in the trade winds and move to the
west
1. Reach the latitude of the westerlies, they switch direction and travel toward the
north or northeast
x. Hurricanes are assigned to categories based on their wind speed. The categories are
listed on the Saffir-Simpson hurricane scale
Category
Kph
Mph
Estimated Damage
119-153
74-95
Above normal, no
real damage to
structures
154-177
96-110
Some roofing, door,
and window
damage,
considerable damage
to vegetation,
mobile homes, and
piers
178-209
111-130
Some building
damaged, mobile
homes destroyed
210-251
131-156
Complete roof
failure on small
residences, major
erosion of beach
areas, major damage
to lower floors of
structures near shore
>251
>156
Complete roof
failure on many
residences and
industrial buildings,
some complete
building failures
xi. Damage from hurricanes comes from the high winds, rainfall and storm surge
xii. Storm surge occurs as the storm’s low pressure center comes onto land, causing the sea
level to rise unusually high
1. Often made worse by the hurricane’s high __________________ blowing
seawater across the ocean onto the shoreline
xiii. Flooding can be devastating, especially along low-lying coastlines, such as the Atlantic
and Gulf Coast
xiv. Hurricanes typically last for 5 to 10 days
xv. Over _____________________ water or land the hurricane’s latent heat source shuts
down and the storm weakens
1. When a hurricane disintegrates it is usually replaced with intense rain and
tornadoes.
xvi. As people develop coastal regions, property damage from storms continue to rise
xvii. However, scientists are becoming better at predicting the paths of these storms and
fatalities are decreasing
xviii. The 2005 Atlantic hurricane season was the longest, costliest, and deadliest hurricane
season so far
1. Total damage from all the storms together was estimated at more than $128
billion, with more than 2,280 deaths
2. Hurricane Katrina was both the most destructive hurricane and the most costly
g. Blizzards:
i. Blizzards have certain conditions:
1. Low temperatures, high winds, heavy snow with low ____________________
ii. Happen across the middle latitudes and towards the poles, usually as part of a midlatitude cyclone
IV.
iii. Are most common in winter, when the __________________________ has traveled
south and a cold, northern air mass comes into contact with a warmer, semitropical air
mass
iv. Can also produce sleet of freezing rain
h. Lake-Effect Snow:
i. In winter, a continental polar (cP) air mass travels down from Canada
ii. As the frigid air travels across one of the Great Lakes, it warms and absorbs moisture
iii. When the air mass reaches the leeward side of the lake, it is very unstable and it drops
tremendous amounts of snow
i. Heat Wave:
i. Is different at different locations
1. It is a long period of hot weather for at least three days in cooler locations
2. Much more longer and hotter in hotter locations
ii. Heat waves have increased in frequency and duration in recent years
1. Can result when a high pressure zone keeps the
___________________________ further north/south than normal
16.4: Weather Forecasting:
a. Introduction:
i. Forecasters now use advanced technologies to gather weather data, along with the
world’s most powerful computers
1. Together the data and computers produce __________________ models that
more accurately represent the condition of the atmosphere
ii. Weather is extremely difficult to predict because it is complex and chaotic systems
b. Collecting Weather Data:
i. Temperature, air pressure, and other characteristics of the atmosphere must be
measured and the data collected
ii. ____________________________ - measures temperature
iii. ____________________________ - measures air pressure
1. A change in barometric pressure indicates that a change in weather is coming
a. If the air pressures rises, a high pressure cell is on the way and clear skies
ca be expected
b. If the air pressure falls, a low pressure cell is coming and will likely bring
storm clouds
iv. Weather Stations – contain some types of thermometer and barometer
v. Radiosondes – measure atmospheric characteristics, such as temperature, pressure, and
humidity as they move through the air
c. Radar (Radio Detection and Ranging):
i. A transmitter sends out radio waves that bounces off the nearest object and then return
to a receiver.
ii. Doppler radar can also track how fast the precipitation falls
iii. Radar can outline the structure of a storm and can be used to estimate its possible
effects
d. Satellites:
i. Weather satellites are they best way to monitor large scale systems, such as storms
ii. Are able to record long-term changes, such as the amount of ice cover over the Arctic
Ocean
e. Numerical Weather Patterns:
i. The most accurate weather ______________________ are made by advanced
computers, with analysis and interpretation added by experienced meteorologists
ii. Meteorologists can use these results to give much more accurate weather forecasts and
climate predictions
f. Weather Maps:
i. Simply and graphically depict meteorological conditions in the atmosphere
ii. Meteorologist use many different symbols as a quick and easy way to display
information on the map
iii. _______________________ - lines of equal temperature, show temperature gradients
and can indicate the location of a front
iv. Isobars – lines of equal average air pressure at sea level
1. Closed isobars represent the locations of high and low pressure cells