chapter 24 (quiz 3) Flashcards
1
Q
hurricane characteristics
- definition: sustained winds of …
- size (diameter)
- duration
- strength: central pressure averages…
- power
A
Definition: Hurricanes have sustained winds of 120 km/hr (74 mph) or greater.
Size: Average diameters are approximately 600 km
(350 mi). (one third the size of mid-latitude cyclone)
Duration: days to a week or more.
Strength: Central pressure averages about 950 mb but
may be as low as 870 mb.
Power: The energy released by a single hurricane can
exceed the annual electricity consumption of the US
and Canada
2
Q
naming convention
- hurricane
-typhoon
- cyclone
A
Hurricanes: extreme tropical storms over Atlantic and eastern
Pacific Oceans.
Typhoons: extreme tropical storms over western Pacific
Ocean.
Cyclones: extreme tropical storms over Indian Ocean and
Australia
3
Q
what do hurricanes depend on
A
Hurricanes depend on a large pool of warm water
4
Q
annual hurricane frequency
- where are there no hurricanes
- where are the hurricanes the strongest
A
No hurricane in the Southern Atlantic Ocean.
Western Pacific hurricanes are the strongest
5
Q
conditions necessary for hurricane formation
- where do hurricanes form
- when are water temperatures usually below the threshold above
- when are hurricanes most fequent
- what is an important contributor to hurricanes
- what do hurricanes need
- what must be absent for hurricane formation
A
Hurricanes form only over deep
(several tens of meters) water
layers with surface temperatures
in excess of 27 C.
Poleward of about 25 degrees, water
temperatures are usually below
this threshold.
Hurricanes are most frequent in
late summer and early autumn
during high SST times
Coriolis force is an important contributor, and as such, hurricanes do
not form equatorward of 5o.
Need an unstable atmosphere: available in the western tropical ocean
bur not in the eastern parts of the ocean.
Strong vertical shear must be absent for hurricane formation
6
Q
hurricane seasons
- where do hurricanes obtain their energy from
- where do hurricanes occur
- in the northern hemisphere what is the most active months for hurricanes
- in the southern hemisphere what is the most active months for hurricanes
A
- Hurricanes obtain their energy from latent heat release in the cloud formation process.
- Hurricanes occur where a deep layer of warm waters exists and during the times of highest SSTs (sea surface temperature).
- For the N.H., August and September are the most active months.
- For the S.H., the hurricane season is January-March
7
Q
1938 New England Hurricane
- also referred to as
- where did it form? what category?
- where did it hit? what category?
- how many deaths? damages? estimated property losses?
A
- (also referred
to as the Great Long Island - New England Hurricane and the
Long Island Express Hurricane)was one of the deadliest and most
destructive tropical cyclones to strike the United States - Formed near the coast of Africa on September 9, becoming a
Category 5 hurricane on the Saffir–Simpson hurricane scale,
before making landfall as a Category 3 hurricane on Long Island
on Wednesday, September 21. - Estimated that the hurricane killed 682 people, damaged or
destroyed more than 57,000 homes, and caused property losses
estimated at $306 million ($4.7 billion in 2024). Also, numerous
others estimate the real damage between $347 million and almost
$410 million
8
Q
tropical cyclone stages (4)
A
- Potential tropical: disorganized low
- Tropical depression: organized low <39 mph winds
- Tropical storm: 39-73 mph winds
- Hurricane: 74+ mph winds
9
Q
hurricane intensity scale
- name
- five categories
A
- The Saffir-Simpson scale.
- Five categories: larger numbers indicate lower central pressure, greater winds, and stronger storm
surges
10
Q
hurricane track
- hurricanes are affected by (3)
- hurricanes typically form within ___ and move ____
- due to subtropical high and Coriolis force hurricanes tend to move ___
- eventually hurricanes will …
A
- In the Atlantic: east to west initially than curve north but there are exceptions
- Many hurricanes that form in the Atlantic never make landfall
Hurricane tracks are affected by
(1) subtropical high, (2) trade
wind, and (3) Coriolis force.
Hurricanes typically form
within the trade wind belt and
normally moves westward with
the winds.
Due to the subtropical high and
the Coriolis force, hurricanes
tend to move poleward.
Eventually hurricanes cross
from the trade wind belt into the
mid-latitude westerly belt, and
begin to move eastward
11
Q
Heat Engines as model of Hurricanes
- a heat engine acts by
- basic model was developed by
—> led to….
- the efficiency produced relative to heat taken depends only upon…..
A
A heat engine acts by transferring energy from a warm region to a cool region of space and, in the process, converting some of that energy to mechanical work.
* The basic model for this engine
was developed by Nicolas
Léonard Sadi Carnot in 1824 in
an analysis aimed at improving
the steam engine
* Led to the fundamental
thermodynamic concept of
entropy and second Law of
Thermodynamics.
* The efficiency (amount of work
produced relative to heat taken
up) depends only upon the
absolute temperatures of the hot
and cold heat reservoirs between
which it operates
12
Q
Simplified Conceptual Model of a Heat
Engine
A
Heat from T1 (Q1) is used to create work (W) and in the process looses heat (Q2) to T1
13
Q
The Four Stages in a Carnot
Cycle
A
- Isothermi expansion at Th
- Adiabatic expansion from Th to Ti
- Isothermi compression at Ti
- Adiabatic compression from Ti to Th
14
Q
Identify which part of a hurricane is
associated with each stage of a Carnot Cycle
A
- Isothermal Expansion: Formation and intensification, absorbing heat from the warm ocean.
2 Adiabatic Expansion: Rising air, central updraft and strengthening of the storm. - Isothermal Compression: Outer downdraft regions, releasing heat to the environment.
- Adiabatic Compression: Compression of air as the storm weakens and dissipates.
15
Q
- How will increasing sea surface temperature affect the efficiency of converting heat energy into work in a hurricane?
- How will this affect the power of hurricanes?
A
Increased sea surface temperature is likely to increase the efficiency of converting heat into work in a hurricane, primarily by providing more heat and moisture, which intensifies the storm and strengthens its dynamics
- increase the power of the hurricane
16
Q
When the Levees Broke
- Hurricane Katrina
A
- Hurricane Katrina was a devastating
tropical cyclone that caused 1,392 fatalities and damages estimated at $186.3 billion (2022 USD) in late August 2005, particularly in the city of New Orleans and its surrounding area
17
Q
When the Levees Broke: A
Requiem in Four Acts
A
- a 2006 documentary film directed by Spike Lee about the devastation
of New Orleans, Louisiana following the failure of the levees during
Hurricane Katrina. - Filmed in late August and early September 2005, and premiered at the
New Orleans Arena on August 16, 2006 and was first aired on HBO
the following week. - . It has been described by Sheila Nevins, chief of HBO’s documentary
unit, as “one of the most important films HBO has ever made.“ - The title is a reference to the blues tune “When the Levee Breaks” by
Kansas Joe McCoy and Memphis Minnie about the Great Mississippi
Flood of 1927
18
Q
Spike Lee
A
- Shelton Jackson “Spike” Lee (born March 20, 1957) is an American film director, producer, screenwriter, actor, and author
- His work has continually explored race relations, issues within the black community, the role of media in contemporary life, urban crime and poverty, and other political issues
19
Q
1927 flood in music
A
- Many people are familiar with Led Zeppelin’s 1970 version of this song, but this (link below) is the original recording of it from 1929.
- In 1927, the Mississippi River flooded over 27,000 square miles of land under 30 feet of water, killing hundreds of
people and destroying towns, farms, and homes in Louisiana, Arkansas, Mississippi, and the Mississippi Delta. - Considered the most destructive river flood in U.S. history, two years later “The Great Flood of 1927” inspired
Mississippi natives, Kansas Joe McCoy and Memphis Minnie, to write and record “When the Levee Breaks” in
1929
20
Q
Led Zeppelin’s “When the Levees Breaks”
A
- Led Zeppelin recorded “When the Levee Breaks” for their untitled fourth album. When considering material for the group to record, singer Robert Plant suggested the Kansas Joe McCoy and Memphis Minnie song.
- Jimmy Page commented that while Plant’s lyrics identified with the original, he developed a new guitar riff that set it apart.
- However, it is John Bonham’s drumming that is usually noted as the defining characteristic of the song
21
Q
Mississippi Drainage
A
- the primary river of the largest drainage basin in the United States.
- From its traditional source of Lake Itasca in northern Minnesota, it flows generally south for 2,340 miles (3,766
km)to the Mississippi River Delta in the Gulf of Mexico. - With its many tributaries, the Mississippi’s watershed drains all or parts of 32 U.S. states and two Canadian provinces between the Rocky and Appalachian mountain
22
Q
Some Mississippi History
A
- Native Americans have lived along the Mississippi River and its tributaries for thousands of years. Many were hunter-gatherers, but some, such as the Mound Builders, formed prolific agricultural and urban civilizations, and some practiced aquaculture.
- Served sometimes as a barrier, forming borders for New Spain, New
France, and the early United States, and throughout as a vital transportation artery and communications link. - In the 19th century, during the height of the ideology of manifest destiny, the Mississippi and several tributaries, most notably its largest, the Ohio and Missouri, formed pathways for the western expansion of the United States
23
Q
Some More Mississippi History
A
- Formed from thick layers of the river’s silt deposits, the Mississippi embayment, and American Bottom are some of the most fertile regions
of the United State. These form when the river floods; - Steamboats were widely used in the 19th and early 20th centuries to
ship agricultural and industrial goods. - During the American Civil War, the Mississippi’s final capture by Union forces marked a turning point to victory for the Union.
- Because of the substantial growth of cities and the larger ships and
barges that replaced steamboats, the first decades of the 20th century
saw the construction of massive engineering works such as levees,
locks and dams, often built in combination
24
Q
levee
- natural levees
- artificial levees
- ancient levees
- levees present day
A
- An elevated ridge, natural or artificial, alongside the banks of a river, often intended to protect against flooding of the area adjoining the river.
- It is usually earthen and often runs parallel to the course of a river in
its floodplain or along low-lying coastlines. - Naturally occurring levees form on river floodplains following flooding, where sediment and alluvium is deposited and settles, forming a ridge and increasing the river channel’s capacity.
- Alternatively, levees can be artificially constructed from fill, designed
to regulate water levels. In some circumstances, artificial levees can
be environmentally damaging. - Ancient civilizations in the Indus Valley, ancient Egypt, Mesopotamia
and China all built levees. - Today, levees can be found around the world, and failures of levees
due to erosion or other causes can be major disasters, such as the
catastrophic 2005 levee failures in Greater New Orleans that occurred
as a result of Hurricane Katrina and the 1927 Great Mississippi Flood.
25
Levee flooding steps (3)
1) River channel and floodplain prior to flooding
2) During flood stage
- Granular sediment (sands and gravels) deposited adjacent to channel
- Fine sediment (silts and clays) deposited farther from active channel
3) After repeated flooding
- Natural levees deposited by repeated flooding
26
Artificial Levees
Build bigger levees on top of the natural levees
27
when was the first artificial levee built in new orleans
1718
28
Critical Events in New Orleans’
Hurricane History
- how many hurricanes since 1759
- frequency of hurricanes
- how many have caused significant flooding
- hurricane flooding frequency
* Since the year 1759, 176 hurricanes have struck the Louisiana Coast
* Frequency is about two hurricanes every three years
* 38 hurricanes have caused significant flooding in New Orleans
* Hurricane Flooding frequency is about once every 6.5 years
29
The Great Mississippi Flood of
1927
* Most destructive river flood in the history of the United States, with 27,000 square miles (70,000 km2) inundated in depths of up to 30 feet (9 m) over the course of several months in early 1927.
* Cost of the damage has been estimated to be between $246 million and $1 billion, which ranges from $3.5–$14.1 billion in 2023 dollars
* About 500 people died and over 630,000 people were directly affected; 94% of those affected lived in Arkansas, Mississippi, and Louisiana, especially in the Mississippi Delta region.
* More than 200,000 African Americans were displaced from their homes along the Lower Mississippi River and had to live for lengthy periods in relief camps
30
Hurricane Structure
- central eye
- eye wall
- cloud bands
* A central eye surrounded by large cumulonimbus thunderstorms occupying the adjacent eye wall.
* Weak uplift and low precipitation regions separate individual cloud bands
31
Hurricane Eye and Eye Wall
- eye
- shrinking eye indicates
- eye wall is comprised of
* The eye is an area of descending
air, relatively clear sky, and light
winds which is about 25 km (15
mi) in diameter on average.
* A shrinking eye indicates storm
intensification.
* The eye wall is comprised of the
strongest winds, the largest
clouds, and the heaviest precipitation with rainfall rates as high as 2500 mm/day (100 in.).
The eye moves at a speed of 20
km/hr. The calm weather
associated with the eye will last
less than an hour.
32
vertical cross section of hurricane
- how the air in the eye descends
- how the eye warms
- how air in the eye wall ascends
- where pressure gradient is the strongest
- where strongest rainfall is produced
- where strongest storm surge is produced
Most of the air in the eye descends very slowly, taking days to traverse the eye’s depth.
Air sinks in the eye warms adiabatically and make the eye much warmer than other regions of the hurricane.
In the eye wall air ascends from
the surface to the tropopause.
Pressure gradient is the strongest near the eye wall, where the most violent winds are produced.
Strongest rainfall is also produced near the eye wall.
Strongest storm surge occurs to
the right of the hurricane
33
pressure structure
* The horizontal pressure gradient
with altitude decreases slowly.
* At about 400 mb, pressures
within the storm are approximate to that outside.
* Surface-400mb: Cyclonic
circulation.
* 400mb-tropopause: anticyclonic
circulation.
The upper portions of the storm
are blanketed by a cirrus cloud
cap due to overall low temperatures
34
Development of Hurricane:Hurricane Formation
----> Trigger Mechanisms for Initial Thunderstorms: (3)
----> Environment Required for Hurricane Formation: (4)
----> Spin up of thunderstorm clusters into Hurricane: (2)
Trigger Mechanisms for Initial Thunderstorms:
1. Intertropical convergence zone
2. Easterly waves in trade wind flow
3. Cold fronts extending into tropics
Environment Required for Hurricane Formation:
1. Sea surface temp > 80F
2. Deep layer of warm water
3. Weak wind shear
4. At least 5 degrees from equator
Spin up of thunderstorm clusters into Hurricane:
1. Wind induced transfer of heat from the ocean to the atmosphere
2. Conservation of angular momentum
35
Hurricane Wind Structure
- where are winds and surge typically most intense
* Winds and surge are typically most intense in the right front quadrant
of the storm where wind speeds combine with the speed of the storm’s
movement to create the area of highest potential impact
36
Tropical Storm Triggers
Tropical Cyclones start with groups
or clusters of thunderstorms
37
Need uplift to create storms.
Why?
Uplift of air causes it to cool. If the
air holds a lot of moisture, when it
cools, thunderstorms can form and
release latent heat.
Convergence can cause uplift
38
convergence
- definition
- importance
- the horizontal in-flow of air into a region
- Convergence is crucial for hurricane development because it causes a buildup of air near the surface. As the air converges, it creates an area of low pressure. This low-pressure area helps initiate the rising of warm, moist air from the surface, which provides the fuel for the hurricane. The rising air leads to the formation of the storm's central vortex (eye), and this process is vital for the intensification and strengthening of the hurricane
39
divergence
- defintion
- importance
- the horizontal outflow of air from a region
- Divergence at higher levels is important for allowing the storm to grow and strengthen. As air rises in the lower levels (due to convergence), it must leave the system at upper levels for the hurricane to sustain itself. If there is strong divergence aloft, it ensures that air continues to rise and does not stagnate, thus promoting ongoing convection (rising warm air) and helping maintain or intensify the hurricane
40
Convective Cells can Cause
Convergence
- Convection cells cause convergence because warm air rises, creating a low-pressure zone at the surface.
- The surrounding air moves toward this low-pressure area to replace the rising warm air, causing convergence.
- This inflow of air enhances the upward motion of warm, moist air, feeding into the convection cycle and promoting the formation or intensification of weather systems like hurricanes
41
How convergence causes a storm
the meeting and piling up of air, forces air upwards, which can lead to cloud formation and precipitation, ultimately contributing to thunderstorm development
42
atmospheric stability
- unstable
- stable
- neutral
* If air that starts to move up continues to accelerate up, the air is unstable.
* If air that moves up returns down to its original altitude, it is stable.
* If the air doesn’t move air being lifted, it is neutral
43
on a diagram of hadley circulation where are thunderstorms
On a diagram of Hadley circulation, thunderstorms, which form the Intertropical Convergence Zone (ITCZ), are found along the equator and in the rising air of the Hadley cells
44
Tropical Waves and Surface Convergence
- tropical wave aka (3)
- in and around ...
- what is it
- moves from
- causes
A tropical wave (also called easterly wave, tropical easterly wave, and African easterly wave), in and around the Atlantic Ocean, is an elongated area of relatively low air pressure, oriented north to south, which moves from east to west across the tropics, causing areas of cloudiness and thunderstorms
45
- wind speed around the north side of wave crest
- wind speed around southern trough
- this causes ...
Wind is slow around the north side of the wave crest and faster around the southern trough. This causes convergence to the west of the trough
46
tropical storm genesis: convergence behind an easterly wave
- in typical hurricane season how many easterly waves develop in north atlantic
- how many becomes a tropical depression
In a typical hurricane season some 60 easterly waves develop in the North Atlantic. Only about 1 wave in 5 becomes a tropical depression. Strong upper level troughs and westerly winds commonly suppress hurricane formation
47
another way to get air to lift and start storms
Cold fronts are another way to get air to lift and start storms. But are less common for formation of hurricanes.
48
Cold front thunderstorm
The moving cold air front pushes the
moist warm air up.
49
Tropical Disturbances and Easterly Waves
- most tropical disturbances develop from...
* Some tropical disturbances form in association with mid-latitude troughs
migrating toward lower latitudes, some form from ITCZ-related convection, but most develop from easterly waves.
* Easterly waves, or undulations in the trade wind pattern, spawn hurricanes
in the Atlantic (typically 2–3000 km).
* Only about 10% tropical disturbances intensify into more organized,
rotating storms.
50
Hurricanes can cause upwelling of cold water. Why?
Hurricanes cause upwelling of cold, nutrient-rich water because their strong winds push surface water away, allowing deeper, colder water to rise and replace it
- The Earth's rotation (Coriolis effect) and the wind direction combine to cause a phenomenon called Ekman transport. In the Northern Hemisphere, the surface water is deflected to the right of the wind direction, and in the Southern Hemisphere, it is deflected to the left.
- The combination of strong winds and Ekman transport causes a horizontal movement of surface water, which is displaced away from the storm center. To replace this displaced water, cooler water from deeper in the ocean is brought up to the surface, creating upwelling
51
coastal upwelling
coastal upwelling is the most common type of upwelling, and the most closely related to human activities as it supports some of the most productive fisheries in the world. It is normally due to along-shore winds: these force water to move, and because of the Coriolis force the flow turns to the right in the Northern hemisphere, and to the left in the Southern hemisphere. If that happens to be the offshore direction, surface water moves offshore and is replaced by cold, nutrient rich water from the depth.
52
upwelling at the equator
equatorial upwelling is again due to the Coriolis force, acting on the sides of equatorial currents, that pulls the water in different directions in the two hemispheres. Water immediately to the North of the equator will feel a force pulling to the right, while water immediately to the South of the equator will feel a force pulling to the left. This causes a divergence at the surface of the equator, which drags up nutrient-rich water from below. Equatorial upwelling is. very clearly seen in the Pacific and in the Atlantic, while it is absent in the Indian, mainly because the trade winds are different in either season of the year and also due to the absence of an equatorward eastern boundary current that feeds into the equatorial current.
53
wind shear
a wind direction and/or speed change over a vertical or horizontal distance
54
The Source of Strong Rotating Winds
- strong rotating winds in the core of the hurricane is a result of
- where do small rotating thunderstorms (cyclones) move towards
- where do anticyclonic storms move out of
The strong rotating winds in the core of a hurricane is a result of the conservation of angular momentum.
The small rotating thunderstorms (cyclones) move towards the center
of a “pouch”.
The anticyclonic storms move out of the “pouch”
55
How do tropical disturbances organize
into hurricanes? (2)
1. Easterly waves form pouches that
trap smaller cyclones and eliminate
small anti-cyclones.
2. These create a positive feedback
system fueling the building of the
hurricane engine
56
