Download Severe Weather, Hurricanes and Flooding in Developing Nations

Severe Weather, Hurricanes and
Flooding in Developing Nations
Solar Heating and Latitude
Solar Heating and the Seasons
Relationship of sun angle and
solar radiation received on Earth
Solar Heating and Atmospheric
Circulation
• Air at high elevations: • Air at sea level:
– Cooler
– Expands
– Water vapor tends to
condense
– Warmer
– More compressed
– Can hold more water
vapor
Air Circulation & Convection
Currents
Atmospheric Circulation &
Convection Cells
Global Wind
Patterns
• Fronts
– Different air masses do
not mix
– Boundaries called “fronts”
– Cold air over warm =
unstable
Rotating Air Bodies
• Low Pressure Zone
Formation
– Warm air rises
– Creates a low pressure
zone
– At the Earth’s surface,
air “feeds” the low
pressure zone, moves
counterclockwise
• High Pressure Zone
Formation
– Cool air sinks
– Creates a high pressure
zone
– At the Earth’s surface,
winds blow clockwise
Rotating Air Bodies
• Bends in the polar jet create troughs and
ridges
• Forms cyclones and anticyclones
Cyclones and Anticyclones
Rotating Air Bodies
• Cyclones
– Low pressure zone in
polar jet trough
– Winds at surface flow
counterclockwise towards
the core
– Air is updrafted and
cooled
– Forms clouds, rain and
upper level outflow of air
Rotating Air Bodies
• Anticyclones
– High pressure zone at
ridge of polar jet
– Air converges in upper
atmosphere
– Descends towards the
ground
– Flows outward at surface
– Dry, windy conditions
Cyclonic and anticyclonic winds
in the Northern Hemisphere
Cold Fronts and Warm Fronts
High pressure system
Rain!
Low pressure system
Rain/Snow
High pressure system
Low pressure system
Thunderstorms
Types of Severe Weather
• Thunderstorms
• Snow / Rain storms
• Mid-latitude cyclones
– Blizzards
– Tornadoes
• Tropical cyclones
– Typhoons in the western Pacific
– Cyclones in the Indian Ocean
– Hurricanes in the U.S.
Hurricanes
Hurricanes
• How a Hurricane Works
– Tropical disturbance
• Low pressure zone develops and draws in clusters of
thunderstorms and winds
Hurricanes
• How a Hurricane Works
– Tropical disturbance
– Tropical depression
• Surface winds strengthen, move about the center of
the storm
• Central core funnels warm moist air up towards
stratosphere
• Air cools, vapor condenses, latent heat released
• Fuels more updrafts, cycle repeats, storm grows
Hurricanes
• How a Hurricane Works
– Tropical disturbance
– Tropical depression
– Tropical Storm
• Storm has sustained surface wind speeds of +39
mph
Hurricanes
• How a Hurricane Works
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Tropical disturbance
Tropical depression
Tropical Storm
Hurricane
• Surface winds consistently over 74 mph
Hurricanes
• How a Hurricane Works
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Tropical disturbance
Tropical depression
Tropical Storm
Hurricane
The Eye
• As wind speed increases, winds are spiraled
upwards prior to reaching the center
• A distinctive clear “eye” is formed
• Strongest winds are located on the walls of the eye
Hurricane Wind Patterns
Hurricane Origins
• Form in the tropics ~ 5° and 20 ° latitude
• Cannot form at the equator (Coriolis effect = 0)
Hurricanes
• Hurricane Damages
– Storm Surges
• Large mound of water builds up beneath the eye
• Reaches land as a surge of water
Hurricanes
• Hurricane Damages
– Storm Surges
• Wind speed varies
depending upon which
side of the hurricane
you’re on
• Amount of damage on the
coastline will vary
accordingly
Hurricanes
• Hurricane Damages
– Heavy Rains
– Mudflows and Debris Avalanches
– Flooding
Cyclones and The Bay of Bengal
Cyclones and The Bay of Bengal
• The Indian “Super Cyclone” 1999
– Deadliest since April 1991 cyclone
– NOTE:
• The North Indian Ocean is the only area of the
world where tropical cyclones are not given names.
• However, the Joint Typhoon Warning Center in
Hawaii gives identifiers to all tropical cyclones and
this one was designated as "05B".
Cyclones and The Bay of Bengal
• Bangladesh
– Climate: Tropical
• mild winter
(October to March);
• hot, humid summer
(March to June);
humid,
• warm rainy
monsoon (June to
October)
Cyclones and The Bay of Bengal
• Bangladesh
– Terrain:
• most of the country is
situated on deltas of
large rivers
• About 6% of the total
land area is permanently
under water, and twothirds is flooded for part
of the year.
Cyclones and The Bay of Bengal
• Bangladesh
– Environment - current issues:
• severe overpopulation;
• many people are landless and forced to live on and
cultivate flood-prone land;
• water-borne diseases prevalent in surface water;
• water pollution, especially of fishing areas, results
from the use of commercial pesticides;
• ground water contaminated by naturally occurring
arsenic;
Cyclones and The Bay of Bengal
• Bangladesh
– Has one of the worst records for natural
disasters
• Floods, cyclones, tidal surges, tornadoes, droughts
and even cold spells.
– 1971
• Over 1,000,000 people dead
• country's entire infrastructure on the south coast was
wiped out.
Cyclones and The Bay of Bengal
• Bangladesh
– 1991
• Cyclone killed nearly 140,000 people, most of them
women and children.
• Casualty rate was lower principally because the
government had embarked on an extensive program
of cyclone shelter construction which continued
until the early 1990s.
Cyclones and The Bay of Bengal
• The Indian “Super
Cyclone” 1999
– Hit the Indian state of
Orissa hardest
– Indian officials state that
“development in the state
has been set back an entire
generation”
Cyclones and The Bay of Bengal
• The Indian “Super Cyclone” 1999
– Orissa is one of India’s poorest states
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India's highest infant mortality rate
2/3 of the rural population living in abject poverty
lowest number of doctors per capita
Lack of electricity and water
< 5% of the population has access to subsidies for
food and fuel aimed at poverty-alleviation.
Oct 29
Landfall
Oct 27
Hurricane
Oct 26
Tropical
Storm
Nov 01
Tropical
Disturbance
Oct 24
Disturbance
forms
Cyclones and The Bay of Bengal
• The Indian “Super Cyclone” 1999
– Most of the damage caused by
• Storm surge
• Heavy rainfall
• Flooding
Cyclones and The Bay of Bengal
An aerial view of the heavily-damaged
Paradip port, where the cyclone made landfall.
Large areas of Orissa are still under water &
entire villages are feared to be submerged.
Cyclones and The Bay of Bengal
• The Indian “Super Cyclone” 1999
– The Human Cost
• As of 10th November 1999 the death toll was
estimated at 7,500, but expected to rise to near
10,000.
• Over ten million were affected by the cyclone of
which at least a million have been made homeless.
Floods
Floods
• Recurrence Interval
– Time between floods of the same magnitude
– Example: there is 1 in 100 chance that a peak
flow of a certain amount (say, 30,000 cf/s) can
occur on a river.
– Thus, that river is said to have a 100-year
interval
Floods
• Types of floods
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Flash Flooding In Arroyos/washes
River (Regional) Flood
Coastal Flood
Urban Flood
Ice Jam
Dam Failure
Floods
• Types of Floods
– Flash Flooding In Arroyos/washes
• Typically caused by:
– Intense rainfall
– Short period of time
– Topography, soil conditions, and ground cover also
important
Floods
• Types of Floods
– Flash Flooding In Arroyos/washes
• Damage:
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Roll boulders
Tear out trees
Destroy buildings and bridges
Scour out new channels
Landslides
How can a foot or two of water cost you
your life?
Floods
• Types of floods
– River (Regional) Flood
• Can take several days to develop
• Can last for a week or more
• Causes:
– Seasonally when winter or spring rains, coupled with
melting snows, fill river basins with too much water, too
quickly.
– Torrential rains from decaying hurricanes or tropical
systems can also produce river flooding.
Upstream vs. Downstream Floods
• Upstream floods
– generally local in extent &
short lag times.
– result from intense storms
of short duration.
• Downstream floods
– regional in extent & longer
lag times
– higher peak discharges.
– Result from regional storms
of long duration or extended
periods of above-normal
precipitation.
Floods
• Types of Floods
– Coastal Flood
• Often caused by storm surges.
• Can also be produced by sea waves called tsunamis
Floods
• Types of Floods
– Urban Flood
• Roads and parking lots prevent infiltration of water
• Urbanization increases runoff 2 to 6 times over what
would occur on natural terrain.
• Streets can become swift moving rivers, can flood
homes and businesses
Floods
• Types of Floods
– Ice Jam
• Floating ice can accumulate at a natural or manmade obstruction and stop the flow of water.
Floods
• Types of Floods
– Dam Failure
• Catastrophic failure of a dam can release millions of
gallons of water
General statistics
• There were 2,200 water-related disasters
from 1990 to 2001.
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Floods: 50%
Water-borne and vector disease outbreaks: 28%
Droughts: 11%
Landslide and avalanche events: 9%
Famine: 2%
Floods
• Floods account for 15% of all deaths related to
natural disasters, famines for 42%.
• Approximately 66 million people suffered flood
damage from 1973 to 1997.
• Between 1987 and 1997, 44% of all flood
disasters affected Asia, claiming 228,000 lives
(roughly 93% of all flood-related deaths
worldwide).
• Economic losses for the region totaled US$136
billion.
More than 2,200 major and minor water-related disasters
occurred in the world between 1990 and 2001.
Asia and Africa were the most affected continents, with floods
accounting for half of these disasters.
Type of water-related
natural disasters, 1990-2001
Distribution of water-related
disasters, 1990-2001
[Figure source]: Extracted from the Executive Summary of the World
Water Development report. CRED (Centre for Research on the
Epidemiology of Disasters). 2002. The OFDA/CRED International
Disaster Database. Brussels, Université Catholique de Louvain.
Mozambique
• Climate:
– tropical to
subtropical
• Terrain:
– mostly coastal
lowlands
– uplands in center
– high plateaus in
northwest
– mountains in west
Mozambique
• Natural hazards:
– Severe droughts
– Devastating cyclones and floods occur in
central and southern provinces
• Environment - current issues:
– A long civil war and recurrent drought in the
hinterlands = increased migration of the
population to urban and coastal areas
Mozambique
• Pre 2000
– Drought conditions
– Was one of Africa's emerging success stories.
• 10% growth in recent years
• 1999 was the first since its ruinous civil war that it
had not needed to ask for food aid.
Mozambique
• Cyclones and flooding in
2000-2001
– February 9 – heavy rains &
flooding
– February 22 – tropical
Cyclone Eline
– March 2 –
• Floodwaters have risen to 8 m (26 feet) in
five days
• 100,000 people need to be evacuated and
around 7,000 are trapped in trees
Mozambique
• Cyclones and flooding in 2000-2001
– Effects in the "cimento" (rich) areas
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Landslides block streets
Streets covered with potholes and sinkholes
Telephones/communications disrupted
Water service disrupted & water quality impaired
• Most problems fixed in about a month
Mozambique
• Cyclones and flooding in 2000-2001
– Effects in the "bairros" (poor) areas
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Streets destroyed or full of large potholes
Hundreds of reed and mud homes underwater
Thousands of people left homeless
Water quality not restored.
• Most problems still evident a month later
Mozambique
• The United Nations estimates 650 people
died, more than 500,000 were left homeless,
and 2 million people suffered severe
economic hardship.
Mozambique
• 2003
– Cyclone Delfina killed 47 people and displaced
200,000
– Cyclone Jephat killed at least 11 people a
month later
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