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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 – – – – Tropical disturbance Tropical depression Tropical Storm Hurricane • Surface winds consistently over 74 mph Hurricanes • How a Hurricane Works – – – – – 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 • • • • • 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 – – – – – – 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: – – – – – 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. – – – – – 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 • • • • 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 • • • • 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 ~ End ~