Hurricane Katrina and New Orleans Hurricane Sandy and New York ...
GEOG 221/NRSC 221 – Lecture 2.1 (Jan. 10th, 2013) Hurricane Katrina and New Orleans Hurricane Sandy and New York Hurricane Katrina and New Orleans Superdome in New Orleans: shelter, crammed people that didn’t have anywhere else to go there, awful conditions (inadequate climate, toilets, etc) Social side of the disaster: African Americans that were affected Hurricanes: a latitudinal energy imbalance Between tropics, the sun is directly overhead: more sunlight going in at the equator than at the poles Earth releases longwave radiation (IR, heat): hotter bodies emit more Earth receives more in tropics than it gives out (surplus), gives out more everywhere else than it receives (deficit) because the earth is tilted at 23.5° The region of peak heating migrates from the northern hemisphere in June to the southern hemisphere in December There is a heat transfer: transport of heat from regions of surplus to deficit: from the tropics towards the poles by winds, ocean currents, and weather Hurricanes: solve energy imbalance, brings heat from tropics to northern regions Water: in 3 phases Abundant in the troposphere Able to change state (phase change) requires energy Solid – liquid – gas liberates energy Latent heat – heat waiting to be released (stored energy – stored within water vapor molecules) Sensible heat – reappears when condensation occurs (warming process) Latent heat Important source of atmospheric energy Water molecules are carried upwards where they change into liquid and ice clouds Tremendous amount of heat energy is released into the environment 70% of the world is water, a lot of it is tropical (warm) – readily evaporates Hurricanes: organized thunderstorms Provides energy for storms (mid-latitude cyclones, hurricanes, thunderstorms) Water vapor transported from tropics condenses at higher latitudes releasing and relocating energy to solve the latitudinal imbalance Vertical motion: Air rises and sinks in response to temperature/density differences Leads to an exchange of latent and sensible heat Clouds are formed by cooling of rising moist air, and subsequent condensation Descending motion tends to suppress cloud formation Evaporation, saturation…
Horizontal motion: in order to reach equilibrium, air moves from areas of high to low pressure (WIND) Cold air sinks: more dense Hot air rises: less dense (buoyancy) Dots: molecules in the air – atmospheric pressure: pressure exerted by everything in the air above you At one point in the cold column, there are less dots above you (less atmospheric pressure) than if you are at the same point in the hot column (higher atmospheric pressure): this therefore creates a movement from high to low pressure: wind Equally happens at the surface General circulation: surface winds At equatorial regions (intertropical convergence zone) air rises as much as it can before it reaches the stratosphere where it is forced to stop (set temperature) so it moves north Surface winds consist of trades and easterlies in the equatorial and polar latitudes and westerlies at midlatitudes Air as it rises from the equator and goes north, it reaches a lower temperature and goes down: part goes north, part comes back south Because of the curvature of the earth, air doesn’t travel straight, it is deflected As the air moves down from north to south it is deflected to the right: northeast trades Gulf stream current: water is moving due to wind pushing it Average air movement from west to east All major deserts: about 30° latitude in both hemisphere (sinking motion – not forming clouds, no precipitation desert region) Warm equatorial air (moist) rises and moves towards the poles (Hadley cell) leading to cloud formation Hurricane anatomy Center: eye They come from tropical waters where winds are light, humidity is high in a deep layer through the troposphere and average surface water temp is >26.5°C summer and early fall it takes a lot more energy to heat water up 1° than air: it takes time for water to warm up enough to form hurricanes and storms energy is derived from sensible heat and latent heat a lot of tropical water changing from water to gas means a lot of latent heat Formation (organized convection theory) Release of latent heat warms the upper troposphere creating high pressure aloft Upper-level winds move outward away from high Air near surface converges, rises and fuels thunderstorms A chain reaction develops and hurricane forms: thunderstorms become organized and become hurricanes Convection: vertical motion A lot of storms form and never hit land, some hit land (we hear about these because people are affected)
Life cycle: tropical disturbance, tropical depression, (named) tropical storm, hurricane (dissipates when winds die down and it reaches further north – moved away from its energy source (warm waters)) All about wind speed – but the wind isn’t what causes devastation, it’s what it’s blowing (hurricanes push ahead a lot of water (storm surge): floods) Sandy: three times bigger than Katrina Katrina at landfall: Category 3, top wind speed: 200km/h Lower the pressure gets: stronger winds (the faster the air is trying to go to the low pressure) Sandy: 86cm of snowfall (what made it so deadly) Katrina: 1800+ deaths, partly over Caribbean Center of the eye: most winds, hit New Orleans dead-on (Katrina) Sandy: as it rose up towards New York, it didn’t lose as much energy as it was thought it would, and joined an existing storm system Real issue: storm surge Strong winds push tremendous amounts of water ahead of storm Katrina was capable of generating a locally higher surge, Sandy was capable of generating a destructive surge over a larger length of coastline New Orleans: below sea level Air is descending in the eye (no wind or rain), rising everywhere else Eye wall: fastest winds Hurricanes form in the tropics due to warm water: latent heat from evaporation (change of phase), energy originally comes from the sun Warm water favors evaporation (closer to boiling point, particles already moving fast) Self-organization
Horizontal motion: in order to reach equilibrium, air moves from areas of high to low pressure (WIND) Cold air sinks: more dense Hot air rises: less dense (buoyancy) Dots: molecules in the air – atmospheric pressure: pressure exerted by everything in the air above you At one point in the cold column, there are less dots above you (less atmospheric pressure) than if you are at the same point in the hot column (higher atmospheric pressure): this therefore creates a movement from high to low pressure: wind Equally happens at the surface General circulation: surface winds At equatorial regions (intertropical convergence zone) air rises as much as it can before it reaches the stratosphere where it is forced to stop (set temperature) so it moves north Surface winds consist of trades and easterlies in the equatorial and polar latitudes and westerlies at midlatitudes Air as it rises from the equator and goes north, it reaches a lower temperature and goes down: part goes north, part comes back south Because of the curvature of the earth, air doesn’t travel straight, it is deflected As the air moves down from north to south it is deflected to the right: northeast trades Gulf stream current: water is moving due to wind pushing it Average air movement from west to east All major deserts: about 30° latitude in both hemisphere (sinking motion – not forming clouds, no precipitation desert region) Warm equatorial air (moist) rises and moves towards the poles (Hadley cell) leading to cloud formation Hurricane anatomy Center: eye They come from tropical waters where winds are light, humidity is high in a deep layer through the troposphere and average surface water temp is >26.5°C summer and early fall it takes a lot more energy to heat water up 1° than air: it takes time for water to warm up enough to form hurricanes and storms energy is derived from sensible heat and latent heat a lot of tropical water changing from water to gas means a lot of latent heat Formation (organized convection theory) Release of latent heat warms the upper troposphere creating high pressure aloft Upper-level winds move outward away from high Air near surface converges, rises and fuels thunderstorms A chain reaction develops and hurricane forms: thunderstorms become organized and become hurricanes Convection: vertical motion A lot of storms form and never hit land, some hit land (we hear about these because people are affected)
Life cycle: tropical disturbance, tropical depression, (named) tropical storm, hurricane (dissipates when winds die down and it reaches further north – moved away from its energy source (warm waters)) All about wind speed – but the wind isn’t what causes devastation, it’s what it’s blowing (hurricanes push ahead a lot of water (storm surge): floods) Sandy: three times bigger than Katrina Katrina at landfall: Category 3, top wind speed: 200km/h Lower the pressure gets: stronger winds (the faster the air is trying to go to the low pressure) Sandy: 86cm of snowfall (what made it so deadly) Katrina: 1800+ deaths, partly over Caribbean Center of the eye: most winds, hit New Orleans dead-on (Katrina) Sandy: as it rose up towards New York, it didn’t lose as much energy as it was thought it would, and joined an existing storm system Real issue: storm surge Strong winds push tremendous amounts of water ahead of storm Katrina was capable of generating a locally higher surge, Sandy was capable of generating a destructive surge over a larger length of coastline New Orleans: below sea level Air is descending in the eye (no wind or rain), rising everywhere else Eye wall: fastest winds Hurricanes form in the tropics due to warm water: latent heat from evaporation (change of phase), energy originally comes from the sun Warm water favors evaporation (closer to boiling point, particles already moving fast) Self-organization
