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Weather, Climate and the Environment Pt. 3
Terms in this set (47)
Rapidly rotating column of air that circulates around a small area of intense low pressure with a circulation that reaches the ground
-develop when warm surface air is overlaid by cooler, drier air aloft
rotating column of air that doesn't reach the ground
how do you calculate tornado wind speeds?
Add the tornado velocity along track to the circulation velocity to find the maximum
-For southwest approaching storms, winds strongest in the northeast of the storm
when do tornadoes occur most often?
occur most often in the spring and least often in the winter
-classifies tornadoes according to rotational wind speed
-based on the extent of tornado damage to frame houses
Enhanced Fujita Scale
Attempts to provide a wide range of criteria in estimating a tornado's winds by using a set of 28 damage indicators including small barns, mobile homes, schools, and trees
what is needed for a tornado to form?
intense thunderstorm, conditional
instability, and strong vertical wind sheer
-Wind sheer causes spinning vortex tube
that is pulled into thunderstorm by the updraft
-(look at difference between 500-mb winds and surface winds: 35 kt diff means conditions favorable for mesocyclone development)
rotating precipitation in the shape of a hook
-can be seen on a doplar radar
step 1 of tornado formation
Vertical directional and speed wind shear causes the air near the surface to rotate about a horizontal axis creating a vortex tube
step 2 of tornado formation
-A strong updraft will tilt the vortex tube upward and draw it into the storm.
-The tilted rotating tube becomes a rotating column inside the storm, known as a mesocyclone
step 3 of tornado formation
-Air rushes upwards, cools, and condenses into a visible cloud called the funnel cloud
-When the circulation reaches the ground, it picks up dirt and debris making it appear dark
what determines the strength of a tornado?
central pressure of the mesocyclone
how are non supercell tornadoes formed?
-Horizontal rotation (spin) is created by wind blowing in opposite directions
-If a developing cloud moves over the region of rotating air, the spinning column may be drawn into the cloud by the updraft
Rotating column of air that is connected to a cumuliform cloud over a large body of water
-Waterspout does not draw water up into its core
-Swirling spray can be lifted several miters when the funnel touches the water
how are seasons determined in the tropical regions of the world?
Seasons defined instead by precipitation: greatest precipitation in high-sun period, when ITCZ is overhead
what are used rather than isobars in the tropics?
map streamlines instead of isobars because the variation in sea-level pressure is so low
-show where flow converges or diverges
-general direction of flow is westward
trough of low pressure that moves westward
-Fair weather on west side (air is diverging)
-Converging air on the east side rises, cools,
releases latent heat & produces showers & t-storms
-when these tropical waves intensify, they become hurricanes
hurricane stages of development
-Tropical Disturbance (group of t-storms, only slight circ.)
-Tropical Depression (22-34kts)
-Tropical Storm (35-64kts) (storm gets a name)
-Hurricane (> 65kts or 75 mph)
reverse order for stages of dissipation
conditions needed for the formation of a hurricane
-Tropical waters with light wind
-warm sea surface temperatures (June-November)
-Humidity high throughout troposphere
-Triggered by converging surface winds (tropical wave)
-Spin needs Coriolis effect: form > 5º latitude
-Not strong upper-level winds because strong wind shear tends to disrupt the organized convection
describe the anatomy of a hurricane
characterized by a clear eye, towering clouds
around the eye called the eye wall, bands of rain that spiral outward from the eye wall
-strongest winds in a hurricane are in the eye wall
-Energy comes from transfer of sensible and latent heat from warm ocean surface
-Air flows outward away from the center
-Adjacent to the eye, the air rises and condenses
to produce huge cumulonimbus clouds
-Moist tropical air flows inward toward the center (cyclonic flow)
why do hurricanes dissipate?
-sinking air can inhibit hurricane formation
-hurricanes weaken rapidly when they travel over colder water and lose their energy source
-also weaken if layer of warm water is shallow, because waves stirred up by storm mix cooler water up to surface
-landfall: lose energy source and suffer friction
-vertical wind shear will rapidly dissipate system
describe the movement of hurricanes
-Hurricanes tend to form along the edges of the ITCZ.
-Initially they move toward the west as they are carried along by the tropical easterly winds.
-However, the subtropical highs cause the storms to eventually curve poleward.
-Then they get caught up in the mid-latitude westerly winds and move toward the east
when the storm surge arrives at high tide
-High water due to low pressure of the storm
-High winds pushing water towards the coast
-Transport of water towards the coast as winds blow south parallel to the coast
-Made landfall south of Miami on Aug 24, 1992.
-Weakened as it traveled across southern Florida
then regained strength over the Gulf of Mexico.
-Reached the shores of Louisiana as a Category 3 storm
-The most damaging hurricane to ever hit the US.
-Made landfall in Florida as a Category 1.
Passed over a deep band of warm water in the Gulf of Mexico that allowed the hurricane to rapidly intensify.
~$160 billion in damage.
-Lost its hurricane status about three hours before
-Remarkable for its size, leading to strong storm
surges over a wide area due to the long fetch of its winds over the ocean
why was hurricane sandy known as a superstorm?
-Transition from tropical (warm core) cyclone
-Energy source: release of latent heat from warm ocean waters
-To extra-tropical (cold core) cyclone
-Energy source: temperature difference across front
-First major hurricane (Category 3 or higher)
to make landfall in the US since 2005
-Stalled over southern Texas after making landfall
-Top rainfall was 60.58 inches
~$125 billion in damage
-90% of the island lost power for an average of 84 days.
-Nine months later, power was finally restored to 99.9% of resident (~2,000 without power as of July)
~$90 billion in damage. (3rd most damaging)
-Current death toll is ~3,000.
why is a tropical cyclone thought of as a heat engine?
takes energy from the ocean and converts to energy used to power its winds and its
-BUT limit of conversion efficiency depends on Tin & Tout
what limits the strength of hurricanes?
friction, which gets stronger as wind speed increases
issued 24-48 hours before hurricane expected to make landfall
issued when storm expected to strike coast within 24 hours and probability of strike in a given location provided
things that could increase the intensity of hurricanes
-Warmer air à more moisture content
-Warmer air à warmer oceans
things that could decrease the frequency of hurricanes
-Increased wind shear
-Increase in upper troposphere temperatures
current predictions of hurricanes
Total number of hurricanes may remain same
• Frequency of intense storms may increase
• More rain
• Stronger winds
• Form at higher latitudes
tropical moist climates
Tropical moist climates are found in a band about 15o to 25o N and S of the Equator
-year-round warm temperatures, abundant rainfall
deficient precipitation most of the year; potential evaporation and transpiration exceed precipitation
-extend around 30º latitude in large continental regions of the middle latitudes, often surrounded by mountains
Moist Subtropical Mid-latitude Climates
humid with mild winters
• Extent: on the eastern and western regions of most
continents, from about 25º to 40º latitude
Moist Continental Climates
warm-to-cool summers and cold winters; winters are severe with snowstorms, blustery winds, bitter cold; climate controlled by large continents
• Extent: north of moist subtropical mid-latitude climates
year-round low temperatures
• Extent: northern coastal areas of North America and Eurasia;
Greenland and Antarctica
The evidence for past climates can be found from
• Fossils: different fossils indicate different climates
• Sediment cores: sedimentation patterns reflect climate changes
• Ice cores: gases, dust and spores trapped in ice layers on Greenland and Antarctica help reveal past climate
• Oxygen isotope ratios: in ocean sediments, these ratios help show past temperature patterns
• Dendrochronology: the study of tree rings provide data on past temperatures and precipitation
an ice core
a core sample that is typically removed from an ice sheet, most
commonly from the polar ice caps of Antarctica, Greenland or from high mountain glaciers elsewhere
-As the ice forms from the incremental build up of annual layers of snow, lower layers are older than upper, and an ice core
contains ice formed over a range of years
reasons for climate change
-continental shifts changed clime due to difference in absorption of solar radiation by land and sea, effects of prevailing winds, etc.
• Cold, salty water (dense) sinks near Greenland driving warm water north.
• Continent locations affect circulation: continental drift affects circulation, and climate, on multi-million-year timescales
three natural variations in the Earth's orientation and orbit around the sun have an effect on the
- eccentricity, variation period of 100,000 years
- obliquity, variation period of 41,000 years
- precession, variation period of 23,000 years
Recommended textbook explanations
Glencoe Earth Science
Applications and Investigations in Earth Science
Dennis G. Tasa
Dennis G. Tasa, Edward J. Tarbuck, Frederick K. Lutgens
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