week 4-lily Flashcards
what helps us understand circulation patterns of atm, and oceans, storm systems
Coriolis effect
in the northern hemisphere what way does the wind shift (which way does the Coriolis effect shift)
right
- anti-clockwise
in the southern hemisphere what way does the wind shift (which way does the Coriolis effect shift)
left
- clockwise
what is the Coriolis effect
- An effect, not a force
- Ground moving relative to
airborne/waterborne
objects (matter) - creates a deflection of mass (water, air)
why does the deflection happen?
Earth rotates faster at the Equator than it does at the poles – Earth is ‘wider’ (laterally) at the Equator
- Near the poles, the rotational speed is much slower because the circumference is smaller.
Why does rotation at 2 different speeds matter?
2 cities – same line of longitude; need to travel same distance at different speeds
Buffalo disk
- earths “skinner” here
- further north
- spins slower than quito disk
Quito
- at the equator (fat here)
- spins faster here
This change in velocity with latitude
is the true cause of the Coriolis effect.
example of Coriolis effect
Imagine a Spinning Carousel
You’re sitting at the center of a spinning carousel (like the North Pole).
Your friend is sitting near the edge (like the Equator).
The outer edge moves faster than the center because it has to cover a greater distance in the same time.
Scenario 1: Rolling a Ball from the Center (North Pole) to the Edge (Equator)You try to roll a ball straight toward your friend.
But the carousel is spinning underneath the ball.
Since the outer part is moving faster, your friend moves ahead before the ball reaches them.
From your perspective, the ball appears to curve to the right (even though you rolled it straight).
Scenario 2: Rolling a Ball from the Edge (Equator) to the Center (North Pole) Your friend tries to roll a ball straight to you. Since they started on a faster-moving part of the carousel, the ball carries extra motion.
The ball moves ahead of you, curving to the right again.
Global atmospheric circulation patterns; Coriolis effect
- Create global wind belts that are bent to the right in NH and to the left in SH
- we have different circulation cells and the air is getting bent by the Coriolis effect
what are the 3 circulation cells
- polar cell
- ferrel cell
- hadley cell
Polar Cells (Dry Polar “Deserts”)
- At the poles, the air is cold and dense so it sinks.
- Sinking air forces it to move away from the poles toward the Equator.
- As the air warms and travels, it becomes drier, creating polar deserts or dry conditions around 30° latitudes (the horse latitudes).
Ferrel Cells
- Between 30°–60° latitudes, the air from the Hadley and Polar Cells meets, and the warm air from the tropics and cold air from the poles causes storms and rising air
Hadley Cells
- At the Equator, the sun heats the air, making it warm and light. This causes the air to rise.
- Rising air leads to low pressure and forms clouds and precipitation
- more rising air forces air away from equator, travels toward 30° latitude, where it cools, and then descends
north pole
polar deserts
60 degrees north
temperate forests
30 degrees north
horse latitudes deserts
equator
tropical forests
too look at circulation cells
slide 12 lecture 4
Polar Jet and Subtropical Jets are?
are fast-moving air currents that occur in the upper atmosphere (in the troposphere) and play a significant role in weather patterns around the world
Polar Jet
narrow band of strong winds that occurs at high altitudes (up to 400 km/hr)
- Can and do merge at different points in space and time, also interruptions
- forms at the boundary where the cold polar air meets the warmer mid-latitude air.
subtropical jet stream
- narrow band of strong winds that occurs at a higher altitude than the polar jet
- slower than polar jet
- boundary of the Ferrel and Hadley Cells.
Series of major wind belts what are they
global wind systems that create patterns of airflow in the atmosphere. The movement of air is caused by differences in temperature and pressure across the Earth’s surface
Trade Winds: location
Near the Equator (between 0° and 30° latitude).
about trade winds
- blow from high pressure areas (around 30° latitude) towards the low pressure at the Equator and deflected
- blow from the northeast to the southwest in the Northern Hemisphere, and from the southeast to the northwest in the Southern Hemisphere.
Subtropical highs “horse latitudes”
- 30° latitude (air sinks here, creating high-pressure zones)
- where the Trade Winds are deflected, and winds are light and variable at the surface
Roaring 40s,” “Furious 50s,” and “Screaming 60s
- strong winds found in the Southern Ocean near the latitudes of 40°, 50°, and 60° South.
- Circumpolar vortex westerlies → very strong
Circumpolar Vortex and Westerlies
refers to the strong westerly winds found near the Antarctic region. These winds are particularly strong in the Roaring 40s, Furious 50s, and Screaming 60s.
what are trade winds driven by
hadley cell
- mid-latitude highs–> equatorial lows
about the subtropical highs
- calm zones around of the mid latitudes
- dry, descinding air masses
- high pressure zone
what are the subtropical winds in juncture with
Hadley and Ferrel cells
what are Roaring 40s, Furious 50s, Screaming 60s drive by
the Ferrell cell
what is the only continuous lateral current around the world (wind)
Roaring 40s, Furious 50s, Screaming 60s
what is the reason antarctica is so cold
the circumpolar vortex
Inter Tropical Convergence Zone (ITCZ)
Area of low atmospheric pressure
Inter Tropical Convergence Zone (ITCZ) where does it form
where NE trade converge with SE trade winds
about Inter Tropical Convergence Zone (ITCZ)
- Vertical air movement, little horizontal movement
- Also known as the doldrums or climate equator
- Light winds
- it shift
Intertropical convergence zone (ITCZ) when does it shift
annually – dependent on where ‘hot’ weather is
- moves toward the hemisphere experiencing summer because the hottest weather in that hemisphere results in the strongest convective lifting.
Convective lifting happens when
the warm air rises, cooling as it moves upward, leading to cloud formation and precipitation (resulting in rainstorms).
what plays a key role in monsoons
Intertropical convergence zone (ITCZ)
monsoons and the ITCZ
- The ITCZ is a zone of low pressure where the trade winds from the Northern and Southern Hemispheres converge.
- Seasonally, the ITCZ shifts its position northward and southward depending on which hemisphere is experiencing summer (and therefore the hottest weather). This shifting of the ITCZ is directly tied to seasonal monsoon winds.
examples of where monsoon occurs
- near Darwin Australia
- India
A monsoon
seasonal wind pattern that brings heavy rains and changes in weather in certain regions of the world influenced by the ITCZ
Storms
Regional atmospheric disturbances characterized by strong winds often accompanied by precipitation
what are storms a result of
ocean-atmosphere interactions
Largest systems: storms
- Tropical cyclones
- extratropical cyclone
what are storms
Huge rotating masses of low
pressure air in which winds
converge and ascend
what are storm associated with
air masses
- which are large bodies of air that have uniform temperature and humidity
Air mass
large volume of air with nearly uniform Temp., water vapour content and density; adapts to characteristics of surface below it
air masses nerve what?
mix
- one air mass will move over or under another
what does the none mixing of air masses result in
turbulence in the boundaries of air masses
Boundary between 2 air masses
front
Cold Front:
occurs when a cold air mass pushes into a warmer air mass. The cold, dense air forces the warm air to rise quickly, leading to stormy weather, particularly heavy showers and thunderstorms.
Warm Front:
warm front occurs when a warm air mass moves into and overrides a colder air mass. The warm air rises gently over the cold air, leading to steady precipitation, such as light rain or drizzle, which can last for a longer period.
mP
maritime polar
mT
maritime tropical warm, moist
cT
continental tropical hot, dry
cA
continental Arctic very cold, dry
cP
continental polar cold, dry
what fronts make bigger storms
cold fronts
storms and Coriolis effect, what happens
- air starts moving toward a zone of low pressure and veer off course because of the Coriolis effect
what way to storms go in northern hemisphere
turn counterclockwise (to be deflected to the right of its original path.)
what way to storms go in the southern hemisphere
clockwise (deflects moving air to the left of its original path)
what are tropical cyclones
Rotating masses of warm,
humid air; very strong winds
and torrential rain
how fast and big can tropical cyclones be
Can be up to 1000 km wide, 15
km high, eye 15 km wide
Hurricane Patricia, 2015 speed
Up to 345 km/h winds
Hurricanes
North Atlantic and
eastern Pacific
Typhoons
Western Pacific
Cyclones
Southern Hemisphere
(clockwise rotation - Coriolis)
Ingredients and mechanisms of tropical cyclones (TC)
Form within one warm, humid air mass located between 5 and 25 degrees
air temp needed for tropical cyclones
Air temp must be 26ºC – need warm humid air
what is needed for tropical cyclone
- air temp must be 26
- pre-existing weather disturbance (deep low pressure)
what is the source of energy for the system
warm surface of ocean water
steps of tropical cyclones
- warm, moist air moves over the ocean
- water vapor rises into the atmosphere
- as the weather vapor rises it cools and condenses into liquid droplets
- condensation releases heat (latent heat) into the atmosphere, making the air lighter
- the warmed air continues to rise, with moist air from the ocean taking its place and creating more wind
where does energy for tropical cyclones come from
latent heat stored in evaporated moist air brought into low pressure zone
Positive Feedback Loop of the tropical cyclone
As more air rises and more moisture condenses, the process becomes a feedback loop. The more latent heat released, the stronger the storm becomes, drawing in even more moist air from the surrounding environment
Low Pressure Zone: of tropical cyclone
The rising warm air creates a low-pressure center at the surface.
what causes the tropical cyclone to stop
when energy source is cut off
(moving from warm water to land)
for review of tropical cyclone
slide 30 lecture 4
wind speeds of tropical cyclones
- Wind speeds > 119 km/hr
structure of tropical cyclones
Powerful rain bands and a central eye (calm)
category 1 hurricane
- 120-153hm/hr
- minimal: minor damage to buildings
category 2 hurricane
- 154-177km/hr
- moderate damage: some roofing material, door, and window damage, some trees blown down
category 3 hurricane
- 178-209km/hr
- extensive: some strutural damage and wall failures; foliage blown off trees and large tress blown down
category 4 hurricane
- 131-155km/hr
- extreme: more extensive structural damage and wall failures; most shrubs, trees, and signs blown down
category 5 hurricane
- greater than 250km/hr winds
- catastrophic damage: complete roof failure and entire failures common; all shrubs, trees, and signs blown down; flooding of lower floors of coastal structures
Hurricanes – where they occur
(Atlantic)
- Follow a typical track – either veer left or right of Florida
- Track influenced by atmospheric circulation
where do hurricanes originate
in the low latitude regions that have warm surface temperatures
what happens once hurricanes are formed
are influenced by the trade winds, so they generally travel from east to west
what way to hurricanes curve
to the right in the northern hemisphere because of the coriolis effect, so they are steered into the middle latitudes
As hurriances move into the middle latitudes
they are influenced by the prevailing westerlies, which cause them to move from west to east
Storm surges
- Abnormal rise in seawater level during a storm
- Can reach >6 m in the largest tropical cyclones
stripped bark
indicative of how high storm surge was when it came ashore
storm motion
create bulge of water which is pushed on shore
- water on ocean-side flow away without raising sea level much
- as water approaches land it “piles up” creating storm surge
what do tides do to surges
can push higher and further inland
types of storm surges
wind-driven surge
pressure-driven surge (5% of total)
Hurricanes Katrina, New Orleans, 2005
New Orleans levies breeched
* Levies prevented water draining away
* $75 Billion dollars worth of damage
* ~1600+ lives lost
Hurricanes Katrina, New Orleans, 2005
* Surprisingly, not deadliest
Hurricane “Galveston” (Texas, USA) 1900
Beach resort avg. of 1.5 m above sea level
* Category 4 Hurricane:
* 6 m high storm surge + heavy rainfall + 150-200 km/h winds
* ~6000 deaths
* Lack of early warning systems
Hurricane/Superstorm Sandy
combination of hurricane and Nor’easter; October 2012
- Category 3 Hurricane at peak intensity (before hitting cuba); peak diameter: 1,850 km
-Largest diameter Atlantic hurricane on record
- coincided with very high tides (full moon – “spring tide”)
- merged with autumn low-pressure area (NW Atlantic) - ↑ storm intensity
what was one of the costliest hurricane in Us history
Hurricane/Superstorm Sandy
Hurricane/Superstorm Sandy surges
- 4-5 m storm surge to places that are not accustomed to storm surges
- Damage (US, DR, Haiti, Cuba, Bahamas, Jamaica, Canada)
- ~ US$69 Billion damage.
- 233 deaths
2020 Hurricane season
30 named storms
* Ran out of names
* Moved on to
Greek alphabet
* 0x Cat 5 (1st since 2015)
* 7x >Cat3
* US$51B damage
* ~420
2005 hurricane season
4x Cat5
* 7x >Cat3 (major)
* 15 hurricanes
* US$172B damage
* ~4000 deaths
2017 hurricane season
2x Cat5
* 6x >Cat3 (major)
* 10 hurricanes
* ~US$300B damage
* ~3400 deaths
2023 Hurricane season
20 named storms; 7 hurricanes, 3 majors
cat 5 hurricane in 2023
Otis (Mexican Pacific coast - strongest)
* Lee (Landfall in NS as post-tropical cyclone)
* Lee and Otis two of the 5 fastest intensifying Hurricanes
on record
cat 3 hurricane in 2023
Idalia: cat-3 landfall in Florida ($20B damage)
2024 hurricane season
18 named storms; 11 hurriances, 5 majors
* 2x Cat 5 (1st since 2023
2x Cat 5 2024 Hurricane season
Beryl earliest Cat-5 hurricane ever (June!)
* Milton (Landfall in NS as post-tropical cyclone)
2024 cat 4 hurricane
Helene: cat-4 landfall in Florida/Carolinas
($80B damage, 220 deaths)
cat 3 hurricane in 2024
Milton: cat-3 landfall in Florida ($50B damage)
* Rapid intensification
Rapid intensification
- increase of maximum sustained windspeeds of >55 km/hr in 24hrs
- 20-30% of all tropical cyclones undergo rapid intensification
Extratropical cyclones
Low pressure systems that form between two air masses
- Cloudy skies, rain, thunderstorms, blizzards…
- ‘comma shape’
where do Extratropical cyclones occur
Occur at mid-latitudes ~ 30 to 60 degrees
Extratropical cyclones in NH
typically move south from Ferrel – Polar cell convergence Low P zones
Extratropical cyclones derived from
hurricanes (cyclones) moving north in fall
what do Extratropical cyclones merge with
North Atlantic frontal systems
about strength/size of Extratropical cyclones
Can increase the size of the
system, but typically
weakens the core
what’s a nor’easter weather conditions
- polar jet stream transports cold artic air southward from Canada
- the gulf stream moves warm water from the gulf of mexico northward
- difference of air and water temps over the atlantic ocean, combined with colder water of the Labrador current moving southward
Pressure-Driven Surge (Smaller Contribution, ~5%)
- hurricanes have low atmospheric pressure at their center (the eye).
- Lower pressure allows water to rise slightly, but this effect contributes only a small amount to the total surge.
