Storms 1 Flashcards by Ashley Wu

Thunderstorm hazards

lightning
tornado
hail
downpours of rain (flash flood)
downbursts of air (gustfronts)

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Hurricane hazards

contain thunderstorms
storm surge / costal flooding
high waves
coastal erosion

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in a lightning strike, what does the stepped leader do?

makes the first electrical connection between the cloud and the ground

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what happens to the air when lightning strikes?

becomes super hot and explodes as a supersonic shockwave
- rapid expansion of air molecules create sound waves radiate out abt 1 mile/ 5 secs

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What are the two most common lightning

intracloud (IC)
cloud to ground (CG)

1 to 10 more IC than CG

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Is air a good conductor?

Nope, insulator
- can only flow thru if voltage very high

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Where do CG negative strikes come from?

cloud base

most initiate btwn mid-level -charge region & small positive charge region at base

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What kind of CG strike is more common?

Negative strikes

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What is a return stroke?

when there is a connection between the leaders from cloud (+) and ground (-), channel forms and electrons accel thru it causing heat and flash

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How does a CG Negative strike happen?

negatively charged step leaders -> ground
positively charged leader from the ground reaches up
the first connection completes the channel and electrons accel thru it = heat

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Where do CG positive strikes come from?

the anvil
(higher in the thunderstorm)

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Which is stronger and more dangerous, positive or negative CG strike?

Positive
-> travel greater distance, so they’re much hotter, brighter, longer in duration

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CG Positive strikes strength and frequency

less frequent

can be 10x more strong (5x hotter than surface of sun)
are primary cause of wildfires

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Where is lightning alley

Florida in North America

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highest density (most frequent) of lightning worldwide

Central Africa

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how many deaths does CG lightning strikes cause every year?

2.4 million CG strikes/year
6-12
- can be killed if directly struck

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How do we detect lightning

ground based networks
space based satellites

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Sound travels ____ than light

slower

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How far away is lightning?

time (sec) between seeing lightning and hearing thunder
÷ 3
= number of km away

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30/30 rule

if 30 seconds or less btwn the flash and bang,
move indoors and stay for 30 min after the last lightning/thunder

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What are some safe areas to hide from lightning?

strong buildings
fully enclosed metal cars

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What are some unsafe areas to hide from lightning?

small structures
metallic objects (pole, fence)
trees (can explode), water, open fields

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What can we do if we are caught in the open during a lightning storm?

lightning safety crouch
- CPR can revive smb if striked

Explain the lightning safety crouch

feet together (if apart, it’ll make a circuit thru you)
hands on ears
bend down

Thunderstorm scientific term

Cumulonimbus (CB)

What are thunderstorms? Describe their appearance.

thick clouds w lightning & thunder, made of large cells that evolve in 15-30 min Overshooting top or dome (if updraft too strong) anvil/mushroom (can be 100 kms!) mammatus clouds right below anvil rain main updraft (15km) & striations flanking line / cloud base near ground (1km) wall cloud funnel cloud or tornado

What is the anvil?

thick cloud top near top of troposphere (10-15km, but can be 100km)

What causes /are the fuel for thunderstorms?

energy comes from temperature and humidity

Multicell thunderstorms

contain 2+ cells

Squall line

a line of thunderstorms

What are the three types of supercell thunderstorms

low precipitation classical high precipitation

supercell thunderstorm

very large, rotating single cell can cause tornadoes, hail, lightning, heavy rain, strong winds

What are the three stages of thunderstorm devleopment?

1. Cumulus stage - updraft - no rain - no anvil 2. Mature Stage - up & down drafts - heavy rain - crisp anvil 3. Dissipating stage - downdraft - light rain - fuzzy anvil

Name the layers of atmosphere

Thermosphere Mesopause (85km) Mesosphere Stratopause (45km) Stratosphere Tropopause (11km) Troposphere

How does the warm ground affect the air?

Sensible heat - warms air in troposphere - increases TEMP Latent heat - evaporates water from lakes - increases HUMIDITY Together, they power storms!

What solar energy Is absorbed at the 3 heights?

1. thermosphere -> absorb non visible light 2. stratopause -> absorb UV by good ozone 3. earth surface -> absorbs light & heats ground

Describe the charging cycle for Tstorms

Charge: solar heating input (day) Discharge: Infrared radiation cooling (day & night)

When is the most likely time for Tstorm formation and why?

Late afternoon & early evening End of charging cycle - Greatest accumulation of heat near sunset everyday

most thunderstorms happen in which part of the atmosphere?

troposphere

How is lightning born

btwn two oppositely charged regions -> thunderstorms have ability to separate charge = powerful electric fields leaders - electrically conductive channels - tunnel path through air - branch out in two directions in attempt to neutralize charge separation

lightning that occur inside the cloud are called?

cloud flashes intercloud lightning

lightning that connects to the ground is called?

ground flash cloud to ground lightning (CG)

what happens to the air when lightning strikes?

becomes super hot and explodes as a supersonic shockwave - rapid expansion of air molecules create sound waves radiate out abt 1 mile/ 5 secs

the sound we hear is called

thunder

What are recoil leaders

positive - scout path thru air with flickering segments following - form on decayed segments of highly branched positive leaders

How are CG lightning characterized as positive or negative? Where do the electrons go?

depend on net charge of bolt shifts to the ground -CG negative leader w surplus of electrons connect to ground, ground gains net negative charge +CG positive leader w deficit of electrons connect to ground, ground gains net positive charge

Multistroke CG Flash

- after -CG return stroke, multiple other return strokes follow = causes main channel to flicker

Do return strokes of positive CG flicker?

rarely

Smooth channel lightning

positive CG due to lack of branching and strong positive leaders "Branchless lightning" -> leaders hidden in clouds

Bolt from the blue

bolt lead miles away from storm startling zaps r prolly negative lots of branching

How much volts is needed to make a spark in the air?

3 billion volts / km

What percent of Canadian CG lightning is positive?

10-25%

Percent of people who survive a lightning strike

90%

Favorable Tstorm locations in CANADA

praries cuz of advection

Favorable Tstorm locations in US

Florida, gulf states

Favorable Tstorm locations in general

close to equator - warm ocean currents = warm humid air

Advection

warm humid air carried by wind