Exam 2 Weather, climate, and society

What is humidity?

The amount of water vapor in the air

What is condensation?

- Water vapor to liquid

- Releases latent heat

What is evaporation?

- Liquid to water vapor

- Absorbs latent heat

What is saturation?

Air holds the maximum water vapor possible at that temperature (RH=100%)

Dew point temperature means?

The temperature of the air must cool to become saturated

How does relative humidity vary is the temperature is high?

Relative humidity is low

How does relative humidity vary is the temperature is low?

Relative humidity is high

Warmer air can hold more moisture

Daily cycle of relative humidity at its highest:

Early morning (coolest)

Daily cycle of relative humidity at its lowest:

Afternoon (warmest)

When is relative humidity useful?

- Comfort levels

- Fog prediction

- Fire danger

- Evaporation rates

Types of air masses: mT

- Maritime tropical

- Warm

- Moist

Types of air masses: mP

- Maritime polar

- Cool

- Moist

Types of air masses: cT

- Continental tropical

- Hot

- Dry

Types of air masses: cP

- Continental polar

- Cold

- Dry

Types of air masses: cA

- Continental arctic

- Very cold

- Dry

what are the air masses that affect the U.S?

- Winter (cP, cA)

- Summer (mT)

- West coast (mP)

- Southwest summer (cT)

What is an anticyclone?

- High pressure system

- Clear skies

- Dry weather

- Clockwise (Northern hemisphere)

What is the most deadly severe weather?

Heat waves

What components of an urban environment cause the Urban Heat Island effect?

- Concrete/ asphalt absorb heat

- Few trees

- Building trap heat

- Cars and AC release heat

What is a meteorological drought?

Lack of rainfall

What is an agricultural drought?

Crops are affected

What is a hydrological drought?

Rivers and lakes get low

What is a socioeconomic drought?

Water shortages affect people and economies

What is adiabatic cooling?

Air rises then expands then cools

What is adiabatic warming?

Air sinks then compresses then warms

What are the 4 lifting mechanisms?

- Convection

- Orographic (mountains)

- Frontal lifting

- Convergence

Why does saturated air cool slower?

Condensation releases latent heat

What is instability?

Rising air continutes to rise causing storms

What is the stability cycle?

- Morning: stable

- Afternoon: unstable (surface heating)

How big must water droplets be to be rain?

2 mm in diameter

What are the conditions of collision-coalescence process?

Warm clouds above freezing

How does collision-coalescence process work?

Droplets collide and merge then grow then rain

What is the Bergeron process?

When ice crystals grow at expense of droplets causing snow

What are the conditions of the bergeron process?

Cold cloud, ice and supercooled water

What is sleet?

Rain refreezes before hitting the ground

What is freezing rain?

Rain freezes on contact with a cold surface

How does Lake Effect Snow work?

Cold air moves over warm lakes, picks up moisture resulting in heavy snow downwind

What is a cirrus cloud?

High and wispy

What is a stratus cloud?

A layer cloud that covers the whole sky

What is a cumulus cloud?

A puffy cloud which may grow vertically

What is a nimbus cloud?

Rain-producing

What is a cumulonimbus cloud?

Thunderstorm clouds

What fogs add moisture to the air?

- Steam fog

- Frontal fog

What fogs form by diabatic cooling? (Lowers air temp)

- Radiation fog

- Advection fog

What fog form by adiabatic cooling? (Lowers air temp)

Upslope fog

What does "Fog is lifting" mean?

Temperature is rising making fog evaporate

What conditions aloft are required for cyclogenesis?

Divergence aloft (Jet stream support)

What role does pressure gradient force in cyclogensis?

Pushes air toward low pressure

What role does coriolis effect play in cyclogensis?

Causes air rotation, counterclockwise in Northern Hemisphere

How do fronts develop in midlatitude cyclones

When cold polar air meets warm tropical air

What types of precipitation is associated with warm fronts?

Steady, light rain

What types of precipitation is associated with cold fronts?

- Heavy

- Short rain and thunderstorms

What types of precipitation is associated with occluded fronts?

Mixed precipitation

What happens before MLC pass in your area?

- Pressure falling

- Winds from the south

- Warmer

What happens during a cold front?

- Heavy rain

- Wind shift

What happens after MLC passes in your area?

- Pressure rising

- Cooler temperature

- Clear skies

What is a blizzard?

a severe snowstorm with high winds and low visibility.

What is a bomb cyclone?

a rapidly intensifying storm caused by a quick drop in atmospheric pressure at the center of a weather system

What conditions are required for a thunderstorm to form?

Warm humid air and unstable environment

What causes lightning, and how does lightning cause thunder?

- Heated air expands explosively, creating a shockwave

- Rapid air expansion from lightning heat

What are the three types of thunderstorms?

- Air mass

- Multi-cell

- Supercell

Describe the life cycle of an airmass thunderstorm?

1. Cumulus (updraft)

2. Mature (updraft+ downdraft)

3. Dissipating (downdraft only)

How do multi-cell and super cell thunderstorms differ from air mass thunderstorms?

They are more severe because of stronger and more severe wind shear

What are downdrafts?

Sinking air

What is gust fronts?

Cool air spreading out ahead of storm

What is a severe thunderstorm?

1. Wind gusts at the surface greater than 50 mph (57.5 knots)

2. Hail with a diameter greater than 1 inch

3. Tornado

What is a derecho?

Long lasting line of severe thunderstorms with widespread wind damage

What role does wind shear play in tornado formation?

Change in wind speed/direction with height

Why are tornadoes hard to study?

Short lived, small, and unpredictable

How is tornado intensity classified using the EF scale?

Rates tornado intesnsity based on damage (EF0-EF5)

What are tornado myths?

- When traveling by car seek shelter under an overpass (speed increases)

- Mobile homes attract tornadoes (More wind damage)

- Cities, hills, rivers deflect or inhibit tornados (Observed in thee areas)

Where is tornado alley?

Midwest, great plains

How does radar detect tornados?

Winds, precipitation, rotation

What are the geographical locations where most hurricanes occur?

Tropical areas, ocean cities

What are conditions that hurricanes occur?

- Unstable atmosphere

- Absence of wind shear

- Very warm sea surface temperature

Where and what conditions does a hurricane form?

Warm ocean water, low wind shear, at 5-20 degrees latitude

What is the difference between the tropics and mid-latitudes?

Tropics have weak coriolis, warm, no fronts

Mid-latitudes have strong fronts, large temperature differences

1. What is tropical disturbance?

No closed isobars

2. What is tropical depression?

1 or more closed isobars (winds <39mph)

3. What is tropical storm?

Many closed isobars winds 39-74 mph circular shape, given a name

4. What is tropical cyclone?

Many closed isobars, winds 75+ mph

What are the major characteristics of hurricanes?

- Eye (calm center)

- Eyewall (strongest winds)

- Rainbands

- Warm-core low pressure

How do Atlantic hurricanes get steered to the US from the Bermuda High?

Steers Atlantic hurricanes west towards US

What are the 4 hurricane hazards?

- Storm surge

- Wind damage

- Flooding rain

- Tornadoes

What are efforts to protect society from hurricanes?

- Satellites

- Hurricane hunters

- Evacuation plans

- Seawalls

- Building cods