Weather and Climate Chapters 5 and 6

What is the average temperature of the Moist Adiabatic Rate?

6 degrees C per 1000 m or 3.3 degrees F per 1000 feet

ELR less than MAR or DAR Most stable early in the morning around sunrise

Absolutely Stable Atmosphere

The cooling of a surface may be due to: Radiational cooling at night Cold surface air brought in by wind (advection)

Absolutely Stable Atmosphere

As air parcel rises, it forms a vertical cloud Convection, thunderstorm, severe weather often result Limited to a very shallow layer near the ground on hot, sunny days

Absolutely Unstable Atmosphere

ELR greater than the DAR or MAR

Absolutely Unstable Atmosphere

Greatly influences the growth of cumulus clouds

Air Stability

Also known as ice-crystal process

Bergeron-Findeision Process

Occurs within a cold cloud Ice crystals grow at the expenses of supercooled water droplets, eventually they may grow large enough to precipitate

Bergeron-Findeision Process

The more unstable, the greater the _________

Cloud growth

Develop as an air parcel rises and cools below the dew point

Clouds

______ clouds are made up of ice crystals and/or supercooled water droplets in temps below freezing (Appear wispy, especially at edges) (Important raid producers)

Cold

Cold dry air displaces warm and humid air by sliding under it and forcing the warm air upward This leading edge is....

Cold front

Occurs within a warm cloud Droplets of different sizes ... and ..., built into large droplets

Collision-Coalescence Process

Air that descends the leeward slopes is...

Compressed and warms

A sinking parcel of air ___________ and __________

Compresses and warms

Clouds need what to form?

Condensation Nuclei

Atmosphere is usually in this state

Conditionally Unstable Atmosphere

Exists when the ELR is between the MAR and DAR

Conditionally Unstable Atmosphere

Stable below cloud, unstable above cloud base

Conditionally Unstable Atmosphere

What are the four triggers for cloud development?

Convection and Clouds, Orographic Lifting, Convergence of Surface Winds, and Frontal Lifting

Responsible for clouds and precipitation in a low pressure system

Convergence of Surface Winds

_______ air sinks or is stable

Cool

Where are the driest regions of the US?

Desert SW, Death Valley, CA

The principle advantage is that it can provide the public with advance warning of hazardous weather such as severe thunderstorms, tornadoes, and potentially flooding rain

Doppler Radar

Consists of liquid water drops having diameters less than 0.02 in Drift very slowly to Earth's surface Originate in low stratus clouds

Drizzle

Periods of abnormally dry weather that produces a number of negative consequences such as crop damage, and an adverse impact on a community's water supply

Drought

______ climates on the leeward slopes

Dry

For an unsaturated parcel of air (RH<100%) the rate of heating or cooling is 10 degrees C for every 1000 meters (5.5 degrees for every 1000 feet)

Dry Adiabatic Rate (DAR)

The rate at which the air temperature surrounding us will change

Environmental Lapse Rate (ELR)

A rising parcel of air _________ and _______

Expands and cools

Flood waters that rise rapidly with little or no warning

Flash Floods

Results when thunderstorms stall or move very slowly over a relatively small area

Flash Floods

Occurs primarily in the spring when heavy rain and melting snow cause rivers to overflow their anks

Floods

Snow falling from developing cumulus clouds Usually light showers that fall for short durations and produce light accumulation

Flurries

Cloud base forms at a level of _____________

Free convection

Consists of rain/drizzle that freeze on contact with a cold surface Forms a coating of ice (glaze) on exposed surfaces Can produce black ice

Freezing Rain

Where do the driest regions of the world lie?

Frigid polar region, Leeward sides of Mountains, Subtropical high pressure belt

Consists of balls or jagged lumps of ice Characterized by alternating layers of opaque and clear ice

Hail

What form of precipitation has the greatest ability to overcome an updraft?

Hail

Hailstones that cover the landscape in a long, narrow stripe

Hail streak

What are the four wettest areas in the US

Hawaii, South Coast of Alaska, Coastal Pacific NW, Southeastern states

Differential land surface heating creates areas of ________________

High surface temperature

Form when raindrops or partially melted snowflakes fall into a layer of subfreezing air Refreeze into ice particles prior to striking the ground Transparent and bounce when they hit the ground

Ice Pellets (Sleet)

Occurs where there is a substantial accumulation of freezing rain or drizzle Can be highly localized and persistent

Ice storm

______________ promote formation of ice crystals only at temperatures well below freezing

Ice-Forming Nuclei

Air that is forced to ascend the windward slopes (facing oncoming winds) expands and cools...

Increasing RH

A blanket of snow is a good ...

Insulator

Snowstorms that form on the downwind side of one of the Great Lakes (Most common in the Autumn and Early Winter) Cold air moves over warmer lakes, water vapor absorbed, becomes snow

Lake-Effect Snow

_______ climates on the windward slopes

Moist

Rate less than the DAR and not constant due to release of latent heat

Moist Adiabatic Rate

The rate of temperature decreases for a saturated (RH=100%) parcel of air Lifting results in cooling, condensation, cloud formation and release of latent heat

Moist Adiabatic Rate (MAR)

Snowflakes more readily stick together at air temps of?

Near or slightly above freezing

Rainiest places located...

On the windward side of mountains

Occurs where air is forced upward by topography

Orographic Lifting

For clouds to precipitate, cloud particles must grow large enough to....?

Overcome updrafts (air resistance)

Takes into account average temperature and precipitation valves to define drought severity 0 (normal) to -4 (extreme drought)

Palmer Drought Severity Index (PDS)

Associated upward motion means increased _______, and eventual clouds and possible precipitation

RH

Drops of liquid water Air resistance causes these to fall as slightly flattened spheres They usually begin as snowflakes

Rain

Dry conditions that often extend many miles downwind of a prominent mountain range

Rain Shadow

Clouds form as air ____ and ______

Rises and cools

Intermittent precipitation from cumuliform cloud Usually short, but heavy in duration (cloudburst)

Shower

What size are snowflakes at very low temperatures when water vapor is low?

Small

An agglomeration of ice crystals in forms of flakes Vary in shape in size

Snow

_____ is heavier where cool, moist air rises along the windward slopes of Mountains

Snowfall

When does hail usually occur

Spring or Summer

A state of equilibrium in terms of atmospheric movement (No vertical movement occurs)

Stability

Cumulonimbus cloud extends into the stratosphere because it is...

Stable

Water drops that remain liquid even when at temperatures well below freezing

Supercooled Drops

In the US, hail is most likely in..

The Western Great Plains

Occurs when thunderstorms keep passing over the same area

Training

Streaks (streamers) in the sky when the water vaporizes before reaching Earth's surface

Virga

_____ clouds have above freezing temperatures at all levels (Their boundaries are more sharply defined) (Common in tropics)

Warm

______ air rises or is unstable

Warm

As a cold air mass retreats, the warm air advances by riding up and over the cold air This leading edge is a ...

Warm front

__________ air mass is less dense than cold and dry air mass

Warm, humid

Valuable remote sensing tool for determining the location, movement and intensity of areas of precipitation

Weather Radar

When do you use the MAR?

When saturation is reached

How does hail develop?

Within intense updrafts of cumulonimbus clouds

Air above warm land surface heats, forming a "bubble" of warm air that ______

rises