Atmospheric Water & Weather Flashcards
What is weather?
what’s happening now; what you get
What is climate?
long term weather conditions; what you expect
What are the unique qualities of water (6)?
- most common compound on Earth
- colorless, odorless, tasteless
- only substance on Earth which occurs in all three states
- expands as it freezes
- high specific heat
- phase change requires addition/absorption/release of energy
What is latent energy?
type of energy absorbed/released when water changes phases
What is evaporation?
liquid to gas
What is condensation?
gas to liquid
What is freezing?
liquid to solid
What is melting?
solid to liquid
What is sublimation?
solid to gas
What is deposition?
gas to solid
Which phase changes release latent heat?
evaporation, melting, sublimation
Which phase changes absorb latent heat?
condensation, freezing, deposition
What is humidity?
the amount of water vapor in the air
What is the relationship between heat and humidity?
warmer temperatures result in greater capacity for humidity because warm air has more enrgy to evaporate water
What is relative humidity?
ratio of the amount of water in atmosphere to how much water the atmosphere can contain
How does relative humidity change throughout the day?
amount of water stays the same but capacity for water increases due to increse in temperature, causing realtive humidity to drop
What is saturation?
point at which relative humidity hits 100%; results in condensation
What is dew point temperature?
temperature at which relative humidity hits 100%
Can you have a freeze without the formation of frost?
yes, if the temperature passes below freezing but is not low enough to hit the dew point
When does the highest relative humidity occur?
sunrise, at the lowest temperature
When does the lowest relative humidity occur?
midafternoon, at the highest temperature
What is specific humidity?
actual amount of water vapor in atmosphere
What are two instruments for measuring humidity?
haar hygrometer and sling psychrometer
What are air parcels?
bodies of air with specific temp. and humidity characteristics
What do rising air parcels do?
expand and cool (lower pressure)
What do sinking air parcels do?
compress and heat (higher pressure)
What is stability?
the tendency of an air parcel to rise, stay in place, or fall
What are unstable air parcels?
air parcel is warmer than surrounding air and rises until surround air is same temp. (results in clouds and precipitation)
What are stable air parcels?
air parcel stays in place or sinks (same or cooler than surrounding air)
What is the normal lapse rate?
average rate at which temp. decreases with in crease in altitude (3.5 F / 1,000 ft)
What is the environmental lapse rate?
actual lapse rate for local conditions
What are adiabatic rates?
rates at which moving air parcels cool off/heat up
What is the dry adiabatic rate (DAR)?
5.5 F / 1,000 ft; unsaturated air parcels; faster
What is the moist adiabatic rate (MAR)?
3.3 F / 1,000 ft; saturated air parcels; slower
Why is MAR slower?
latent heat of condensation
What is the lifting condensation level?
elevation at which shift from DAR to MAR occurs
What are clouds?
visible groups of moisture-laden droplets or ice crystals suspended in the air
How do clouds form?
water vapor condenses onto condensation nuclei (particles of dust, soot, ash, etc.)
What is fog?
a cloud at the surface
What is precipitation?
liquid or solid water that falls from clouds
What are the cloud shapes (3)?
stratiform, cumuliform, and cirriform
What do stratifrom clouds look like?
flat, layered clouds which develop horizontally
What do cumuliform clouds look like?
puffy clouds which develop vertically
What do cirriform clouds look like?
whispy, high altitude clouds which frequently contain ice crystals rather than liqid
What are the three types of low clouds (0-6500 ft)?
stratus (flat and light), nimbostratus (flat and dark; rainy), and stratocumulus (individual, puffy)
What are the two midlevel clouds (6500-20000 ft)?
altocumulus (slightly puffier than stratocumulus) and lenticular (occurs on crest of mountain)
What are the four high clouds (20000+ ft)?
cirrus (thin and whispy), cirrocumulus (slightly thicker), cirrostratus (halo), and cumulonimbus (narrow and tall)
What are the types of fog?
advection (form over bodies of water at night) and radiation (radioactive cooling)
What is virga?
precipitation falls from clouds but evaporates before it can hit the surface
What are air masses?
areas of uniform temperature, humidity and stability (larger than air parcels)
What do air masses do?
interactions between air masses frequently cause weather events, especially in North America
What letters are used to classify air masses?
moisture: m or c (maritime/continental)
temperature: a, p, t e, or aa (arctic/polar/tropical/equatorial/antarctic)
What are the air masses of North America?
cP: continental polar (winter, cold, stable, clear, high pressure)
mP: maritime polar (cool, moist, unstable, storms, low pressure)
mT: maritime tropical (warm, moist, unstable, low pressure)
What processes lift air?
convergent lifting, convectional lifting, orographic lifting, frontal lifting
What is convergent lifting?
air converging into an area of low pressure (tornado, hurricane)
What is convectional lifting?
local surface heating causes warm surface air to be pushed up (afternoon clouds, tropical environments)
What is orographic lifting?
air is pushed aloft to go up and over a certain barrier (mountains)
What is frontal lifting?
lifting of air masses in cold fronts/warm fronts
Describe the process of orographic lifting.
Incoming air masses are forced to rise by a barrier, causing them to cool at the DAR and become saturated. Just before they pass over the barrier, they release this moisture in the form of precipitation. This produces the rain shadow affect, where the windward side of a mountain is more lush and green than the leeward side. By the time the air passes over the barrier, it begins to sink and heat up at the MAR, producing dry winds on the leeward side called chinook winds.
Describe the process of frontal lifting.
warm front: gentle lifting of warm air over cold air; covers a larger area; more humidity
cold front: rapid and dramatic lifting of warm air over cold air/ covers a smaller area; less humidity but precipitation
What is a midlatitude cyclone?
a low pressure cell in the midlatitudes in which cold fronts and warm fronts conflict
What is the life cycle of a midlatitude cyclone (4)?
- cyclogenesis: cold, dry air mass and warm, moist air mass form a low pressure cell
- open stage: fully developed warm front and cold front confront each other
- occluded stage: combination of cold and warm front
- dissolving stage: cyclone falls apart
How long do midlatitude cyclones last?
5-7 days
What are thunderstorms?
storms that form when atmospheric conditions are unstable
What is the life cycle of a thunderstorm (3)?
- cumulus stage: warm, moist air is lifted upward by convergent, convectional, or frontal lifting - a low pressure cell is fromed at the base of a cumulus cloud - updraft draws air to a high altitude and the cumulus cloud transfroms into a cumulonimbus cloud
- mature stage: updraft continues and precipitation occurs, resulting in downdrafts of cool air
- dissipating stage: downdraft cuts off flow of warm, moist air into the updrafts
How long do thunderstorms last?
about an hour
What is lightning?
flashes of light caused by an electrical discharge between clouds or between a cloud and the ground that superheats the atmosphere
What is thunder?
the sound associated with lightning (sonic boom)
Where in the U.S. is there a concentration of thunderstorms?
the southeast, especially Florida, because warm, moist air is drawn in from the Gulf of Mexico/Atlantic Ocean (very rare on the west coast)
Where on the globe is there a concentration of thunderstorms?
southeast U.S., west coast of Mexico, central South America, central/souther Africa, eastern India, east coast of Asia, Polynesia, northern Austrailia, and at the ITCZ
What is hail?
ice pellets that form within a cumulonimbus cloud
How do tornadoes form?
- in a low pressure cell, surface winds decrease in strength while higher winds increase in strength, creating circular movement
- as updraft develops, the circular winds are pulled upward and tip 90 degrees
- a funnel cloud forms; once that funnel cloud touches the ground, it becomes a tornado
Where in the U.S. are tornadoes most likely to form (5)?
central United States: Oklahoma, Texas panhandle, Kansas, Nebraska, northern Indiana (tornado alley)
When are tornadoes most likely to occur?
late spring
What are tropical cyclones?
large, low pressure storms in tropical environments that form over warm bodies of water characterized by high winds, heavy rainfall, and flooding
What do different cultures refer to tropical cyclones as?
- Austrailia, Africa, southern Asia: cyclones
- eastern Asia: typhoons
- United States: hurricanes
When are tropical cyclones most likely to form?
summer
Why do these storms not form close to the equator?
Coriolis Force
What factors account for the pattern of storm tracks (4)?
ocean currents, winds, fronts, midlatitude cyclones
When is hurricane season in Texas?
June 1 - November 30; most powerful hurricanes occur mid August - mid September when ocean temp. is warmest
What are the wind speeds for different levels of a tropical cyclone (4)?
- tropical disturbance: < 38 mph
- tropical depression: 38 mph
- tropical storm: 39-73 mph
- hurricane: greater than 74 mph
Where will the most damage occur as the storm makes landfall?
NE quadrant (highest wind speed and movement)
