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83 Cards in this Set

  • Front
  • Back
Pressure produced by the motion, size, and number of gas molecules in the air and exerted on surfaces in contact with the air, that is measured by a barometer.
Barometric Pressure
Air weight is _______ at sea level
14.7 lbs/sq inch
Standard pressure at sea level_______, or ________
1013.2 mb / 29.92 inches of Hg
A device that measures air pressure using a column of mercury in a tube, one end of which is sealed, and the other end inserted in an open vessel of mercury
Mercury barometer
a device that measures air pressure using a particularly evacuated, sealed cell.
Aneroid barometer
Wind blows down the gradient from _______ to _______
highs to lows
The apparent deflection of moving objects (wind, ocean currents, missiles) from traveling in a straight path, in proportion to the speed of Earth’s rotation at different latitudes. Deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere; maximum at the poles and the Equator.
Coriolis effect
The effect of drag by the wind as it moves across a surface. Slows the wind, therefore reduces the effectiveness of the coriolis force.
Frictional Drag
The gradient force is clockwise in a high pressure zone, and counter-clockwise in a low pressure zone, hurricanes, and tornadoes.
Gradient force
A dynamically or thermally caused area of low atmospheric pressure with converging and ascending airflows. Rotates counter-clockwise in the Northern Hemisphere, and clockwise in the Southern hemisphere.
A dynamically or thermally caused area of high atmospheric pressure with descending and diverging airflows that rotate clockwise in the Northern hemisphere, and counter-clockwise in the Southern hemisphere
A wind moving between areas of different pressure along a path that is parallel to the isobars. It is a product of the pressure gradient force and the Coriolis force.
Geostrophic wind
An isoline connecting all points of equal atmospheric pressure.
The wetter intercepting slope
The drier far-side slope
A device that measures wind velocity
A weather instrument used to determine wind direction; winds are named for the direction from which they originate
Wind vane
Santa Anna winds- easterlies driven by clockwise rotation
California high
the gatekeeper of hurricanes.
Bermuda high
acts as a steering current/high velocity wind current that effects weather patterns
uses the principle that human hair changes as much as 4% in length between 0% and 100% relative humidity
Hair hygrometer
Bring tongues of cold air southward, with warmer tropical air moving northward. Mid-latitude cyclones follow these.
Rossby waves
used to measure relative humidity.
Sling psychrometer
Fabric tube that fills w/air that goes downwind, away from prevailing winds
takes place when temperatures drop below the dewpoint.
a cloud layer on the ground, with visibility restricted to less than 1 km (3300ft.) Tells us that the air temperature and the dew-point temperature at ground level are nearly identical, indicating saturated conditions.
when radiative cooling of a land surface, especially on clear nights in areas of moist ground; occurs when the air layer directly above the surface is chilled to the dew-point temperature, thereby producing saturated conditions.
active condensation formed when warm, moist air moves laterally over cooler water or land surfaces, causeing the lower layers of the air to be chilled to the dew-point temperature
Advection fog
Forms when moist air is forced to higher elevations along a hill or mountain and is thus cooled.
Upslope fog
A tiny water particle that constitutes the initial composition of clouds. Each droplet measures approximately 0.002cm in diameter and is invisible to the unaided eye.
Cloud droplet
Microscopic particles necessary as matter on which water vapor condenses to form moisture droplets; can be sea salts, dust, soot, or ash.
Condensation nuclei
A combination of fog and smoke containing sulfur gases.
Concentration of microscopic particles and air pollution that diminishes air clarity)
Wispy, filamentous ice-crystal clouds that occur above 6000 m (20,000 ft); appear in a variety of forms, from feathery hair-like fibers to veils of fused sheets.
Bright and puffy cumuliform clouds up to 2000 m in altitude. (6500 ft.)
A stratiform (flat, horizontal) cloud generally below 2000m (6500 ft)
a relatively cooler air parcel tends to settle back into its original position
The less dense air parcel will continue to lift.
small droplets, swirl on the way down to the ground.
More vertical fall, bigger droplets
Biggest droplets
ice crystals that form due to sublimation- goes straight from water vapor into an ice crystal
snow that melts, then re-freezes
Formed when a raindrop is repeatedly circulated above and below the freezing level in a cloud, with each cycle freezing more moisture onto the hailstone until it becomes too heavy to stay aloft
frozen rain
Cold air falls to the ground and warm air rises up into the cloud. The Earth’s surface is heated. Is the most common in DFW
In the mountainous areas
cool air crashes into warm air
Happens near the Equator. Warm air rises up into the cloud
Summer. Warm and moist. Fuels tropical cyclones and severe thunderstorms.
Martime Tropical, mT
Hot and dry
Continental Tropical cT
cool, moist
Martime polar, mP
from Canada, cold, dry
Continental polar, cP:
from the arctic, cold, dry
Continental Acrtic, cA:
equatorial calms
the winds converging on the equatorial low-pressure trough
Trade Winds
zones of windless, hot, dry desert air, deadly in the era of sailing ships
Horse latitudes
Where masses of air with different characteristics battle.
Polar front
The descend and diverge clockwise in the Northern Hemisphere (counterclockwise in the Southern Hemisphere) form weak, variable winds
Polar easterlies
steep air mass that hugs the ground, caused by its greater density and uniform physical character. Is shown on weather maps as a line with triangular spikes that point in the wind direction
Cold front
leads the edge of an advancing warm air mass, which is unable to push cooler, passive air out of the way; it tends to push up the cooler, underlying air into a wedge shape; identified on a weather map as a line with semicircles pointing in the direction of frontal movement.
Warm front
A frontal area of contact between contrasting air masses that shows little horizontal movement; winds in opposite direction on either side of the front flow parallel along the front.
Stationary front
an organized area of low pressure, with converging and ascending airflow producing an interaction of air masses; migrates along storm tracks. Such lows or depressions form the dominant weather pattern in the middle and higher latitudes of both hemispherers
Mid-latitude cyclone
 Updraft,
 Convection
 Vertical development
 Darkens at base
 No precipitation
Cumulus stage
 Precipitation starts
 Updraft intensifies
 Downdraft starts
 Lightning
 Anvil top
 Develops hail
Mature Stage
 Energy cut off
 Rain decreases
 _______ broadens
 Rain stops
Dissipating stage
The violent expansion of suddenly heated air, created by lightning discharges, sending out shock waves as an audible sonic bang.
Flashes of light caused by tens of millions of volts of electrical charge heating the air to temperatures of 15,000 to 30,000 degrees Celsius
F0- 18-32m/s and F1 – 33-49 m/s
Weak Tornadoes
F2 – 50-69 m/s and F3 – 70-92 m/s
Strong Tornadoes
F4 – 93-116 m/s and F5 – 117-142 m/s
Violent Tornadoes
A tropical cyclone that is fully organized and intensified in inward-spiraling rainbands; ranges from 160-960 km in diameter, with wind speeds in excess of 119 kmph; a name used specifically in the Atlantic and eastern Pacific
A cyclonic circulation originating in the tropics, with winds between 30 and 64 knots; characterized by closed isobars, circular organization, and heavy rains.
Tropical Cyclone
Tropical Depression
0- 38 mph
Tropical Storm
39-73 mph
74 mph
can form from the tail end of frontal zones in the subtropics and tropics All form in the easterly flow along the southern side of the subtropical ridge or belt of high pressure which lies north and south of the Intertropical Convergence Zone (ITCZ)
Easterly Wave
an Atlantic hurricane that develops near the Cape Verde islands, off the west coast of Africa
Cape Verde Storms
an electroluminescent coronal discharge caused by the ionization of the air during thunderstorms inside of a strong electric field. a low density, relatively low temperature plasma caused by massive atmospheric electrical potential differences
St. Elmo’s Fire
forms as precipitation falls into drier air below the cloud, the liquid droplets evaporate into water vapor. The water vapor cools and at the dewpoint it condenses and fog forms
Frontal Fog
the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. The winds are predominantly from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere. Together with the trade winds, the westerlies enabled a round-trip trade route for early European sailing ships