Exam 2 Flashcards
What is the average sea-level pressure is …
1013.25 mb
What is sea level pressure expressed in?
1013.25 mb
inches and Pascals.
101,325 Pa
29.9 inches
1mb = .02953 in of Mercury
what does a barometer measures
An instrument used to measure air pressure and monitor its changes
There is what distance to the top of the atmosphere
None- no set distance
sea-level is the base measurement of
Earths pressure
They adjust local air pressure readings to approximately what the air pressure would be if the station were actually located at sea level the simplest adjustment assumes an imaginary column of air having the properties of the standard atmosphere expensing from the station down to sea level= reduction to sea level
pressure _______ with height
Decreases
Air pressures decreases with increasing altitude
What are characteristics of an air mass
Temperature and humidity
Air mass is a huge volume of air that is relatively uniform horizontally in temperature and water vapor concentration .
understand pressure differences and exerted pressure between cold and warm, and dry and moist air.
Hot air- air density decreases, the number of molecules per unit volume decreases
Cold air- air pressure drops more rapidly with altitude within a cold column of air than in a war column of air
Increasing humidity- affects air density in the same way as rising air temp. The greater concentration of water vapor the less dense the air. Water vapor reduces the density of air because the molecular weight of water is less than the average molecular weight of dry air
Remember _______ air is less dense, _______ air is more dense.
Warm— cold
understand basic info around phase changes … evaporation, sublimation, deposition, and so forth … understand how they relate to each other.
1) Evaporation - if more water me used enter the atmosphere as vapor than as liquid, a net loss occurs in liquid water mass
2) Condensation -If more water molecules return to the water surface as liquid than enter the atmosphere as vapor a new gain of liquid water mass results.
3) Transportation - water that is taken up from the soil by plant roots eventually escapes as vapor through tiny pores in the underside of leaves.
4) Sublimation - ice or snow becomes vapor without first becoming a liquid.
5) Deposition - water vapor becomes ice without first becoming a liquid. (Frost in automobile windows)
The maximum pressure that water vapor molecules could exert if the air were saturated is called
the saturation vapor pressure.
The vapor pressure at equilibrium.
What is a temperature inversion
Is the inverse of the usual temperature profile of the troposphere
stable air means
nice and usually clear weather, suppressed cloud development
unstable air enhances
cloud development and vertical lift
instability can be caused by
heat / colder temps promote stability
leeward side of a mountain is the _____ side and the windward side of a mountain is the ______ side
Leeward=dry
Windward= wet side
Clouds have _______ relative humidity or just about ______.
100%
know the cloud types and the weather associated with certain clouds …
Cirriform- wispy and fibrous
Stratiform- layered
Cumuli form- heaped or puffy
Cirrus- transparent and occur as delicate silky strands- mares tails
Cirrostratus- nearly transparent- thin white veil or sheet that partially or totally covers the sky.. You see these when approaching middle latitude storm.
Cirrocumulus- small white rounded patches arranged in a wavelike or mackerel pattern.
Altostratus- gray or blueish white layers that totally or partially cover the sky.
Altocumulus- roll-like patches or puffs that often form waves of parallel bands
Stratocumulus- large irregular puffs or rolls separated by areas of clear sky.
Stratus- gray layer stretching from horizon to horizon.
Nimbostratus- drizzle falls from stratus clouds but significant amounts of rain or snow may fall.
Cumulus is a low warn cloud that can be caused by local convection, and “nimbo” means rain.
Stratiform cloud- clouds that form in horizontal layers
Cumuliform cloud- clouds that appear puffy
Cirrus clouds- look fibrous because they are composed of mostly tiny ice crystals
Cumulus clouds- small white clouds that look like puffs of cotton
usually vaporize rapid
Cumulonimbus clouds- cumulus clouds that build vertically and merge laterally and turn into thunder clouds
Warm cloud
Precipitation
Droplets grow by colliding and coalescing(merging), with one another in the collision-coalescence process. It happens when a cloud is composed of different size droplets. They have different terminal velocities.. Faster falling then they collide and coalesce with slower droplets in the path. Larger droplets from initially on larger nuclei through random collisions between smaller droplets or via mixing between cloud droplets and the surrounding drier air.
LARGE DROPLETS COLLIDE WITH SMALLER DROPLETS AND COALESCE CREATING DROPLETS LARGE ENOUGH TO SURVIVE THE TO EARTHS SURFACE AS PRECIPITATION
Radiation fog
Mist-suspension
Radiation fog- clear night sky, light winds, an air mass that is humid near the ground and relatively dry aloft, radiation all cooling may cause the air near the ground to approach saturation. Ground level cloud. Marshy areas of where soil has been saturated by recent rainfall or snow melt.
Condensation nuclei can be made from
several types of particulate matter and several different sources
Terminal Velocity is
the maximum rate at which gravity pulls an object towards earth.
How many cloud droplets does it make to form 1 raindrop
it takes 1 million cloud droplets
drizzle falls from?!
nimbostratus clouds
on average … 1 foot of snow equals
1 inch of water.
Understand how doppler radar works and know that Doppler radar detects particles moving towards and away from the radar site
X
What is pressure gradient force
A force operating in the atmosphere that accelerates air parcels away from regions of high air pressure directly across isobars toward regions of low air pressure in response to an air pressure gradient
What is the Coriolis Effect and how does it work and know it’s direction in each hemisphere. Where is it strongest and weakest.
Term
- an apparent reflective force arising from the rotation of the earth on its axis; affects principally synoptic- scale and planetary- scale winds. Winds are deflected to the right of their initial direction in the Northern Hemisphere and to the left in the Southern Hemisphere. Magnitude depends on latitude and speed of the moving object.
What is a geostrophic wind
A hypothetical, unaccelerated horizontal wind that flows along a straight path parallel to isobars or height contours about the atmospheric boundary layer; results from a balance between horizontal pressure gradient force and Coriolis effect
winds are named for the direction where they ____ ____.
Come from
- As space grows between isobars,
pressure gradient force and wind speeds decrease.
Air pressure changes more gradually with distance between, the pressure gradient is weaker
Wind is light
know the scales of the atmospheric circulation in order from smallest to largest and largest to smallest
Planetary-scale systems- large scale wind belts encircling the planet are global.. Weeks or months
Synoptic- scale systems- are continental or oceanic in scale; extra tropical cyclones, hurricanes, and air masses… Several days to a week or so as they travel over distances of thousands of kilometers.
Horizontal winds are stronger than vertical flow
Mesoscale system- thunderstorms and sea and lake breezes, circulation systems that are small that they may influence the wearer in only a portion of a large city or county… Hours or a day
Microscale systems- a weather system covering a very small area such as several city blocks of a small town represents the smallest spatial subdivision of the atmospheric motion… Minutes or less.
Vertical wind speeds may be comparable in magnitude to horizontal winds.
the different types of barometers- 1.
Mercury barometer- invented in 1643 by Evanglista Torricelli an Italian mathematician and student of Galileo. It’s a class tube a little less than 1.0m in length, sealed at one end, open on the other end, and initially filled with Mercury which is 13 times denser than liquid water. The open end is inverted into a small open container of mercury. Mercury settles down the tube until the pressure of Mercury column exactly balances the pressure of the atmosphere acting on the surface of the Mercury in the open container
The average air pressure at sea level will support the Mercury column in the tube to a height of 760mm. The height of the Mercury column changes as air pressure changes. Falling air pressure allows the Mercury column to drop, where as increasing air pressure forces the Mercury column to rise, with the height of the Mercury column directly proportional to air pressure. This is the origin of the common practice of expressing air pressure in units of length or the Mercury column. Air pressure readings by a Mercury barometer require adjustments for 1 the expansion and contraction of Mercury that accompany changes in temp and 2 the slight variation of gravity with latitude and altitude that affects the weight of the Mercury column by convention readings are adjusted to standard conditions of 0C and 32F and 45 degrees latitude at sea level
the different types of barometers- 2
Aneroid Barometer
Is more portables. It consists of a flexible seed chamber from which much of the air has been evacuated. An internal spring prevents the chamber from collapsing. As air pressure changes, the chamber flexes, compressing when air pressure rises and expanding when air pressure drops. A series of gears and levers transmits and magnifies these movements to a pointer on a dial, which is calibrated to read in equivalent millimeters or inches of Mercury, or to read directly in units of air pressure. The latest aneroid barometers provide direct digital read outs. Electronic.
Advection fog
Advection fog- when the advecting air passes over a relatively cold surface, the air mass may be chilled to saturation in its lower layers. Advection cooling.. Example early spring when miles humid air flows over relatively cold, snow covered ground. Snow on the ground may chill the overlying air to the dew point and fog develops. ADVECTION COOLING
Steam fog
(Arctic seam smoke)
Late fall or winter when extremely cold and dry air flows over a large unfrozen body of water. Evaporation and sensible heating cause the lower portion of the air mass to become more humid and warmer than the air above. Heating below destabilizes the air and the consequent mixing of mild humid air with cold dry air brings the aid to saturation and fog forms. Because the air is stabilized fog appears.
Cold cloud
Precipitation
Most precipitation falling in middle and high latitudes originates in cold clouds (temps below 0) that contain some ice crystals. Precipitation is most likely to fall from a cloud initially composed of a mixture of supercooled water droplets and ice crystals.
Cloud condensation nuclei are much more abundant than ice forming nuclei and are more efficient in forming a cloud particle so that a mixed cloud consists of far more supercooled water droplets than ice crystals, supercooled water droplets quickly vaporize as ice crystals grow
As it gets colder.. Water freezes into ice crystals, aka SNOW
ICE CRYSTALS GROW BU DEPOSITION SND BECOME LARGE ENOUGH TO FALL
