Weather Theory

Question 1

What causes weather

Answer 1

•Temperature differences
•Pressure differences
•Effects of temperature and pressure differences
•Large scale air masses

Question 2

Weather properties

Answer 2

•Temperature:
•Measure of the motion of molecules
•Density:
•Mass of the molecules in a given volume
•Pressure:
•Force exerted by a moving fluid molecule on a given area (psi – Pounds per Square Inch)

Question 3

Atmospheric composition

Answer 3

•Nitrogen (78%)
•Oxygen (21%)
•Trace Gases (1%)
•Argon
•Carbon Dioxide

Question 4

Standard temperature/pressure

Answer 4

•Standard Temperature; 15°C (59°F)
•Standard Temperature Lapse Rate: 2°C per 1000 ft
•Standard Pressure: 29.92 inches Hg

Question 5

Troposphere

Answer 5

•Temperature decreases with altitude (2ºC per 1000 feet)
•Surface to approximately 36,000 feet msl. (Middle Latitudes)
•Layer is thinner near the poles and thickest at the Equator

Question 6

Tropopause

Answer 6

•Temperature remains relatively constant with increases in altitude
•Related to Jet Stream and Thunderstorms

Question 7

Stratosphere

Answer 7

Temperature increases with altitude

Question 8

Stratopause

Answer 8

•Temperature at maximum value in this layer
•Exists around 160,000 feet msl.

Question 9

Mesosphere

Answer 9

Temperature decreases with altitude

Question 10

Ozone layer

Answer 10

•Found in lower Stratosphere
•Is the reason for an increase in temperature
•Exists around 80,000 feet msl.

Question 11

Ionosphere (mesosphere through thermosphere)

Answer 11

•Layer of charged particles
•Exists from lower Mesosphere upward through the Thermosphere
•Caused by incoming solar radiation displacing electrons from matter

Question 12

The sun

Answer 12

•The sun is the source which causes all weather
•Solar Energy heats the equator more than the poles.
•Warm air flows toward poles and cold air flows toward equator.

Question 13

Convection

Answer 13

•The Atmosphere is essentially a closed system
•This system is constantly attempting to achieve a physical equilibrium
•Energy from the sun results in global differences in temperature and pressure
•The effort to equalize is called Convection

Question 14

Forces

Answer 14

•Pressure Gradient Force:
•Movement of air from High to Low pressure
•Frictional Force:
•Result of slowing of movement of air, opposes pressure gradient force
•Coriolis Force:
•Apparent deflection of objects when viewed from a rotating frame of reference
•Earth Rotates causes bend in PGF to the right in Northern hemisphere and left in Southern

Question 15

Atmospheric pressure

Answer 15

•Changes in temperature also result in changes in pressure
•Changes in both temperature and pressure are tracked by Meteorologists
•By knowing the location of airmasses of given temperatures and pressures, we can forecast weather

Question 16

Isobars and pressure gradients

Answer 16

•Lines of equal pressure
•Delineate pressure systems and features
•Tightly packed lines indicate tight pressure gradient → Strong Winds

Question 17

Low pressure systems

Answer 17

•Cyclonic Flow
•Counterclockwise
•Upward Motion of Air
•Rising Air
•Clouds with vertical development
•Precipitation – Showery
•Turbulence

Question 18

High pressure systems

Answer 18

•Anticyclonic
•Clockwise Flow
•Downward Motion of Air
•Descending Air
•No clouds
•Good Weather

Question 19

International standard atmosphere

Answer 19

•Created by ICAO (International Civil Aviation Organization)
•Pressure: 29.92” in. Hg., 1013.2 mb
•Temperature: 15°C or 59°F

Question 20

Stability

Answer 20

•Atmospheric resistance to vertical motion
•Standard Lapse Rate: 2°C per 1000 feet
•Determined by the combined effects of temperature and moisture
•As air becomes warmer and dewpoint increases, instability increases
•Temperature Inversions
•Occur in stable air with little or no turbulence
•Common after clear nights with calm winds
•Act as a “cap” for weather and pollutants

Question 21

Dew point

Answer 21

•Dewpoint is temperature at which a given parcel of air is cooled for water vapor to condense into water
•Point at which the air can hold no more water
•100 % relative humidity
•When air reaches it dewpoint moisture becomes visible

Question 22

When are clouds formed

Answer 22

When the invisible water vapor in the air condenses into visible water droplets or ice crystals

Question 23

Cloud types

Answer 23

•Cumulus- Vertical development, Billowy
•Stratus- Layered
•Nimbo- Rain
•Cirrus- Wispy

Question 24

Cloud families

Answer 24

Low < 6,500
•Stratus (St)
•Stratocumulus (As)
•Cumulus (Cu)

•Middle 6,500 - 23,000
•Altocumulus (Ac)
•Altostratus (As)
•Nimbostratus (Ns)

•High 16,500 - 45,000
•Cirrus (Ci)—PRIMARILY ICE CRYSTALS
•Cirrocumulus (Cc)
•Cirrostratus (Cs)
•Extensive vertical development
•Towering cumulus
•Cumulonimbus—THE WORST TURBULENCE

Question 25

Radiation fog

Answer 25

•During the day, the surface is heated by the sun
•At night, the surface radiates that heat into the atmosphere
•As this happens, the air very close to the surface cools to the dew point

Question 26

Advection fog

Answer 26

Forms when a low layer of warm, moist air moves over a cooler surface

Question 27

Steam fog

Answer 27

Cold air moves over warmer water, evaporates into the air

Question 28

Upslope fog

Answer 28

Moist air forced aloft and cooled to dewpoint

Question 29

Precipitation induced fog

Answer 29

Evaporation of falling moisture cools the air to the dewpoint

Question 30

Unfrozen precipitation

Answer 30

•Drizzle: Fairly uniform precipitation composed exclusively of fine drops
•Rain: Precipitation, which in contrast to drizzle, are widely separated
•Virga: Visible wisps or strands of precipitation falling from clouds that evaporate before reaching the surface

Question 31

Frozen precipitation

Answer 31

•Ice Pellets: Transparent or translucent pellets of ice, which are round or irregular
•Snow: Precipitation mostly branched in the form of six-pointed stars
•Hail: Small balls or other pieces of ice falling separately or frozen together in irregular lumps