Meteorology Test 1 Objectives (Ch. 16 & 17)

Question 1

What is the difference between weather and climate?

Answer 1

weather: atmospheric conditions for a short period of time
climate: average weather conditions over a long period of time (30 yrs); the sum of all the statistical weather information for an area

Question 2

Name the six elements of weather and climate.

Answer 2

temperature
humidity
type and amount of clouds
type and amount of precipitation
air pressure
wind speed and direction

Question 3

Name the four main gases in the atmosphere and the approximate percentage of each.

Answer 3

Nitrogen 78.08%
Oxygen 20.95%
Argon 0.93%
Carbon Dioxide 0.037%

Question 4

Name some variable components of the atmosphere and describe some effects of each.

Answer 4

Water Vapor
-required for formation of clouds and precipitation
-absorbs radiated heat energy
-source or sink of heat energy (latent heat); movement of atmosphere transports this heat to other areas; this provides driving force for many storms
Aerosols
-required for formation of clouds, fog, and precipitation
-reflect and scatter light; cause red sunrises and sunsets
Ozone
-absorbs harmful ultraviolet radiation from the Sun

Question 5

Where is most of the naturally occurring ozone located? Why is it important? What is the most important material that leads to its destruction?

Answer 5

the stratosphere at altitudes of 6-30 miles
absorbs harmful UV radiation from the Sun
CFCs (chlorofluorocarbons): most commonly freons and halons

Question 6

What are some harmful effects to humans of UV at the surface of the Earth?

Answer 6

skin cancer risk
risk of impaired immune systems
occurrence of cataracts

Question 7

Briefly describe the troposphere and stratosphere.

Answer 7

Troposphere: up to about 7 miles
-temperature decreases uniformly with altitude
-normal (environmental) lapse rate
avg. = -3.5degF/1000ft
-the atmosphere is continually mixed
-nearly all clouds occur in the troposphere; weather sometimes described as the atmospheric conditions of the lower troposphere
Stratosphere: from about 7 miles to about 30 miles
-temperature is constant with increasing altitude, then increases
-there is little mixing of the atmosphere

Question 8

Describe the meaning of “lapse rate” and calculate the approximate temperature for altitudes up to 30,000 ft. Memorize the average lapse rate of …

Answer 8

Lapse rate is the average drop in temperature with increased altitude in the troposphere.
-3.5 degrees Farenheit/1,000 ft.

Question 9

How is the inclination of the earth’s axis related to the seasons?

Answer 9

The inclination causes the seasons

Question 10

For each of the following, state the approximate date, the season it begins, where the sun's rays are falling most directly, and the length of day vs. night inside the arctic and antartic circles. 
vernal equinox
autumnal equinox
summer solstice
winter solstice

Answer 10

vernal equinox:
March 21-22; equator; half and half Everywhere
autumnal equinox:
Setptember 22-23; equator; half and half Everywhere
summer solstice:
June 21/22; summer; 23.5deg north latitude; arctic - daylight lasts for 24 hours; antarctic - night for 24 hrs
winter solstice:
December 21-22; 23.5deg south latitude; arctic - night for 24 hrs; antarctic - daytime for 24 hrs

Question 11

What is meant by the albedo of an object?

Answer 11

reflectivity; specifically, the fraction of the total radiation that is reflected by a surface

Question 12

What is the cause and effect of Rayleigh scattering?

Answer 12

Rayleigh scattering refers to the scattering of light off of the molecules of the air, and can be extended to scattering from particles up to about a tenth of the wavelength of the light. It is Rayleigh scattering off the molecules of the air which gives us the blue sky.

Question 13

Briefly discuss and/or identify the major controls on the average temperature of a location.

Answer 13

1. Latitude - most significant
2. Altitude - higher altitudes, lower temperatures
3. Geographic Position
   - Land vs. Water: land warms up and cools down more rapidly and to a greater extent than water. Large bodies of water serve as huge heat reservoirs which tend to prevent extremes in temperature.
   - Coastal Areas vs. Continental Interiors
   - Mountains Act as Barriers
   - Wind Direction
4. Cloud Cover - during day, clouds reflect incoming radiation and reduce the high temp from what it would have been under clear skies
   - during night, clouds act like insulation and raise the nighttime low temp from what it would have been otherwise
   - net effect is that clouds reduce the daily temp range

Question 14

Describe and/or identify January and July world temperature patterns and what causes the differences.

Answer 14

In January, southern hemisphere warmer. In July, northern hemisphere warmer. Tilt of Earth’s axis causes this as it causes the seasonal migration of the Sun’s vertical rays. (also latitude, currents)

Question 15

What is the difference between absolute humidity and relative humidity?

Answer 15

absolute: weight of water vapor per cubed feet of air
relative: compares the actual amount of water vapor present to the maximum amount the air can hold at that temperature (RH)

Question 16

Calculate the percent relative humidity given the absolute humidity and the maximum moisture content.

Answer 16

RH=(actual moisture content/maximum moisture capacity) and convert to percentage

Question 17

What is meant by the dew point temperature?

Answer 17

the temperature to which air must be cooled to reach saturation (temp at which RH=100%)

Question 18

Determine the percent relative humidity, maximum moisture capacity, actual moisture content, and dew point given a set of psychrometer readings and an appropriate table.

Answer 18

like in class

Question 19

What time of day are we most likely to have the highest percent relative humidity? the lowest?

Answer 19

sunrise; late afternoon (3:00-4:00)

Question 20

What is meant by “latent heat” and “latent heat of condensation”?

Answer 20

latent heat: energy that is absorbed or released without a change in temperature
latent heat of condensation: during condensation, water vapor molecules release energy/heat in an equal amount to what was absorbed during evaporation

Question 21

Why is the dew point so significant in describing and predicting the weather?

Answer 21

• best measure of amount of moisture in the air
• dew point often used to forecast low temp for the night b/c heat is released during condensation
• Allows a judgment as to whether fog is likely to form or not.
• High dew points combined with a rapidly moving cold front indicate the possibility of severe weather.
• Helps determine how fast air heats up or cools down. Air with a high moisture content (high dew point) requires more heat to warm up and releases more heat when it cools down than does dry air.
• It is a major contributor to comfort levels in warm temps.

Question 22

What are adiabatic temperature changes and when do they occur?

Answer 22

changes in temperature that occurs even through heat is neither added nor subtracted. They result when air is compressed or allowed to expand. (expand, cool; compress, warm)

Question 23

What is meant by the Dry Adiabatic Rate and the Wet (or Saturated) Adiabatic Rate?

Answer 23

DAR - rate at which a parcel of unsaturated air cools or warms as it changes altitude
WAR - same definition as DAR but applies only to rising, saturated air

Question 24

Given the temperature of a parcel of air at a particular elevation, its dew point, and its Dry and Wet Adiabatic Rates, determine the temperature and dew point at other elevations as it rises up and over a mountain.

Answer 24

like in class

Question 25

Name some examples of condensation nuclei and briefly describe their role in cloud and rain formation.

Answer 25

dust, smoke, pollen, salt particles (in coastal areas); provide a surface for water vapor to condense upon in the air

Question 26

Name and briefly describe four ways in which air may be lifted, cooled below the dew point, and form a cloud.

Answer 26

1. Convergence - air forced to slow down (by object on ground or terrain change, etc.), or air flows together from opposite directions
2. Frontal Wedging - warmer air is forced over colder air
3. Orographic Lifting - air is forced over mountains
4. Local Convective Lifting - localized warmer pockets of air (thermals) rise because of unequal surface heating

Question 27

How can a parcel of rising air be determined to be stable or unstable?

Answer 27

Compare the temp of a parcel of rising air using the dry/wet adiabatic rate to the environmental lapse rate (ELR). If a rising parcel of air is warmer, and less dense, than the surrounding air, it is unstable and will rise. If a rising parcel of air is cooler, and more dense, than the surrounding air, it is stable and will resist rising or sink.

Question 28

Given the surface temperature, the ELR, the LCL, the DAR, and the WAR, determine if the parcel of air exhibits “absolute stability,” “absolute instability,” or “conditional instability.”

Answer 28

like in class

Question 29

What is the general difference in the type of clouds and precipitation produced in stable vs. unstable air?

Answer 29

Stable air produces clouds that are widespread but not very thick. Any precipitation formed is not heavy.
Unstable air produces clouds that are tall and towering. May produce tall, cauliflower clouds that produce thunderstorms with heavy rains.

Question 30

Name and describe the meanings of the four basic cloud root names.

Answer 30

cirrus: high, white, thin; wispy, feathery, veil-like
cumulus: billowy, rounded forms; may have a flat base; “cauliflower” structure
stratus: sheets or layers; cover much of the sky; no distinct individual clouds
nimbus: produces precipitation

Question 31

cirrus

Answer 31

“mare’s tails” or “artist brush” clouds

Question 32

cirrocumulus

Answer 32

rippled patches, waves, or rows; may produce a “mackerel” sky (scales)

Question 33

cirrostratus

Answer 33

thin veil, give sky a milky appearance, may cause a halo around the sun or moon

Question 34

altostratus

Answer 34

thin white to grayish blanket; may produce very light precipitation; the sun or moon may appear as a bright spot, but no halo

Question 35

altocumulus

Answer 35

waves or rows joined together; often composed of separate globules; associated with fair weather; “sheep-back” clouds

Question 36

stratus

Answer 36

low, uniform, fog-like layer covering much of the sky; a “high fog”; may have light drizzle

Question 37

stratocumulus

Answer 37

soft, gray clouds in globular patches or long parallel rolls

Question 38

nimbostratus

Answer 38

nearly uniform cover of dark gray clouds usually associated with steady precipitation (associated with stable conditions)

Question 39

cumulus

Answer 39

dense, billowy clouds; often have a flat base; common in summer; may occur as isolated clouds or closely packed; the fair weather “cotton balls” clouds of summer

Question 40

cumulonimbus

Answer 40

massive, towering cloud with great vertical development; may extend above 50,000 ft; may form an “anvil head”; “thunder heads”; may produce heavy rain, thunder, lightning, gusty winds, or tornadoes; form in unstable air

Question 41

radiation fog

Answer 41

produced when the Earth’s surface cools rapidly by radiation on cool, calm, clear nights; form in low-lying areas

Question 42

advection fog

Answer 42

produced when warm, moist air moves over a cool surface and is cooled below the dew point; “roll in”; more prominent on west coast