Meteorology

I. Weather-

A. Causes of Weather1. Energy from the

a. Through theseasons, it heats our world,some parts more and some parts less

The state or condition of the variables of the atmosphere for a location at a given period of time.

sun

LOW latitude

b. This causes earth’s atmosphere to react and become a gigantic engine that produces an infinite variety of

uneven heating

MEDIUM Latitude HIGH latitude

weather

B. Weather/Atmospheric Variables:

1.

2.

3.

4.

C. Weather Instruments:

Temperature

Barometer

Wind (Speed and Direction)

Moisture (Precipitation and Humidity)

Air Pressure

Measures

Air Pressure

Sling Psychrometer

Measures

Relative Humidity

Rain Gauge

Measures

Rainfall

Wind / Weather vane

Measures

Wind Direction

Anemometer

Measures

Wind Speed

Thermometer measures Temperature

II. Atmosphere: The envelope of air (mixture of gases) that surrounds earth

A. Composition of the lower atmosphere (troposphere)

1. (78%)

2. (21%)

3. (.84%)

4. (.03%)

5. (.01%)

Nitrogen

Oxygen

Argon

Carbon Dioxide

Other

N + O2 + Other Gases

Oxygen

Helium

Hydrogen

Heterosphere

Homosphere

B. Composition vs. Altitude

U-V

Rays

Thermosphere

Mesopause

Mesosphere

Stratopause

Stratosphere

Tropopause

Troposphere

14

O3

Weather takes place only in the

troposphere

As altitude increases, temperature in the troposphere______________decreases

‘s atmosphere

D. Mapping a Temperature Field

1. are lines that connect to points of equal temperature. Showing temperature distribution in this way makes patterns easier to see

Isotherms

2. The greatest temperature gradient is betweenand which is

indicated because the isotherms are Richmond Hatteras

closest together

3. Temperature gradient calculation from Cincinnati to Chicago

G=(60° - 40°)

250 mi =20°F

250 mi = .08°F

mi

E. General Information – Heat and TemperatureWind Chill

2. Heat affects body- when your body is overheated the additional stress can cause medical problems.

A. Your body’s thermostat, the determines that your body is too warm.

B. increases in an effort to carry heat from deep inside the body to the surface of the skin.

C. If lost by sweating is not replaced, dehydration and heat exhaustion can result.

D. High humidity can interfere with thethat carries

away large amounts of heat.

V. Air PressureA. Cause of Air Pressure

1. The force of causes the air to have -this creates air pressure

less

more

Gravity weight

Gra

vity

Air

Pre

ssur

e

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2. Air pressure acts equally in allit also exists within any object

containing air like a building, the human body and “empty” bottles

3.

4. Air pressure at sea level is

AIR

20,000 mi. MERCURY

30 inches

14.7 p.s.i.

14.7 lb/in22

directions;

B. Measuring Air Pressure1. Mercury Barometer 2. Aneroid barometer

An aneroid barometer consists of an air tight metal box from which most of the air has been removed.

A change in air pressure causes a small metal disk on the side or top to bend. A spring is attached to the metal disk. The bending metal disk causes the spring to move. A needle attached to the spring indicates the changing air pressure on the dial.

29.92 inches

76 cm

760 mm

Air pressure

23

3. Units for measuring air pressure Inches (of mercury) & millibars

C. Atmospheric Pressure Scale (Reference table page 13)1. Standard sea level atmospheric pressure is:

2. Conversions:

1. 997 mb =

2. = 30.15 in.

3. 1006 mb =

4. 982 mb =

5. = 29.53 in.

6. = 30.21 in.

7. 1019 mb =

29.44 in.

1021 mb.

29.71 in.

29.00 in

30.09 in.

1000 mb.

1023 mb.

One atmosphere or 29.92 in. or 1013.2 mb.

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D. Changes in atmospheric pressure1. Factors/variables that cause atmospheric

pressure to change

a) Temperature

b) Moisture

c) Altitude

2. Effect of on air pressure:

As air temperature increases; (air molecules move farther apart/ become less dense) the air pressure decreases

temperature

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HOT STEAMHOT STEAM Air expands

Density decreases

Vent is open

Vent is closed

COOLING STEAM

COOLING STEAM

Density increases

Air contracts

3. Effect of on air pressure:a. The diagrams represent a specific volume of air in three

different circumstances. They show how the density or mass of this volume of air changes when water vapor enters the air.

Dry

H2O

H2O H2O

H2O

Water vapor molecules replace

air moleculesHumid

More dense Less dense

moisture

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b. As humidity increases,air pressuredecreases – because when water vapor molecules enter dry air they replace heavier air molecules

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4. Effect of on air pressure:a.

b. As altitude increases air pressure decreases. (less air above and air is less dense)

Low

Medium

High 1013 mb.

altitude

26

c.

26

E. Mapping An Air Pressure Field1. are lines that connect

points of equal pressure. Showing air pressure distribution in this way makes patterns easier to see.

On U.S. weather bureau maps, the interval between isobars is

2. On weather maps barometric pressure is represented by a three-digit number to the upper right of a circle; this circle represents a city on the map

Isobars

4 mb

27

a. Rules to follow to determine the value of this number:

1. A decimal point is omitted between the last two digits on the right.2. The number nine or ten is omitted in

front of this number. If the original number is above 500, place a 9 in front. If it is below 500, place a ten in front. (Hint: use whichever will give a result closest to 1000 mb.)

Ex.: 053Special note: the determined value of this number should be on the pressure scale (millibars) on page 13 of the Earth Science Reference Tables

1005.3

27

On the map, draw isobars for 1004, 1008, 1012, 1016, and 1020 millibars.

VI. Wind-

A. Causes of winds1. Uneven heating of the earths surface

2. Examples:a. Land vs. water

b. Poles vs. equator

c. Dark forest vs. snowfield

3. Winds help to distribute energy from areas of surplus to areas of energy deficit.

The horizontal movement of air parallel to the earths surface

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B. Sea Breeze Vs. Land Breeze1. Sea Breeze

COOLWARM

High

Low

Less dense

More dense

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2. Land Breeze

WARMCOOL

Low

High

More dense

Less dense

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C. Wind Direction1. Winds always blow from regions of

pressure to regions of pressure

2. The Coriolis Effect- Earth’s on its axis causes winds to be deflected to the in the hemisphere and to the

in the hemisphere.

highlow

rotation

right northernleft southern

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3. a. Map View

b. side/profile view

LH

30

4. Cyclones and Anticyclones

clockwise counterclockwise

REMEMBER HI CLOCK!

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a. Winds move in a clockwise outer spiral around a

b. Winds move in a counterclockwise inward spiral around a

Activity: On the map on page 28,a. for each station model extend the shaft of the wind arrow and draw the head of the arrow to show the “direction the wind is blowing”b. Draw larger arrows to show the general direction the wind is blowing

high pressure system

low pressure system

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On the map, draw isobars for 1004, 1008, 1012, 1016, and 1020 millibars.

D. Wind Speed1. The speed of the wind is determined by the

difference in air pressure

2. Pressure Gradient-

3. As the pressure gradient increases, wind speed increases

Difference in air pressure between two places

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a. Where is the pressure gradient the greatest?

b. Where are the winds strongest/highest wind?

Near Holland

Near Holland

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E. Global WindsThe unequal distribution of solar energy (insolation), in terms of both intensity and duration, causes unequal heating of Earth. Differences in temperature cause differences in pressure which result in winds.Cooler air, being denser, sinks toward earth due to gravity. This causes warmer less dense air to rise.

Global winds or circulation on a non-rotating earth

Earths rotation causes the Coriolis Effect” which results in three (or six) cell circulation of winds as illustrated on the next page

32

HIGH

HIGH

HIGH

HIGH

LOW

LOW

LOW

Reference Table 14

33

IV.Moisture

A. The Water Cycle

precipitationcondensation

transpiration evaporation

absorption runoff

infiltration

8. The primary source of energy for the water cycle is the

9. is the process by which plants release water into the atmosphere; 2 in diagram

10. is the falling liquid or solid water from the clouds to earth's surface; 4 in the diagram. Examples:

A. RainB. SnowC. HailD. Sleet

Transpiration

Precipitation

sun

6. Sublimation-Ex. And7. Deposition-

B. Moisture in the Atmosphere1. The primary source of moisture in our atmosphere

is the other sources include:1. Moisture in the atmosphere exists in all three

states/phasesa. -Known as water vaporb. - tiny droplets suspended

in the air that form cloudsc. - tiny crystals suspended in

the air that form clouds.

Solid changing directly to a gas.

Moth balls Dry IceGas changing directly to a solid

Ocean

Gas

Liquid

Solid

Lakes, rivers, soil, plants

3. Is the general term used to describe the

4. determines the amount of water vapor the air can hold.

a.

b. As air temperature , the amount of water the air can hold

Humidity

Temperature

increases

increases

amount of water vapor in the air

c. At 35°C, a cubic meter of air can hold of water vapor.

5. Saturation-

6.

When air holds as much water as it can at a certain temperature

Saturation occurs when condensation = evaporation

35 grams

a. At 1, no has occurred

b. At 2, is proceeding faster than .

c. At 3, the rate of equals the rate of .has been reached and the air is

evaporation

evaporation

evaporation

condensation

condensation

Equilibriumsaturated

7. Factors affecting the rate of evaporation:

a. -

b. -

c. -

d. -

Temp.

Humidity

As temp. increases. the rate of evaporation increases

As humidity increases the rateof evaporation decreases

Wind

Surface Area

As wind increases the rate of evaporation increases

As surface area increases evaporation increases.

HumidityTemperature Wind Surface Area

9. Dew Point Temperature- The temperature to which air must be to reach saturation.

a. Using a sling psychrometer to measure the dew point temperature

A sling psychrometer consists of two thermometers mounted on a narrow frame which has a handle used to whirl it. The thermometer always remains dry (dry bulb). The other has a cloth sock or wick over its bulb that is moistened before use (wet bulb)

After a psychrometer is whirled around for a little less than one minute, both thermometers should be read.

Evaporation of water from the wick will have lowered the temperature reading on the wet bulb (if the air is not saturated). Remember: evaporation absorbs heat and is a cooling process.

16

b. The drier the air the evaporation will occur resulting in cooling. In turn the difference in temperature between the dry bulb and the wet bulb will be

c. The more humid the air, the evaporation will occur resulting in cooling of the wet thermometer. In turn the difference in temperature will be

d. At saturation the temperature difference between the dry and wet bulbs would be

faster/more

greater/more.

greater/more

lessless

smaller

0

16

10. Relative Humidity- the ratio (comparison) between the actual amount of water in the air to the maximum amount of water vapor the air can hold at a given temperature.

Reference Tables

page 1219° 5° 10° 10° -7° 3° 17°

17

a. Changing Air Temperature1.

2. If temperature increases, and moisture in the air remains the same, relative humidity will decrease.

3. Time of dayHighest Relative Humidity =Lowest Relative Humidity =

Temperature

Relative Humidity

Coolest time of day – 5:00 AMWarmest time of day – 3:00 PM

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a. Changing in Absolute Humidity (actual water vapor content)

1.

2. If the moisture content of the air increases, and temperature remains the same, relative humidity increases.

Water Vapor

Relative Humidity

18

3. Determine the relative humidity for the following data:

11. Cloudsa. Clouds are tiny droplets of liquid water or ice suspended in air.b. Combination of conditions needed for a cloud

1. Moisture in the air2. Cooling temperatures3. Dust particles “or condensation nuclei”

Reference Table 12

51% 74% 33% 83% 70% 100% 39%

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c. Condensation Nuclei-

1.

2. Condensation in cloud formations incorporates some of the aerosols as , and thus, these aerosols are removed from the atmosphere during precipitation. Precipitation therefore

Dust particles

Salt Particles

= Water molecules

Aerosols in the atmosphere which provide a surface for water molecules to condense on

Condensation nuclei

Cleans the air

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d. Cooling in the Atmosphere-Adiabatic Cooling

As air , the atmospheric pressure surrounding the parcel of air decreases. Therefore the parcel of air

in volume as it rises. As it expands, it becomes When the temperature of this parcel of air falls to its

, the water vapor in the air

and a appears in the sky

Cooler.

rises

expands

dew point tempcondenses

cloud

19

19

Clouds float

•Now go to page 141 in your book to see the different types of precipitation!

12.Cloud Types

a.Key meanings

1) - wisps or curls

2) - Spread or layers

3) - heaps or piles

4) - prefix meaning “high”

5) - rain-bearing or snow-bearing

cirrus

stratus

cum

alto

nimbus

ulus

20

b.Establish a key on pg 21 and then identify these

Cloud link

20

c. Classification of clouds

CirrusCirrostratus

Cirrocumulus

AltostratusAltocumulus

StratocumulusStratus

Nimbostratus

Cumulus

Cumulonimbus21

1

23

4

5

6

78

9

10

Go back to page 20

13. Humidity and Temperature

a. The combination of high heat and humidity makes people feel warmer than the actual temperature alone. When humidity is high, less sweat evaporates. Evaporation is a cooling process, If less sweat evaporates,

b. How hot does it feel when the air temperature is 90° and the relative humidity is 70%? _______105°F

The body doesn't cool - feels warmer

Health Dangers:

Extremely Hot- heatstroke is imminent

Very Hot- Heatstroke possible with prolonged exposure. Heat cramps and heat exhaustion likely.

Hot- Heat cramps and heat exhaustion possible with prolonged exposure.

Very Warm- Physical activity could be more fatiguing than usual.

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VII. Air masses and FrontsA. Air mass- a large body of air in the troposphere

with similar characteristics of temperature moisture and pressure.

1. Source Region- a geographic region where an air mass develops. - This happens as air stagnates over a particular part of the earths surface for a period of time acquiring the temperature and/or moisture of the surface

2. Types of Air Massesa. - originates in the tropics (low

latitudes). Characterized byb. - originates in polar regions (high

latitudes). Characterized byc. - originates in arctic regions (in

winter only), it is .d. - Originates in doldrums

near the equator. Very hot and humid. Almost never influences the U.S.

e. - originates over land masses

f. - originates over water

Tropical

Polar

Arctic

Equatorial

ContinentalMaritime

High temperatures

Low Temperatures

Very Cold/Dry

DryWet

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3. Air masses are a combination of temperature and moisture conditions.

Symbol Name of Air Mass Characteristics

cP Continental Polar Cold + Dry

mT Maritime Tropical Warm + Moist

cT Continental Tropical Hot + Dry

mP Maritime Polar Cool + Moist

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4. Illustrated below are the source regions of air masses that affect the weather of North America. The arrows indicate the path/tracks that these air masses follow

mP cP mP

mTmT

mT cT

35

mPmP

cP

cA

mT mT

cT

FRONTS

• The boundary between two air mass.

• Little mixing of air occurs at fronts.

• Unstableness of fronts is the cause of precipitation.

• 4 types of fronts and they are . . .

COLD FRONT

• The boundary between an advancing air mass pushing a warmer air mass.

• Underlying cold air pushes warm up and over like a plow.

• A fast moving front.

• Symbol used on maps is

WARM FRONT• The boundary between an advancing

warm air mass on a retreating wedge of a cold air mass.

• Warm air rises up and over as its advances because it is less dense.

• A slow moving front.

• Symbol used on maps is

OCCLUDED FRONT

• Occurs when a cold front overtakes a warm front and pushes the warm air between them up off the ground.

• Symbol used on maps is

STATIONARY FRONT

• Boundary between two adjacent air masses of different characteristics remaining in approximately the same position.

• Symbol used on maps is

Symbols point in the direction the air mass is moving.

STORM TRACKS

• Low pressure storms generally track (move) to the east (or northeast) across the United States.

• Due to the wind belt in which the United States is located.

ESRT p 14

WEATHER PREDICTION

• Weather prediction is based on probability.

• A few days predictions are more accurate and reliable than long term predictions.

• Computer analysis and satellite images have improved forecasting in recent years.

VIII. Areas of RainfallA. Regions on Earth where air rises expands

cools (to dew point temp), condenses, clouds + precipitation.

1. Windward Side of Mountain

Prevailing westerlies

PacificSeattle Spokane

risesexpands

cools

condenses

windwar

d

leeward

sinks

compresses

warmsdry

2. Doldrums- The equatorial region where warm humid air rises as a result of convection. This produces thunderstorms almost daily. Reference Table 14

coolsexpands

riseswet

condenses

Dry Dry

De

sert

s

De

sert

s

Tro

pica

l R

ain

Fo

rest

s

IX. Weather MapsA. Station Models – On weather maps the weather conditions

for each weather station are shown by symbols arranged in and around a small circle. These symbols and the circle makeup a station model, which gives the latest readings for the most important weather variables.

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The Weather Station Model

©Steve Kluge 2007 Some images from the NYSED Earth Science Reference Tables

Get accompanying notes here

Draw a Station Model link

C. Weather Map1. Synoptic (a map that describes current weather and is used

for prediction)

2. Satellite Map

D. Lake Effect Snowfall

rises expandsco

ols