Weather

Weather is ….

• The condition of the variables in the atmosphere at a given time and place.

• Variables – temp, air pressure, wind, cloud cover, precipitation, etc.

Measuring Temperature• 3 different scales

to measure temp.

•Celsius•Fahrenheit•Kelvin

ESRT pg 295 (13)

Temp is ….• Measured using a thermometer

(liquid filled glass tube)• Modeled on maps or charts by

using isolines (isotherms)

• The atmosphere is heated in many ways:

– Insolation from the Sun–Conduction–Condensation–Coriolis effect

• Heat energy is transferred in our atmosphere by the process of convection.

A closer look at CONVECTION:Transfer of heat energy through substances which can flow.

waterair

Molten rock

Heat source

1. Heating causes a decrease in density

2. Lower density warmer water rises upward.

3. Water moves in to replace rising warm water

4. Cooler more dense water sinks.

5. Rising heated water moves outward to replace sinking cooler water.

A convection cycle

Air Pressure

• Air Pressure- Pressure due to weight of the overlying atmosphere pushing down on a given area.

• Pressure & Density are directly related

• Density = Pressure

Measuring Air Pressure

Barometers – Mercury barometer

• Standard reference but difficult to transport (inches of mercury)

–Aneroid barometer• Non-liquid barometer that is

smaller (millibars)

1013.2 mb = ________ inches

1022.0 mb = ________ inches

30.53 inches = ________ mb

29.81 inches = ________ mb

ESRT pg 295 (13)

29.92

30.18

1034.0

1009.5

What Effects Air Pressure?

• As the temp of air increases the density & pressure _____________

• As the altitude increases the density & pressure _______________

decreases

decreases

• The greater the amount of water vapor, the lower the air pressure & density…. but WHY?

Water has less mass than

other elements, which it

replaces in the atmosphere.

Practice Questions

According to the Earth Science Reference Tables, an air pressure of 30.15 inches of mercury is equal to

1. 1017 mb 2. 1019 mb 3. 1021 mb 4. 1023 mb

A balloon carrying weather instruments is released at the Earth’s surface & rises through the troposphere. As the balloon rises, what will the instruments generally indicate?

1. An increase in both air temp. & air pressure 2. A decrease in air temp. & an increase

in air pressure3. An increase in air temp. & a decrease

in air pressure4. A decrease in both air temp and air pressure

A temperature of 80°F would be approximately equal to how many degrees on the Celsius scale?

1. 27 3. 1782. 299 4. 34

Layers of our Atmosphere

http://www.youtube.com/watch?v=FHtvDA0W34I

Where was he?

• Jumped from 128,000 feet, or 24 miles!

Mapping Temperature and Air Pressure

Why Use Weather Maps?

• Weather maps help us picture what is going on in the atmosphere.– Data is collected in multiple locations,

and is displayed in a format that can be understood easily by people.• The information is placed on weather

maps.

Isolines

• Connect points of equal value on a map. Ex.: Temperature, Pressure, Elevation.

Types of Isolines

• Isotherms – connect points of equal temperature.

• Isobars – connect points of equal air pressure.

Rules For Drawing Isolines

1. Isolines begin and end at the edges of the map OR form closed circles.

2. Isolines connect points of equal value.3. The isoline interval is the difference

between two neighboring isolines.4. Isolines NEVER cross because the point

of intersection would have two values, and this cannot happen.

Gradient

• Gradient – Shows how much something changes over a distance.

• Calculating Gradient:– Gradient = Change in field value

Distance

Wind

RANDOM FACTS:

• Horizontal movement of air parallel to earth’s surface

10 windiest citiesAvg annual wind speed in

mph1. Blue Hill, Ma 15.4

2. Dodge City, Kansas 14.0

3. Amarillo, Texas 13.5

4. Rochester, Mn 13.1

5. Casper, Wyoming 12.9

6. Cheyenne, Wy 12.9

7. Great Falls, Montana 12.7

8. Goodland, Kansas 12.6

9. Boston, Ma 12.5

10. Lubbock, Texas 12.4

Two of the windiest cities are found in

Massachusetts

Fastest wind struck Oklahoma City on May

3, 1999. (SPEED was 318 mph)

ANEMOMETER– Instrument used to measure wind speed -Measured in miles per hour & knots

AIR PRESSURE GRADIENT

• Caused by DIFFERENCES in air pressures for a specific distance

CLOSER THE ISOBARS =

GREATER Pressure Gradient & FASTER Wind Speed

WIND MOVES FROM: Areas of HIGH pressure to areas of LOW

pressure

Coriolis effect (Earth’s rotation) causes winds to move..

-RIGHT Northern Hemisphere-LEFT Southern Hemisphere

MYTH OF THE TOILETOne can find both

counterclockwise and

clockwise flowing drains in

both hemispheres. Some

people would like you to believe that the

Coriolis force affects the flow of water

down the drain in sinks, bathtubs, or

toilet bowls. Don’t believe them! The

Coriolis force DOES NOT affect

such small bodies of water

Planetary winds in the Troposphere

Unequal heating of Earth causes huge CONVECTION

CELLS around Earth

ESRT pg. 14

Rising Moist Air

Rising Moist Air

Rising Moist Air

Sinking Drier Air

Sinking Drier

Air

Sinking Drier Air

LOW

LOW

LOW

HIGH

HIGH

HIGH

HIGH

Sinking Drier Air

Closer Look

• Bands of easterly moving air at the top of the troposphere called JET STREAMS

-Blow 200 miles an hour or more

Local Breezes

SEA BREEZE

Air blows from the sea onto the land during the day

LAND BREEZE

Air blows from the land out to sea at

night

Surface Ocean Currents

• Caused by wind blowing over the oceans & transferring energy to the water

DIRECTION of CURRENTS is affected by: 1) PLANETARY WIND BELTS

2) ROTATION of EARTH

3) BLOCKING BY LANDMASSES

• AKA - anticyclones

High Pressure System

•Highest Pressure in CENTER

• Winds blow OUT

• Winds move CLOCKWISE

High and Dry!

• AKA - Cyclones

Low Pressure System

•Lowest Pressure in CENTER

• Winds blow TOWARDS the

center

• WINDS move COUNTERCLOCKWIS

ELOUSY DAY!!

Two weather stations are located near eachother. The air pressure at each station is changing so that the difference between the pressures is increasing. The wind speed between these 2 locations will probably

(1) decrease (2) increase (3) remain the same

On which side of the low-pressure center will the wind speed be greatest?

(1) North (2) South (3) East (4) west

Which location is experiencing a southwest planetary wind?

(1) A(2) B(3) C(4) F

Which location is near the center of a low-pressure belt where daily rains, are common?

(1) E(2) B(3) F(4) D

Atmospheric Moisture

3 STATES of MATTER: 1) LIQUID 2) SOLID 3) GAS

- Amount of moisture in the air is constantly changing

**Gaseous water in the atmosphere is called WATER VAPOR**

Water vapor enters the atmosphere by:

TRANSPIRATION

PLANTS release water vapor

EVAPORATION

LIQUID changes to GAS

SUBLIMATION

Change of phase from SOLID to GAS

(NO LIQUID PHASE)

1) MORE ENERGY available

2) INCREASE in SURFACE AREA of the water

3) GREATER WIND SPEED

1) INCREASE in SATURATION of the air

Factors INCREASING Evaporation:

Factors DECREASING Evaporation:

Humidity

ABSOLUTE HUMIDITY – AMOUNT of water vapor present in the air

MOISTURE CAPACITY – TOTAL amount of water vapor the air can hold

RELATIVE HUMIDITY – Ratio between the amount of moisture in the air with the amount the air can actually hold at that temperature

HOT AIR HOLDS MORE MOISTURE THAN COLD AIR

Relative Humidity & Temperature

EXAMPLES:

1) Temperature _______________but amount of water vapor remains the SAME, then the Relative Humidity will _______________.

INCREASES

INCREASES

DECREASES

DECREASES

INCREASES

2) Temperature _________________ but amount of water vapor remains the SAME, then the Relative Humidity will __________________.

3) Temperature remains the SAME, but MORE water vapor is added, then the Relative Humidity will __________________.

Determining Relative Humidity

Smaller the difference between the dry & wet bulb temperature the

more humid the air

-Instrument used to measure called a PSYCHROMETER

Dew Point

Air drops TO the dew point condensation will occur

(CLOUDS FORM)

Temperature at which the air becomes SATURATED with water vapor & the RELATIVE

HUMIDITY is 100%

Determining Dew point on Chart

Pg. 12 Assume a dry-bulb temperature of 10oC & a wet-bulb temperature of 6oC. The difference between these

two readings is 4oC.

Dew point = 1oC

Relative Humidity =

54%

The graph indicates that as the air temperature increases,the relative humidity

1) Decreases, only2) Increases, only3) Increases &

decreases4) Remains the same

Condensation most likely occurred at approximately

(1) 6 am (2) 9 am (3) 7 pm (4) 10 pm

The dry-bulb temperature is 20oC. The wet-bulb temperature is 17oC. What is the dew point?

(1) 12oC(2) 13oC(3) 14oC

(4) 15oC

When was the air at ground level SATURATED with water vapor?

(1) 6 pm MONDAY (2) 6 am Tuesday

(3) 3 pm TUESDAY (4) 12 noon Tuesday

The relative humidity was lowest at (1) 12 midnight (2) 6 am (3) 12 noon (4) 3 pm

Station Model

Open your ESRT to pg 13

82 003

5 = +34 /

65 .1

Cloud CoverTemperature (°F)

Visibility (miles)

Present WeatherDew Point (°F)Wind Speed

Wind Direction

Barometric Pressure

Precipitation (inches)

Barometric Trend

Decoding Barometric Pressure

• If the number given is higher than 500 put a 9 in front and add a decimal in between the last 2 numbers.

–Example:• 642 ___________• 972 ___________• 980 ___________

964.2997.2

998.0

• If the number given is lower than 500 put a 10 in front and add a decimal in between the last 2 numbers.

–Example:• 320 ___________• 240 ___________• 040 ___________

1032.0

1024.01004.0

Example: 1013.7 mba. Drop the decimal point = 10137b. Report the last 3 digits = 137

Practice:

1016.0 _____________

984.0 ____________

160

840

Encoding Barometric Pressure

Understanding Barometric Trend

SYMBOLS + pressure was HIGHER than 3 hours

ago– pressure was LOWER than 3 hours

ago/ pressure is rising\ pressure is falling

- pressure is steady

Number decimal point is missing

Example:

32 = 3.2

Practice Question

• Pressure = 230• Trend = + 34 /

a.____________________

b.____________________

c.____________________

d.____________________

e.____________________

1023.0

Higher

3.4 mB

1023.0 – 3.4 = 1019.6Still Rising

35 199

8 +31 /

10 .03

a. Wind Direction ____________

b. Wind Speed ____________

c. Temperature ________________

d. Dew point Temperature _________

e. Barometric Pressure ____________

f. Barometric Trend ______________

g. Cloud Cover _________________

Northwest

15 knots

35°F

10°F

1019.9 mb

3.1 & Rising

0%

AIR MASS

–Large body of air in the troposphere with similar characteristics of PRESSURE, MOISTURE, & TEMPERATURE

• Forms when a large mass of air remains STATIONARY for a period of time acquiring similar characteristics.

• Temperature:–High Latitude _____________–Low Latitude ______________

• Humidity:–Land _____________–Water _____________

Low Temp

High Temp

Dry AirWet Air

m = maritime (water, wet) c = continental (land, dry)T = Tropical P = Polar (low latitudes & hot) (high latitudes & cold)

Tornado Alley

Cold Front

Cold air is

pushing forward

into warmer

air.

Cold Front

• Strong storms can occur, such as thunderstorms.

Warm Front

Warm air is

pushing forward

into colder

air.

Warm Front

• Steady rain can occur leading up to the warm front.

• High elevation clouds are seen ahead of the warm front.

Why is precipitation associated with fronts?

Adiabatic Heating and Cooling

Adiabatic Cooling When air rises, it expands, and the temperature of the air decreases.Adiabatic Heating When air sinks, it condenses, and the temperature of the air increases.

Elevation• Elevation increases, the air becomes

less dense and expands.

–Less-dense air cannot hold as much HEAT

Elevation = Temperature

Precipitation at High Elevation

The air reaches its dew point–Condensation forms clouds–Precipitation starts to fall

• http://www.phschool.com/atschool/phsciexp/active_art/weather_fronts/

Cold Front

Cold air is

pushing forward

into warmer

air.

Warm Front

Warm air is

pushing forward

into colder

air.

Occluded Front

Warm Air

Warm Air

Stationary FrontBoth cold & warm

air are pushing forward

Practice Questions

A mT airmass would most likely originate over which type of Earth surface?

A) warm and moistB) cold and dryC) cold and moistD) warm and dry

Which map correctly shows the wind directions of the high-pressure and low-pressure systems?

The cold frontal interface is moving faster than the warm frontal interface. What usually happens to

the warm air that is between the two frontal surfaces?

A) Warm air is forced under both frontal interfaces.

D) Warm air is forced over both frontal interfaces.

B) Warm air is forced under the cold frontal interface but over the warm frontal interface.C) Warm air is forced under the cold frontal interface but under the warm frontal interface.

4. Compared to a maritime tropical airmass, a maritime polar airmass has

A) lower temperature and less water vaporB) higher temperature and less water vaporC) lower temperature and more water vaporD) higher temperature and more water vapor

5. How does air circulate within a cyclone (low pressure area) in the Northern Hemisphere?

A) counterclockwise and away from the center of the cyclone

B) clockwise and away from the center of the cyclone

C) counterclockwise and toward the center of the cyclone

D) clockwise and toward the center of the cyclone

• Climate: the overall view of a region’s weather conditions over a long period of time

StationWANTAGH CEDAR

CREEK

Distance 5.3 miles

Jan Temp 24 to 37 F

Apr Temp 40 to 55 F

Jul Temp 67 to 81 F

Oct Temp 47 to 62 F

Annual Precip

42.9 inches

JFK

• The two main factors that determine climate are

• Annual Temp Range – difference between average temp of the hottest month & the coldest month

•Temperature•Precipitation

• Arid or Dry when… –precipitation is

less than the need

• Humid or Wet when…–Precipitation is

more than the need

World Climate Map

Latitude

• Temp varies with latitude because of the relationship between the angle of insolation & duration of sunlight

• Low Latitudes -Sun usually HIGHEST in sky–average temp. is always high

• High Latitudes –Sun usually LOWER in sky–average temp. is low

Moisture• Moisture

varies because of planetary winds & pressure belts

Low Pressure –

___________

High Pressure –

___________

Humid Climates

Dry Climates

**Wet & Dry Belts are in the ESRT Pg 14 (296)**

A high air-pressure, dry-climate belt is located at which Earth latitude?

A) 30°N B) 15°NC) 0° D) 60°N

Practice Questions

The planetary wind & moisture belts indicate that large amounts of rainfall occur at Earth’s equator because air at Earth’s surface is

A) Converging & risingB) Converging & sinkingC) Diverging & risingD) Diverging & sinking

An area with a high potential for evapotranspiration has little actual evapotranspiration and precipitation. The climate of this area is best described as

A) cold and aridB) hot and humidC) cold and humidD) hot and arid

Which generally has the greatest effect in determining the climate of an area?

A) Degrees of longitudeB) Extent of vegetationC) Distance from the equatorD) Month of the year

According to the ESRT, at which of these latitudes would average annual precipitation be greatest?

A) 90°S B) 90°NC) 30°N D) 0°

Large Bodies of Water

• Lake, ocean, seas modify climate patterns

• Water takes time to HEAT up & COOL down because it has a HIGHER SPECIFIC HEAT

Specific Heat – The amount of energy it takes to raise 1 gram of water by 1 degree Celsius.

MARINE CLIMATE

Cooler Summers & Warmer Winters

CONTINENTAL CLIMATE

Cooler winters & warmer summers

-Large annual temperature range

-Small annual temperature range

Ocean Currents• Currents flowing away from the equator

carry WARM water to higher latitudes

-

• Causes WARMER Climates &

MORE precipitation

• Currents flowing toward the equator carry COOL water to lower latitudes

• COOLER climates with LESS

precipitation

Prevailing Winds• U.S. located in the prevailing southwesterly

wind belt

• Weather moves from Southwest to Northeast

CALIFORNIA has more of marine climate because prevailing winds blowing from the

coast

MONSOONS

Weather changes caused by the

seasonal shifts of Prevailing Winds

-Mostly associated with southeast

Asia causing wet summers & dry

winters

El Nino

-Periods of ocean WARMING along the Pacific coast of South America

El Nino ANIMATION

Which graph best represents

the yearly temperature variation for location B?

Which location probably has the highest average yearly temperature?

1)A

2)B

3)C

4)E

Why are temperature variations usually not as great on Long Island as they are in central NYS?

1)Central NYS has a higher elevation

2)Central NYS is more heavily wooded

3)Long Island has a more southerly latitude

4)Long Island is surrounded by a large body of water

According to this diagram, between which 2 latitudes are the prevailing southwesterly winds located?

1)30°N & 60°N 2) 30°N and 0°

3) 30°S and 0° 4) 30°S and 60°S

Elevation• Elevation increases, the air becomes

less dense and expands.

–Less-dense air cannot hold as much HEAT

Elevation = Temperature

Precipitation at High Elevation

The air reaches its dew point–Condensation forms clouds–Precipitation starts to fall

Mount Kilimanjaro

Mountains

• Windward–The side that

faces oncoming winds

–Rain or snow fall in this side

There are two sides to a mountain range:

• Leeward–The downside of the mountain–Dry air, sometimes called the rain

shadow–Often times you will find a desert

located here

Vegetation

• Forests are cut down, deforestation,

more ____________ occursRUNOFF

Without trees to absorb solar energy from sun:-SUN heats the land & atmosphere faster

Cloud Cover

• LESS CLOUDS the more heat reaches the Earth from the sun

DURING DAY

• LESS CLOUDS the more heat is released at night

AT NIGHT

Practice QuestionsWhich graph best shows the general effect that

differences in elevation above sea level have on the average annual temperature?

Location G has a cold, humid climate. Which profile best represents the position of location G with respect to the mountains & the prevailing winds?

The map below shows the location of four cities A, B, C, & D, in the western US where prevailing winds are from the southwest.

Which city most likely receives the least amount of average yearly precipitation?

A) A B) B C) CD) D

What is the best explanation for the two statements below?

* Some mountains located near the Earth's Equator have snow-covered peaks.

*Icecaps exist at the Earth's poles.

A) Both mountain & polar regions have arid climates.B) An increase in snowfall & an increase in temperature have a similar effect on climate.C) Mountain & polar regions receive more energy from the Sun than other regions do.D) High elevation & high latitude have a similar effect on climate.

In the diagram of a mountain below, location A & B have the same elevation.

Compared to the climate at location A the climate at B will be

A) Warmer & drier C) Warmer & wetterB) Cooler & drier D) Cooler & wetter

Phase Changes Of Matter

Melting and Freezing

Evaporation and Condensation

Tem

pera

ture

Heat Energy

Solid

Liquid

Gas

Melting

Vaporization

Condensing

Freezing DRAW

Changing of State of Matter When water is

changing state of matter the temp remains the same