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Climate and Weather. Climates and Seasons. The different climates and seasons we have on Earth are decided mainly by… where our planet lies and how our planet moves around the Sun. Our location in the Solar System. Our Earth is the third planet from the Sun.

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climates and seasons
Climates and Seasons

The different climates and seasons we have on Earth are decided mainly by…

where our planet lies and how our

planet moves around the Sun.

our location in the solar system
Our location in the Solar System

Our Earth is the third planet from the Sun.

Located approximately 93 million miles (150 million kilometers) from the Sun, our Earth is in an ideal position.

not too hot not too cold
Not too hot, not too cold!
  • Earth is positioned between Venus and Mars.
  • Venus’ location is too hot to allow life, and Mars is too cold.
  • Earth is the only known planet in our Solar System that supports life.

Son, my very excellent mother just sent us nine pizzas.

S un

M ercury

V enus

E arth

M ars

J upiter

S aturn

U ranus

N eptune

P luto

earth revolves around the sun
Earth revolves around the Sun
  • The Earth revolves around the sun 1 time every 365¼ days.
  • The Earth’s axis is tilted23½°
  • The revolution of the Earth and the tilt of its axis cause our seasons.
the earth rotates on its axis
The Earth Rotates on its axis
  • The Earth’s axis is tilted 23½°
  • The Earth rotates on its axis

one time every 24 hours.

  • This rotation causes our days

and nights.

what is climate
What is Climate?
  • Climate is the average, year after year conditions of temperature, precipitation, winds, and clouds in an area.
  • Two main factors, temperature and precipitation determine the climate of an area.
what is weather
What is weather?
  • Weather is the day to day events in the atmosphere. It may be rainy and cloudy today and sunny and dry tomorrow.
  • Weather refers to the condition of the atmosphere at a particular place and time.
what are the factors that make up our weather
What are the factors that make up our weather?
  • Energy in the atmosphere.
  • Heat transfer
  • Winds
  • Water in the atmosphere
  • Precipitation
energy at the earth s surface
Energy at the Earth’s Surface
  • Some of the Sun’s energy reaches the Earth’s surface and is reflectedback into the atmosphere.
  • The remainder of the Sun’s energy is absorbed by the land and the water and changed into heat.
energy in the atmosphere
Energy in the atmosphere
  • The Sun provides nearly all of the energy in the Earth’s atmosphere.
  • The Sun’s energy is absorbed or reflected by…

a. Water vapor

b. Carbon dioxide

c. Ozone

d. Clouds

e. Dust

f. Other gases

heat is transferred in three ways
Heat is transferred in three ways
  • Radiation-the heat you feel from the sun or a campfire travels directly to you as infrared radiation
  • Conduction-the direct transfer of heat from one object to another. (Hot sand against bare feet)
  • Convection-the transfer of heat by the movement of molecules in liquids and gases. (Drying your hands under a blow dryer)
convection and conduction
Convection and Conduction
  • Only the first few meters of the atmosphere are warmed by conduction.
  • Convection causes most of the warming of the troposphere.
  • The upward movement of warm air and the downward movement of cool air form convection currents. These currents move heat throughout the troposphere.
  • Temperature is one of the most important elements of weather.
  • Temperature is a measure of how hot or cold a substance is.
  • Air temperature is usually measured with a thermometer.
air pressure
Air Pressure
  • Air pressure is the result of the weight of a column of air pushing down on an area.
  • Air pressure is greater at sea level and decreases as you go higher into the atmosphere.
  • Air Pressure is measured with a barometer.
  • Air pressure is measured in inches or millibars. 1 inch of mercury is equal to 33.87 millibars. (30” = about 1,016mb)
  • Air Pressure is measured with a barometer.
  • Two types of barometers are …

Mercury barometerAneroid barometer

  • Wind is the horizontal movement of air from areas of high pressure to areas of low pressure.
  • All winds are caused by differences in air pressure.
  • Most differences in air pressure are caused by unequal heating of the atmosphere.
measuring wind
Measuring wind
  • Winds are described by their direction and speed.
  • Wind direction is determined by a wind vane. The name of the wind tells you the direction it is blowing from. East Wind is blowing from the east
  • Wind speed is measured with an anemometer or by using the “Beaufort wind scale.”
beaufort wind scale
Beaufort Wind Scale

# MPH Description

0. < 1 Calm - Calm; Smoke rises vertically.

1. 1-3 Light - Air Direction of wind shown by smoke drift not by wind


2. 4-7 Light Breeze - Wind felt on face; Leaves rustle; Vanes moved by

the wind.

3. 8-12 Gentle Breeze - Leaves and small twigs in constant motion; Wind

extends light flag.

4. 13-18 Moderate - Raises dust, loose paper; Small branches moved.

5. 19-24 Fresh - Small trees in leaf begin to sway; Crested wavelets form on

inland waters.

6. 25-31 Strong - Large branches in motion; Whistling heard in telegraph wires;

Umbrellas used with difficulty.

beaufort scale cont
Beaufort Scale Cont.

732-38 Near Gale - Whole trees in motion;

Inconvenience felt walking against the


8 39-46 Gale - Breaks twigs off trees; Impedes progress.

9 47-54 Strong Gale -Slight structural damage occurs.

10 55-63 Storm - Trees uprooted; Considerable damage


11 64-72 Violent Storm - Widespread damage.

12 73-82 Hurricane - Widespread damage.    

sea breezes and land breezes
Sea Breezes and Land Breezes
  • Sea breezes occur when the land heats up and as the warm air rises above the land it is replaced by cool air moving in from above the nearby water.
  • Land breezes take place when the water is warmer than the land and the air above the water rises and is replaced by cooler air from the land. (usually occurs at night as the land cools more quickly than the water)
  • Monsoons are similar to land and sea breezes, but occur over a much larger area.
  • Sea and Land breezes over a large area that change direction with the seasons are called monsoons.
  • Monsoons typically bring in warm moist air from the ocean and cause heavy, seasonal rainfall.
global winds
Global Winds
  • Global winds blow steadily from specific directions over long distances.
  • Like other winds, these are caused by unequal heating of the Earth’s surface.
  • These winds are also directed by the rotating of the Earth on its axis. (Coriolis effect)
examples of global wind belts
Examples of Global Wind Belts
  • Trade Winds
  • Prevailing Westerlies
  • Polar Easterlies
  • Doldrums
  • Horse Latitudes
jet streams
Jet Streams
  • Jet streams are bands of high speed winds about 10 Km above the surface of the Earth.
  • Winds blow from west to east at speeds of 200 to 400Km per hour.
  • Jet streams wander north and south as they travel around the Earth.
  • Changes in their location allow warm air from the Equator or cold air from the Polar Regions to affect weather patterns.
water in the atmosphere
Water in the atmosphere
  • Water enters the atmosphere through the process of evaporation from the oceans, rivers and lakes.
  • Water also enters the atmosphere by living things. Water enters the roots of plants, rises to the leaves and is released as water vapor. (Transpiration)
  • Humidity is the amount of water vapor in the air.
  • Relative humidity is the amount of water vapor in the air compared to the amount of water vapor the air could hold at a given temperature.
measuring relative humidity
Measuring Relative Humidity
  • Relative humidity is read as a percentage (%). If the relative humidity is 50%, it means the air is holding ½ of the moisture it could hold at that particular temperature. Warm air can hold more water vapor than cold air.
  • Relative humidity is measured with a psychrometer. (Wet/Dry bulb thermometer)
measuring relative humidity1
Measuring Relative Humidity
  • Psychrometer or Wet / Dry Bulb Thermometer
  • Hygrometer and Sling Psychrometer
relative humidity table
Relative Humidity Table



  • _____________________________________________________________________________
  • _____________________________________________________________________________
  • C 1 2 3 4 5 6 7 8 9 10
  • _____________________________________________________________________________
  • 10 88 77 66 55 44 34 24 15 6
  • 11 89 78 67 56 46 36 27 18 9
  • 12 89 78 68 58 48 39 29 21 12
  • 13 89 79 69 59 50 41 32 22 15 7
  • 14 90 79 70 60 51 42 34 25 18 10
  • 15 90 80 71 61 53 44 36 27 20 13
  • 16 90 81 71 63 54 46 38 30 23 15
  • 17 90 81 72 64 55 47 40 32 25 18
  • 18 91 82 73 65 57 49 41 34 27 20
  • 19 91 82 74 65 58 50 43 36 29 22
  • 20 91 83 74 67 59 53 46 39 32 26
  • 21 91 83 75 67 60 53 46 39 32 26
  • 22 92 83 76 68 61 54 47 40 34 28
  • 23 92 84 76 69 62 55 48 42 36 30
  • 24 92 84 77 69 62 56 49 43 37 31
  • 25 92 84 77 70 63 57 50 44 39 33
  • ______________________________________________________________________________
  • Clouds of all kinds form when water vapor in the air becomes liquid water or ice crystals.
  • This process is called condensation.
  • The temperature at which condensation begins is called the dew point.

When water vapor condenses on dust particles, salt crystals or smoke, clouds form.

  • When this takes place near the surface of the Earth, it is called fog.
dew and frost
Dew and Frost
  • Water vapor that condenses on blades of grass and other solid surfaces is called dew.
  • Frost is ice that has been deposited directly from the air onto a cold surface.
why do clouds form
Why do clouds form?
  • Air that is warmed near the ground becomes less dense and rises in a convection current.
  • When this rising air expands and becomes cooler, clouds may form.
mountains and precipitation
Mountains and precipitation
  • Air rising against the side of a mountain also cools and forms clouds. Rain and snow from these clouds falls on the windward side of the slope.
  • Often the moisture from these clouds is gone by the time it reaches the other side of the slope. These leeward slopes are often dry and may form deserts.
windward slope
Windward Slope
  • Water vapor condenses as air rises up over mountains causing rain and snow to fall on the windward slopes.
leeward slope
Leeward slope
  • Leeward slopes are usually dry. Most precipitation falls on the windwardside of the mountain. Desert areas are often found on the leeward side.
types of clouds
Types of Clouds
  • Clouds are classified into three main types.

Cumulus – “Heap or mass”

Stratus – “Spread out or flat”

Cirrus – “Wispy or feathery”

clouds names refer to height
Clouds names refer to height
  • Cumulus clouds – form less than 2Km above ground but may reach up to 18Km
  • The prefix Alto refers to “High” clouds. They form between 2 and 6 Km above Earth.
  • Cirrus clouds only form at levels above 6Km where temperatures are very low.
  • “Fog,” Clouds that form at or near the ground.
cumulus clouds
Cumulus Clouds
  • Fluffy, shape forming clouds that have a base and then extend upward
  • Fair weather clouds – may develop into Cumulonimbus (Thunderheads).
  • Low, layered cloud – may appear as fog lifting off of the ground

Thin clouds at high altitudes, made of ice crystals. Often indicate falling weather within 24 – 48 hours.


Very large, anvil shaped clouds associated with thunderstorms.

Upper part of cloud is flattened out because of high winds at the top of the troposphere

nimbostratus nimbus means rain low level cloud flat layered cloud that looks like its going to rain
Nimbostratus (Nimbus means rain) (Low level cloud)Flat layered cloud that looks like its going to rain
  • Precipitation always comes from clouds, but not all clouds produce precipitation.
  • Precipitation is any form of water that falls from clouds and reaches the Earth’s surface.
  • Precipitation is measured with a rain gauge.
types of precipitation
Types of Precipitation
  • Rain – drops of water at least .5mm

Mist and drizzle are smaller in size

  • Sleet – Drops of rain that freeze as they fall through layers of air below 0°C, <5mm
  • Freezing rain - Rain falling through cold air near the ground that freeze when they touch a cold surface.
types of precipitation cont
Types of Precipitation Cont.
  • Hail – Drops of rain that are >5mm in size, only form in cumulonimbus clouds during thunderstorms. Form during strong updrafts that carry them up and down during cold layers many times
  • Snow – Water vapor in the air that is converted directly into ice crystals called snowflakes. All have 6 sides or branches. (On average 10cm of snow = 1 cm of rain)

Sleet is precipitation that freezes before reaching the Earth and is less than 5mm in size.

air masses
Air Masses
  • A huge body of air that has similar temperature, humidity and pressure throughout it is called an air mass.
  • A single air mass may spread over an area of millions of square kilometers and be up to 10 Km high.
types of air masses
Types of Air Masses
  • Tropical – Warm air mass that forms in the tropics and have low air pressure
  • Polar – Cold air mass that forms north of 50° N latitude and south of 50° S latitude. Polar air masses have high air pressure.
  • Maritime – Air masses form over oceans. Water evaporates from the ocean causing the air to become very humid.
  • Continental – Air masses form over land, in the middle of continents and are dry.
how air masses move
How Air Masses Move
  • The prevailing westerlies are the major wind belt in the continental U.S.
  • These winds typically push air masses from west to east.
  • The weather associated with these air masses travels from west to east across the country.
  • Air masses traveling across the country “bump” into one another.
  • Air masses have different temperatures, humidity and pressures. Their different densities and temperatures do not allow them to mix.
  • The area where these masses meet but do not mix are called fronts.
types of fronts
Types of Fronts
  • Cold Fronts
  • Warm Fronts
  • Stationary Fronts
  • Occluded Fronts
cold front
Cold Front
  • Cold Front – cold air is dense and tends to sink. Warm air is less dense and tends to rise.
  • Cold air moving under warm air pushes it up quickly. Warm air holds more moisture, and as it is pushed up, the air cools and condenses forming clouds and if enough water vapor is present, heavy rain or snow.
  • Cold fronts move quickly, causing rapid changes in weather including violent thunderstorms.
cold front1
Cold Front

Symbol used to show cold front on weather maps. Arrows show direction front is moving.

warm front
Warm Front
  • Clouds, Storms and Rain also accompany warm fronts.
  • Warm fronts occur when warm air collides with slow moving cold air.
  • Less dense warm air rises up over the colder air.
  • Humid warm air causes showers and light rain.
  • Dry, warm air, causes scattered clouds.
  • Slow movers, Warm fronts often cause days of rainy, foggy or snowy weather.
stationary front
Stationary Front
  • Warm air and cold air masses may meet and neither has enough force to move the other.
  • These masses collide, but remain in place, often causing days of clouds, fog, rain or snow.
  • Eventually the air masses move and the weather clears.
occluded front
Occluded Front
  • An occluded front occurs when a warm air mass gets trapped between two cold air masses.
  • The less dense warm air gets pushed up, cools and condenses.
  • Occluded fronts may cause weather that is cloudy, rainy, snowy.
lows cyclones
Lows (Cyclones)
  • Lows are marked with a red L on weather maps.
  • Warm air in Low Pressure Cells rises.
  • This causes Cooler air to fill in as the warm air rises.
  • Winds spiral inward, in a counterclockwise direction.
  • Cyclones and decreasing air pressure are associated with storms and precipitation.
highs anticyclones
Highs (Anticyclones)
  • Highs or Anticyclones are marked with a blue H on weather maps.
  • Anticyclones are High Pressure centers of dry air.
  • Winds spiral outward from anticyclones toward areas of lower pressure.
  • Winds move in a clockwise direction away from the H.
  • Highs are associated with dry, clear weather.
  • A storm is a violent disturbance in the atmosphere
  • Storms involve sudden changes in air pressure
  • Conditions that bring one kind of storm often cause other kinds of storms in the same area
types of storms
Types of Storms
  • Thunderstorms
  • Tornadoes
  • Hurricanes
  • Winter Storms


Lake-effect snows

  • Thunderstorms are heavy rain-storms accompanied by thunder and lightning
  • Thunderstorms form within large cumulonimbus clouds or thunderheads
  • Thunderstorms produce strong upward and downward winds – updrafts and downdrafts – inside the clouds
  • Thunderstorms produce areas of positive and negative electrical charges in storm clouds.
  • Lightning is a sudden spark or discharge
  • Lightning can be within a cloud, between nearby clouds or between the cloud and the ground.
  • Lightning heats the air near it to as much as 30,000° C - much hotter than the surface of the Sun.
  • This rapidly heated air expands suddenly and explosively.
  • Thunder is the sound of the explosion.
  • Because light travels faster than sound, we see the lightning before we hear the thunder.
  • Tornadoes form in low, heavy cumulonimbus clouds – the same clouds that bring thunderstorms.
  • Tornadoes are rapidly whirling funnel clouds that reach down from a storm cloud to the ground. (If they touch down over water, they are called waterspouts)
  • Tornadoes are most likely to form when thunderstorms form
tornadoes cont
Tornadoes Cont.
  • Tornadoes are most likely in spring and early summer
  • Form where cold air meets warm air and squall lines of thunderstorms occur
  • Frequently move from SW to NE
  • Extremely destructive, tornadoes may have wind that approach 480 Km/hr.
  • About 800 tornadoes occur in the US each year, more more than any other country.
  • A Hurricane is a tropical storm that has winds of 119 Km / Hr or more.
  • A typical hurricane is 600 Km across
  • Hurricanes form over warm water as low pressure areas or tropical disturbances
  • A hurricane gets its energy from warm humid air at the water’s surface
  • Hurricanes are the largest and most destructive of all storms
winter storms
Winter Storms
  • Blizzards
  • Lake Effect Snow
the moon1
The Moon
  • The Moon is the only natural satellite of the Earth.
  • The Moon orbits the Earth every 27.3 days
  • The Moon’s Rotates 1 time during each orbit
  • Because of the Moon’s rotation, we always see the same side of the moon. The “dark side’” is only visible from Space.
  • The Moon’s phases repeat every 29.5 days
  • The Moon is approximately 384,403 Km from the Earth. (About 238,857 miles)
phases of the moon
Phases of the Moon

New moon

Waxing Crescent

First Quarter

Waxing Gibbous

Full Moon

Waning Gibbous

Last Quarter

Waning Crescent

the moon and tides
The Moon and Tides

Spring Tides

When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon.