Weather FactorsWeather Factors

Chapter 16Chapter 16

What does the What does the movement of heat in movement of heat in the atmosphere cause?the atmosphere cause?

The movement of heat The movement of heat in the atmosphere in the atmosphere causes temperatures causes temperatures to change, rain to fall, to change, rain to fall, and winds to blow.and winds to blow.

Energy from the SunEnergy from the Sun

Most of the energy from the sun Most of the energy from the sun travels to Earth in the form of travels to Earth in the form of visible light and infrared visible light and infrared radiation. A small amount arrives radiation. A small amount arrives as ultraviolet radiation.as ultraviolet radiation.

Energy in the Energy in the AtmosphereAtmosphere Some sunlight is absorbed or reflected Some sunlight is absorbed or reflected

by the atmosphere before it can reach by the atmosphere before it can reach the surface. The rest passes through the the surface. The rest passes through the atmosphere to the surface.atmosphere to the surface.– AbsorbedAbsorbed

Water vapor and other gases absorb infrared Water vapor and other gases absorb infrared radiation.radiation.

Ozone layer absorbs ultraviolet rays.Ozone layer absorbs ultraviolet rays. Clouds, dust, and other gases also absorb energy.Clouds, dust, and other gases also absorb energy.

– ReflectedReflected Dust particles and gases in the atmosphere reflect Dust particles and gases in the atmosphere reflect

light in all directions, a process called scattering.light in all directions, a process called scattering.

Energy at Earth’s Energy at Earth’s SurfaceSurface When Earth’s surface is heated, it When Earth’s surface is heated, it

radiates most of the energy back radiates most of the energy back into the atmosphere as infrared into the atmosphere as infrared radiation.radiation.

The process by which gases hold The process by which gases hold heat in the air is called the heat in the air is called the greenhouse effect.greenhouse effect.

How are thermal How are thermal energy and energy and temperature related?temperature related?

Thermal energy and temperature Thermal energy and temperature are related because temperature are related because temperature is the average amount of energy is the average amount of energy of motion of each particle of a of motion of each particle of a substance whereas thermal substance whereas thermal energy is the total energy in a energy is the total energy in a substance.substance.

How Heat is How Heat is TransferredTransferred Heat is transferred throughHeat is transferred through

– RadiationRadiation– Conduction – the direct transfer of heat Conduction – the direct transfer of heat

from one substance to another substance from one substance to another substance that it is touching.that it is touching.

– Convection – the transfer of heat by the Convection – the transfer of heat by the movement of a fluid.movement of a fluid.

Radiation, conduction, and convection Radiation, conduction, and convection all work together to heat the all work together to heat the troposphere.troposphere.

WindsWinds

What is Wind?What is Wind?

A wind is the horizontal movement A wind is the horizontal movement of air form an area of high pressure of air form an area of high pressure to an area of lower pressure.to an area of lower pressure.

Winds are caused by differences in Winds are caused by differences in air pressure.air pressure.– Winds are measured using an Winds are measured using an

anemometer.anemometer.– Wind–Chill factor is the increased Wind–Chill factor is the increased

cooling a wind can cause.cooling a wind can cause.

Local WindsLocal Winds

Local winds are winds that blow Local winds are winds that blow over short distances.over short distances.

Local winds are caused by the Local winds are caused by the unequal heating of Earth’s surface unequal heating of Earth’s surface within a small area.within a small area.– A sea breeze or a lake breeze is a local A sea breeze or a lake breeze is a local

wind that blows from an ocean or lake.wind that blows from an ocean or lake.– A land breeze is a flow of air from land A land breeze is a flow of air from land

to a body of water.to a body of water.

Global WindsGlobal Winds

Global winds are winds that blow Global winds are winds that blow steadily from specific directions steadily from specific directions over long distances.over long distances.– Global Convection CurrentsGlobal Convection Currents– The Coriolis EffectThe Coriolis Effect

Global Wind BeltsGlobal Wind Belts

The major global wind belts are the The major global wind belts are the trade winds, the polar easterlies, and trade winds, the polar easterlies, and the prevailing westerlies.the prevailing westerlies.– DoldrumsDoldrums– Horse latitudesHorse latitudes– Trade windsTrade winds– Prevailing westerliesPrevailing westerlies– Polar easterliesPolar easterlies– Jet StreamsJet Streams

Water in the Water in the AtmosphereAtmosphere

HumidityHumidity

Humidity is the measure of the Humidity is the measure of the amount of water vapor in the air.amount of water vapor in the air.– Relative humidity is the percentage Relative humidity is the percentage

of water vapor that is actually in the of water vapor that is actually in the air compared to the maximum air compared to the maximum amount of water vapor the air can amount of water vapor the air can hold at a particular temperature.hold at a particular temperature.

– Relative humidity can be measured Relative humidity can be measured with an instrument called a with an instrument called a psychrometer.psychrometer.

How Clouds FormHow Clouds Form

Clouds from when water vapor in Clouds from when water vapor in the air condenses to form liquid the air condenses to form liquid water or ice crystals.water or ice crystals.

Molecules of water vapor in the air Molecules of water vapor in the air become liquid water in the process become liquid water in the process of condensation.of condensation.– The temperature at which The temperature at which

condensation begins is called the dew condensation begins is called the dew point.point.

Types of CloudsTypes of Clouds

Scientists classify clouds into three main Scientists classify clouds into three main types based on their shapetypes based on their shape– Cirrus Clouds – wispy, feathery cloudsCirrus Clouds – wispy, feathery clouds– Cumulus Clouds – fluffy, founded piles of Cumulus Clouds – fluffy, founded piles of

cotton.cotton.– Stratus Clouds – clouds that form in flat Stratus Clouds – clouds that form in flat

layerslayers Autocumulus and autostratus refer to Autocumulus and autostratus refer to

high clouds.high clouds. Clouds that form near the ground are Clouds that form near the ground are

called fog.called fog.

PrecipitationPrecipitation

Types of PrecipitationTypes of Precipitation

– RainRain– SleetSleet– Freezing RainFreezing Rain– SnowSnow– HailHail

Modifying PrecipitationModifying Precipitation– Droughts are long periods of unusually low Droughts are long periods of unusually low

precipitation.precipitation.– Cloud seeding is one method used to Cloud seeding is one method used to

modify precipitation.modify precipitation.

Measuring Measuring PrecipitationPrecipitation Scientists measure precipitation Scientists measure precipitation

with various instruments with various instruments including rain gauges and including rain gauges and measuring sticks.measuring sticks.