Chapter 2 – Weather factors 2.1 Energy in the Atmosphere

Think about it… Where does the energy of our Earth come from?

Electromagnetic Radiation Nearly all of the energy in Earth’s atmosphere comes from the sun Energy travels as electromagnetic waves. Electromagnetic waves are a form of energy that can move through the vacuum of space. Electromagnetic waves are classified by their wavelengths

Electromagnetic Radiation The direct transfer of energy by electromagnetic waves is called radiation. Most energy from the sun reaches the Earth in the form of infrared radiation, visible light, and ultraviolet radiation.

Wavelengths

Analyze the picture …take 1 minute and discuss with a partner… Why do we see different colors? How do color and wavelength compare? Which colors have the shortest wavelengths?

Which colors have the longest wavelengths? What type of radiation has wavelengths that are shorter than visible light? Longer?

Were you right? Why do we see different colors? Because of different wavelengths How do color and wavelength compare? Short and long wavelengths result in different colors Which colors have the shortest wavelengths? Blue and Violet Which colors have the longest wavelengths? Red and orange What type of radiation has wavelengths that are shorter than visible light? Longer? Ultraviolet radiation, x-rays and gamma rays / infrared radiation and radio waves

Visible Light: ROY G BIV Infrared Radiation – wavelengths are longer than red light. The color of visible light with the longest wavelength is Red. The color of visible light with the shortest wavelength is Blue. Ultra-violet Radiation – wavelengths are shorter than violet light

Think about it… What role does our atmosphere play in the ability of energy to reach our Earth?

Energy Water Vapor and Carbon Dioxide absorb some infrared radiation Some of the sun’s rays are reflected by clouds, dust, and molecules of gases called scattering. Gas molecules scatter short wavelengths of blue and violet more than red and orange making the daytime sky look blue.

Energy The ozone layer absorbs most of the ultraviolet radiation Green house effect- natural process by which gas holds heat in the air. Gases include water vapor, carbon dioxide, methane, and other gases that form a blanket around earth. Some energy reaches the surface and warms the land and water

Energy in the atmosphere

What are your thoughts? What might conditions on Earth be like without the Greenhouse effect?

Chapter 2 – Weather factors 2.2 Heat Transfer

Energy and Temperature Thermal energy is the total energy of MOTION of the molecules in a substance. Temperature is an average amount of energy of motion of the molecules in a substance.

Hot = fast moving molecules Cold = slow moving molecules

Measuring Temperature Thermometers are used to measure temperature Liquids expand when they are heated and contract when they are cooled Temperature is measured in units called degrees. (Celsius or Fahrenheit) Water freezes at 0ºC and boils at 100ºC

How Heat is Transferred Heat is the energy transferred from a hotter object to a cooler one.

Heat is transferred 3 ways Radiation is the direct transfer of energy by electromagnetic waves. ex) feeling the warmth of the fire on your skin

Heat is transferred 3 ways Conduction is the direct transfer of heat from one substance to another substance ( must be touching)

Heat is transferred 3 ways Convection is the transfer of heat by the movement of a fluid. ex) heating up soup in a pan.

Heat Transfer in the Troposphere

A comparison…

Chapter 2 - Weather factors 2.3 Winds

What Causes Winds? Wind is the horizontal movement of air from an area of high pressure to an area of lower pressure. All winds are caused by differences in air pressure. Differences in air pressure are caused by unequal heating of the atmosphere.

Measuring Wind Wind vanes are used to determine wind direction. The name of a wind tells you where the wind is coming from. Anemometers are used to measure wind speed. Wind over your skin removes body heat. The increased cooling that a wind can cause is called the wind- chill factor.

Local Winds Winds that blow over short distances. Caused by unequal heating of Earth’s surface within a small area. Usually occurs near a body of water.

Local Winds Land heats up faster during the day, warming the air above it. Warm air expands and rises, creating a low-pressure area. Cool air blows inland from the water to replace the warm air.

Local Winds sea breeze – a wind that blows FROM an ocean or a lake onto land land breeze – the flow of air FROM land to a body of water

Monsoons Sea and land breezes over a large region that change direction with the seasons

Global Winds Winds that blow steadily from specific directions over large distances. Caused by unequal heating of Earth’s surface. (equator vs. poles) Global Convection Currents cause wind at Earth’s surface to blow from the poles to the equator. Higher in the atmosphere, air flows away from the equator and toward the poles.

Global Winds The movement of air between the equator and the poles produces global winds. Coriolis Effect – winds do not blow in straight lines because the Earth is spinning underneath them. This causes the winds to curve. In the NORTHERN HEMISPHERE – the Coriolis Effect causes our wind to turn towards the right. It is the opposite in the southern hemisphere.

Jet Stream Bands of high-speed wind about 10km above Earth’s surface. They blow from west to east at about 200-400 km per hour

Global Wind Belts DOLDRUMS: Caused by rapid warming of air near the equator air is almost always warm so there are little to no winds

Global Wind Belts HORSE LATITUDES: Caused when air from equator stops moving towards poles and sinks Latitude is the distance from the equator, measured in degrees 30º north and south latitudes, Calm air

Global Wind Belts TRADE WINDS: Caused when cold air over the horse latitudes sinks and produces a high pressure region Blow towards the equator from about 30º north and south

Global Wind Belts PREVAILING WESTERLIES: Caused when winds that blow toward the poles are turned toward the east by the Coriolis effect. Between 30º and 60º north and south latitudes. Blow FROM West to East They play an important role in the United State’s weather

Global Wind Belts POLAR EASTERLIES: Caused when cold air near the poles sinks and flows back toward lower latitudes They meet the prevailing westerlies at about 60º north and south latitudes at the Polar Front. The polar front has a major effect on weather changes in the US.

2.4 Water in the Atmosphere Chapter 2 2.4 Water in the Atmosphere

Water cycle- movement of water between the atmosphere and earth’s surface

2-4 Water in the Atmosphere Evaporation – the process by which water molecules in liquid water escape into the air as water vapor.

Humidity Humidity – a measure of the amount of water vapor in the air. Relative Humidity – the percentage of water vapor in the air compared to the maximum amount the air could hold. Used on weather reports!

Measuring Relative Humidity Relative humidity can be measured using a psychrometer. A psychrometer has two thermometers, a wet bulb and a dry bulb. The wet bulb is covered with a damp fabric. Evaporation cools the wet bulb. Relative humidity can be found by comparing the temperature of the wet and dry bulb thermometers.

A problem… What would the relative humidity be if your dry bulb showed a temperature of 60ºF and the wet bulb showed a temperature of 54ºF? ( a difference of 6º)

Answer 60 – 54 = 6 Dry bulb temp is 60 Relative Humidity = 68%

How Clouds Form Clouds of all kinds form when water vapor in the air becomes liquid water or ice crystals. Condensation – the process by which molecules of water in the air become liquid water Cold air can hold less water vapor than warm air As air cools, the amount of water vapor it can hold decreases Some of the water vapor in the air condenses to form droplets of liquid water

How Clouds Form Dew Point – the temperature at which condensation begins For water to condense, tiny particles must be present so the water has a surface on which to condense Particles are usually salt crystals, dust from soil, and smoke. Dew is water than condenses above the freezing point and land on a solid surface such as a blade of grass. Frost is ice that has been deposited directly onto a surface that is below the freezing point. Clouds form whenever air is cooled to its dew point

Types of Clouds Meteorologists classify clouds into three main types: cumulus stratus cirrus.

Types of Clouds Cumulus clouds look like fluffy, rounded piles of cotton that indicate nice weather when not tall

Cirrocumulus-rows of cotton balls indicating a storm is on the way.

Cumulonimbus clouds often produce thunderstorms

Stratus clouds form in flat layers that can thicken and can produce drizzle, rain, or snow (nimbostratus)

Cirrus clouds are wispy and feathery and only form at high altitudes Cirrus clouds are wispy and feathery and only form at high altitudes. (made of ice crystals)

Altostratus and Altocumulus are clouds that form 2-6km above earth’s surface. Middle level clouds

Clouds that form at or near the ground are called fog Clouds that form at or near the ground are called fog. Form when the ground cools at night after a warm humid day.

Chapter 2 Weather 2.5 Precipitation

Precipitation Precipitation is any form of water that falls from clouds and reaches Earth’s surface

Types of Precipitation Common types of precipitation include rain, sleet, freezing rain, hail and snow. Rain – most common type of precipitation, drops of water are at least 0.5mm in diameter, smaller drops are mist and drizzle which usually fall from nimbostratus clouds Sleet – raindrops freeze as they fall, ice particles are smaller than 5mm in diameter

Freezing Rain – raindrops freeze when they touch a cold surface Hail – round pellets of ice larger than 5mm in diameter, only forms inside cumulonimbus clouds during thunderstorms Snow – water vapor in cloud is converted directly into ice crystals called snowflakes, all have six sides or branches

Measuring Precipitation Meteorologist measure rainfall with a rain gauge. Rain gauge – an open-ended can or tube that collects rainfall.

Controlling Precipitation Droughts – long periods of unusually low precipitation In cloud seeding, tiny crystals of dry ice (solid carbon dioxide) and silver iodide are sprinkled into clouds from airplanes. The super cooled water droplets in the cloud can then condense around the silver iodide particles. Dry Ice cools the water even more so it freezes without a surface to condense on.