Climate System and Weather

Unit 5Mrs. O’Connor

Weather

Weather refers to: The state of the atmosphere in a particular place and time.

Weather occurs over short time periods. The weather predictions usually cover days or weeks.

Types of Weather

• What terms do you associate with weather?

What Causes Weather?

• Weather is an expression of the climate system.

• The climate system is the interaction of the atmosphere, biosphere, and other parts of the Earth that determine weather at a time or place

1. The Atmosphere

2. The Biosphere

3. The Oceans

The Atmosphere

Troposphere

• TroposphereLiving at the surface of the Earth, we are usually only aware of the events happening in the lowest layer, the troposphere, where all weather occurs.

• The base of this layer is warmer than its top because the air is heated by the surface of the Earth, which absorbs the Sun’s energy.

Stratosphere

• Stratosphere: Above the troposphere lies the stratosphere where jet airplanes fly.

• Temperatures increase with altitude because of increasing amounts of ozone.

• The ozone layer within the stratosphere absorbs harmful ultraviolet rays of sunlight

Mesosphere

• Mesosphere: As the mesosphere extends upward above the stratosphere, temperatures decrease. The coldest parts of our atmosphere are located in this layer and can reach –90°C.

Thermosphere

• Thermosphere: In the forth layer from Earth’s surface, the thermosphere, the air is thin, meaning that there are far fewer air molecules. The thermosphere is very sensitive to solar activity and can heat up to 1,500°C or higher when the Sun is active making an aurora that lights up the night sky. Astronauts orbiting Earth in the space station or space shuttle spend their time in this layer.

Exosphere

• ExosphereThe upper layer of our atmosphere, where atoms and molecules escape into space, is called the exosphere.

Atmospheric Pressure

• Atmospheric pressure is the force per unit area exerted on a surface by the weight of air above that surface in the atmosphere of earth

Atmosphere Layers

• Interactive Diagram• http://earthguide.ucsd.edu/earthguide/diagra

ms/atmosphere/

Video Clip: Bill Nye on the Atmosphere

http://www.youtube.com/watch?v=45kf3oP0eGI

http://data.giss.nasa.gov/gistemp/graphs/

Studying Climate Involves Long-term Weather Trends

Relating Climate and Weather

-What do the thick red and thick blue lines represent?

-What do the fluctuating red and blue lines represent?

Why is the Climate System Important?

• The climate system determines the weather. The weather affects many of our daily decisions.

• Climate affects long-term decisions by humans and changes in ecosystems.

Weather Terminology

Walk Around Activity

Air Masses

• Large stationary or slow moving body of air with uniform temperature and moisture content is called an air mass

Air Masses

– Air masses are categorized by their source region

– There are four main types: maritime polar, maritime tropical, continental polar and continental tropic

– Maritime form over the ocean and continental form over land

Polar Air Masses• Polar air masses that affect North

American weather can be from: – Continental polar Canadian air masses

• Form over land covered by ice and snow• Bring cold, dry weather

– Maritime polar Pacific air masses• Moist, but not extremely cold• Bring ice, snow, fog

– Maritime polar Atlantic air masses• Bring cold, cloudy weather and precipitation

Tropical Air Masses• Tropical air masses that affect North America

are:– Continental tropical air masses

• Only in the summer• Bring clear, dry and hot weather

– Maritime tropical Gulf/Atlantic air masses• Bring hot, humidity, thunderstorms, hurricanes

– Maritime tropical Pacific air masses• Bring heavy precipitation and thunderstorms

Fronts• A boundary that forms between air masses

is called a front– Fronts remain separate due to density

differences– Four types of fronts include:

• Cold front • Warm front• Occluded front• Stationary front

Types of Fronts• Cold Front

– When a cold air mass overtakes a warm air mass

– The cold air lifts the warm air– If the warm air is moist, clouds will form– Storms that are created are short-lived and

violent• A squall line: a long line of heavy thunderstorms,

may occur just ahead of a cold front

Types of Fronts

• Warm Front– When warm air overtakes a cooler air mass– Less dense warm air rises over the cooler air– At the beginning of the pattern are many clouds,

producing precipitation over a large area– Warm fronts may produce some violent weather

as well

Types of Fronts

• Stationary Front– When two different air masses meet but neither

are displaced

• Occluded Front– When a fast moving cold front overtakes a warm

front, lifting the warm air completely over the ground

– The warm front is completely cut off, or occluded, from the ground by colder air

High Pressure and Low Pressure Systems

• Low pressure system: An area of rising air usually marked by cloudiness, often referred to as a storm.

• High pressure system: An area where more air has been added overhead than in surrounding areas. That accounts for higher barometric pressure. Typically, the air enters at high altitudes, sinks, and exits at ground level. The sinking motion causes warming and drying, leaving the clear sky often found in high pressure areas.

Weather and Climate

• Weather is observed, measured, and recorded at weather stations around the world.

• Weather stations are an important aspect in predicting weather patterns.

Weather and Climate

• Weather stations record temperature, dew point, cloud cover, visibility, height of cloud base, amount of precipitation, barometric pressure and trend, wind speed, and wind direction

Station Model Lab

• How exactly does the meteorologist on the news predict the weather?

Station Model Lab

• The best forecasts take into account the weather events that are happening over a broad region.

• Using weather stations helps meteorologist to know where storms are which can help predict where storms will be tomorrow and the next day.

• Technology, such as weather stations, weather satellites, computer technology, and Doppler radar, helps the process of looking over a large area, as does the network of weather observations.

Technology

• Doppler Radar: Able to report the location and strength of precipitation, the wind direction, wind speed and boundaries between warm fronts and cold fronts.

• Computers: To generate weather predictions, they perform many calculations that take into account broad-scale factors such as air pressure differences, solar radiation, and the earth’s rotation.

Terms for Laboratory Investigation

• Temperature• Precipitation Type• Visibility• Dew Point• Wind Speed (knots)• Wind Direction• Precipitation amount (inches)• Barometric Pressure• Air pressure• Dew Point

Storms

Hurricanes, Thunder and Lightning, Tornadoes

Storms

• Storms are extreme weather caused by the heat of the sun, water in the air, and spin of the earth.

Storms

1. Sun is out which heats up the surface of the earth

2. Air near the ground gets warm3. Cooler air from surrounding areas flows in and

forces the warm air up 4. Causing a upward/downward flow of air masses

This creates extreme weather!

Hurricanes

• Hurricane: Atlantic and East Pacific• Typhoon: West Pacific• Cyclone: Indian Ocean

• Intense Low-Pressure Systems• Need 60 m (200 feet) of ocean water at

26.5 C or warmer to form

Hurricanes• Tropical storms are violent, destructive

storms• A hurricane is a severe tropical storm

– Have wind speeds over 155 mi/hr– Develop over warm, tropical oceans– Warm, moist air over the evaporating ocean

rise rapidly– The rising warm air condenses and a large

amount of energy in the form of latent heat

Hurricanes• A fully developed hurricane has a series of thick

cloud bands spiraling upward around the center of the storm

• Rain is torrential• Winds increase in velocity toward the center (eye)

of the storm, with the eye being a region of calm, clear, sinking air

March 2004

World Hurricane Tracks 1995-2003

Eye of Hurricanes • 100 km or less in diameter• 30 minutes or so calm weather• Definitely not the end of the storm!• Post-eye storm is stronger• “Centrifugal” force counteracts inward air

flow• In strongest storms, air flow can get so

congested a second eyewall forms (Andrew)

Decay of Hurricanes

• Need warm water for energy• Decay rapidly over land• Lose strength over cold water• Can still cause destructive flooding long after

cyclonic structure is gone• Degenerate into low pressure systems

Saffir-Simpson Scale

Defined by instrumentstropical storm: <74mphCategory 1: 74-95 mph 1-2m storm surgeCategory 2: 96-110 mph 2-3 mCategory 3: 111-130 mph 3-4 mCategory 4: 131-155 mph 4-6 mCategory 5: >155 mph > 6 m

Naming Hurricanes• No naming system until 1953• Women’s names 1953-79• Regional Name Lists• Lists maintained by World Meteorological

Organization• Names can be retired after especially

significant storms

Thunderstorms• A storm accompanied by thunder,

lightning and strong winds– Occur when a portion of air in a warm, moist

maritime tropical air mass heats and rises due to high surface temperatures

– This is why thunderstorms are often in the late afternoon or early evening

Three Stages of Thunderstorms• Cumulus stage:

– First stage; when warm, moist air rises until the water vapor within the air forms a cumulus cloud

• Mature stage:– Violently rising warm, moist air swells higher– Cumulus cloud gets darker and heavy, torrential rain

showers (or hail) falls from the cloud

• Dissipating stage:– When the air currents stop rising

What is thunder and lightning?

• Thunder– Rapid expansion and collapse of the air– Causes a loud noise, called thunder

• Lightning– Clouds at times have distinct electrical

charges– Lightning is a spark that travels between the

two oppositely charged parts of the cloud

Tornadoes• The smallest, most violent and shortest-

lived severe storm • A whirling, funnel-shaped cyclone

– Forms when a thunderstorm meets high-altitude, horizontal winds, causing the air in the thunderstorm to rotate at speeds up to 320 miles per hour

– If the bottom of the spinning extension of a tornado touches the ground, it moves in a wandering, haphazard path, destroying everything in the path

The Fujita Scale

Based on Damage and Engineering Studies• F0 40-73 mph 29%• F1 74-112 mph 40%• F2 113-157 mph 24%• F3 158-206 mph 6 %• F4 207-260 mph 2 %• F5 261-318 mph <1 %• F6? How to identify?

Bill Nye: Storms

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

Climate

What is climate?• The average weather conditions of a

region• Usually described in terms of average

monthly and yearly temperature and amount of precipitation

• The climate is affected by several factors including: latitude, heat absorption and release and topography

Latitude

• Latitude is defined as the distance from the equator– It determines the amount of solar energy

received by, and the prevailing wind belts of, the region

Latitude

• Solar Energy– The amount of solar energy that a location

receives depends on two factors• the angle at which the rays of the sun strike the

earth• the number of hours of daylight the location

receives

Solar Energy

• At the equator…– the rays always strike the earth at a very high

angle (90 degrees)– Both day and night are about 12 hours long

throughout the year– This results in steady high temperatures year

round• There are no summer or winters; only dry and rainy

seasons

Solar Energy

• At higher altitudes…– The sun’s rays strike the earth at angles less

than 90º– They therefore do not heat up the area as

much, resulting in lower average temperature

– There is then varying lengths of night and day

Solar Energy

• In the polar regions…– The sun only sets for a few hours each day

in the summer and rises for only a few hours each day in the winter

– Annual temperature range is very large, but the daily temperature ranges are very small

Wind Patterns

• Latitude also affects the global wind belts and the direction of the wind in a particular location

• Wind can affect many things:– Humidity– Precipitation– Temperature– Cloud cover

Wind Patterns

• In the equatorial belt…– There is very low pressure; it is called the

doldrums– The air rises and cools, the water vapor

condenses– There is heavy precipitation– As the latitude increases, the rainfall

decreases

Wind Patterns

• In the subtropical areas…– The air is sinking, drying and warming– There is little precipitation– Most of the world’s deserts are located in

this region

Wind Patterns

• Heading toward the poles…– This is a belt of higher precipitation yet again– This is where warm tropical air meets cold polar

air– At the poles themselves, precipitation decreases

due to cold, dry, polar high air masses

Ocean Currents

• Ocean currents affect the amount of heat absorbed or released by the air– If winds blow toward the shore, currents

will effect air masses more strongly

Seasonal Winds• Winds can also shift seasonally due to

heat differences between land and ocean– These seasonal winds are called monsoons

and are largest over larger land areas/regions

– In the summer time, the land heats more quickly than the ocean

– In the winter, the land also loses heat more quickly

Topography

• The topography, or shape of the land is the last major feature that can influence climate– The temperature decreases as altitude

increases– Air flowing down mountain slopes as a

tendency to be warm and dry

A Chinook is a dry, warm wind that flows down a mountain and can raise the air temperature very rapidly in a short amount of time.