Weather & Climate

Weather Intro How much do you already know about weather? What cycle is the basis of our weather? What causes precipitation to occur? Where do storms usually occur?

Weather Temporary behavior of atmosphere (what’s going on at any certain time) Small geographic area Can change rapidly The study of weather is called meteorology Someone who studies weather is called a meteorologist

Climate Long-term behavior of atmosphere (100+ years) Large geographic area Very slow to change

SEASONS

POLAR 90o -60o latitude Cool summers, cold year-round Dry EX: Arctic and Antarctic

TEMPERATE 60o-30o latitude True Seasons Variety of climate patterns Moderate precipitation (rain/snow) EX: United States

TROPICAL 30o - equator No winter, warm year-round High temp, rainfall, humidity EX: Caribbean

What Factors Affect Weather & Climate? The Sun The Water Cycle The Atmosphere The Ocean

How Does the Sun Affect Weather? It warms the atmosphere & oceans It creates climate zones It keeps the water cycle going It affects weather patterns

The Water Cycle All the water on the planet is recycled in this manner!

Parts of the Cycle Evaporation—Water going from a liquid to a gas (gains energy from the sun)

Parts of the Cycle Condensation—Water going from a gas to a liquid (cools or loses energy) When this happens in the atmosphere, CLOUDS form.

Parts of the Cycle Precipitation—when water falls out the atmosphere. Forms when the water droplets in clouds become too heavy to stay up. Liquid water = rain Frozen water = snow, sleet, or hail

Parts of the Cycle Transpiration—evaporation of water from/out of plants. Locate this on the diagram!

The Water Cycle

Atmosphere The atmosphere is a mixture of gases that surrounds the Earth Nitrogen (78%), Oxygen (20.9%), Less than 1% Ar, CO2, He, Methane, Krypton, Hydrogen Has five different layers; each has different properties Air Temperature and Pressure change with altitude Weather occurs in the layer closest to Earth (troposphere)

Atmosphere

Atmosphere

Exosphere - the outermost layer of the Earth's atmosphere, where atmospheric pressure and temperature are low. Ionosphere - the atmospheric layer between the mesosphere and the exosphere; it is part of the thermosphere. Mesosphere - the atmospheric layer between the stratosphere and the ionosphere. Stratosphere - the atmospheric layer between the troposphere and the mesosphere. The stratosphere is characterized by a slight temperature increase with altitude and by the absence of clouds. Thermosphere - the layer of the atmosphere located above part of the ionosphere (starting at the coldest part of the atmosphere) and below outer space; it consists of the exosphere and part of the ionosphere. Troposphere - the lowest layer of the Earth's atmosphere. The weather and clouds occur in the troposphere.

Air Masses An air mass is a body of air with a certain temperature and moisture level Can be warm or Cold Can contain a lot of moisture or not a lot of moisture

Fronts where air masses meet 4 Types: Warm Cold Occluded Stationary Fronts are places where air masses meet 4 Types: Warm Cold Occluded Stationary Each kind can bring different kinds of weather

Air Pressure How much the earth’s atmosphere is pressing down on us Measured with a barometer If it changes, then new weather is on the way: Falling Air Pressure = stormy weather coming Rising Air Pressure = fair weather coming Steady Air Pressure = no change is coming

Demo-The hot plate is turned on with a spiral above it What happens to the air above the hot plate? Why does the spiral start to spin? What direction is it going? (clockwise or counterclockwise?) When the spiral is moved to colder air, how does the motion change? WHY…What is going on with the air?

Air Currents Determined by heat and temperature of the earth’s surface, and the air around it. Conduction: Heat transfer is from direct contact between heat source and matter Ex-When heat from blacktop or sand is transferred directly to a bare foot Convection: Heat transfer is from indirect contact Ex-When the surface of the earth heats up, the air just above the surface rises. It rises, it also cools and therefore, it sinks back down. This rising and sinking creates surface winds (convection currents) Radiation: Travels in waves Ex-The sun’s energy traveling to Earth

Winds Winds are created from differences in air pressure Moves from areas of HIGH to LOW pressure Greater the difference in pressure, the FASTER the wind blows Measured with wind vanes (or wind sock) and anemometers or you can estimate with the Beaufort Wind Scale

Beaufort Wind Scale

Local Winds Day time breeze towards land because warm air over land rises (LOW), then cools and sinks (HIGH) towards water. Wind blows from High to Low. Night time breeze towards water because warm air over water rises (LOW), then cools and sinks (HIGH) towards land. Wind blows from High to Low.

Global Winds Thousands of kilometers long; can cause weather to move in different directions Jet stream, prevailing westerlies, doldrums, horse latitudes, trade winds Caused by the temperature difference in different regions Hot Tropical Regions—causes air to rise Cold polar Regions—causes air to sink

Global Winds Also affected by Earth’s Spin Coriolis Effect = causes winds to curve to the right in the N. Hemisphere; to the left in the S. Hemisphere

Relative Humidity Measure of the amount of moisture in the air compared to what the air could hold How “full” of water the air is Expressed as % 100% relative humidity = saturated air (precipitation is occurring)

Relative Humidity 1. Warm air holds more moisture than cool air (more space for water vapor between air molecules) 2. As air warms, relative humidity increases 3. As air cools, relative humidity decreases

Dew Point Dew point is the temperature at which the air is saturated (100% relative humidity) Several events can occur when the dew point temp. is reached: 1. If dew point temp. is above freezing: a. water vapor condenses as liquid b. dew will form on surfaces c. cloud droplets will form in air 2. If dew point temp. is below freezing: a. water vapor condenses as a solid b. frost on surfaces c. snow (or hail) in the air

Severe Weather

Thunderstorms Requires a mature cumulonimbus cloud Signs Sudden reversal of wind direction Noticeable increase in wind speed Sudden drop in temperature

Thunderstorms Possible weather a. heavy rains (flash floods) b. lightning (forest fires) c. thunder (frightens animals) d. hail (crop damage) e. tornadoes f. strong, gusty winds Safety Rules a. Stay indoors b. Prepare for lightning, strong winds c. Listen to radio/TV for tornado watch/warning d. Thunderstorms don’t last long

Lightning Storms Cumulonimbus cloud becomes electrically charged and ground below has opposite charge Lightning strike: flow of current thru air (a poor conductor) from the – to the + Lightning can flow from cloud to ground, cloud to cloud, and from ground to cloud Bright light is caused by glowing air molecules heated by the current Lightning follows the path of least resistance (easiest way to positive) Lightning rod offers lightning an easy, safe path to the ground (+)

Lightning Storms Sound travels @ about 1100 ft/sec in air Thunder is the shock wave caused by the explosive expansion of heated air Sound travels @ about 1100 ft/sec in air 5,280 ft in one mile Distance from you to lightning = number of seconds between seeing the flash and hearing the thunder divided by 5. (5,280 ft / 1100 ft/sec = 5 seconds) https://www.youtube.com/watch?v=JFtJh5pUpgQ

Types of Lightning Streak or bolt Single or branched lines of light

Types of Lightning Sheet a. shapeless flash over wide area b. a cloud-to-cloud bolt hidden by the clouds

Types of Lightning Other Types a. heat, ribbon, beaded (types of bolt) b. ball (only other shape lightning can have) https://www.youtube.com/watch?v=9wBhVhcDDLc

Safety rules for lightning storms Stay indoors Stay away from anything that conducts electricity (stove, sink, telephone, TV) Get out of the water and off of small boats Stay away from open doors, windows, fireplaces Stay in your car (very safe place to be) Don’t stand under lone trees or in open places Avoid hilltops If your hair stands on end, or your skin tingles, drop to the ground but try to keep as little contact with the ground as possible People struck by lightning https://www.youtube.com/watch?v=OLh3q94n8iw

Tornado (a.k.a twister, cyclone) Counterclockwise column of rotating air extending from cumulonimbus cloud Per square foot, is the most destructive atmospheric event Rated by wind speed (EF1 to EF5) “Tornado season” = April, May, June Tornadoes that form over water are called “waterspouts” How do tornadoes form http://safeshare.tv/w/HeDLSNRRRe

Tornado Behavior of a tornado is unpredictable Typical tornado will: 1. Occur between 3-7 pm 2. Travel 4 miles 3. Be 300-400 m wide 4. Travel 25-40 mi/hour 5. Have wind speeds up to 300 mi/hr 6. Produce extremely low pressure 7. Be dark due to debris picked up

Tornado 1. Take immediate action! 2. Move away from tornado’s path (90O to the path of the twister) 3. Lie flat in nearest ditch, etc. At home a. open windows, doors b. seek shelter in basement or under heavy table in middle of house

Tropical Cyclone Nicknames 1. Atlantic: hurricane 2. SE Asia, Japan: typhoon 3. Australia: willy-willy 4. Indian Ocean: cyclone Rated by wind speed (category 1 to 5) Starts and grows over warm ocean water Composed of bands of thunderstorms spiraling counterclockwise around a low pressure center

Tropical Cyclone Characteristics Several hundred miles wide Last many days (even weeks) Winds from 74-200 mi/hr Contains an “eye” Small region of low pressure Surrounded by highest winds Calm, peaceful, sunny weather Last for about 1 hour as hurricane passes by

Tropical Cyclone Safety 1. Prepare for high winds 2. Prepare for flooding (greatest source of damage) Up to 20 in. of rain Flooding by coastal water 3. Prepare for thunderstorms 4. Have on hand stored food, water, blankets, candles, matches, radio, etc. 5. Seek shelter https://www.youtube.com/watch?v=ZCunblkAnik