Chapter 5 Weather

Lesson 1 Describing Weather

What is weather? The atmospheric conditions, along with short- term changes, of a certain place at a certain time Includes temperature and rainfall Weather helps you decide what to wear that day Air temperature, air pressure, wind speed, wind direction, humidity, cloud cover, and precipitation ________________________________________

What is temperature? The average kinetic energy of molecules in the air Varies with time of day, season, location, and altitude _______________________________________

What is air pressure? The pressure that a column of air exerts on the air or a surface below it Decreases as altitude increases Barometric pressure – measured in millibars (mb) ______________________________________

What is wind? Air moving from areas of high pressure to areas of low pressure Measured using an anemometer _________________________________ ______

What is humidity? The amount of water vapor in the air Measured in grams of water per cubic meter of air _______________________________________

What is relative humidity? The amount of water vapor present in the air compared to the maximum amount the air can hold _________________________________ _______

What is dew point? The temperature at which air is fully saturated because of decreasing temperature while holding the amount of moisture constant (when air is full of water because temperature decreased and some of the vapor condenses) Dew is the water droplet you see on leaves when water vapor condenses _______________________________________

What are clouds or fog? Condensed water droplets or ice crystals in the air Stratus clouds – flat, white, and layered Cumulus clouds – fluffy and piled up Cirrus clouds – wispy and high in the air What about fog? A cloud that forms near the Earth’s surface ___________________________________________

What is precipitation? Water in liquid or solid form falling to Earth from the atmosphere Rain – droplets of water Snow – frozen crystals Sleet – frozen or freezing rain Hail – large pellets of ice _______________________________________

What is the water cycle? The series of natural processes by which water continually moves among oceans, land, and the atmosphere _____________End Lesson 1________

Lesson 2 Weather Patterns

What is a high-pressure system? A large body of circulating air with high pressure at its center Cold, dense air sinks and pushes air away Weather is usually fair and sunny _______________________________

What is a low-pressure system? A large body of circulating air with low pressure at its center Less dense air rises and cools Weather is usually cloudy and can include precipitation _______________________________

What are air masses? Large bodies of air that have uniform temperature, humidity and pressure Form when high pressure systems stay in an area for several days _______________________________

Types of Air Masses Arctic – form in the arctic Continental polar – form over cold land Maritime polar – form over cold water Continental tropical – form over warm land Maritime tropical – form over warm water _______________________________

Air Masses Continental Maritime Polar Cold land Cold water Tropical Warm land Warm water

What is a front? A boundary between two air masses Cold – cold air pushing under warm air; thunderstorms common Warm – warm air pushing over cold air; wide blanket of clouds Stationary – two air masses not moving Occluded – a cold front passing a warm front _______________________________

Severe Weather Thunderstorms Forms from cumulus clouds that grow tall into cumulonimbus Lots of lightning caused by ice crashing into each other Strong wind and rain Three stages – cumulus, mature, and dissipation _______________________________

What are tornadoes? A violent, whirling column of air in contact with the ground Usually only last a few minutes, but have winds strong enough to send large objects flying Form in thunderstorms when parts of an updraft swirl toward the ground in a funnel cloud When the funnel cloud reaches the ground it becomes a tornado Measured by the Fujita scale (F1 – F5) _______________________________

What is a hurricane? An intense tropical storm with winds over 119 km/h Have a circular shape based on air movement Warm, moist air rises forming an area of low pressure As more air rises, it strengthens into a tropical depression (37-62 km/h) and then a tropical storm (63 km/h) Damage comes from winds and flooding Also called typhoons or cyclones _______________________________

What is a blizzard? A violent winter storm characterized by freezing temperatures, strong winds, and blowing snow Snow can reduce visibility Ice storms can cause structures to break under the weight of ice _______________________________

Lesson 3 Weather Forecasts

Measuring the Weather Who measures weather? A meteorologist _______________________________________

What is a surface report? It describes a set of weather measurements made on Earth’s surface What is an upper-air report? It describes wind, temperature, and humidity above Earth’s surface _______________________________________

Satellite and Radar Satellites can provide information about clouds and heat What is Doppler radar? Specialized radar that detects precipitation and wind speed This is useful during severe weather _______________________________________

Weather Maps Maps of station models can help provide information on weather over a large area They can show fronts and other patterns What are isobars? Lines that connect all places on a map that have the same pressure _______________________________________

Predicting the Weather What are computer models? Detailed computer programs that solve a set of complex math formulas They are used to predict temperature, wind, and cloud formation _______________________________________