Weather

WeatherPressure, Winds, and Precipitation

1Heating the EarthWeather is the daily conditions of the atmosphereWeather is caused by the unequal heating of the EarthThe factors that interact to cause weather are heat energy, air pressure, winds, and moisture

2Heat Energy and the AtmosphereThe Suns energy that is absorbed by the Earth is spread throughout the atmosphere, some is reflected back into space

3Heat TransferRadiation is the transfer of energy by waves such as light, UV rays hit the surface of the Earth and heat it up.Conduction is the direct transfer of heat energy from one substance to another, UV is changed into IRConvection is the transfer of heat energy in a fluid, hot air rises causing currents4The Greenhouse EffectInfrared light is absorbed by carbon dioxide, water vapor, and other gases in the atmosphere and forms a blanket that traps heat around the Earth.

5Unequal heating of the Earths surface

6Air PressureAir pressure depends on the density of the air in a particular placeDensity is affected by temperature, water vapor, and elevationAs temperature increases density decreasesAs water vapor increases density decreasesAs elevation increases density decreases7Measuring Air PressureA barometer measures the pressure of the air

Mercury BarometerAneroid Barometer8Air Pressure and WeatherLow air pressure usually means stormy weather and high air pressure usually means fair weather

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WindsBoth local winds and global winds are caused by differences in air pressure due to unequal heating of the atmosphere

Isobars that are closer together indicate stronger windsWinds travel from areas of high pressure to areas of low pressure

12Measuring WindWind is measured by an anemometer for speed and a weather vane for direction

13Local WindsLand and sea breezes

14How they form

Global Winds draw a big circle on your paper and fill in what we talk about each time.

16Unequal heating of the Earths surface causes the global wind patternWinds do not blow in a straight N to S or S to N pattern, they curve to the right in the Northern hemisphere and to the left in the Southern hemisphere due to the Coriolis effect, which is caused by the Earths rotation.

17Doldrums are located at the equator where the winds are very calm because the air is warm and rises producing a low pressure belt (Low pressure means precipitation, what biome is found around the world at the equator?)Trade winds are from the equator to 30 degrees N and S where the warm equatorial winds cool and sink, winds are warm and steady high pressure

18Horse latitudes are located about 30 degrees N and S, winds are calm with little precipitation(High pressure means no precipitation, what biome is found ar 30 around the world?)

Prevailing westerlies are located between 30 and 60 degrees latitudeCaused by cool sinking air moving toward the poles These westerly winds are usually strong1960 degrees is a zone of low pressurePolar easterlies are cold, but weak winds caused by the rising and sinking of the westerliesN and S poles are high pressure

20Jet StreamThe jet stream is a narrow belt of strong, high speed, high pressure air that flows across, from west to east, the Earth

21Moisture in the AirWater vapor or moisture in the air is called humidityHumidity can vary from place to place and time to timeWater condenses at a point called the dew point22Relative humidity is the percent of moisture the air holds relative to the amount it could hold at a particular temperatureMeasuring humidity using a psychrometer that consists of 2 thermometers, one wet and one dry

23CloudsClouds form when moisture in the air condenses on small particles of dust or other solids in the airThey are classified as to where they are found in the atmosphere

24Cumulus clouds are white and puffy and indicate fair weather

Cumulonimbus or thunderheads indicate thunderstorms with lightning and possibly tornadoes if the conditions are just right

Stratus are gray clouds that cover the whole sky . Day is mostly cloudy and can drizzle.

Nimbostratus are gray clouds that cover the sky but are associated with drizzle and rain. Usually form in a warm front26Cirrus clouds are feathery clouds that are found very high in the atmosphereThey are associated with fair weather, but rain or snow could come within the next 12-24 hours

27Fog is formed when the temperature and the dew point temperature are the same.

28Weather Patterns: Air MassesChanges in the weather are caused by very large areas of air with specific temperature and humidity called air massesThere are four main air masses that affect the weather in the United StatesThey are named for the regions they originate in29

30Maritime massesMaritime tropical air mass originates near the equator over the ocean, it brings warm moist air onto the continentMaritime polar air mass forms over the Pacific Ocean in both winter and summer, it forms over the North Atlantic and brings cold winter weather in the winter and cooler temperatures during the summer to the east coast31Continental massesThe continental tropical forms over land in the Southwestern US it brings dry hot airThe continental polar mass forms over the land in Canada and brings very cold dry air into the US32FrontsFronts form when large air masses meet that have different temperatures and humidityThe weather at a front is can be very unstable and stormyThere are four different types of fronts: cold front, warm front, occluded front, and stationary front33

Cold FrontA cold front forms when a mass of cold air pushes over a mass of warm airThe cold air pushes its way below the warm airViolent storms, even tornadoes can be associated with these frontFair, cooler, and drier air usually follows35Cold Front

36Warm FrontA warm front forms when a mass of warm air overrides a mass of cooler airRain showers can accompany a warm frontHot and humid weather follows37

38Occluded FrontWhen a very fast moving cold air mass overtakes a slower moving warmer air mass, an occluded front formsIt produces less severe weather than a warm or cold front can

39Stationary FrontA stationary front is formed when a cold air mass and a warm air mass meet and do not moveThis produces several days of rain

40High and Low Pressure Systems

41High PressureSome high pressure systems are associated with cold air systems that move in and change the weatherSubtropical high pressure systems are slow moving, usually bring very warm conditions

42Low Pressure SystemsLow pressure systems are associated with precipitation and a change to the weather for an extended timeLow pressure systems can bring rain or snowLow pressure systems can bring a sudden dramatic drop in temperatures43Predicting the Weather and ClimatesJust think the end is near!!!!

44Predicting the WeatherMeteorologist is a person who studies and predicts the weatherThey interpret weather information from local weather observers, balloons, satellites, and weather stations around the world45Weather MapsData from stations around the country is gathered and put on weather mapsThis includes temperature, air pressure, precipitation, and the wind speed and directionInformation about cloud cover, air masses, and fronts may be includedThe information is recorded by a number of symbols and numbers46Recording Weather Data

47Isotherms and IsobarsIsotherms connect points of equal temperaturesIsobars connect points of equal pressure

48Symbols

49Controlling the WeatherAt the present time, weather control is limited to seeding of cloudsThis is done by placing dry ice or silver iodine crystals into the super cooled layers of the stratosphere These cause large ice crystals to form that eventually fall as rain50